Compensation for reduction in seed set due to sorghum midge (Contarinia sorghicola) in midge-susceptible and midge-resistant sorghum (Sorghum bicolor)

Abstract

The relationship between percentage seed set on grain sorghum (Sorghum bicolor) panicles damaged by sorghum midge, Contarinia sorghicola (Coquillett), and percentage compensation (percentage increase in weight) of undamaged seed was examined in 11 experiments covering a wide range of environmental variation and incorporating various sorghum midge susceptible and resistant genotypes. In contrast to previous findings where negative compensation was found after sorghum midge damage, compensation was generally positive, but the slope of the response with respect to seed set changed from positive to negative as seed set increased to >30-50%. Expression of the relationship was similar for susceptible and resistant genotypes. The slope of the relationship for seed sets above the point of maximum compensation was -0.51 for sorghum midge susceptible hybrids, -0.42 for resistant genotypes (various lines and hybrids), and -0.38 for resistant hybrid ATx2755/RTx2767. The pooled slope was -0.45.