**Present Address: Faculty of Genetics, Agricultural College and Research Institute, Coimbatore-3 and Millet Research Station, Lam, Guntur-2 (Andhra Pradesh).
*Part of the thesis submitted by T. NAGUR for M.Sc.(Ag.) Degree of Andhra University.
A diallel analysis of heterosis and combining ability involving four diverse Indian sorghum varieties was undertaken for ear weight, grain weight, volume of 100 grains and density of grain during the winter season. The studies revealed that heterosis was limited in Indian X Indian crosses in comparison with some known exotic X exotic combinations. The present study has indicated predominantly non-additive gene action for all the four characters. However considerable additive gene action was also indicated for the characters, ear weight and grain weight. Studies on the nature of combining ability in Indian crosses brought out the importance of general combining ability in general and specific combining ability for some specific characters like ear weight and grain weight and are in general agreement with other findings. The causes of limited heterosis in Indian X Indian crosses and their implications in utilising the indigenous germ plasm in sorghum breeding are discussed.
