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Bao-Rong Lu, Ma. Elizabeth B. Naredo, Amita B. Juliano, and Michael 7: Jackson

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Bao-Rong Lu, Ma. Elizabeth B. Naredo, Amita B. Juliano, and Michael 7: Jackson Grass!.: Systematicsand Evolution. (2000). Eds S.W.L. Jacobs and J. Everett. (CSIRO: Melbourne) PRELIMINARY STUDIES ON TAXONOMY AND BIOSYSTEMATICS OF THE AA GENOME ORYZA SPECIES (POACEAE) Bao-Rong Lu, Ma. Elizabeth B. Naredo, Amita B. Juliano, and Michael 7: Jackson GeneticResources Center, International Rice Research Institute, P.O. Box 933, 1099Manila, Philippines. Abstract The genus Oryza L (Oryzeae) include$ 22 wild species and two cultivated species-a. sativa L (Asian rice) and O. glaberrima Steud. (African rice). Asian rice is an economically important crop; it is the staple food for half of the world's population. Eight taxa, including the cultivated ones, are classified In the O. sativa complex on the basis of their morphological similarity and their common AA genome. Wild species in this complex are the most accessible and valuable genetic resources for rice breeding. Because of considerable variation in the mor- phology and habitat preferences of these rice species, taxonomy in this complex has long been a problem in terms of species delimitation and nomenclature. This paper summarizes recent biosystematic studies of the AA genome Oryza species through interspecific hybridization and meiotic analysis of F I hybrids and their P!ir'ental species. It concludes that most of the AA genome species in the O. sativa complex. such as O. rufipogon, O. bar- th;;, O. g/umaepatula, O. meridiana/is, and O. /ong;staminata, are distinct species with prominent reproductive bar- riers between them, although differentiation of the AA genome is limited between different species in the complex. A hypothetical biosystematic relationship of the AA genome Oryza species is proposed. Key words: Poaceae, Oryza, wild rice, taxonomy,. biosystematics, meiotic pairing. differentiation. INTRODUCTION bution of Dryza species,the taxonomy has long been a prob- lem, particularly in the D. sativa complex, in terms of species The genus Oryza L. is classified in the tribe Oryzeae,which delimitation and nomenclature. contains 12 genera (Table 1), and includes 22 specieswidely distributed throughout the tropics. Great diversity in morphol- There are two cultivated rice speciesthat originated independ- ogy and habitats has been observedfor the various Oryzaspe- ently from differentwild ancestralspecies in Asia and Africa. The cies. Following the taxonomic treatment of Vaughan (1989), Asian cultivated rice (Dryza sativa L.) is an economicallyimpor- speciesin this genusare classifiedin four complexes,with some tant world cerealcrop and is the staplefood for about half of the speciesnot yet placed in any (Table 2). Six basic genomes,AA, world's population. This speciesprobably originated acrossa BB, CC, EE, FF, and GG, as well as three genomic combina- broad areaextending over the foothills of the Himalayasand its tions, BBCC, CCDD, and HHJJ, have beendesignated respec- adjacent.mountain regions in Asia,and is now grownworldwide. tively in diploid and tetraploid Oryza species,although the The African cultivated rice (D. glaberrima Steud.)was domesti- origin of DD, HH, and JJ is still unknown. This reflects cated in West Africa and is still cultivated in some farming remarkablegenetic variation in the genus.Because of consider- systemstoday. Rapid expansion of human populations and able morphological variability, the frequent occurrence of decreasesin agricultural land require much higher rice produc- intermediate types betweensome species,and the wide distri- tion than that which is now achieved.Wild relatives of rice, 51 Baa-RangLu et at. Table I. Genera, number of species, distribution, and chromosome number in the tribe Oryzeae (adapted from Vaughan 1989). China, japan (t) a Chikusiochloo 3 24 Hygroryzo I Asia (t + T) 24 Leersia 17 worldwide (t + T) 48.60. 96 Luziola II North and South America (t + T) 24 Maltebrunia 5 tropical and southern Africa (T) Unknown Oryza 24 pan-tropics (T) 24.48 Porteresia South Asia (T) 48 ProsPhytochloa southern Africa (t) Unknown Potamophila Australia (t + T) 24 Rhynchoryza South America (t) 24 Zizania 3 Europe, Asia, N. America (t + T) 30.34 Zizaniopsis 5 North and South America (t + T) 24 aT; tropical area.t ; temperate area. particularly thosehaving the AA genome,are extremelyvaluable speciesin this complex from different continents have been geneticresources that serveto broadenthe geneti~background of reported to have considerablemorphological similarities and cultivated tice becausethe two cultivated tice speciesalso have intermediatetypes arealso found betweenspecies occurring sym- the samegenome. They aretherefore the most accessiblegenetic patrically. This hasled to considerabletaxonomic and nomencla- resourcesin the tice genepool. ture changesin the wild speciesin this complex. Eight Oryza species,including the two cultigens,have the AA genome and are classified in the O. sativa complex (Table 2). NOMENCLATURE AND TAXONOMIC CHANGES IN AA Theseare O. rufipogon,O. nivara,and O. sativa,which arenative GENOME ORYZA SPECIES to Asia, although the Asian cultivated tice is now grown world- The two cultivated rice specieshave beengiven a large numberof wide; O. longistaminata,O. barthii, and O. glaberrima,which are namesand undergoneconsiderable nomenclature revision (see endemic to Africa; and O. meridionalisand O. glumaepatula, Sampath1962; Harlan and de Wet 1971; Vaughan 1989 for a which are only found in Australia and Latin America, respec- review), but Oryza sativa L. and O. glaberrima'Steud. have tively (Fig. I). Although geographicallyand geneticallyisolated, becomewell acceptedand widely adoptednames. ...". ~~~r.:£:F~;"""=~--'-~~~pQ CJ:.o"'"J\) ~ Q ~ ~ ~. ~ <:) .. '\") " _J ,c- -"" ~ L.I~ ( ~ """""""'."" I '0. ~ ~ -- " ~ ~ ~<::)J'~ '\ -:1 oryza sat,va . warId WI' d e O. barthii ~~~J_D -~ o. nivara 1111111111.O. glaberrima I'////J. o. glumaepatula (::::::::::::]O. rufipogon Q r---" I o. longistaminata o. meridiana/is Fig. I. Distribution of the AA genome Oryza species in different geographical regions. 52 TAXONOMY AND BIOSYSTEMATICS OF AA GENOME ORYZA Table 2. Chromosome number, genome content, and distribution of species in the genus Oryza (modified from Vaughan 1989) O. sativa complex O. barthi; A. Chev. 24 AA Africa O. glaberr;ma Steud. 24 AA West Africa O. glumaepatula Steud. 24 AA South & Central America O. lang;staminata Chev. et Roehr. 24 AA Africa O. meridiana/is Ng 24 AA tropical Australia O. n;vara Sharma et Shastry 24 AA tropical & subtropical Asia O. rufipogon Griff. 24 AA tropical & subtropical Asia. & tropical Australia O. sativa L. 24 AA worldwide O. officina/is complex O. alto Swallen 48 CCDD South & Central America O. australiensisDomin. 24 EECC. tropical Australia O. eichingeri Peter 24, 48 South Asia & East Africa O. grandig/umis (Doell) Prod. 48 CCDD South & Central America O. latifolia Desv. 48 CCDD South & Central America O. minuta J. S. Presl. et C. B Presl. 48 BBCCCC. Philippines & Papua New Guinea O. officina/isWall. ex Watt 24, 48 tropical & subtropical Asia, & tropical Australia O. punctata Kotechy ex Steud. 24, 48 BB & BBCC Africa O. rhizomatis Vaughan 24 CC Sri Lanka O. meyeriana complex O. granulata Nees et Arn. ex Watt 24 GG South & Southeast Asia O. meyeriana (Zoll. et Mor. ex Steud.) Baill. 24 GG Southeast Asia O. ridleyi complex O. longiglum;sJansen 48 HHJJ Irian Jaya, Indonesia. & Papua New Guinea O. ridley; Hook. f. 48 HHJJ South Asia Species not assigned to any complex O. brachyantha Chev. et Roehr. 24 FF Africa O. neoca!edon;caMorat 24 Unknown New Caledonia O. schlechter; Pilger 48 Unknown Papua New Guinea a A tetraploid fonT1 with 48 chromosomes has also been found in the species The closerelatives of O. sativahave beennamed differently over (Morishima etat. 1961)and intermediateperennial-annual pop- time. The speciesname O. perennisMoech was widely used for ulations havealso beenfound in nature (Morishima 1986). Our wild speciesin the O. sativa complex (Sampath1962; Oka and morphologicalanalysis also demonstrated a greatdegree of over- Morishima 1967; Morishima 1969). The perennialO. rufipogon lapping betweenthese two speciesQuliano et at. 1998). was referred to asAsian O. perennis,in line with other wild spe- ciesof the complex from different continents,which were called There has also been considerabletaxonomic and nomenclature Mrican, American,and OceanianO. perennis.This influencehas confusionwith the African wild rice species,although morpholog- been so significant that many scientistsstill use O. perennisin ical differencesbetween these species are significant. The annual their recent publications (Pental and Barnes 1985; Oka 1988; O. barthii, which has beenwidely acceptedas the ancestorof the Morishima et al. 1992; Ishii et al. 1996). The annual specieswas Mrican cultivatedrice O. glaberrima(Chang 1976),was referred called O. fatua Koenig ex A. Chev. or O. sativa f. spontanea to as O. brevitigulataChev. et Roehr. (Sampath1962; aka and Roshev.,and was describedas O. nivara by Sharmaand Shastry Morishima 1967; Second1982; Ishii etaL 1996)or asAfrican O. (1965) to distinguish it from O. rUfipogon.But the name O. perennisby someauthors (Pental and Barnes1985). The perennial nivara has been interpreted differently. Some scientists have speciesO. longistarninatawas called O. barthii (Sampath1962; acceptedO. nivara as an independentspecies (Chatterjee 1951; Clayton 1968) or O. perennissubsp. barthii (aka and Morishima Chang 1976; Vaughan 1989, 1994) and considered it as the 1967; Clayton 1968). It was alsocommon to namethis perennial ancestorof the Asian cultivated rice. Others,
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