Evaluation of common bean lines for their reaction to tomato yellow leaf curl virus-Ir2

Tomato yellow leaf curl virus (TYLCV) can cause an economically relevant disease in the major tomato growing regions, and no resistance has been identified in commercial and wild tomato cultivars in Iran. In the present study, 34 common bean lines were screened for their reaction to TYLCV-Ir2 under greenhouse conditions. The experiment was conducted in a randomized complete block design with three replications. Bean plants were inoculated at the first trifoliate stage with viruliferous whiteflies (Bemisia tabaci biotype B) and were then sprayed with an insecticide and maintained in whitefly-proof greenhouse. The inoculated plants were monitored for the development of symptoms and the presence of viral DNA by polymerase chain reaction (PCR) four weeks after inoculation. Results revealed that out of the 34 lines, five were resistant. These lines exhibited either no symptoms or very mild symptoms and no viral DNA was detected in them by PCR. Two lines, which showed no typical disease symptoms but contained viral DNA, were identified as tolerant to TYLCV-Ir2. The vector feeding preference for common bean lines was assessed. Results indicated a significant difference in adult whitefly numbers among bean lines but there was no relationship between the number of whiteflies and disease symptom severity. The resistance to TYLCY-Ir2 expressed in common bean lines may be useful as source of resistance for the development of resistant commercial common bean cultivars.