Impact of high planting density on tomato susceptibility to Verticillium wilt and pepino mosaic virus

This study aimed to investigate the effect of tomato planting density on susceptibility to Verticillium wilt and pepino mosaic virus diseases. Data analysis using ANOVA and Tukey's test (P < 0.05) revealed significant differences between planting densities, highlighting a positive correlation between high planting density and increased susceptibility of three different tomato cultivars to Verticillium dahliae and pepino mosaic virus. There was a significant difference between plants grown under high and low density in their responses to the two pathogens. Growth parameters were higher in plants grown under high density compared to those grown under low density. However, disease severity, including leaf alterations and browning index caused by V. dahliae, was significantly reduced in tomato plants grown under low density compared to those grown under high density. Similarly, the severity of leaf mosaic, leaf scorching, and leaf nettle head symptoms caused by pepino mosaic virus were more pronounced in plants grown under high density and were associated with reduced photosynthetic parameters and a higher viral load, as detected by Double Antibody Sandwich - Enzyme Linked Immuno Sorbent Assay. In both pathosystems, the increased susceptibility observed in the three inoculated cultivars grown under high planting density was linked to elevated accumulation of reactive oxygen species and higher activity of Ascorbate peroxidase. These findings emphasize the importance of density management in greenhouse tomato production to mitigate disease severity.