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Ecology and Epidemiology

Influence of Temperature and Wetness Duration on Infection of Pearl Millet by Claviceps fusiformis. R. P. Thakur, Senior plant pathologist, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh 502 324, India; V. P. Rao, and S. B. King. Research associate, and principal plant pathologist, respectively, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh 502 324, India. Phytopathology 81:835-838. Accepted for publication 24 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-835.

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 (1435 C) and wetness (95% relative humidity) duration (064 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 1435 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 (7072% severity; 3249% sclerotial formation) than a temperature range of 2135 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 1624 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 2496 h of panicle wetness.

Additional keywords: Pennisetum glaucum, epidemiology.