Institute for Agricultural Biology, Okayama University, Kurashiki, 710 Japan
A spontaneous mutant with open-hull male sterility was found in an experimental line (Fig. 1). The mutant was characterised also by lower seed fertility,
Table 1. Segregation of the 'open hull male sterile' mutant in F2 populations _______________________________________________________________ Number of plants Sample ____________________________________ X2 (3: 1) Normal Mutant Total _______________________________________________________________ 1 88 28 116 0.05 2 96 25 121 1.22 3 112 20 132 6.83** 4 82 28 110 0.01 5 73 14 87 3.68 6 84 26 110 0.11 7 69 13 82 3.66 8 91 23 114 1.42 Total 695 177 872 10.28** _______________________________________________________________ **Significant at the 1% level. Heterogeneity: X2 = 6.70(df = 7),P=0.3-0.5.smaller caryopsis, darker leaf color, and remarkable ratooning. The anthers of the mutant were white and small, without viable pollen. No seed was developed in the panicles when bagged before anthesis. Spikelet fertility of naturally open- pollinated panicles was 5-20%. All the plants derived from the seeds set on the mutant were phenotypically normal, suggesting that the seeds were produced by cross pollination with normal plants.
F2 segregation indicated that this mutant was controlled by a single recessive gene, although the observed number of mutants was somewhat smaller than expected (Table 1). As this mutant is distinguishable from other open-hull mutants (RGN 1, p. 40) by its male sterility, the new gene may be named oms (open-hull male sterile).