EFFECT OF CYTOPLASMIC MALE-STERILITY IN SORGHUM ON HOST-PLANT INTERACTION WITH SORGHUM MIDGE, CONTARINIA-SORGHICOLA

Sorghum midge, Contarinia sorghicola Cog. (Diptera: Cecidomyiidae) is one of the most important pests of grain sorghum worldwide. We studied the reaction of midge-resistant and midge-susceptible genic-cytoplasm ic male-sterile (A-lines) and their maintainers (B-lines), and the eff ect of resistant and susceptible restorers on sorghum midge. Midge dam age and adult emergence were significantly lower on the B-lines of mid ge-resistant genotypes (PM 7061 and PM 7068) than their corresponding A-lines, while the reverse was true for the midge-susceptible genotype s (296A and ICSA 42). Differences in midge damage and the number of mi dges emerged were not significant between the midge-resistant and midg e-susceptible A-lines when infested without pollination (except midge emergence on PM 7061A). Pollination with a midge-resistant restorer (D J 6514) reduced midge emergence significantly in one of two seasons. S ource of pollen did not influence midge emergence on the highly-resist ant A-line, PM 7061A. The implications of these observations in the de velopment of midge-resistant hybrids were discussed.