Innate Root Exudates Contributed to Contrasting Coping Strategies in Response to Ralstonia solanacearum in Resistant and Susceptible Tomato Cultivars.

Tomato cultivars with contrasting resistance to pathogens regulate root exudates differentially in response to Ralstonia solanacearum attacks. However, strategies using innate root exudates against infection remain unknown. This study analyzed the innate root exudates of two tomato cultivars and their functions in regulating R. solanacearum infection. The innate root exudates differed between the two cultivars. Astaxanthin released from resistant plants inhibited colonization by R. solanacearum but promoted motility, while neferine released from susceptible plants suppressed motility and colonization. The secretion of astaxanthin in resistant tomatoes promoted the growth of biocontrol fungi in soil and reduced the abundance of pathogenic fungi. Neferine secreted by the susceptible cultivar inhibited the relative abundance of the bacterial-biocontrol-related Bacillus genus, indirectly reducing the soil's immune capacity. This study revealed contrasting strategies using root exudates in resistant and susceptible tomato cultivars to cope with R. solanacearum infection, providing a basis for breeding disease-resistant cultivars.

[Effects of microbial agent inoculation on bacterial community diversity in the process of pig manure composting].

PCR-DGGE method was adopted to study the effects of inoculating exogenous microbial agent on the bacterial community diversity in the process of fresh pig manure high-temperature aerobic composting. Exogenous microbial agent inoculation promoted the composting process, with the high-temperature period being advanced by 2 days than that of non-inoculation. DGGE pattern analysis showed that during composting, the dominant bacteria changed significantly, with the Shannon-Wiener index of bacterial community at different composting periods varied obviously. The sequencing of DGGE-distinguished bands showed that Clostridium stercorarium subsp. thermolacticum sp. was the dominant group in the whole composting process. Uncultured bacteria Bacillus coagulans sp. and Clostridium thermocellum sp. became the main groups on the 10th and 16th day after microbial agent inoculation, while uncultured Firmicutes sp. and delta proteobacterium became the dominant groups on the 5th and 16th days in the treatment non-inoculation, respectively. Un-dominant group Ureibacillus thermosphaericu sp. and uncultured Silvimonas sp. appeared in the late period of well rotted composting, while uncultured soil bacteria mainly appeared in the initial and high-temperature periods. UPGMC cluster analysis showed that exogenous microbial agent inoculation obviously affected the bacterial community structure in different composting periods, and the main component analysis of DGGE patterns in composting process showed that the bacterial community was mainly affected by the exogenous microbial agent inoculation.