Monogenic Male‐sterility in Rice: Induction, Identification and Inheritance 1

Monogenic male‐sterility has not been utilized so far in the improvement of rice ( Oryza sativa L.) because it is not available to breeders in an agronomically useful genetic background. The objective of this study was to induce male‐sterility in a widely grown rice cultivar ‘IR36.’ One hundred grams each of dried seeds of the rice cultivar IR36 were treated with 0.2, 0.4, 0.8, 1.2, and 1.6% concentrations of ethyleneimine for 1 or 3 hours to obtain monogenic male‐sterile mutants. Seed treatments with higher concentrations and longer durations had greater reductions in the percent seed germination than treatments with lower concentrations and shorter durations. Treatments for 1 hour with 0.4% and for 3 hours with 0.2% concentrations reduced seed germination to 69 and 30%, respectively, and were considered more satisfactory than other treatments. In four M 2 progenies, male‐sterile plants with normal meiosis were crossed with control IR36 and segregation in F 2 indicated that one recessive gene controlled inheritance for male‐sterility in each of these lines. The male‐sterile plants showed high seed set from outcrossing. Possible use of recessive genes for male‐sterility in rice improvement was discussed.