Standardization of inoculation method for the maintenance of pure inoculum of leaf crinkle virus in Urdbean (Vigna mungo L. Hepper)

Urdbean or blackgram (Vigna mungo (L.) Hepper) is one of the important leguminous crops cultivated in India, Pakistan and South-East Asian countries. Among the biotic stresses, Urdbean leaf crinkle disease (ULCD) is economically a significant one and devastating the crop in major urdbean cultivating countries. ULCD causes severe crinkling and rugosity of lamina, stunting of plants, malformation of buds inflicting heavy yield losses. Due to occurrence of ULCD as mixed infection along with other major viruses infecting urdbean, maintenance of pure inoculum under glasshouse conditions is a prerequisite for the etiology confirmation work. In the present study, seeds were mechanically inoculated by sprout seed abrasion method as well as on to 2-leaf stage through infected sap. Influence of artificial inoculation on ULCD incidence has been studied in VBN 8 cultivar of blackgram. Symptoms started appearing 20 DPI and disease incidence was up to 88% in sprout seed abrasion method and 84% in sap inoculation at two leaf stage. The protocol mentioned in the present study helps in maintenance of pure inoculum of virus under glasshouse conditions and further investigations proved sprout seed abrasive method as efficient protocol to obtain transmission at higher levels at the earliest.