Effects Of Genic Male Sterile Mutation On Combining Ability And Heterosis In Maize

In crop hybrid seed production, the use of male sterility, can thoroughly solve the maternal emasculation problem, and have great significance on increasing the seed purity, ensuring the seed quality and reducing the production cost. The male sterile population K305ms controlled by a single recessive nuclear gene were developed from a widely used maize inbred line K305 after the 60Co-y irradiation. The wild type K305(MsMs), sterile plant(msms) and fertile plant(Msms) in K305ms population, and their 30 combinations derived from an incomplete diallel cross by using 10 testers, were selected to carry out the field trials in different places and different seasons to analyze and compare the effects of 3 kinds of genotypes on the combining ability and heterosis of the main characters in maize, in order to clear the application potential of K305ms. The main results were as follows:1. The comparative studies of traits among 3 genotypes showed that, there were no significant differences between the sterile plant(msms) and fertile plants(Msms) in K305ms population for all of the detected agronomic and economic characters including days to silking, plant height and yield, which indicated that the genic male sterile population is tidy and stable. Compared with the wild type K305(MsMs), the leaf area per plant of sterile plant(msms) was significantly increased, and the tassel reduced, which benefited to compounding and accumulating the dry matter; Although its ear length was extremely significant increased, the kernel rate and 100-kernel weight were extremely significant decreased, and the other characters including yield were not significant difference. Preliminary study suggests that there were no effect on the yield of seed production with the sterile plants(msms) as female parent, and it could save the cost of artificial emasculation and improve the seed purity.2. Analytical results of general combing ability (GCA) indicated that, there were significant or extremely significant differences in GCA’s of ear length, bald tip length, ear rows, kernels per row and 100-kernel weight among three genotypes, but that of the other five traits including yield per plant were not significant; the interaction effects between the locations and three trait GCA’s of ear length, kernels per row and 100-kernel weight were significant, and that of seven traits including yield per plant were not significant. Compared with K305(MsMs), the sterile plants(msms) have extremely significant positive effect on GCA of ear rows, and have extremely significant negative effects on that of four other traits including ear length, bald tip length, kernels per row and 100-kernel weight; In K305ms population, the performance trends of GCA of traits between sterile plant(msms) and fertile plants(Msms) are basically identical. Thus, it has a better potential on increasing ear rows and shortening bald tip length of combinations with the sterile plant(msms) as a parent.3. Analytical results of specific combining ability (SCA) showed that, except ear diameter and kernel rate, the SCA’s of remaining eight traits including yield per plant were significant or extremely significant difference; The interaction effects between locations and SCA’s of six traits including yield per plant and ear height are significant, but that of other four traits including plant height are not significant. The performance of SCA effects on the same traits of different combinations and that of the same combination of different traits are complex, among the same combination with three kind of different fertility genotypes, most of SCA of yield per plant showed positive or negative effect in different locations, among them K305(msms)× 698-3 performed extremely significant negative effects in two experimental sites, however, K305(msms)×K389 performed significant or extremely significant positive effect in two locations. The results indicated that there is not necessarily relative between genotypic differences in female fertility and SCA of yield, and we should obtain the reliable results only through the identification in multi-ecological sites in breeding.4. Analysis of yield heterosis showed that, compared with wild type K305(MsMs) combinations, the over-standard heterosis of yield per plant of most the same hybrid with two different fertility genotypes of K305ms had no significant difference, there were extremely significant interaction between heterosis and locations; the heterosis performance of the same combination derived from sterile plant(msms) or fertile plant(Msms) is inconformity. hence, it must be through seriously comparison, identification and screening in practice. According to the combined analytical results of field trails in three locations, we found that the yield heterosis over CK of sterile hybrid K305(msms) × K389 significantly increased by 5.95%. It is proved that K305ms has the further research, development and utilization prospect.