Production of F1 and Backcross Progenies from Wide Cross of Oryza sativa x O. minuta in Rice

Abstract

Wild rices are an important source of useful genes for resistance to diseases, insect pests, tolerance to abiotic stresesand yield increase. Interspecific hybrids were successfully produced between ten accessions of O. minuta (2n=48, BBC) and O.sativa through ovule culture. However, to produce BC1F1 and BC2F1 plants was the most dificult step in this wide hybridizationprogram because grain shattering before and after pollinaton was so severe that the efficiency of obtaining BC1F1 and BC2F1 plantswas below 0.1%. A cros of Hwaseongbyeo x O. minuta (101144) showed the highest F1 production production. A total 46 F1, 11BC1F1, 7 BC2F1, and 47 BC3F1 plants were produced from this cross combination. Hybrids, BC1F1, and BC2F1 showed completesterility. Hybrids had the 36 chromosome number and 0.2% polen fertility. The chromosome number of BC1F1 ranged 33 to 41while BC2F1 showed 27 to 36. The average pollen fertility of BC1F1 plants ranged from 0.3% to 2.8% and BC2F1 ranged from1.5% to 2.9%. From BC3F1 generation, partial fertile plants could be obtained. The reaction to blast and brown plant hoppershowed that resistance was maintained to BC2F1 but as the generation proceeded, resistance was rapidly lost, indicating that recom-bination between O. sativa and O. minuta genome be quite lacking. Non-clipping and successive polination method, comparedwith conventional clipping method, proved to significantly alleviate grain shattering with 11 to 13 fold, and as a result, efficiency ofplant acquisition and ovule seting increased to 1.6% and 5.0% in BC1F1 production and 0.9% and 5.0% in the BC2F1 production.