Gene action for resistance in sorghum to midge, Contarinia sorghicola

Gene action for resistance to sorghum midge (C. sorghicola [Stenodiplosis sorghicola]) was studied in a diverse array of midge-resistant and midge-susceptible females and males under natural infestation and under uniform infestation with a no-choice headcage technique. Gene action for glume and grain characteristics associated with resistance to sorghum midge was also studied to understand their role in expression of resistance to this insect. Gene action for resistance to midge is largely governed by additive gene action. Genotype × environment interaction was significant for midge damage rating under natural infestation, but non-significant under no-choice headcage screening. The GCA effects of midge-resistant CMS females (PM7061A and PM7068A) were significant and negative, and such effects for the midge-susceptible CMS females ICSA42 and 296A were positive. Similar results were observed for the males (except for CS3541 and MR750 for midge damage in one out of two seasons). Dominance (mid-parent heterosis) was also important for midge resistance in some cross combinations. For genotypic non-preference by the midge females, the SCA effects were greater than the GCA effects. The SCA effects for genotypic non-preference were negative for PM7061A. The GCA effects were significant and negative for glume length in PM7061B, glume hardness for 296B, and glume hairiness for PM7061B. The GCA effects were significant and positive for glume length, glume hairiness and glume hardness of ICSB42. Resistance is needed in both the parents to produce midge-resistant hybrid