Prevalence and severity of anthracnose of yam (Dioscorea alata and D. bulbifera) caused by Colletotrichum gloeosporioides in Bhadra Wildlife sanctuary in Karnataka.

摘要

Dioscorea species are known for their pharmaceutical and nutritional values. Two species of Dioscorea - Dioscorea alata and D. bulbifera were studied for occurrence and prevalence of anthracnose disease caused by Colletotrichum gloeosporioides in 12 state forest regions of Bhadra wildlife sanctuary situated in the South central part of the western Ghats region in Karnataka, India during August 2006-July 2009. Data of disease incidence for three years was subjected to heterogeneity test. The healthy and infected foliages were analysed for the variation in secondary metabolites. The study revealed high anthracnose incidence and severity in Muthodi during winter (October-January) in both Dioscorea species. The low incidence and severity was recorded in Kemmannugundi for D. alata and Kakanahasudi for D. bulbifera. Power law estimation revealed that there was a regular pattern of distribution (P<=0.001) of disease incidence in D. alata and a heterogeneous type of distribution (P<=0.001) in D. bulbifera. Secondary metabolite analysis revealed that alkaloid and steroid contents decreased following anthracnose infection, whereas flavonoids and phenols contents increased in both species.