EFFECT OF TEMPERATURE AND PHOTOPERIOD ON SORGHUM RESISTANCE TO BIOTYPE-C AND BIOTYPE-E GREENBUG (HOMOPTERA, APHIDIDAE)

Resistance mechanisms and the effect of temperature and photoperiod on them were assessed for greenbug, Schizaphis graminum (Rondani), bioty pe C on 'Tx2737' and 'Tx2783' sorghums and for biotype E on 'Tx2783' a t 21, 26, and 30 degrees C at photoperiods of 10:14 (L:D) h and 14:10 (L:D) h. Damage to resistant sorghum was less (approximate to 50%) tha n damage to susceptible 'Tx430' sorghum. Tolerance resistance was grea ter at 30 than at 21 or 26 degrees C. Antixenosis resistance also was greatest at 30 degrees C. At 21 and 26 degrees C, resistant sorghum wa s as preferred by greenbug as was susceptible sorghum. Antibiosis resi stance also was affected by temperature. Greenbug development (time fr om birth to maturity) on resistant sorghum was delayed at 30 degrees C but was comparable with that on susceptible sorghum at 21 degrees C. At 30 degrees C, greenbugs on resistant sorghum produced threefold few er progeny than on susceptible sorghum. Greenbug longevity, especially on resistant sorghum, was shorter at 30 than at 21 or 26 degrees C. P hotoperiod had little effect on the expression of resistance. These da ta confirmed that temperature affects the expression of resistance to greenbugs in resistant sorghum and should be considered in plant resis tance assessments.