关键词: 玉米, 熟期, 叶片衰老, 叶际细菌, 群落组成

Abstract: As a photosynthetic organ of crops, the senescence process of leaves has an important impact on yield formation, but the relationship between leaf senescence and interleaf microorganisms has been less studied. In order to explore the influence of the senescence process of maize leaves on the interleaf bacterial community, this study took three maize varieties of different maturity (early maturity variety Heike Yu 17, H17, medium maturity variety Zhongdan 111, Z111, and late maturity variety Shen Yu 21, S21) in the spring maize area of Northeast China as the experimental materials, and the leaves of the ear position of the three maize varieties were sampled five times starting from the blooming stage of early maturity varieties, and the physiological indexes of senescence were determined, and at the same time The community composition of endogenous and exogenous bacteria in the interleaf was determined based on high-throughput sequencing technology. The results showed that at the late reproductive stage, leaf water content, POD and SOD activities were significantly higher in the mid- and late-maturing varieties than in the early-maturing varieties. At the phylum level, Cyanobacteria were endemic to medium- and late-maturing cultivars; at the genus level, the relative abundance of endogenous shared bacteria Sphingomonas, Methylobacterium, and Deinococcus in maize leaves was significantly reduced during IV and V periods The relative abundance of endogenous bacteria Streptomyces and exogenous bacteria P3OB-42 were significantly enriched in the late senescence period, with similar trends and significant differences in relative abundance among the three species. The relative abundance of endogenous and exogenous bacteria differed significantly, with the top 5 exogenous bacteria accounting for more than 60%, while for endogenous bacteria, the top 5 accounted for only more than 30%. Soluble sugar content, photosynthetic pigment content and SOD activity were significantly correlated with bacterial community structure and abundance. In conclusion, medium- and late-maturing varieties were effective in prolonging leaf greening period, maintaining late leaf physiological activity and delaying senescence. The effects of senescence on the composition and diversity of endogenous bacterial communities were significantly greater than those of exogenous bacteria, and there were significantly differentiated genera among varieties of different maturity stages. Moreover, soluble sugar content, photosynthetic pigment content and SOD activity were the key factors affecting the interleaf bacterial communities as well as the dominant species.

Key words: corn, ripening stage, leaf senescence, interleaf microbes, community composition