Influence of Temperature and Wetness Duration on Infection of Pearl Millet byClaviceps fusiformis

Abstract

The influence of temperature and wetness duration on infection of susceptible, moderately resistant, and resistant genotypes of pearl millet by Claviceps fusiformis was studied. In greenhouse and field experiments, panicles of pearl millet inoculated with C. fusiformis were subjected to various regimes of temperature (14–35 C) and wetness (95% relative humidity) duration (0–64 h) for a 15-day period. These environmental conditions influenced the level of ergot severity, but the relative ergot reactions of the genotypes were not changed. In susceptible genotypes, temperatures in the range of 14–35 C, with 8 h/day at less than 20 C and 4.6 h/day at greater than 30 C, were more favorable to ergot infection (70–72% severity; 32–49% sclerotial formation) than a temperature range of 21–35 C, with 6.4 h/day at greater than 30 C (53% severity; 23% sclerotial formation). Results indicated that the minimum temperature is more critical for ergot infection than the maximum temperature. In both greenhouse and field experiments, panicle wetness duration of 16–24 h favored ergot infection. In controlled environment experiments, temperature and the interaction of temperature and wetness duration were significant for latent period (P = 0.001). Wetness duration and the interaction of temperature and wetness duration were significant for ergot severity (P = 0.05). Maximum ergot severity (60.5%) and minimum latent period (117 h) were obtained at a 30 C day/25 C night temperature regimes with 24–96 h of panicle wetness.