The Community Composition Of Phyllosphere Photosynthetic Bacteria And Its Effects On Plant Growth And Disease Resistance

Photosynthetic bacteria(PSB)is an important phyllosphere microorganism,but its function and proportion in phyllosphere as an important biocontrol bacteria are not clear,so there is great potential for the research of PSB in phyllosphere.In this study,high-throughput sequencing technology was used to explore the effects of different growth stages and different tomato varieties on the community composition of photosynthetic bacteria in phyllosphere.In addition,a photosynthetic bacteria strain,Methylobacterium extorquens,was isolated from the leaves of tomato,and its effects on promoting the growth of tomato and preventing and controlling bacterial wilt were discussed.The main results are as follows:1.The community diversity and distribution characteristics of photosynthetic bacteria in different growth stages of tomato,cucumber and soybean were studied by high-throughput sequencing.The results of a diversity analysis showed that the diversity of photosynthetic bacteria community in cucumber and soybean decreased with the growth and development of crops,and the diversity of photosynthetic bacteria community in seedling stage was the highest;The diversity of photosynthetic bacteria community was the highest at flowering stage.The results of PCo A and dissimilarity analysis showed that there were significant differences in the community structure of photosynthetic bacteria among tomato,cucumber and soybean.Compared with flowering stage and mature stage,photosynthetic bacteria community structure is the most significant difference in plant seedling stage.2.The high-throughput sequencing technology was used to study the community structure of photosynthetic bacteria in the leaves of different tomato varieties.The results of a diversity analysis showed that the diversity of photosynthetic bacteria in the leaves of tomato varieties resistant to bacterial wilt was significantly higher than that of those susceptible to bacterial wilt.The results of PCoA and dissimilarity analysis showed that there were significant differences among different tomato varieties.The results showed that tomato varieties with different resistance to bacterial wilt could affect the formation of photosynthetic bacteria community and the change of community structure to a certain extent3.A strain of bacteria TP-1 was isolated from tomato leaves.The results of 16S rDNA sequencing showed that the strain TP-1 was in the same branch with methylbacterium extorquens,with close relationship and 99%similarity.The results of morphological observation,Gram staining and physiological and biochemical identification showed that the strain TP-1 was methylbacterium extorquens.The results of seed germination test showed that TP-1 solution can significantly promote the germination of tomato seeds.At the same time,the results showed that TP-1 could significantly promote the growth of tomato seedlings.The root length,stem length,plant height and fresh weight of tomato seedlings increased by 28.99%、22.82%、23.86%and 40.67%respectively after spraying TP-1 bacterial solution on the leaves.The content of chlorophyll a and chlorophyll b in tomato seedling treated with TP-1 was 24.62%and 38.63%higher than that of treated with water.The results showed that the control effect of 100 times diluted TP-1 and TP-1 inactivated bacterial solution was 62.55%and 36.65%respectively.TP-1 bacterial solution can effectively prevent and control the occurrence of tomato bacterial wilt,and its inactivated bacterial solution also has a certain control effect on tomato bacterial wilt.