Hok IS( IiI\F 40(6):1686-1689. 2005. ofcertain OP . for instance, a tendency of Champion to resist bolting under winter conditions (Farnham and Garrett. 1996), have Hybridizing and May provided a reason for these older cultivars to persist in spite of the advantages commercial Provide a Means to Develop Collard hybrids provide. Today, the numbers ofcommercially avail- C ultivars able OP and hybrid collard cultivars are both limited. Nearly all cultivars tend to be sus- Mark W. Farnham ceptible to diseases such as fusarium yellows U.S. Department oJA griculture, Agricultural Research Service. U.S. (Farnham et al. 2001), whereas most cabbage Laboratori 2700 Savannah Highway, Charleston, SC 29414 cultivars are highly resistant (Dixon, 1981). Such disease susceptibility makes most collard Glen Ruttencutter2 cultivars vulnerable to severe damage when Seininis Vegetable Seed Co., 3 743 7 State Highwa y 16, Woodland, CA 95695 grown in infested soil under warm conditions (Farnham et al., 2001). J. Powell Smith Previously, it was reported that heading of Clemson Edisto Research andEducation Center, 64 Research Road, Blackville, cabbage is partially recessive to the nonheading SC 29817 nature expressed by collard (Dickson and Wal- lace, 1986). Thus, we hypothesized that hybrids Anthony P. Keinath4 between cabbage and collard would look more Clemson Coastal Research and Education Center; 2700 Savannah Highway like collard than cabbage and that hybridizing between the crop groups might provide a Charleston, SC 29414 means to develop new collard cultivars. Such Additional index words. oleracea, cytoplasmic male sterility, hybrids could exploit the especially large pool of cabbage germplasm available in the United Abstract. Collard ( L. Acephala Group) is a leafy green vegetable adapted States and throughout the world. Making these to the southeastern United States. The number of commerciall y available collard cultivars cabbage—collard hybrids might also provide a is limited, and the most popular cultivars are susceptible to fusarium yellows, a disease strategy for incorporating disease resistances that most cabbage (B. oleracea Capitata group) cultivars are resistant to. We hypothesized from cabbage. Thus, the primary objectives of that hybrids of cabbage and collard would look more like collard, because heading of this study were to synthesize cabbage—collard cabbage is at least partially recessive to the nonheading growth habit of collard. We also hybrids and to compare them to conventional postulated that cabbage—collard hybrids might be used directly as collard cultivars. To collard cultivars in the field to assess their test these postulates, cytoplasmic male sterile cabbage inbreds were crossed to different potential as future collard cultivars. male fertile collard inbreds and hybrid seed was produced. Resulting cabbage—collard hybrids were compared to conventional collard cultivars in three replicated field trials Materials and Methods in . In all trials, cabbage—collard hybrids exhibited size and weight more similar to conventional collard than cabbage, and throughout most of the growing season Plant materials. Materials used in this study the collards remained nonheading. In addition, the cabbage—collard hybrids were much included conventional cultivars of collard more uniform than open-pollinated collard cultivars. Among cabbage—collard hybrids and cabbage obtained through commercial there was significant variation with some hybrids appearing more collard-like than oth- sources as well as a set of cabbage-by-collard ers. The collard inbreds designated A and B may have the greatest potential for making hybrids developed specifically for this work. promising cabbage—collard hybrids. Particular hybrids (i.e., A or B2), derived from these Conventional collard cultivars used in all field inbreds and tested in this study, can perform better than certain conventional collards trials included the open-pollinated cultivars and may serve as possible new cultivars of this vegetable crop. Champion, Vates, and Morris Heading all obtained from the Alf Christianson Co. (Mt Collard (Brassica oleracea L. Acephala (Betts. 1999: Hazzard, 1831). , except as Vernon, Wash.), and the F 1 hybrid cultivars Group) is a uniquely American cole crop a garden vegetable, is a relatively new crop Blue Max, Top Bunch, Flash, and Heavicrop adapted to the southeastern United States. in this region. Secondly, there are landraces obtained from Abbott and Cobb (Feasterville, Results of at least two previous genetic marker of collard grown by seed savers throughout Pa.). Three hybrid cabbage cultivars including studies (Farnham, 1996: Song et al., 1988) North and South Carolina that are generically Blue Vantage, Bravo and Pacifica were also indicate that the likely closest relative to col- called cabbage collard (Farnham. 1996). These grown as checks in the trials. lard is heading cabbage (B. oleracea Capitata landraces look more like collard than cabbage, Cabbage—collard hybrids were made using a Group). Although collard is traditionally but they have a propensity to form a loose cytoplasmic male sterile (CMS) cabbage as the grouped with the kale in the Acephala group, head as plants reach harvest size or become female and a collard inbred as a fertile male. A Farnham (1996) suggested that collard might over-mature. total of 12 CMS cabbage inbreds and four fertile be more appropriately grouped with cabbage Current collard cultivars fall into two cat- collard inbreds were used to make the hybrids. (Capitata Group). Several lines of anecdotal egories. Although they are used less and less, The cabbage inbreds (designated Cab, through evidence support this theory. First, collard and some producers still grow open-pollinated (OP) Cab 12) were relatively advanced inbreds from cabbage have been grown in close proximity populations as cultivars. These OP collard cul- the NorthAmerican cabbage breeding program in the southeastern U.S. for at least 200 years tivars, exemplified by Champion or Vates, ofAsgrow. All of these inbreds expressed fu- tend to be variable for many characteristics. sarium yellows resistance and some expressed Received for publication 4 Mar. 2005. Accepted There has been a tendency to move away from intermediate resistance to black rot. These for publication 12 Apr. 2005. The contents of this these populations in favor of growing F 1 hy- cabbage inbreds differed for many horticultural publication do not necessarily reflect the views or brids such as Blue MaxorTop Bunch. This traits. The four collard inbreds were developed policies of the USDA, nor does the mention of trade shift towards hybrids has occurred primarily names, commercial products, ororganizations imply by the USDA—ARS—U.S. Vegetable Labora- endorsement by the U.S. Government. so producers can attain more uniformity of tory cole crop breeding program and included Research geneticist. harvest typically expressed by the hybrids. two conventional F inbreds (designated A and Research director, large seed, root, and bulb crops. One advantage of OP cultivars over hybrids is B) derived from the hybrids Heavicrop and Associate professor. that seed cost is a fraction of that for hybrids. Top Bunch, respectively, one double haploid Professor. This seed cost advantage and particular traits (designated C) derived from a selection of

1686 HORTSCIENCE VOL. 40(6) OCTOBER 2005 the OP Champion, and one S 4 inbred 0.3 m apart within rows. Row spacing was terminal leaves, 4 = cupping that results in (designated D) derived by selfing a selection 1.02 mat Charleston and 0.97 mat Lexington. a small, loose, cabbage-like head, and 5 = from a South Carolina landrace of collard. The Collards were grown on the flat at Lexington heading similarto the check cabbage cultivars. conventional collard inbreds were developed where the sand drains rapidly and on raised Before plants were cut, plant height and width using a standard pedigree selection scheme for beds at Charleston where soils drain much more were measured for all plants included in the good horticultural phenotype and leaf charac- slowly. All cultural practices (e.g.. cultivation, designated harvest sample. On each harvest teristics similar to that described for cabbage fertilization, and insect control) were based on date, all plants slated for harvest in all plots (Dickson and Wallace. 1986). This scheme commercial standards fir the areas (Johnson et were cut at the soil surface and weighed. includes a cold treatment (e.g., vernalization), al.. 1987). Supplemental water was applied to Statistical anal vsis. All analyses ofvariance which is required to bring about flowering and all trials via overhead irrigation as needed. were performed with Proc GLM of SAS (SAS to facilitate self-pollinations. Plant growth was monitored throughout Institute, Cary, N.C.). Trials from the three dif- Cabbage-collard hybrids were synthesized the growing season in each environment and ferent environments were analyzed separately in field cages during the winter and spring of as maturity approached, the number of leaves to evaluate trait differences among genotypes 1999 atAsgrow facilities in San Juan Bautista, was counted. When a majority of collard and grown in the respective environments. Geno- Calif. Four hybrids were made in a single cabbage-collard hybrids attained a stage with type means were compared using Fishers cage by including a single row each of four about 22 to 24 leaves, a harvest date for each protected LSD. An analysis combining results different CMS cabbage inbreds and two rows environment was chosen for evaluating all for 21 entries grown in all three environments of one of the fertile collard inbreds (i.e.. the entries. Specifically, plants were harvested 19 was also conducted to assess potential environ- only source of fertile pollen in a cage) in the Nov. 1999,23 May 2000. and 21 Nov. 2000 for mental and genotype by environment effects. center of the cage. At flowering, bees were the three respective trials. Just before harvest, a Single degree of freedom contrasts were used introduced into each cage and allowed to pol- representative section ofeach plot that included to compare trait expression of collard-cabbage linate flowers. Upon maturation of seed, plants six plants ( = 1.8 m) was marked for harvest. half-sib hybrid families to expression of OP from each single CMS row were harvested At this time, the entire plot was evaluated collard cultivars, hybrid collard cultivars, and separately; seed was threshed from pods and for plant uniformity and heading habit, using cabbage cultivars. then maintained as an individual hybrid seed different I to 5 scales. For plant uniformity. lot. The hybrids were designated as follows: which was evaluated largely based on leaf Results and Discussion A 1 = Cab, x A; A, = Cab, x A; A, = Cab, x A; characteristics, plant size, habit, and color. I A4 = Cab, xA;B 1 =Cab, xB;B,Cab8XB; = a high degree of uniformity among plants, 2 Results of the three field trials were very B, = Cab, x B; B4 = Cab, x B; C 1 = Cab, x C; = mostly uniform plants with slight variation, comparable in that individual genotypes ex- C, = Cab,, x C; C, = Cab,, x C; C4 = Cab, 3 = significant variation at least among a few hibited similar appearance and performance C; D 1 = Cab9 x D; D, = Cab 10 x D; D, = Cab, of the plants, 4 = a high degree of variation across all environments. Results from fall D; D4 = Cab, x D. A larger set of cabbage among the plants, and 5 = extreme variation 2000 at Charleston are presented (Table I) as inbreds than four was used to maximize the among plants with almost no two plants alike very representative of the other two trials. The number and variation of actual cabbage-col- in a plot. For head habit I = nonheading like combined characteristics of height, width, and lard genotypes that we could evaluate. Since the standard collard cultivar Top Bunch, 2 = head habit at maturity show collard to exhibit we could only place one fertile collard inbred mostly nonheading with a slight cupping of the a height of about 54 to 58 cm, width of about in each cage, this limited the number of col- terminal leaves (e.g., like the collard cultivar 86 to 95 cm, and a head habit rating between lard lines that could be included. In total, 16 Blue Max), 3 = more definitive cupping of I and 2 with most rated as I or nonheading. hybrids were generated for testing. The four hybrids made with one collard male represent Table I. Trait means for fresh weight, height, width, head habit, and uniformity of hybrid and open- a single half-sib family. pollinated (UP) collard cultivars, cabbage cultivars. and experimental cabbage-collard h ybrids grou ii Fieldtrials. Cabbage-collard hybrids were in Fall 2000 at Charleston, S.C. tested in three field trials conducted in South Fresh Head Carolina. Two of the trials were conducted Entry Wi Ht Width habit Uniformity in Charleston; one in Fall 1999 and the other type Entry (kg) (cm) (cm) (rating) (rating) in Fall 2000. A third trial was conducted in F 1 collard Blue Max 1.27 58.3 94.8 2.0 1.5 Lexington in Spring 2000. In the first trial in Top Bunch 1.23 58.5 87.0 1.0 1.8 1999, l-leavicrop and the cabbage-collard Flash 1.28 57.8 94.5 1.0 1.5 hybrids A4, B4, C4, and D4 were not tested, but Heavicrop 1.09 57.3 943 1.0 1.5 all entries described in the previous section OP collard Champion 1.03 54.0 87.3 1.5 3.3 were included in the subsequent trials in 2000. Vates 1.01 57.3 86.0 1.0 4.0 Morris Heading 1.08 57.3 95.3 1.3 4.0 For each trial, entries were seeded to 200-cell F 1 cabbage-col lard Hybrid A 1 0.95 45.8 86.8 2.0 1.8 trays (Speedling Inc., Sun City, Fla.)filled with Hybrid A, 1.12 52.8 91.0 1.8 1.8 Metromix 360 (Grace Sierra, Milpitas Calif.) Hybrid A. 1.13 55.8 93.3 2.0 1.3 4 to 5 weeks before transplanting. Seedlings Hybrid A4 0.97 53.8 88.0 2.0 1.3 were grown in a greenhouse until four days F cabbage-collard Hybrid B 1 1.06 44.8 85.5 2.0 2.3 before transplanting, then placed outside, Hybrid B: 1.21 52.3 92.8 1.8 1.8 allowing them to harden off. During seedling Hybrid B. 1.01 50.0 90.5 1.5 1.5 development, trays were watered as needed. Hybrid B4 1.12 50.5 91.8 2.0 1.8 2.0 1.5 Transplanting dates for the three trials were 1 F 1 cabbage-collard Hybrid C 1 1.15 51.0 87.3 Hybrid C. 1.29 49.5 84.0 2.0 2.3 Sept. 1999 (Charleston). 8 March 2000 (Lex- Hybrid C, 1.28 49.5 83.8 3.0 1.5 ington), and 15 Sept. 2000 (Charleston). The Hybrid C4 1.18 48.5 87.5 2.0 2.0 soil type at Lexington was a Troup sand and at F, cabbage-collardHybrid D 1.18 49.8 90.3 2.0 1.5 Charleston was a Yonges loamy sand. Hybrid D, 1.34 55.8 96.8 2.0 1.8 The field plot design for all three trials Hybrid D, 1.33 55.5 100.8 2.0 1.8 was a randomized complete block. Each study Hybrid D4 1.26 53.5 88.0 2.0 1.3 included four blocks (or full replications) that F 1 cabbage Blue Vantage 1.38 40.5 76.3 5.0 2.3 included plots of every entry indicated above, Bravo 1.25 40.5 73.5 5.0 1.8 2.5 except that in Fall 1999 at Charleston only two Pacifica 1.48 32.0 64.5 5.0 0.27 4.6 6.9 0.5 0.8 blocks were included. Each plot consisted of LSD,,, 5 rating scales. about 30 to 35 plants of a given entry spaced Head habit and uniformity are evaluated using two different I to

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POP-

Table 2. Mean squares lioni the analysis of variance of plant fresh weight, height, width, heading habit, and unilbrmity of collard (6). cabbage-collard (12), and cabbage (3) genotypes (G) grown in three bage-collard test hybrids grown in Fall 20( environments (F). were lower than the three heaviest colla, hybrids that ranged in weight from 1.23 Meansquares 1.28 kg (Table I). None of the test hybri Fresh Head habit Unitormit had significantly lower fresh weights than ar wt Ht Width rating rating OP collard cultivar, and in several instanc E 2.731 5408.2- the test hybrids had significantly greater plat Rep (E) 7 yield than the OPs. The test hybrids also ha 0.067 53.4" 68.7 0.10 0.20 G 20 0.104" a much better crop uniformity rating (i.e x 348.0" 654.3" 13.41" 6.28" 0 E 40 0.022 15.7 usually <2) than the OP cultivars that wet Error 37.4 0.33" 0.81 140 0.029 11.1 25.9 typically rated 3 or higher. Uniformity c Total 0.10 0.30 209 the CMS cabbage collard hybrids was ver "Significant at P 0.05 or 0.0 1, respectively. similar to that of the collard hybrid cultivar (all known to be fertile and likely made usin Table 3. Trait means ofexperimental cabbage-collard half-sib hybrid families compared to those ofF 1 collard a conventional self incompatibility system cultivars, OP collard cultivars, and F cabbage cultivars across three environments in South Carolina. indicating that this important characteristi Trait Cabbage x Cabbage B Cabbage C Cabbage 1) will not limit the potential usefulness of an: shT(kg/plant)97z A Fre0.98 1.06-1.12 of these experimental hybrids. F 1 collard cultivars 1.05. 1.05 Analysis of variance of the combined dat OP collard cultivars 1.05 1.05 0.90 0.90 0.90 from the three test environments indicated tha Cabbage cultivars 0.90 1.20 1.20 1.20 1.20 environmental and genotypic factors accoun Height (cm) 43.9 40.9 for the greatest share of variation in expres. F1 42.3 46.4 collard cultivars 494 494 494 sion of all measured traits (Table 2). With al OP collard cultivars 494 47.9 47.9 47.9 47.9 characters, these two effects were significant Cabhagecultivars 31.1 31.1 31.1 711 A significant genotype by environment inter- Width (cm) 80.2 80.4 77.3 85.2 action was only observed for the head habit F 1 collard cultivars 81.7 81.7 OP collard cultivars 81.7 81.7 rating forall other traits, the interaction was not 81.2 81.2 81.2 Cabbage cultivars 81.2 significant. This observation underscores the 60.0 60.0 60.0 60.0 Head habit (rating) fact that the relative performance ofgenotypes 1.9 2.0 2.7 F 1 collard cultivars 2.2 across environments was consistent. In other 1.3 1.3 1.3 1.3 OP collard cultivars 1.2 1.2 words, although mean height or weight varied Cabbage cultivars 1.2 1.2 between environments, the relative ranking of 5.0, 5.0 5.0. 5.0 Uniformity (rating) genotype trait means among environments did 1.9 2.1 2.0 2.1 F 1 collard cultivars 2.0 2.0 not vary significantly. The significant interac- OP collard cultivars 2.0 2.0 4.3 4.3 4.3 tion effect observed for heading habit is prob- Cabbage cultivars 4.3 2.4 2.4 2.4 24 ably explained by an increased propensity of This is the combined mean for three hybrids making up a half-sib family across the three test environ- some cabbage-collard hybrids to exhibit more ments. definitive cupping of leaves in one environment Indicates that the mean is significantly (p <0.05) different than the mean for the half-sib cabbage-collard and not in another. hybrid family as determined by single degree of freedom contrasts. We deemed it important to evaluate whether certain half-sib cabbage-collard hybrid The superiority of hybrid collard cultivars different from most collard cultivars. families were more collard-like than others over conventional OP collard cultivars is Head habit isa critical characteristic of any to determine if hybrids made using particular demonstrated by greater heights and widths, as cabbage-collard hybrid. If a hybrid heads to a collard inbreds might tend to make more col- well as by greater fresh weights per plant and significant degree, it loses value as a potential lard-like hybrids than those made using others. a higher degree of cultivar uniformity for the collard cultivar because collard leaves are typi- Overall, contrasts between trait expression former (Table I). In general, the check cabbage cally marketed in loose bunches, not as heads. of half-sib families and hybrid or OP collard hybrids are much shorter (32 to 40 cm) than all As with the above traits, the test hybrids were cultivar groups varied when evaluated across collard cultivars. The cabbage cultivars also intermediate between collard and cabbage all three environments (Table 3). The half-sib exhibit a smaller width (64 to 76cm) and have genotypes but most were more like collard than a head habit of 5 (i.e., fully heading). family made using collard inbred D exhibited cabbage. Cabbage genotypes began to cup and means for fresh weight, height and width that Trait expression among the cabbage-collard form a head relatively early in development. were nearly equal to or that exceeded those of hybrids was intermediate between collard and The test cabbage-collard hybrids remained cabbage means, but the overall appearance of the hybrid and OP collard cultivars. This same nonheading for most of the season, but they family exhibited some cupping of leaves and most of the experimental hybrids was consistent began to cup, and in at least one case began had a mean heading habit of 2.2. In addition, it and a majority are best characterized as more to form small heads, just before harvest when exhibited uniformity similarto hybrid collards collard-like than cabbage-like. Test hybrid they were rated. The popular collard hybrid and much better than the OPs. Crosses made heights were all greater than cabbage heights Blue Max normally is rated a 2.0 for head using collard inbred C as the fertile parent had and all but one were significantly greaterthan the habit, because it exhibits slight cupping ofthe a mean fresh weight similar to collard cultivars, tallest cabbage (Table I). Four cabbage-collard terminal leaves. The OPcultivars Champion but it was shorter, had smaller plant width, and hybrids were not shorter than the tallest collard and Morris Heading had head habit ratings cultivars that attained a height of about exhibited the highest propensity ofall families 58 cm, between 1.0 and 2.0 because they contained to form heads (e.g.. mean rating of 2.7). The and thirteen out of sixteen test hybrids were not plants that exhibit some cupping. Most of the other two half-sib families derived from the horterthan the shortest col lard Champion that test hybrids were given the same rating as Blue mcasured 54 cm tall. and B collard parents were similar to collard Max, but three had ratings <2.0, indicating they cultivars for fresh weight and width, were As with height, mean widths of cabbage- were nearly nonheading. These observations collard hybrids also tended to be intermediate smaller in height, and had relatively lowerhead- generally agree with a previous suggestion that ing habit ratings than the other two families. when compared to means for collard and heading of cabbage is partially recessive to the Based on these observations, it may be more cabbage checks (Table 1). However, a greater nonheading characteristic of collard (Dickson number of the test hybrids (10 in all) with and Wallace, 1986). likely to develop a collard cultivar from a cab- bage by collard cross using one collard inbred widths of 88 cm or more were not significantly Fresh weights of only two of sixteen cab- (i.e., possibly D) over another (i.e., Q. 1688 F \1 lIlRIS( [ F 40(() 01 11Th a etable crops. AVI PubI. Co. Westport, Conn. Considering the breadth of collard germ- for developing new collard cultivars. This Dixon,G.R. 1981 .Vegetablecropdiseases. MacMil- plasm (Farnham, 1996) and even greater di- method exploits the relatively close relation- lan PubI. LTD, London. ship known to exist between cabbage and versity in cabbage germplasm pools (Dickson Farnham. M.W. 1996. Genetic variation among and Wallace. 1986) that is available, the actual collard (Famham, 1996 Song et al., 1988). and within United States collard culti ars and number ofdifferent collard by cabbage hybrids Although it is uncertain what the exact response landraces as determined by randomly amplified that it is possible to make is very great. In this of these hybrids in infested soil might be, it is polymorphic DNA markers. J. Amer. Soc. Hort. study, a relatively small number(] 6) ofcabbage safe to assume the fusarium yellows resistance Sci. 121:374-379. by collard crosses were evaluated to determine expressed by cabbage and conferred by a single Farnham, M.W. and J.T. Garrett. 1996. Importance of if any such cross might have potential as a dominant gene should be expressed in the collard and kale genotype for winter production in the southeastern United States. HortScience collard cultivar. If even one hybrid out of the cabbage—collard hybrids. If these hybrids also exhibit some level of resistance to black rot, 31:1210-1214. 16 evaluated approached the standards neces- Famharn, M.W., A.P. Keinath, and J.P. Smith. 2001. conferred by the cabbage parents, their value sary to be grown as a collard cultivar, it would Characterization offusarium yellows resistance appear the likelihood is good for using this as potential collard cultivars will be enhanced in collard. Plant Dis. 85:890-894. method to successfully develop collard culti- further, because they could be grown under Hazzard, T. F. 1831. On vegetable gardens, and the vars. Results from three environments indicate disease-conducive conditions under which all great advantages of a much more general use of that at least two cabbage—collard hybrids. A, preexisting cultivars would become diseased vegetable diet. S. Agr. 4(l2):627-63l. and B,, tested herein (Table I) exhibited good and suffer productivity losses. Johnson, J.R., R.P. Griffin, and C.E. Drye. 1987. 5. potential as collard cultivars. These two hybrids Commercial collard production. Hon. Lfit. Clemson Univ. Coop. Ext. Serv., Clemson Univ., have similar size, mass, and uniformity as the Literature Cited Clemson, S.C. collard hybrid checks and have relatively low Belts, E.M. 1999. Thomas Jeffersons garden book, Song, K.M., T.C. Osborn, and P.H. Williams. 1988. propensity to head. 1766-1824. Thomas Jefferson Memorial Foun- Brassica taxonomy based on nuclear restriction To our knowledge, this is the first formal dation, Charlottesville.Va. fragment length polymorphisms (RFLP5). II. Pre- publication suggesting that hybridizing cab- Dickson, M.H. and D.H. Wallace. 1986. Cabbage limary analysis of subspecies within B. lapa and bage and collard may provide a novel approach breeding. In: M.J. Bassett (ed.). Breeding veg- B. oILracea. Theor. AppI. Genet. 76:593-600.

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