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With 1 figure and 4 tables Abstract Cultivated pigeonpea (Cajanus cajan L. Millsp.) has a narrow genetic base; hence, utilization of wild relatives in the crossing programme would broaden its genetic base and introduce useful traits. Cajanus platycarpus (Benth.) Maesen, an annual wild relative from the tertiary gene pool, was successfully crossed with the cultigen, utilizing hormone-aided pollinations, embryo rescue and tissue culture techniques, and backcrossed using cultigen as the recurrent parent. Advance generation progeny showed a range of useful traits such as resistance to phytophthora blight, pod borer, bruchid and podfly resistance. Variation was also observed for plant type, growth habit and seed colour. A new source of cytoplasmic male sterility was identified in one of the progeny lines. Molecular analysis of the progeny after four backcrosses showed the presence of genomic segments from C. platycarpus accompanied by the presence of recombinant DNA sequences signifying recombination between the parental genomes.

The thermosensitive genic male sterility (TGMS) system has great potential for revolutionizing hybrid rice production through simple, less expensive and more efficient seed production technology. For the successful utilization of this novel male sterility system, knowledge of the breeding and fertility behaviour of a TGMS line is essential. In this study, the fertility transformation behaviour, the critical fertility and sterility temperatures and the mode of inheritance of male sterility were studied for a new TGMS line, TS6, identified at Tamil Nadu Agricultural University, Coimbatore, India. The pollen and spikelet fertilities recorded on plants raised at fortnightly intervals revealed that this line was completely sterile for 78 consecutive days (35/22 to 32/23�C, maximum/minimum temperatures) and reverted to fertile when the temperature was 30/18�C. It remained fertile continuously for 69 days and the maximum pollen and spikelet fertilities recorded were 75 and 70%, respectively. The fertility was highly influenced by daily maximum temperature followed by average and minimum temperatures. It was not influenced by relative humidity, sunshine hours or photoperiod. The critical temperature inducing sterility and fertility was 26.7 and 25.5�C, respectively. The male sterility in TS6 was inherited as a monogenic recessive in the F2 and BC1 populations of TS6 · MRST9 as well as TS6 · IR68281B. Using bulked segregant analysis on an F2 population of TS6 · MRST9, an RAPD marker, OPC052962, was identified to be associated with TGMS in TS6.