Abstract: According to p×q mating pattern,40 hybrid F₁s were made with 4 Rht3 dwarfing lines as female parents and 10 varieties(lines) as male parents.Studies on the expression of grain weight heterosis were made among the hybrids.Results showed that average heterosis changed from -6.49% to 28.83% and its average was 11.95%.Heterosis over higher parents changed from -18.95 to 11.57% and its average was 0.12%.Average of competitive heterosis was -4.96 which changed from -24.24% to 17.74%.It is easier to obtain hybrids with positive competitive heterosis when Rht3 dwarfing lines with relative high 1000 grain weight such as ND35 and ND37 were chosen as female parents and varieties(lines) with the 1000 grain weight higher than that of check varieties were used as male parents.Results of the analysis of combining ability showed that ND35 and ND37 among 4 dwarfing lines and Hanfen 86.13,Lu 895023 and Lu 896018 among 10 varieties(lines)were much more valuable than other parents for breeding hybrids with high 1000 grain weight.Discussions were made on the methods for breeding semi dwarfing hybrids with high grain weight in the case of overcorming disadvangeous effects of Rht3 gene on grain weight.

Key words: graint weight, Heterosis, Competitive heterosis, Combining ability

CLC Number: 

• S512.103