Penetrance, expressivity and inheritance of axillary branching in somaclonal mutant of sorghum (Sorghum bicolor L.)

Abstract

An axillary branched somaclonal mutant (SbABM) in sorghum derived from Annigeri-1 was reported which exhibits branching from every node of the plant. This is the first axillary branched mutant reported in grain sorghum with desirable phenotype and stability of expression of axillary branching over generations. However, this trait was expressed at different levels of intensity (variation for number of axillary branches per plant) within the progenies of a single true breeding plant. The mutant plants selected based on different number of axillary branches were evaluated in plant to progeny rows for two years and the study revealed stable penetrance of more than 85 % and variable expressivity for the character. The axillary branched mutant was found to have important architectural features like medium plant height, increased number of panicles per plant, increased seed size, increased grain and fodder yield, lodging resistance and stay green nature. Therefore, understanding the nature of inheritance of axillary branching will help for the genetic modification of plant architecture for improved yield and fodder qualities. The mutant line, SbABM was crossed with five normal sorghum cultivars both as a male and female parent, to elucidate the effect of cytoplasm on axillary branching if any. All the ten F2 populations showed the same segregation ratio of three mutant to one normal type phenotype based on Chi square test. The results revealed that axillary branching is controlled by a single dominant nuclear gene.