Abstract: The purpose of the study is to identify relationships of the A1, Aw and A3 cytoplasms and present R and B lines of A1 system, fertility percentage and anther characteristics of sorghum hybrids produced by crossing A lines of A1,A2 and A3 cytoplasms wtih R and B lines of A1 system and some of the primary breeding stocks, and to estimate differences in fertility response among the cytoplasms. The results indicated that the maintainers of A1 system are also the maintainers of A2 and A3 male-sterile lines, but the maintainers of A2, A3 cytoplasms expressed restoration except A1 system maintainers when they were crossed with A1 male-sterile. The R Lines of A1 system had a different restorations.The R lines of all Kao Liang types could restor the two cytoplasms well, but some R lines of ICRISAT of A1 system produced sterile F1's when they were crossed with A2 male-sterile lines. All the R lines of A1 and A2 system expressed non-restoration response when they were crossed with A3 male-sterile lines. The study suggested that A2 cytoplasm increased the scope of cytoplasms in heterosis utilization. The study clarified "A2 belt" and Pointed out that we should Pay more attention to use "A2 belt" so as to give great impetus to breeding program and sorghum production.

Key words: Sorghum, Non-Milo cytoplasm, Male sterile line