MOLECULAR CHARACTERIZATION OF MITOCHONDRIAL GENOMES OF RICE LINES CONTAINING WILD ABORTIVE (WA) MALE-STERILE AND FERTILE CYTOPLASMS

Indian rice breeders have developed hybrid rice using primarily the wi ld abortive (WA)type cytoplasm for the male sterile parent. In this co mmunication, we report our studies on the molecular characterization o f the mitochondrial genomes of male sterile lines possessing this cyto plasm as also the respective maintainer, restorer and restored lines u sing 16 mitochondrial gene probes. The results show polymorphism in th e location of several genes and expression of one of the genes, namely orf 156. Polymorphism in five genes namely coxl, cob, afp 6, rrn18 an d orf156 differentiates the sterile cytoplasm from the fertile ones wh ile the RFLPs in coxIII and rps14 can differentiate maintainers and re stores from each other. The WA cytoplasm is very different from the Ch insurah bore II cytoplasm as is evident from the transcription pattern s of atp6. Of the genes studied, only orf156, which encodes a membrane bound 156 amino acid long polypeptide showed differences in the trans cript pattern between the male sterile and fertile cytoplasms. However , it is not clear whether this gene is associated with the CMS trait i n WA type of cytoplasm. These studies show the utility of mitochondria l RFLPs to distinguish different cytoplasms existing in the rice lines .