Occurrence and distribution of viral diseases of mungbean and mashbean in Punjab, Pakistan.
In order to assess the occurrence, distribution and importance of viral diseases of mungbean (Vigna radiata) and mashbean (V. mungo) crops in several districts (Chakwal, Bhakkar, Minawali, Layyah, Sialkot, Narowal and Shakagarh) of Punjab, Pakistan, an extensive survey was conducted during the summer season of 2004. The symptomatic plant samples were collected from farmer's fields and experimental plots at research stations and tested by Enzyme-linked Immunosorbent Assay (ELISA) to detect and identify viruses infecting these two crops. Based on field observations, the incidence of mungbean yellow mosaic virus (MYMV) ranged from 4 to 40% in mungbean depending upon crop variety and location. In case of mashbean, the MYMV incidence was from 5 to 100%. MYMV was observed as a major disease of both these crops distributed in all the districts surveyed with significant importance. Urdbean leaf crinkle virus (ULCV) was the second important viral disease with incidence of 5 to 28%, but was more serious in mashbean than mungbean. Out of 540 symptomatic plant samples collected from commercial plots of mungbean and mashbean and tested by ELISA, only 213 (39%) samples reacted positively with one or more antisera. Based on ELISA results, only five viruses such as MYMV, ULCV, cucumber mosaic virus (CMV), bean yellow mosaic virus (BYMV) and alfalfa mosaic virus (AMV) were detected and identified. AMV was prevalent only at research stations, but not at farmer's fields. The incidence of CMV, BYMV and AMV was recorded as 6 to 20%. The natural infection of CMV, BYMV and AMV on mungbean seems to be first record in Pakistan. Widespread infection of viral diseases in commercial crops and experimental stations is of great concern, especially where individual virus incidence is high and two or more viruses are present. Incorporation of viral disease resistance in the present cultivars is the only practical way to control viral diseases.