Abstract :
Grain sorghum [Sorghum bicolor (L.) Moench] topcrosses produced by crossing 40 randomly selected male sterile A-lines with a genetically broad-based pollen parent, amixture of 100 fertility restore R-lines, were evaluated, for general combining ability (GCA) effects, heritability estimates, and phenotypic and genotypic correlations in two different production environments. Significant differences were detected between environments,among topcrosses,among fertile female B-lines, and between topcrosses and B-lines for grain yield, harvest index,growth rate,plant height,test weght,heading date, and panicle length.Topcrosses appeared to be useful for preliminary screening of sorghum inbred lines.They effectively identified superior A-lines.High heritability estimates were obtained by variance components and parent-offspring regression for all the traits studied,except for growth rate. Positive and very high correlations were found between grain yield,harvest index,and test weight.Negative relationships were detected for grain yield with heading date.Specific parental combinations and heterotic effects were observed.
