Studies On Genetic And Male Sterile Mechanism Of New Genic Male Sterility Cotton Named "21A" In Upland Cotton (Gossypium Hirsutum L.)

The heterosis in cotton is very obvious, especially in increasing the yield potential. And utilization of male sterility in heterosis has a good developmental prospect. In order to get good hybrid seeds, the premise is that breed new male sterile line which has better traits and general combining ability (GCA).In this study, the male sterility of"21A"has been observed successfully by induced mutation breeding and back cross breeding. Flower Morphologies of"21A"plants, pollen is sterile or fertile, genetic and allelic tests,analyzation competitive heterosis and combining ability and microRNA microarray were applied to"21A".The results were as follows:(1) Morphological comparison of flower between"21A"male sterile and fertile plants was made and found that the flowers of male sterile plants were smaller than those of fertile plants.There was no pollen or a little in the anthers of male sterile plants .Stain anthers using potassium iodide of male sterile ones and the results showed that they were not be stained or light staining.The results proved that the pollen of male sterile plants was sterile completely.(2) Genetic analysis for"21A"male-sterile line were made. The ratio between NO. of fertile and sterile plants was 3:1 and 1:1 in the F2 and Ft generations respectively. Segregation results showed that the male sterility in"21A"was controlled by a pair of single-recessive gene.(3) Allelic tests for"21A"male-sterile line were made and the results indicated that the male sterility in"21A"was none-allelic to msc1, msc2, msc3 and msc7 discovered in P. R. China till now. It is proposed that 21A male-sterile gene symbol be tentatively named a new one.(4) Crosses were made by NCâ…¡, using"21A"male sterility line and Lumianyan21 as male parents respectively and five normal cultivars as female parents, to analyze competitive heterosis and combining ability of F1 hybrids. The results indicated that"21A"hybrid cottons showed obvious heterosis in seed-lint yield, lint yield and elongation percentage and better general combining ability (GCA) , especially in seed index. It is easy to observe better cross combinations and product hybrid seeds using"21A"male sterile line.(5) Total RNA at different stages, i.e., sporogenous cell stage, pollen mother cell (PMC) stage, and pollen grain stage, were isolated using Norgen kit. Microarrays were hybridized with Cy3 and Cy5 fluorescence-labeled probe pairs of sterile pants plus fertile plants. The results showed that 8 new cotton miRNAs which were expressed differently between sterile and fertle plants at diffent stages of buds. And 22 target genes were predicted which maybe related to pollen abortion. MiR166 and miR156/157 could target 3 target genes respectively, ATHE-15, SPL3 and RNA helicase.