Smut Incidence and Yield Losses of Corn Cultivars under Different Plant Population Densities

Abstract

AbstractSix corn cultivars were grown, under field conditions, at two population densities of 14285 and 22875 plants/ acre. All were subjected to an artificial infection at 6‐leaf growth stage to determine their reactions to smut disease and yield losses. Changes in plant chemical composition, including K and N contents of ear‐leaf, were performed at silking stage. The results showed that corn cultivars imposed wide variations to smut reaction. Susceptibility to smut disease was less prevalent on D.H 204 and 3‐way cross 310 and more abundant on D.H 215, Iskandria 11 and El‐Kabera 1. The corn cultivar Giza 2 appeared an intermediate reaction. Smut incidence at high population density was markedly depressed by 6.6 % below the comparable level at low population rate. Differences in yield losses between low and high plant population densities were actually limited for smut resistant cultivars, while the opposite was true for the more susceptible ones. On average, the yield losses at the low population density varied from 2.5 % for D.H 204 to 14.4 % for Iskandria 11. The calculated losses of the respective cultivars declined to 2.3 and 9.2 % at the thicker stand. The overall effect of increasing smut infection on yield losses, as revealed from the regression coefficients of the response curves, was clearly pronounced at the higher plant population, whereas the yield was substantially improved by 9.7 %. Varietal response to smut performance was explained on the basis of vigor growth and K/N ratio of ear‐leaf.