Non-preference as a mechanism of resistance of sorghum to the greenbug

Abstract

A free choice test of twenty-eight previously selected sorghum sources of resistance to the greenbug Schizaphis graminum (Rondani, 1852) was carried out under greenhouse conditions. These sources were divided in tour groups of seven genotypes each and randomized together with two common susceptible lines incide a pot. Each group was evaluated in different occasions. The space between genotypes was five centimeters. After emergence, the plants were covered by a cylindrical cage, made of a wire frame and a fine cloth. Eleven days after the planting date, 45 wingless adult greenbugs were released in the conter of the pots over the soil surface. The number of adult greenbugs per genotypes was recorded 24, 48, 72 and 96 hours after the infestation. A complete ramdomized block design was used for all occasions. The number of replications was generally 18 (16 in some case). It was concluded that non-preference is one of the mechanisms of resistance present in the gonotypes TX 430 x GR, GSBT x 399, GH, 083, H 8012, S 9743. S 9750 and KS 9B.