All India Coordinated Sorghum Improvement Project IARI-Regional Station, Rajendranagar, Hyderabad, 500 030, India
*XXXIV part of'Genetic Analysis of some Exotic X Indian crosses of sorghum’.
Two sets of F2 and F3 diallel progenies among seven parents were evaluated for charcoal rot resistance under artificial epiphytotic conditions during post-rainy season without any supplementary irrigation. Progenies in F3 were relatively more susceptible than in Fa. Reduction in F3 resistance due to inbreeding was 24%, 64% and 74% respectively for susceptibility index (SI), % infection and number of nodes crossed by charcoal rot. These resistance parameters in F3 were positively and significantly correlated among themselves.
General combining ability effects of parents showed significant differences in both generations. ‘SPV 34’ was most effective parent to transmit resistance in crosses. Resistance is mainly governed by non-additive genetic variance, with high degree of dominance. Heritability varied from 10–28% and was low for different resistant parameters. Though F3 mode pertains to 0–4% class interval of disease infection, the genetic advance is expected to be low. Thus, resistance to charcoal rot can only be built up gradually in the newly developed tropical varieties of sorghum.
