Effects of simulated rust epidemics on the growth and yield of sunflower

Abstract

Oil yield losses in sunflower (cv. Peredovic) caused by rust infection (Puccinia helianthi) were greatly influenced by the growth stage of the plant when infection occurred and by the intensity of infection. Simulated epidemics produced under greenhouse conditions, where plants were first inoculated at the vegetative, budding, anthesis or seed development stages of growth and thereafter at 10 day intervals, resulted in reductions in oil yield of 85, 73, 38 and 13% respectively relative to those in uninoculated controls. In contrast, plants inoculated once only at each of these growth stages showed reductions in 011 yield of 13, 42, 35 and 10% respectively. When plants were inoculated at the vegetative stage and thereafter at 10, 20 and 40 day intervals, the reductions in oil yield were 85, 79 and 64% respectively relative to uninoculated controls. The reduction in oil yield of infected plants was caused by a reduction in the number of seeds produced per head, the weight of individual seeds and the percentage oil content of seeds. The effects of rust infection on other parameters showed similar trends to that on oil yield.