Effects of leaf age of faba bean and inoculum level of Uromyces viciae-fabae on pustule development and spore production

Abstract

Leaf age and inoculum level are important factors for the development of rust disease epidemics in faba bean. The effect of these two factors on spore production and pustule density of rust causd by Uromyces viciae-fabae on faba bean was studied in growth room at Wye College in 1998. Three leaf ages and four levels of inoculum density were used in a crossed and nested design. High pustule number was recorded on young leaves followed by middle and then old leaves in all inoculum levels. In terms of overall spore yield, young leaves gave more spore mass than middle aged leaves. Application of highest inoculum level resulted in the highest pustule number. Generally, pustule number significantly ( P < 0.001, d f=2) decreased while spore production increased with decreasing inoculum levels (P< 0.001, df= 3 ). Regression analysis of spore weight (dependent variable) and pustule number (independent
variable) showed an inverse relationship (R2 = 0.88 and R2 = 0.83) while spore weight (dependent variable) and pustule size (independent variable) showed positive relationship (R2 = 0.89 and R2 = 0.80) all with significant differences between young
and middle aged leaves respectively. In this experiment younger leaves were found to be more susceptible to rust than old leaves. Interaction of leaf age and inoculum level was observed for rust development.