Effect of Powdery Mildew on the Photosynthetic Parameters and Leaf Microstructure of Melon

Abstract

Powdery mildew is a fungal disease devastating to crops, causing significant quality and yield loss. As one of the most important fruits in the world, melon also is damaged by powdery mildew. The present study investigated the effect of powdery mildew on the photosynthetic parameters and leaf microstructure of melons, the ultrastructure of the leaf surface, photosynthetic index, chlorophyll content, yield, and quality index of five thick-skinned and differently shaped melon varieties. The net photosynthetic rate, transpiration rate, leaf water use efficiency, and chlorophyll levels were significantly (p < 0.05) higher in Kangbing F3800 plants compared to the other four varieties. In the case of powdery mildew infection, the total number of stomata in the upper and lower epidermis was particularly high in the Zhongtian No. 8 and Zhongtianxueqiong varieties, respectively. The stomatal length and width were highest in the upper epidermis of Zhongtian No. 12 leaves and in the lower epidermis of Zhongtian No. 8 leaves compared to the other varieties. The total yield and meat thickness were significantly (p < 0.05) higher in the Zhongtianxueqiong variety than the others, along with the low edge sugar content. Overall, powdery mildew impacted differently the photosynthetic and leaf surface characteristics of the five melon varieties. Kangbing F3800 emerged as the most resistant variety, making it the preferred choice for introducing and promoting thick-skinned melon varieties in the Ningxia Hui Autonomous Region of China.