In the year, 1994, male sterile plants with open florets were detected among F3 progenies derived from a cross between selection 212 (wheat-rye recombinant possessing resistance to leaf and stem rusts of wheat) and HD2009, an Indian rust susceptible wheat. Out of these, one plant showing resistance to leaf and stem rusts produced 7 seeds from 10 selfed spikes. Four viable plants were obtained from these seeds.
The expression of genie male-sterility in the present case was caused due to the conversion of anthers into fully fertile ovaries. Since the phenomenon of anther conversion into ovaries was incomplete, therefore male- sterility was partial, thus it was designated as partial genic male-sterility (p-mst). Genic male sterility has been reported in Triticum aestivum formerly by Pugsley and Oram (1959), Lupton and Bingham (1966-1967), Krupnov (1968), Lemekh et al. (1971) and Jan and Qualset (1977). The p-mst strain, stabilized for six generations was considered appropriate to study its inheritance.
To study the inheritance of p-mst trait, it was crossed with an Indian semi-dwarf wheat variety Kundan. At appropriate stage of anthesis, some spikes from p-mst plants were emasculated to make sure that no pollen grain remained in the maternal floret. After 24 hours of emasculation, all the florets were pollinated with fresh pollen grains taken from var. Kundan and sufficient number of crossed seeds were obtained. Parents, F1's and F2 plants,were planted together at IARI, New Delhi. Observations on dominance/recessive behavior of p-mst trait in F1 and pattern of segregation in F2 were recorded. Chi-square test was applied to test the goodness of fit for the assumed segregation ratio.
Breeding behavior of genic male-sterility trait was studied for 6 generations (1994-1999). During this period, selfed p-mst spikes produced 6.1 seeds per spike, which was much lower than 40.4 seeds per spike observed in Sel. 212 (one of the parent). The observed range of seed set was 0 to 15 seeds per spike in p-mst. In terms of sterility p-mst plants exhibited 85% to 100% male-sterility (Table 1).
The p-mst plants were late in maturity and fully resistant to leaf and stem rusts of wheat (resistance from rye). Anthers in most of the florets in p-mst plants were modified ovaries (Fig. 1). In some frorets, anthers appeared little normal and produced normal pollen grains. The seeds formed on p-mst plants were partially shrivelled (sub-normal development of endosperm).
In p-mst plants the meiosis proceeded normally. Their female fertility was normal, including the modified ovaries which could produce two to three seeds by cross pollination.