The response of root-associated bacterial community to the grafting of watermelon
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Background and aims
Grafting is commonly used to overcome soil-borne disease but how it affects the root-associated microbiome of concerned crops and the linkage between the microbiome and the resistance of soil-borne disease remain unknown. This study addressed the variation in the microbial activity and bacterial community in the rhizosphere of own-root bottle gourd (rootstock), own-root watermelon, and grafted-root watermelon under field conditions and tried to clarify how bacterial communities in the rhizosphere responded to grafting of watermelon.
Seven types of soil enzyme activities were tested by microplate fluorometric assay, and the root-associated bacterial community was compared using 454 pyrosequencing.
Clear distinctions in microbial activity and taxonomic levels between the different treatments were obtained. Compared with grafted-root watermelon, ungrafted watermelon recruited significantly higher beneficial bacterial genera, such as Bacillus spp. and Paenibacillus spp., suggesting the grafted watermelon root could not have the ability to harbor highly beneficial bacteria to exert soil-borne disease resistance. However, a significantly higher Shannon-Wiener index at any reads level was found in the rhizosphere of grafted watermelon compared with ungrafted watermelon.
Root-associated bacteria of grafted watermelon possess a broader niche overlap which would provide the potential to exclude the pathogen challenge. We proposed that the grafted watermelon might exert soil-borne disease resistance by maximizing the niche occupancy of rhizosphere rather than by recruiting more beneficial bacteria.
KeywordsGrafting Watermelon Soil enzyme Bacterial community 454 Pyrosequencing
Financial supports from the National Basic Research Program of China (2015CB150503), Natural Science Foundation of China (31301853) and from the Fundamental Research Funds for the Central Universities (KYZ201307) are acknowledged. Many graduate students and staffs involved in maintaining the field plots and collecting soil samples but not listed as coauthors are grateful.
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