Co-infection of two criniviruses and a begomovirus enhances the disease severity in cucumber

Abstract

In the past two decades, viruses in the genera Crinivirus and Begomovirus, transmitted by whiteflies, have emerged as threatening diseases to cucurbit cultivation. The criniviruses Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV) occur in mixed infection at high rates in cucumber greenhouses in Lebanon. The begomovirus Squash leaf curl virus (SLCV) is also present in the country infecting cucumber but at a lower incidence. The effect of single, dual or triple virus infections on cucumber was studied. Single infection by SLCV did not lead to any symptoms or yield reduction. CYSDV or CCYV infections led to development of characteristic yellowing symptoms. In single infections, CYSDV caused the greatest reductions in height and yield that ranged from 25 to 62 % and 52 to 63 %, respectively, depending on season and variety. CCYV induced less severe reduction in height, 10 to 33 %, and in fruit number, 10 to 12 %. Yellowing symptoms induced by dual infections in any combination were similar to those of singly-infected plants. Triple infections resulted in substantial reductions in plant height and yield as compared to single or dual infections. This is the first report that characterizes a significant increase in disease severity upon co-infection between cucurbit-infecting criniviruses and begomoviruses. The implications of these observations on integrated disease management strategies are discussed.