Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. CROP efforts. breeding ued contin- justify and States United ofthe legumes forage major to the be willcontinue clover white and red that ensure competitiveness general high seedling vigor, ease of establishment, with along species improved ofthese qualities and unique The cultivars. ofimproved development the in have cooperated southeast the in states several in clover, white For researchers states. southern the for Florida in and states, middle the for Kentucky in states, northern the in use for Wisconsin in bred have been cultivars ver to the area of use. New, more-adapted red clo- adaptation general for by breeding somewhat infl be can but senescence grammed three to four years, to about is ofclovers life limits which largelyPersistence, governed by yield. and pro- adaptability general with association ofits because plants) ofindividual (longevity breeding programs is increased persistence clover ofmost goal One future. the for lenges chal- and falls, short successes, objectives, programs—their improvement clover of status present the describes paper This legumes. havegen prices stimulated interest in forage systems, andgrated high nitro- crop–livestock inte- farming, organic agriculture, sustainable Recently, States. United eastern the in ticularly United States during the past century, par- the in feeding livestock for legumes important ( clover white L.) and ( red clovers, perennial The

SCIENCE , VOL Developments in the United States United Developments the in ABSTRACT . 48 , A Century of Clover Breeding A Century T. repens T. JANUARY Trifolium pratense Trifolium – FEBRUARY L.), have been uenced

2008 1

Norman L. Taylor* L. Norman humans, and the drastic rise in the number of domestic animals animals ofdomestic number the in rise drastic the and humans, mon mosquito ( mosquito mon in northern Europe. of malaria decline the ofclover advent and the between Thetionship scenario is arela- as suggest went on to Kjaergaard follows: population. cattle the in The most com- ( for cattle feed excellent Clover is fertilization. grain to notwere limited eff The Europe. northern of the seventeenth century, clover became widespread throughout ofanitrogen-defi aresult as ishment it aff because (1347–1352) Death Black the due to occurred mortality unrivaled acute, the that suggested Kjaergaard or death. of life a matter increasingly almost became crops of starvation nitrogen centuries, fourteenth and thirteenth the In population. expanding an feed to needed forcereals nitrogen ofatmospheric provider chief the was and Europe, throughout spread 1000, year the around ticated fi Clover was follows: as situation the explained (2003) Kjaergaard prices. low nitrogen from resulting offertilizer use increased been has factor aprimary decline, this involved in are fi last the in declined has usage but States, United the in century past forthe feed livestock tant regional virus resistant. virus regional ver yellow vein virus; clo- CYVV, PSV, virus; mosaic yellow BYMV, bean peanut virus; mosaic stuntalfalfa virus; SRVR, Southern Abbreviations: ([email protected]). author *Corresponding 2007. Sept. 27 Received KY, 40546. Lexington, Stn., Exp. Agric. tucky KY, Ken- Univ. ofKentucky-Lexington, Sciences, Soil and Dep. Plant has been obtained by the publisher. the by herein obtained been contained has material the reprinting for and printing for from Permission writing in publisher. the permission without system, retrieval and storage information any or recording, photocopying, including mechanical, or any in electronic means, any by or form transmitted or reproduced be may periodical this of Nopart reserved. rights All 53711 WI USA Madison, Rd., Segoe S. 677 ofAmerica Society Science © Crop doi: 10.2135/cropsci2007.08.0446 48:1–13 Sci. (2008). Crop in Published T pratense he perennial clovers ( Bos L.) and white clover ( white L.) and ected a population already weakened byundernour- weakened already apopulation ected spp.) and therefore helped spur a dramatic increase increase adramatic spur helped spp.) therefore and Anopheles atroparvus Anopheles 2,4-D, 2,4-dichlorophenoxy acetic AMV, acid; 2,4-D, 2,4-dichlorophenoxy ects of cloverects revolution on nitrogen the ve decades. Although several factors factors several ve Although decades. REVIEW &INTERPRETATION Trifolium T. cient agriculture. At the close close Atthe agriculture. cient ) in that area prefers cattle to to cattle prefers area that ) in

repens spp.), especially red ( L.), have been impor- rst domes- T. T. Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. that did the potato ( potato the did that infl agreater had Clover probably composers. and painters, bypoets, depicted romantically fl awonderful into countryside clover red fi and white The landscape. ofthe transformation was Another tion. quences, including an increase in and milk honey produc- conse- indirect other many Clover had Europe. northern in elimination virtual its to leading severed, was cycle life mosquito’s the malaria, donot develop cattle as Inasmuch bitten. being ofhumans number the in adecline to led 2 fact, without clover, potatoes could not have thrived. could clover, without potatoes fact, trol. Although usage of the clovers in the Corn Belt has has Belt Corn the in clovers ofthe usage Although trol. rophenoxy acetic acid (2,4-D) for weed broadleaf con- of2,4-dichlo- use the been has pastures mixed in clovers of reduction the to contributing factor Another needed. no longer was Project Seed Foundation the and cultivars, to rights exclusive have that companies seed by private over taken was function clover.red however, Later, this ‘Kenland’ was program this in cultivar pilot The cultivars. U.S. ofeastern-adapted seeds increase rapidly to initiated was Project Seed Foundation National 1950s, the the In 2005). (Wong, world combined ofthe rest the in than produced are seeds legume and Valley, more grass where the crop. Much of this production is in the Willamette sow to needed are West, the fewer in hectares higher are yields seed Because Oregon. particularly States, United western the to production ofseed shift the was clovers the infl factor Another biodiesel. fi intensi- has ofrow crops use More recently, the 2005). al., et clover red (Naylor such as forforages need the lessened ( [ ofsoybeans a monoculture to shifted Belt, Corn the in particularly landscape, the and icago sativa ( alfalfa such as legumes alternative to ashift included States, United the in decline the to contributing use gen nitro- increased than 1996). other Afactor Quesenberry, 1950 about peaked (Taylor and Canada except countries in other countries. Seed production of red clover in most and environment the on acceptable. no were longer climate nitrogen produced industrially of eff deleterious and costs energy enormous when the confi became Europe Clover in charm. picturesque its lost and culture bymono- dominated became landscape The areas. many ofclover in disappearance the to led alow at price izer forfertil- use its and dramatically, expanded of nitrogen production By World 2000). War industrial II, (McNeill, synthesis ammonia through nitrogen ofextracting cess pro- the developed Haber Fritz chemist when German Zea mays ed due to interest in fuel production, that is, ethanol and and ethanol is, that production, fuel in interest due to ed The defi A similar decline in the use of clovers has occurred occurred has ofclovers use the in decline A similar L.). The decoupling of livestock from the land land the from of livestock L.). decoupling The L.). Cattle were no longer fattened on the land, land, the on fattened longer no were L.). Cattle ning year for the decline of clover was 1909, ofclover was decline forthe year ning ned to botanical gardens, awaiting the day day the awaiting gardens, botanical ned to Solanum elds in blossom transformed the Glycine max Glycine

uencing the decline in use of use in decline the uencing tuberosum ower garden that has been has ower that garden uence on civilization oncivilization uence L.) (Piper, 1924). L.) (Piper, In (L.) Merr.] or corn corn or Merr.] (L.) WWW Med- ects ects . CROPS turned out to be very productive over wide areas. In fact, fact, In over areas. productive wide out bevery to turned cultivars clover. early ofwhite These type intermediate an S-1’, ‘Louisiana clover red and Kenland such as cultivars clover early to led This selection. bymass developed were cultivars early most widely. Generally, them distribute to and strains farmer these from cultivars adapted widely more develop to desirable however, itbecame Eventually, Europe, locally. adapted well were from that strains” “farmer developed Over process the in sweepings. and introduced seeds their maintained hayloft or farmers were time, hay from or States accidentally United either the in Clovers Variation of Genetic Sources clover. ofwhite case the in stolon characteristics and types, grazing pubescence, as have involved changes in morphological characters objectives Other such resistance. disease and insect greater to led often has adaptability forimproved breeding hand, other the On resistance. insect and disease augment to necessary been often it To has yield. persistence, improve and adaptability general with association ofits because longevity) plant (individual persistence to emphasis primary given have programs clover breeding Most OBJECTIVESBREEDING as suggest research for the future with possible avenues of possible with future forthe research suggest as eff breeding past white, red, with and primarily Ideal century. last Kura the in clovers nial clover ( in the United States of breeding ofneglect. period along after be reconsidered eff to beginning are programs clover breeding consequence, a As legumes. offorage use forgreater well bodes also runoff nutrient through supplies water donot pollute that crops organic in Interest factors. also are concentrates onprotein reliance and costs input feed ofreducing possibility The nitrogen. ofsynthetic use the eff environmental deteriorating and costs energy in forage legumes, including clovers, because of increasing purpose. forthis together sown are endophytes in grasses. Often,the mixture, especially for ameliorating the red eff and white clover in included are whenclovers begreater to shown been seeds have rates reproduction and gains Cattle midsouth. the in renovation forpasture used still clover is seed declined, 1995, 1998). 1995, 1996; Taylor, Quesenberry, and 1987; Taylor Smith, and made to update previous reviews (Pederson, 1995; Taylor to impact potential the have may that countries other from U.S.research breeding to bedrawn will but attention forU.S. agriculture, tions programs.approach. An attempt Particular will be emphasis will be given to applica- . ORG The objective of this paper is to describe the status status the describe to is paper ofthis objective The ofinterest aresurgence indicates evidence recent Some

CROP orts, accomplishments, short falls, as well well as falls, short accomplishments, orts,

SCIENCE T. ambiguum T. , VOL . 48 , JANUARY orts with the peren- Bieb.) include and and soil erosion – FEBRUARY ofthe ect ects from from ects

2008 Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. changes lead to infertility. to lead changes induced ofthe many Also, genes. recessive in changes method exists as in self-pollinatedto eff crops for uncovering inability The clovers. cross-pollinated forthe useful 1987). have particularly been methods None ofthese Taylor, and (Bagley 1961), variation somaclonal and (Taylor etal., radiation ionizing mutagenesis, include signifi has and grown 1947, about being released still is Kenland, CROP using method polycross the than laborious less is method This asynthetic. form to combined are populations rior supe- most the testing, after and separately, maintained and developed are Populations by clones. than rather populations byseed maintained are parents that except 1970). etal., son a fi ‘Regal” ofwhich legumes, other in developed been have in bred cultivars Synthetic type my knowledge. to States United the this of cultivar clover red only the is 1974b), (Taylor Anderson, and synthetic a10-clone ‘Kenstar’, reason, it Forthat ofselection. cycle involved foreach has expense the not and been required oftime length the is disadvantage a major used much However, characters. ofcomplex forselection insuitable clover is method the thus and tested, progeny are breeding. materials ing (Hollowell, 1962). 1953 in released type, clover, aladino white ‘Pilgrim’ and 2003), (Taylor Collins, ofpubescence and forabsence bred clover, red ‘Freedom!’ include method this by developed been have that Cultivars asward. in ofperformance typical not be may plants spaced ofindividual performance that Quesenberry, (Taylor and possible are process ofthe variations Many 1996).method is It the most that suggests which is selection, mass to eff similar tested worth emphasizing, ratherually than bulked. Parent plants are not progeny is that seeds of however, half-sib families are maintained individ- diff selection. The main mass to cyclic similar very eff not be may selection Mass plants. ofselected intercrosses artifi or cages, coverings, of use the by encouraged be may area the to common are that pathogens orother nematodes, cultivar is to the where be that to grown. similar environment an in sown are Epiphytotics of diseases,highly eff insects, a been has ofpollination control with selection Mass Procedures Breeding ective for characteristics with low heritability. with forcharacteristics ective ve-clone white clover synthetic is an example (John- example an is clover synthetic white ve-clone Other sources of genetic variation for the clovers clovers forthe variation ofgenetic sources Other Strain building is to similar the polycross method breed- that is method polycross ofthe advantage The is forclovers used as selection phenotypic Recurrent cial inoculation. Seed is usually harvested from only only from harvested usually is Seed inoculation. cial

byectively selfi inbreed SCIENCE cant certifi ective method for clover breeders. Usually, seeds seeds Usually, forclover breeders. method ective , VOL ed seed hectarage. . 48 ective for simply inherited characters. characters. inherited forsimply ective , JANUARY – ng means that no suitable FEBRUARY

2008

erence WWW . CROPS trol crossing. Such hybrids exploit both general and and general both exploit Such hybrids crossing. trol con- to S-alleles homozygous clover red using in duced depression. of overcoming inbreeding necessity the and backcrosses the make to necessary time of length excessive the are procedure ofthe disadvantages primary The synthetic. forthe combined were later that fi form to crossed single were that lations popu- 10 corresponding overcome bydeveloping was that inbreeding in resulted of of the 10 Kenstar parents clonal ‘Kenton’. each to as released been Backcrosses has which (Taylor 1986), etal., cultivar Kenstar the into (BYMV) to incorporate variance. genetic onadditive only bebased to resistance likely are gains genetic and not prevented is crossing intrapopulation that is vantage Adisad- Wisconsin. clover in ofred to cultivars other and beanthis method successfully in the yellow development of ‘Arlington’ (1973) used Maxwell and Smith needed. are tests plant mosaic No spaced conditions. seeding ofnormal typical plots cast broad- as betested may virus materials the and parents clonal yield defi yield seed- if bereleased may one ormore ofthese and consin, Wis- and Kentucky, Florida, in produced been have strains programs breeding have oftime length the to berelated butmay stood been underway. not under- is States United the butnot in Europe in cessful suc- are Tetraploid tetraploids reason The tetraploids. develop to used be may ofmethods one or acombination any that experimentalindicate 1996). data The (Taylor Quesenberry, and nonreduction bygametic and oxide, ofnitrous use ofcolchicine, use ways: three beproduced in may Chromosome doubling counterparts. diploid their in lower than are yields seed greater, are persistence and yields forage and larger are the United States. Although tetraploid fl in not asuccess been 1986) buthas Ellerstrom, and (Sjodin been produced Europe has in clover respects several in (1999). byBrummer delineated have been crops forage in heterosis ofexploiting methods Other parents. inbred ability combining high isolate to enough large breeding programs willoff be funded be must production at seed and parents levels ability combining suffi clover red high- ofisolating expense butthe Hybrid potential, great has 1972). al., et Anderson 1974a; son, (Taylor Ander- and orpersistence yield in cultivar star Ken- the not exceed did developed were that hybrids double-cross the Unfortunately, S-alleles. homozygous (1996), is that parental clonesmethod, must be inbred to isolateclover as diagrammed (Andersonspecifi et al., by Taylor 1974). A disadvantage and Quesenberry of the . ORG benefi economic by set Single- and double-cross hybrids have been pro- been have hybrids double-cross and Single- Kentucky in used was procedure backcross The Tetraploid red clover (2 clover red Tetraploid 3 c combining ability that have been shown in red in shown have been that ability c combining ciencies can be overcome. Incidentally, research research beovercome. Incidentally, can ciencies t. It is doubtful that clover n = 28) that exceeds diploid diploid exceeds that =28) owers and seeds seeds and owers ve populations populations ve ciently ciently Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. Williams and Verry (1981) Verry and of cross forthe Williams (1978) and Williams by initiated was clover white with The most extensive interspecifi reproductive and clover data. of on crossing ease based ofwhite relatives ofputative diagram and for areview of version doubled a as clover white that originated hypothesized They tion involving combina- hybrid any from released been have cultivars (1998), etal. butno (1997) Marshall and etal., Hussain repens of cross The backcrosses. the in low fertility the is uum of character rhizomatous ofthe expression the diffi (1997) Apparently, it New quite in is Zealand. Williams and (1998) Hussain and Wales, etal. in Abberton tucky, ambiguum, unifl orum clover with of white showed affi close research Their hybrids. in pairing chromosome and species ofrelated crossability studied annuals. forthe GA, Griffi and WA, perennials forthe Pullman, at located System Germplasm Plant National the at and Lexington in ofKentucky University the at maintained are species 200 ofmore than seeds ofwhich species, 230 ofabout sists genus The attention. considerable received has hybridization clover red via and white to species nial 1988). (Taylor Chen, and series trisomic complete the produced diploids to oftriploids 1987). Backcrosses (Taylor Wiseman, produced and occasionally are triploids diploids, with crossed are tetraploids When weak. ver is fi showed forthe 4 four backcrosses ofa backcrosses four made (2002) etal. Isobe fertility. not increase did doubling the off sarosiense with crossed clover red was To perenniality, obtain (2 hybrid fertile acompletely in resulted cross the remaking and ents par- ofboth chromosomes the Doubling annual. a sterile fi Taylor (1963) etal. the relatives. produced close its and ofinterspecifi results the rized likewise has been limited. Cleveland (1985) has summa- pallescens that suggests sequences intron roplast ribosomal DNA internally transcribed spacer and(2006) chlo- involving phylogenetic analyses based on nuclear obtained adequate fertility to select for increased persis- forincreased select to fertility adequate obtained rst hybrid, hybrid, rst cult to obtain transgressive segregates necessary for necessary segregates transgressive to obtain cult In white clover, Chen and Gibson (1970, clover, Gibson white Chenand In 1971, 1972) peren- from genes bybringing diversity Adding Success in interspecifi in Success in the white clover background. A further challenge challenge Afurther clover background. white the in with spring were completely sterile, and chromosome Hazsl. (2 Hazsl. are the likely parents of parents likely the are and somewhat less affi n continued by Anderson et al. (1991) in Ken- = 30), which, unfortunately, remained annual. annual. remained unfortunately, which, 30), = T. pratense T. T. nigrescens T. T. repens T. rst time that the triploid block in red clo- red blockin triploid the that time rst n = 48) (Phillips et al., 1982). etal., However, (Phillips =48) T. occidentale. T. T. pratense T. (2 T. nigrescens T. . The research by Ellison et al. etal. byEllison research . The has been further investigated investigated further been has n c hybridization of red clover

= 14) × clover red with c crosses c hybridization c program nity with with nity × T. repens T. See Cleveland (1985) Cleveland See , T. medium T. T. diff usum diff T. T. occidentale T. T. occidentale T. . T. repens T. Trifolium T. ambiguum. T. hybrid and and hybrid (2 T. ambig- T. , and , and n and =16), nity WWW con- × n, n, T. T. T. T. T. T. T. T. T. . CROPS

for neomycin phosphotransferase II using using II phosphotransferase neomycin for clover red transform to material (1996) this use went onto regenerated than southern cultivars. Quesenberry et al. more easily are cultivars more northern the Apparently, 1995). Quesenberry, NewRC and (Smith germplasm the increasing regeneration effi (1993) Smith and for selection recurrent used senberry clover is genotypefor regeneration. However, plant red dependent regeneration in plant (Myers (1979) Smith clover, red and In Beach worked out details et al., 1989). techniques. oftransgenetic development the to primarily Que- progress limited has programs ofbreeding funding and number the in Undoubtedly, developed. adecline been have no cultivars and States, United the in little very used problems. ofsterility because primarily genus cifi no interspe- summary, In data. crossability the ment with sarosiense clover by caused trolled in this manner was southern anthracnose of red fi ofthe One of stand. assurance least orat longevity stand increase may resistance Disease varieties. of resistant development the through is control most-effi and least-expensive The PROGRESS BREEDING legumes, It is expected that mapping the genomes of the model ing of forage plants including white clover in Australia. breed- molecular the summarized (2001) has etal. berg Spangen- and 2005), etal., (Sato Japan in underway is States. Structural United the in limited quite clover are white and of red investigations analyses Genomics programs. breeding ventional of the genome con- strong be achievedcannot without accompanying of red clover breeding ofmolecular potential the that cautioned They selection and the impact of genomics for forage legumes. marker-assisted including techniques, ofmolecular tial Woodfi eff is selection diffi less Schmidt et al. (2004) apparently is showed that phenotypicregeneration recurrent clover, plant white In deactivation. gene ofthis aresult as browning orno postharvest little exhibit that plants four clover. red obtained in They genes oxidase polyphenol the one of silencing in succeeded (2004) Rierson and Sullivan and (2004) etal. Sullivan protocol, this Using detail. in protocol this described (2006) Quesenberry and Sullivan of red and white clover. white and of red genetics molecular the into insights provide will mately and clover ofred are relatives close the confi (2006) etal. ofEllison research The tence. . ORG c hybrids have been released as cultivars in the the in cultivars as released been have c hybrids Despite great promise, molecular breeding has been been has breeding molecular promise, great Despite T. andricum T.

eld and Brummer (2000) detailed the poten- the detailed (2000) Brummer eld and and Lotus japonicus T. medium T. CROP ective for increased transgene expression. expression. transgene forincreased ective , and the more distant relatives include include relatives more distant the , and

Colletotrichum trifoliii Colletotrichum SCIENCE , all of which is in very close agree- close very in is ofwhich , all , and , and , of release in ciency, resulting VOL . 48 Medicago truncatula cult than in red clover. rst diseases to be con- , cient method of pest pest of method cient T. diff usum diff T. JANUARY B. & E. Kenland – FEBRUARY Agrobacterum. , T. pallidum T. rmed that Trifolium , ulti-

2008 T. T. ,

Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. CROP sarcinaeforme Stemphlium below. onpersistence, section the in subject more reviewed is in detail This relationship. diam- root reduce to tended eter, Taylor and (unpublished a similar observed data) selection such that indicated afi in seasons two one or after of rot clover forlow ofred incidence roots 1996). select to is method One (Taylor Quesenberry, and techniques various using frequently attempted been has genus ofthe those ably to attributed been have many diff clover white and red of rots Root selection. ofnatural aresult as disease the to of tolerance amount alimited has clover ofred apparently cultivar disease, but breeding has been diffi this to resistance have limited Europe, in mostly tivars, rum by clover caused is white and red both pathogens. Probably the most explanation. apossible is change butclimatic unknown, is forthis reason The aggressiveness. increased developed have occurred but that possibly the existing races have races in no changes that suggesting resistance, of their not all, if most, maintained have still Marathon, such as cultivars, resistant strongly The susceptible. 100% almost become have infection mildew of levels moderate showed that Kenland, as such Recently, Kentucky. cultivars, in developed FreedomMR, and Wisconsin, in developed Marathon, and Arlington include cultivars Resistant level ofresistance. ahigh obtain to necessary are selection orfi four about dominant, is resistance ity. Inasmuch qual- and yield forage reducing thereby die, and wither, as yellow, turn several leaves clover. Infected Kura and on white occasionally races clover onred and frequently occurs Salm. of the fungus occur, 2000). etal., (Pederson and 2 Syn. Loam Brown clover, white especially adapted et al., 1998). (Pratt factors byother stressed have been that ver plants Resistance clo- by ofwhite death causes to frequently Goidanich (Tassi) this caused rot pathogen stolon Summer waston. found Ken- and Marathon, in Arlington, Lakeland, cultivars the in present is genes, dominant orthree bytwo controlled (Smith and Maxwell, 1973). Resistance to the disease, red clover fi caulivora ella ner, northern anthracnose caused by the fungus man- 1950s. asimilar In early the since important been not has disease the and resistant, are southward) Illinois clover ofthe belt(mid- part southern the in cultivars all fi the was Erikss. Some diploid and tetraploid red clover red cul- tetraploid and diploid Some Erikss. Leaf spot diseases of red clover, mostly caused by fungal by several caused rootCrown are and rots by caused mildew Powdery

SCIENCE rst cultivar bred for resistance. Now practically Now practically forresistance. bred cultivar rst erent fungi, but the most important are prob- are important most butthe fungi, erent elds in the northern part of the clover belt (Kirch.) Karak. has been eliminated from , VOL . 48 eld. However, Pederson et al. (1980) , JANUARY (Cav.) Wiltshire (target spot), (target (Cav.) Wiltshire Fusarium. – FEBRUARY

important crown rot on rot crown important Erysiphe polygoniErysiphe Macrophonina phasealina Resistance breeding breeding Resistance Kenland The cult.

ve generations of of generations ve 2008 Sclerotinia trifolio-

D.C. em em D.C. Kabati- WWW . CROPS

myces trifolii myces included in northern U.S. cultivars. Rust caused by probablyper cycle. have Some been materials resistant by about about 24%, 6% resistance increased selection 1989). ofphenotypic cycles Four Kretschmer, and (Smith ofWisconsin University the at Service Research cultural have been controlled by breeding by the USDA Agri- tie, 1986, for a project report). As a part of that project, project, ofthat apart As report). 1986, foraproject tie, Chris- and (see Edwardson Productivity for Improved Legume Viruses: Identifi Forage S-228, Project ofRegional formation justify to suffi clover ranked white and red in viruses to resistance in Unitedinterest theIn southeastern States, 2005). etal., (Bouton ofPatriot registration the in made were resistance forvirus However, Patriot. no claims tivar of SRVR plants 40 with developed the cul- type mediate inter- the of plants 40 Crossing clover. white in resistance eff eff genetic additive using cedures pro- concluded breeding that Pederson McLaughlin and 2000). Pederson, and 1994; McLaughlin McLaughlin, and (Pederson viruses these to resistance possesses that released been has nocultivars) (but (SRVR) germplasm resistant virus 1989). regional Southern McLaughlin, and tion is controlled by reac- necrotic The a necrotic. become single plants other whereas factor (N) that is dominantoccur in the Kenland cultivar; some plants are mottled, 1986). (Taylor etal., Two ofreactions Kentucky types in ofBYMV strain important most the byfar is 204-1 consin havetivars Kenway been clover, red cul- In the from forresistance. breeding justify to Kentucky bred and Marathon forto infect from resistance Wis- clovers,clovers. only Although a 30 or few more viruses have are been reported of suffi to BYMV.is probably Strain available. resistance inherited been developed, simply even though have cultivars No resistant states. northeastern the in severe petioles ofand red clover be particularly may and located in the the in located been has viruses to ofresistance source Another (AMV). virus mosaic alfalfa and (CYVV), virus clover vein yellow aff clover adversely is 1978). etal., White (Kahn gene byadominant trolled ver resistance vein to isolate a mosaicsingle is con- virus, controlled by polygenes (Martin, 1989), and for red clo- clover mosaic Forwhite virus, factor. hypersensitive the to epistatic is ently tolerance in red cloversingle factor, is apparently R, dominant over of susceptibility resistance type Another (h). necrosis over and appar- dominant is that (H) gene that shows bythe controlled are leaves onthe no localized spots necrotic symptoms is response, hypersensitive the In occur. controlled also systemic, and by local Two ofnecrosis, (n) reaction. types a mottling the to . ective in improving PSV, CYVV, and possibly AMV AMV PSV, possibly and CYVV, improving in ective ORG Breeding also effi also Breeding 5 var. T. repens T. fallens ected by peanut stunt virus (PSV), (PSV), virus stunt bypeanut ected of diseases virus controls ciently produces pustules on leaves, stems, × Resistance Genetic and cation T. occidentale T. ects would be the most most bethe would ects cient importance importance cient hybrid (Pederson (Pederson hybrid ciently high high ciently Uro- Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. a strain of red clover resistant to the pea aphid ( aphid pea the to clover ofred resistant a strain (1979) etal. Gorz released method. economical most the be may resistance plant host parasites, and by insecticides tance. Although most if not all insects forresis- programs may be breeding major develop to controlledimportance clover, ofsuffi white butnone deemed havebeen nema- released. have been root-knot resistance tode with cultivars clover white no However, nematodes. root-knot southern to ofresistance source that concluded (1989) Windham 1995). and Pederson Windham, and son MSNR4 (Peder- of release a in germplasm, resulted that 1991, Pederson, 1992) and (Windham selected were plants 1998). etal., Resistant (Kouame available was breeding suffi species, root-knot all sions tested clover red cultivars. Belle’ ‘Southern ‘Cherokee’ and ofthe release the in were culminated has research This tions. moderately have that heldroot-knot nematodes up fi under (1989) fi conducted etal. Quesenberry bybreeding. is infestation nematode to highly eff the oflessening method feasible most the control, cultural 1958). than Baxter, Other (McGlohon and susceptibleStates United southern the in clover particularly white and red ( group root-knot the to of species four are States United the in ofthese important 1996). clover most red The (Taylor Quesenberry, and operations. offarmer typical tions condi- broadcast seed under evaluations conduct to need the the from emphasize data These eliminated be seedlings. new volunteer and crop will PSV and BYMV as such viruses non-seed-borne 3yr, about only persist plants clover parent white and red both since and plants; fected ofnonin- ability compensating the due to losses yield of plants infected in farmer fi of fi cal normal typi- conditions broadcast under occur would that losses should not be to used estimate transplanting even after or before infected plants from data persistence and yield than those without grass. The fi crop companion agrass with plots lower in was dence inci- virus Also, plants. spaced adjacent in found was incidence ahigh even though plots broadcast in detected was orno virus clover, white little and red both With grasses. companion without and with plots broadcast with compared spaced plants The experiments systems. of virus-resistant clover germplasm into grass legume benefi yield the (1995) quantify to Taylor by al. et Mississippi and Kentucky clover in white and red with were initiated experiments near identical 6 phon pisum A considerable number of insect pests attack red and red and attack pests A considerable of number insect 95% of171 clover more than acces- white Although attack to reported have been species nematode Several Harris) that lowered the reproductive rate and and rate reproductive lowered the that Harris) eld operations. Moreover, eld operations. percentage the Trifolium nigrescens Trifolium ve cycles of selection for resistance to to forresistance ofselection ve cycles Meloidogyne forresistance variability cient elds may not correlate with with not correlate may elds nal results indicated that that indicated results nal spp.) aff seriously that Viv. may be a valuable Viv. beavaluable may ts from incorporation eldcondi- Acyrthoci- ect of ect cient cient WWW ect ect . CROPS cloudiness, and less snow cover (Pederson et al., 1996). etal., snow cover (Pederson less and cloudiness, lower spring precipitation, greater summer temperatures, winter high with sites at and low at altitudes collected clover plants white in greater was frequency Cyanogenic [ weevil clover the head and (Gyllenhal)] [ weevil by the alfalfa to attack exposed vars culti- among damaged S-1, least was Louisiana cultivar, (1992) acyanogenic etal. showed that Ellsbury attack. insect against mechanism adefense apparently clover is white in Cyanogenesis cultivars. susceptible with pared fi forthe time development increased hispidulus ( clover curculio the root including insects, feeding European cultivars (Taylor and Collins, 2003). Root- glabrous comparable than more resistant is pubescence, forreduced bred Freedom!, cultivar the as inasmuch vers, tors are involved in the resistance of American red clo- fac- clover. ofred However, undetermined other cultivars byU.S. possessed pubescence the lack they because ently appar- susceptible particularly are species two latter The pest of alfalfa, also attacks red, white, and Kura clover. resulted in the release of the cultivar Freedom! No of the release the in cultivar resulted pubescence reduce to conducted associated selection, of cycles Five 2003). lins, with slow (Taylor Col- petioles and and ofstems pubescence ver is drying and dusty hay, characters. other in changes morphological undesired incurring without character cal diffi extremely but it was demonstrated, clover ofred again were plasticity genetic the eff summary, In ofstems. fasciation to related was heads multiple-parted of production the ofselection, generations later In heads. off to enough not was it increased, head per seeds Even though declined. plant per butheads increased, head largest ofthe parts selection, of cycles six the Over rare. are heads triple and common, fl oftwo rence fl 125 sessile upto with parted single are usually clover. red Red clover in heads parts head multiple increased likewise ofselection cycles Six check cultivar. the with compared decreased persistence and declined, ber However, num- stem height. over cycles, plant increased dramatically 1985).(Taylor ofselection etal., cycles Six heads ofmultiple-parted number 1984) increased and al., et (Bowley length stem increased cloverof red includes below on persistence). (see section unanswered remains ofclovers persistence to ofrelation question the and not present, are insects the where 1973). Byers, areas and in However, occurs rot root (Leath complexes rot root beinvolved in to thought are ( clover borer red root the . ORG The potato leafhopper ( leafhopper potato The Another character that has been changed in red clo- red in changed been has that character Another characteristics morphological in forchanges Breeding

F.), which attacks both red and white clover, white and and red F.), both attacks which CROP ower heads tightly compressed together is is together compressed tightly ower heads ectiveness of recurrent selection and the the and selection ofrecurrent ectiveness

SCIENCE cult to change one morphologi- one change to cult set the reduction in number of number in reduction the set , VOL Empoasca fabae Hylastinus obscurus . 48 , JANUARY rst instar larvae com- owers. The occur- The owers. Hypera meles Hypera Harris), a major amajor Harris), – FEBRUARY Hypera postica Hypera Marsham), Sitona (F.)].

2008

Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. CROP diff yield compared S-1, with Louisiana released in the 1930s. This except yield in gain genetic appreciable not indicate did study New Zealand the in included U.S. cultivars Seven stolon number. clover mean and percentage in gains rable compa- and decade per weight dry in a6% gain found they plants, spaced Using conditions. NewZealand under vars clover culti- ofwhite group ofaworldwide improvement tence. Woodfi persis- and resistance insect and involved disease mostly systems. production in for use enough high levels tolerance obtain to be necessary would more concludedauthors of cycles several selection that The 35%. byapproximately tolerance of2,4-D levels increased selection ofrecurrent clover. red cycles Four in grazing. under forpersistence selected specifi were cultivars two latter The type. ofthis are 2005) etal., (Bouton Patriot and Durana such as tivars new cul- and S-1 Louisiana old cultivar The seedlings. volunteer and stolons, originals, ofplants: types of three consist may then, Stands, soil. the from seedlings unteer vol- and onstolons depends maintenance Stand years. two about only clover persist ofwhite crowns original the because important is 1999). etal., 1999; Pederson This seed yielding than higher and tolerant the grazing more are ladino populations, ized or large type natural- mostly (Brink type, intermediate ofthe et Cultivars al.,tures. standard cultivars remains to be seen. than longer live will these butwhether tolerance, grazing commercial cultivars of red Several clover States. United the in extent alimited to havebut only been selected for 2003) etal., (Rumball New Zealand in development var tion, 1989). communica- personal (Forde, across ameter upto patches These germplasms nodes, forming from rooting strongly wet in and pastures have persistent, butappearing productive, been not very prostrate, used extremely as type the in Shedescribed Spain. in culti- type similar a collected Forde Dr. Margot system. orfour-cut three- a under lower yielding and leafhopper, potato the to tible suscep- highly being States, United the in adapted well not is cultivar This cultivars. Australian other than ing graz- under lived longer and more productive being as (1993) Bishop and bySmith described was introductions, Portugal from developed Astred, clover red cultivar, nian Tasma- 1993 In astoloniferous type. grazing is interest bemonitored. to need will ofFreedom! increase of seed tends to pubescence be intensifi as inasmuch However, resistance. leafhopper potato less slightly than other observed, cence been have adverse eff Another morphological character of considerable ofconsiderable character morphological Another Genetic investigations of yield in the clovers have clovers the in ofyield investigations Genetic Taylor et al. (1989) examined the tolerance of 2,4-D forpas- adapted is stoloniferous, clover, being White

SCIENCE erence was likely associated with the introduc- the with associated likely was erence ects associated with the reduction in pubes- , eld and Caradus (1994) evaluated the genetic genetic the (1994) evaluated Caradus eld and VOL . 48 selection, generations ed by natural , JANUARY – FEBRUARY

2008

WWW cally cally . CROPS ers because of its relation to yield. Many factors have been have been factors Many yield. to relation ofits because ers breed- to interest ofspecial been has clover plants, vidual defi ofclovers, Persistence CLOVER OF PERSISTENCE New Zealand cultivars. than yield matter dry greater 79 222% to and spread plant 49 53% to greater had States United the in originating clover (1999) white etal. showed that Pederson results. diff produce might such tests in of newer cultivars inclusion and U.S. conditions under Evaluation programs. U.S. breeding the into type orladino large ofthe tion tannin levels. Although 11 of species Although levels. tannin increase beto would problem bloat the to solution One bloat, isofl consideration. deserve avones,andslaframine including factors antiquality several forage, high-quality synthetic. aWisconsin and Marathon, Arlington, have Lakeland, beenimproved include that experimentals and Cultivars resistance. disease and forpersistence ing of four decades breed- from ofmance red clover resulting perfor- in improvement (1996) progressive Smith cited occurred. have undoubtedly States United clover the in red breeding from resulting However, gains cultivars. ofolder seeds ofviable lack ofthe because part in obtain, shown to contain varying levels of tannin (Fay and Dale, Dale, and (Fay oftannin levels varying contain to shown sheep ( in infertility cause to shown been have formononetin, clover. white Isofl and red byboth bloat especially avones, prevent to used often is pasture the in grass with dilution genetic techniques. transfer Forage management such as improved with and biosynthesis of tannin understanding improved with only possible be likely will oftannins fer trans- clover. red Genetic with hybridize 1984), none will decreased protein degradation during ensiling. during degradation protein decreased in the postharvest browning reaction associated with result These substrates. o-diphenol and activity oxidase Red levels clover of high polyphenol contains ruminants. 1994, in al., utilization protein improve could et breeding that gested (Broderick sug- and degradability for rumen cloverred introductions alfalfa as such among variation genetic demonstrated 2001). also forages They in than ibility more effi in results degradability protein ered has been found. fungus the to resistance No genetic salivation. excessive haysuming contaminated may with fungus exhibit this con- 1985). Animals (Essig, disease spot ofblack agent gus fun- the with clover red contaminated consume animals mine is a piperidine alkaloid metabolite produced when for lower isofl Slafra- States. the United in avone content beenconducted on breeding has research Little animals. . ORG Estimates of genetic gain for red clover are diffi clover forred are gain ofgenetic Estimates Although red clover is generally considered to be to considered clover generally red is Although Among quality factors exhibited by red clover, byred low- exhibited factors quality Among Rhizoctonia leguminicola 7 Ovis ) but generally do not adversely aff donot adversely ) butgenerally ned as the length of life ofindi- oflife length the as ned Gough & Elliott, the causal causal the &Elliott, Gough Trifolium cientdigest- have been ect larger larger ect cult to to cult erent Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. Figure 1. Impact of cultural hazards and root rots on longevity of red fl to earlier- shifts with associated apparently persistence, in seed that showed decline did ofadaptation area the outside increased lots experiments These 1991). 1979, al., et lor (Tay- practice the from results no positive indicated shifts on genetic experiments However, from persistence. data fi justi- been has stands onthird-year only production seed and low temperatures, and most plants survive. Further, days ofshort onset the before restored are reserves hydrate carbo- fall, the in growth top byremoving rosettes strong cate that if seed-producing indi- Kentucky from Data conducted. were character plantsthis are allowed to developthat producedfl seed. However, Chooand (1984) not red did found clover that that plants no heritability (1957) Smith ofsowing. year the in production seed is studies on diseases. ofthe absence the clover red in ofsusceptible persistence above the is, that increased, was production potential that doubtful is However, it ofproduction. seasons four to three about to States United the in persistence the have maintained adaptation forgeneral selection concurrent and viruses of resistant cultivars. Resistance to diseases, insects, and development the with eliminated was anthracnose ern north- States, United ofthe sections northern in ilarly, Sim- Kenland. cultivar resistant ofthe development the solved with largely above, was indicated as problem, This stands. clover depleted ofred severely anthracnose ern south- States, United clover. southern the white In and investigated as causes of short-lived stands both in red 8 clover stands. owering, nonpersistent types. nonpersistent owering, ower in the year of sowing persisted longer than those ed on the assumption that the practice would select for select would practice the that assumption onthe ed Another factor considered to infl to considered factor Another uence persistence persistence uence WWW . CROPS or biennial habit by producing stolons, as was suggested suggested was evo- as stolons, byproducing its habit or biennial during time some annual the clover at escaped white history, life lutionary Apparently, stolons. of tion stands may persist indefi gation by stolons. In some environments, propa- due tovegetative simultaneously do not occur white clover parts ofplant death which in opensystem the having as beclassifi clover may clover. red and White by white typifi are (2000), etal. (1938) Thomas Molisch and persistence. not increase did size, crown ing byreduc- breakdown ofinternal problem the eliminating for fi rot complex. Two phenotypic selection cycles of recurrent root so-called the to leading issue the complicated fungi nature. in bephysiogenic to shown later but was persistence to berelated to thought originally was down break- 1967). This (Cressman, plant ofthe death to led ultimately that crown ofthe disintegration a progressive breakdown,” “internal clover red was in ofpersistence lack the ability to develop adventitious roots (Montpetit and and (Montpetit roots adventitious develop to ability the however,Interestingly, some possess red clover types whole plant. ofthe death the in results root tap of the invade. Subsequently, pathogenic organisms weakly loss or saprophytic later, and breakdown), (internal gens patho- even without begins taproot ofthe deterioration ages, plant the As system. reproductive closed of the aplant primarily is Red clover, contrast, in yield. tative perenniality likely was off (1989). (1966) etal. Forde by Hollowell and However, . ORG Two types of reproductive systems, delineated by delineated systems, Two ofreproductive types and bacteria ofsecondary ofahost presence The with associated be to thought factor a later, Somewhat brous root system by Smith (1989), perhaps bySmith system root although brous expected to be strongly persistent for a time but for atime persistent tobestrongly expected well-adapted A growth. plant less-than-luxuriant to with contributes that little stress load orpathogenic, would physiogenic whether factor, any as be bedefi may load Stress load. stress its and plant result of interactions between the adaptation of the the is constraints life-cycle within persistence fore, There- occur. will plant ofthe death senescence, tually, regardless of all factors,Even- withshortened. be the onset will persistence of hazards, other or management poor to exposed is crop the or if and Smith, 1977). 1(modifi Fig. in illustrated is life stand and factors ofenvironmental relationship The persistence. orincrease senescence delay will which adaptability, forgreater byselection be increased system. open ofthe clover red a plant to change would systems oneofthese ofeither 1993). development Strong Bishop, and 1991) (Smith stolons and Coulman,

As root-rotting organisms build up in the soil soil the upin build organisms root-rotting As limits, may, clovers within ofthe cycle life The CROP

SCIENCE nitely by vegetative propaga- vegetative by nitely , set by somewhat lower vege- VOL . 48 , JANUARY e fo Taylor from ed – FEBRUARY

ned ned 2008 ed ed Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. necessitate genetic restructuring of these clover species. ofthese restructuring genetic necessitate will probably worth- a longevity is However, increasing goal. spans while life potential achieve haz- to breeding biological by of ards Control spans. life natural by controlled off transformation tetraploid level, in interspecifi ining the eff beovercome. Exam- could yield in ofreduction problem the clover if white to similar ofreproduction open system eff be may that method Another beconsidered. should tion, selec- load or bymarker-assisted stress such byadjusting as earlier, beevaluated could persistence bywhich Means eff bean may microplots in means ily fam- onhalf-sib selection characters, morphological these than heritable much less probably is persistence Because characters. long-stem and multiple-head the are cases sic considerable amount of hidden or latent variability. Clas- a shown has particular Red clover in adaptation. general for onbreeding concentration begreater would ver species plant. ofthe span life usual beyond the not beincreased will persistence and invade, still will agents pathogenic weakly other because failure to doomed is but ultimately lio ( (Hylastinus obscurus CROP grazing conditions with grasses. However, under persist would that legume long-sought the as hailed 1944 was in and States United the into introduced was cies diff radically forit are goals breeding and clover, white and red from distinct clover quite is Kura AMBIGUUM ( CLOVER KURA the fungi as such agents root-rotting ofthe one oranother to tance forresis- Selection maintained. is stand the that so tion rejuvena- and ofsenescence stages various in of plants It should be noted that open-system populations earlier. die and beweakened would load a lower stress consist oreven same the with plant adapted apoorly hand, other the On due senescence. to succumb eventually would cies necessary for nitrogen fi fornitrogen necessary cies same size as red clover. Shortly after germination, when germination, after clover. red Shortly as size same the about are seedlings and seeds even though establish to some defi serious 1989). McLaughlin, 1989; and Pederson ham, aff seriously that nematodes and diseases root and stem, foliar, virus, tomost resistant It also is depletion without of stand. ing graz- withstand to ability its and persistence long-term its clover are ofKura advantages 1954. obvious The until ective for red clover would be changing the plant to an an to plant the clover bechanging forred would ective In summary, persistence of clover plants is primarily One possible means of increasing the span life of clo- It has now become apparent that the species possesses possesses species the that now apparent become It has Sitona hispidulus Fabricius

SCIENCE Fusarium ect red and white clover (Pederson and Wind- and clover (Pederson white and red ect ect of genes for the stoloniferous habit at the the at habit stoloniferous forthe ofgenes ect , VOL ciencies. First and foremost, it is diffi it is foremost, and First ciencies. . BIEB.) ers intriguing possibilities. intriguing ers 48 Marsham), and the clover curcu- the root and Marsham), and , JANUARY TRIFOLIUM Leptodiscis xation were not introduced werenot introduced xation – ) may have limited success success have limited ) may by genetic and c hybrids, FEBRUARY , the clover borer , the root

etv procedure. ective 2008 erent. This spe- This erent. Rhizobium

WWW cult spe- . CROPS Kura clover was fi clover was Kura Procedures Breeding 1.05 Mg ha Mg 1.05 by increased was year second the in yield forage total and by27%, increased was population hexaploid the in size Seed germplasm. hexaploid and tetraploid, diploid, in (1995) usedmeans two of vigor in Kura increasing seedling clover. Smith cycles of eff an is size selection for seedling greenhouse that selection to aff not increase seed did shoot/root ratio forhigh Selection shoot/root ratio. size eff was fi under evaluated As conditions. greenhouse under biomass plant for large selection acontrol and forshoot/root ratio selection gent ofdiver- cycles three (2001) conducted etal. DeHaan Breeding Progress Kentucky. and Wisconsin, Minnesota, at ducted con- been have programs selection recurrent Phenotypic KY. at selection Quicksand, of natural generations several after ofPI 325489 Taylor, increase aseed 1989). was This and (Henry ofKentucky University the with cooperation in Service USDA Conservation bythe developed Soil cultivar of Kura releasedinto in the United States introduced the was Zealand), (New Seeds pany, Wrightson is ‘Rhizo’, United com- byaprivate developed Endura, cultivar, hexaploid States A vigorous. most out bethe to turned form hexaploid 1987). The (Anonymous, hexaploid and from tetraploid, loid, New dip- ploidy levels, three at Hely, cultivars who developed Zealand. The only and aftermath vigor. After six cycles of selection, the the ofselection, cycles six After vigor. aftermath and seedling greater with beassociated may blooming son for fi content, it is likely to cause bloat. cause to likely it is content, orno tannin little with legume asucculent being tion, addi- subsequent In recovery in seasons. lack of aftermath the in beafactor may and production limit to tends This not fl will plant the legumes, of species most cultivated unlike Finally, adapted. best is species the where States, United northern the even in below may yields consequently, ofshoots; expense the at roots the to growth much ofits partitions plant The States. United northern the to use its but limit will probably perennially, itself lack maintain will of plant the summer developed, is moisture system root butshallow extensive the Once competition. in the reduce to used is herbicide southern weed-inhibiting and a grass United unless crop acompanion orwith seeded besod cannot cies States spe- the that means This ofstands. loss in result may sort ofany orcompetition drought from stage this at Stress system. root extensive ofan beginnings develop the to inhibited is growth top 10 15 are tall, to cm seedlings the . ORG rst-seasonfl 9 ect seedling size in the fi the in size seedling ect ective for an increase in shoot yield and reduced reduced and yield shoot in increase foran ective –1 . Taylor and Cornelius (1994) selected plants (1994) plants . Taylor selected Cornelius and owering. The rational was that fi that was rational The owering. eld conditions, the selection program program selection the eld conditions, rst introduced into Australia by F.W. ower in the year of sowing. sowing. of year the in ower eld. The authors concluded concluded authors The eld. rst-sea- ective ective

Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. and organic farming are receiving more recognition. more recognition. receiving are farming organic and tion tillage, minimum tillage, regenerative agriculture, 1987). Stromberg, and 1990; House, Byers and diffi Insect, effi manure in nutrients the use to disease, of cropland ity and when supply the capac- exceeds local ofresults manure weed problem that problems water-quality regional the often-severe reduce to step anecessary is production oflivestock alsotern becomelikewise detrimentally more aff 1987). Frye, effi Water-use and (Hargrove documented beenadequately has monoculture under soil 1987). from Erosion 1987; Burt, al., and Scott et (Elliot prevalent is ofnitrogen, particularly Leaching, sink. anitrogen as serve to legumes other clover and red of lack ofthe because ofaproblem more becomes also diff upthe make to be purchased must more fertilizers and products, crop as farms from removed are Nutrients systems. production specialized than compatible more environmentally and competitive economically being while ecosystems farm diversify to off base land same onthe stock live- and ofcrops integration that suggest (2007) Tracy zluebbers, 2007). As a part of that symposium, Sulc and fortems Profi in the 2005 symposium “Integrated Crop-Livestock Sys- quences 1990). of etal., Conse- (Parr subsidies crop this ofall fourths decline haveand soybeans, been plus cotton ( recently ( wheat grains, feed other the and highlightedbeen encouraged by government policies has as well. Suchmonoculture orsoybeans. Corn, corn continuous primary rotation clover, red the and grains, small ofcorn, rotation of the now is Instead states. midwestern the corn in land the from livestock followed of bydecoupling accompanied was alfalfa, primarily by soybeans legumes, other to Ashift agriculture. U.S. in changes or major due to States United the in continued and process Haber–Bosch bythe synthesis ofnitrogen development the with started decline This programs. ber of breeding num- the in consequently, and, States United the in vers ofclo- use the in adecline been has there we have seen, As CONCLUSIONS clover. ofKura usage farmer widespread to ensure necessary likely is more breeding eff mental ordetri- depression inbreeding with have associated been may reductions yield The yields. seed and forage in tion reduc- progressive to led butalso well as season second and fi 10 modi- be to have will programs government However, rst-cycle program led to increased fl increased to led program rst-cycle (Luna systems monoculture under control to cult Systems such as sustainable agriculture, conserva- agriculture, suchSystems sustainable as much persistence, outstanding its despite summary, In ects of fi ects t and Sustainability” (Russelle and Fran- and (Russelle Sustainability” t and rst-season fl pat- A more-dispersed ected. Gossypium owering. ers tremendous potential potential tremendous ers ciency and quality are are quality and ciency erence. Denitrifi erence. Triticum aestivum owering in the fi the in owering L.), receive three- ciently. ciently. cation WWW L.), rst . CROPS Anderson, J.A., N.L. Taylor, and E.G. Williams. 1991. Cytology 1991. Cytology Taylor, Williams. E.G. N.L. and J.A., Anderson, M.T., K. Abberton, T.P.T. Marshall, A.H. Michaelson-Yeates, by multinational seed companies and consequent and eff seed companies by multinational supplies ofseed control due to impacts Socioeconomic world. ofthe parts many in plants crop oftransgenic tance ofaccep- lack the to relating challenges many faces ise, available. becoming of improved cultivars and less seed of common types are eff positive had has areas specialized to medium. clover from white into perenniality greater forincorporating hold promise interspecifi Also, conditions. ing graz- under foruse bedeveloped to beginning ver, are clo- white Patriot and clover Durana red and ‘Astrid’ such as Cultivars, increased. has hays and ofpasture ity qual- ahigher provide to use its declined, has rotations in clover use Although forresistance. bred by cultivars control under are nematodes and diseases major All use. of areas to adaptation greater possess that developed been have cultivars More-persistent systems. ofthese goals the attain helpto can and types common over early improved fi References eff breeding ofcontinued worthy are thus and States United ofthe area forage the in legumes be major to continue will clovers these that ensure competitiveness of high-seeding vigor, ease of establishment, qualities clover. and unique white The and red general with familiar is that community farming bythe acceptance general to road along faces ofnew crops However, introduction the interspecifi of fertility clover, red increased oftetraploid especially antiquality factors, of elimination persistence, greater include ever. higher These yields of how- both remain, Challenges clovers. better more and breed forage and seed breeding tools; they plant- are important are and base expected knowledge our much to to maximize add eff genomics and selection Marker-assisted procedures. transformation usual the to amenable less are and genes bymany controlled are persistence and yield such as istics character- to the clovers. Important capabilities formation trans- move their will companies seed multinational these whether govern will undoubtedly Economics addressed. be must that factors all are agriculture on sustainable Anderson, M.K., N.L. Taylor, and R.R. Hill. 1974. Combining 1974. Combining Hill. Taylor, R.R. N.L. and M.K., Anderson, ed to promote these practices. Today’s much are clovers practices. these promote to ed . ORG and fertility of the interspecifi ofthe fertility and 117:494–496. clover Caucasian and ( clover white between ofhybrids acteristics char- Morphological 1998. I. Rhodes. and Holdbrook-Smith, Molecular breeding, although holding much prom- holding although breeding, Molecular T. repens T. grown. being clover are Kura such as New legumes

Further, the movement of clover seed production production seed clover of movement the Further, c hybrids, and adapting to climatic change. climatic to adapting and chybrids, and backcross populations. Crop Sci. 31:683–687. Sci. Crop populations. backcross and CROP

T. ambiguum T. SCIENCE (Trifolium ambiguum , VOL and into red clover from clover red from into and c hybrid hybrid c . c hybridization programs 48 , JANUARY Trifolium ambiguum Trifolium Bieb.). Plant Breed. Bieb.). Breed. Plant Moreects. seed Trifolium repens Trifolium – FEBRUARY orts. orts to to orts

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