Bio mechanisms changes of Downy mildew fungi Pseudoperonospora cubensis on Cucurbits

Impact of downy mildew on chlorophyll, nitrogen, protein and reducing sugar content of cucurbits was studied. Chlorophyll a, chlorophyll b pigment of the infected leaf was found to be decreased due to downy mildew. Loss in nitrogen, protein and reducing sugar contain due to infection of downy mildew were also observed. Downy mildew caused by Pseudoperonospora cubensis significantly affects the physiological and biochemical composition of cucurbits. The present study evaluated its impact on chlorophyll, nitrogen, protein, reducing sugars, phenols, and starch in infected leaves. Results revealed a marked reduction in chlorophyll a and b, nitrogen, protein, and reducing sugar contents across most cucurbit species, with the greatest protein loss recorded in Cucumis melon. Conversely, phenolic content increased consistently in infected plants, indicating a possible defense response. Interestingly, starch levels remained largely unaffected or showed a slight increase under infection. These findings highlight the biochemical alterations induced by P. cubensis, providing insight into host–pathogen interactions and contributing to strategies for disease management in cucurbits.