Application of Certain Bacterial Bioagents to Control Watermelon Mosaic Virus.

Squash is an important vegetable crop in Egypt. Squash can be infected with many plant viruses; among these viruses Watermelon mosaic virus (WMV) is considered as the most prevalent one under Egypt conditions. Traditional methods to control WMV are not very useful. In the current study, six bacterial isolates (two isolates of Bacillus amyloliquefaciens and one isolate from each B. velezensis, B. cereus, Brevundimonas diminuta, and Streptomyces enissocaesilis) were applied to squash plants as bioagents to control WMV in three different application methods (soil drench, seed treatment and foliar spray) during two consecutive seasons under greenhouse conditions. The results revealed that all 6 bacterial bioagents significantly reduced the disease severity of WMV either 3 or 6 weeks after inoculation. During the first season, the most efficient bioagents were B.cereus (B6) and Brevundimonas diminuta (B5). While the bioagents B. amyloliquefaciens (B1) and Streptomyces enissocaesilis (B2) were the most efficient isolates to control WMV in the second season. Evidently, the application of bacterial isolate led to a significant increase in chlorophyll content in treated plants compared to infected control ones. These results proved that the application of bacterial bioagents can be a useful method to control WMV in squash plants. [ABSTRACT FROM AUTHOR]