Disease incidence, lesion size, and sporulation in Colletotrichum truncatum as influenced by lentil genotype and temperature

Abstract

The development of anthracnose [Colletotrichum truncatum] was studied at four temperatures (16:12, 20:16, 24:20, and 28:24°C, day:night) on five partially resistanl lentil (Lens culinaris) genotypes (PI 299331, PI 320937, PI 345629, 458-57, and cv. Indianhead) and the susceptible cv. Eston, using a single pathogen isolate. Disease incidence was 100% across the temperature range in the susceptible cultivar, but varied between 33 and 100% among the resistant genotypes, The increase in disease incidence with temperature was linear, but was affected by the level of hos' resistance. For each genotype, lesion size increased with increasing temperature. Maximum lesion size was reached at 24:20°C and sharply decreased at 28:24°C. Percent sporulating stem lesions also increased with temperature, but at each temperature the highest sporulation occurred on cv. Eston, consistently remained lowest on PI 320937, and was intermediate in the other genotypes. The results showed that both temperature and genotype significantly affected disease incidence, lesion size, and sporulation and that the optimal temperature for anthracnose development occurred with day time temperatures of 20-24°C. regardless of level of host resistance.