Components of resistance to the sorghum head bug, Calocoris angustatus

Sorghum head bug, Calocoris angustatus Lethiery (Hemiptera: Miridae) is an important pest of grain sorghum. Population increase, grain damage, and non preference of C. angustatus were studied on 10 sorghum genotypes under mult i- and no-choice conditions during the 1989-1990 rainy and post-rainy seaso ns. Under multi-choice field conditions, IS 14334, IS 19955, IS 20740, IS 2 1444, IS 23748, and IS 17610 (except in rainy season) were not preferred by the adults at the half-anthesis stage, and IS 14334, IS 19955, IS 21444, a nd IS 17610 also had lower head bug numbers at the milk stage. Head bug pop ulation increase was lower on IS 19955, IS 21444, IS 20740, and IS 17610 wh en infested with 10 pairs of adults under no-choice conditions in the headc age at the half-anthesis and milk stages as compared with the commercial cu ltivars CSH 1, CSH 9 and ICSV 112. IS 17610 showed high Bevels of resistanc e to grain damage, while IS 20740 and IS 21444 suffered moderate levels of grain damage under no-choice conditions in the headcage. IS 14334 and IS 17 610 also showed tolerance to head bug feeding, i.e., they suffered lower gr ain damage per unit population of the head bugs. Multi-, double- and no-cho ice tests under laboratory conditions confirmed that nonpreference is an im portant component of resistance to head bugs in IS 14334, IS 19955, IS 2374 8 and IS 17610. Sorghum genotypes showing nonpreference to adults, low rate s of population increase (antibiosis), and tolerance to head bug feeding ca n be used in a breeding program to increase the levels and diversify the ba ses of resistance to C. angustatus. (C) 2000 Elsevier Science Ltd. All righ ts reserved.