Abstract
Plant-associated microbiota plays an important role in plant disease resistance. Bacterial wilt resistance of tomato is a function of the quantitative trait of tomato plants; however, the mechanism underlying quantitative resistance is unexplored. In this study, we hypothesized that rhizosphere microbiota affects the resistance of tomato plants against soil-borne bacterial wilt caused by Ralstonia solanacearum. This hypothesis was tested using a tomato cultivar grown in a defined soil with various microbiota transplants. The bacterial wilt-resistant Hawaii 7996 tomato cultivar exhibited marked suppression and induction of disease severity after treatment with upland soil-derived and forest soil-derived microbiotas, respectively, whereas the transplants did not affect the disease severity in the susceptible tomato cultivar Moneymaker. The differential resistance of Hawaii 7996 to bacterial wilt was abolished by diluted or heat-killed microbiota transplantation. Microbial community analysis revealed the transplant-specific distinct community structure in the tomato rhizosphere and the significant enrichment of specific microbial operational taxonomic units (OTUs) in the rhizosphere of the upland soil microbiota-treated Hawaii 7996. These results suggest that the specific transplanted microbiota alters the bacterial wilt resistance in the resistant cultivar potentially through a priority effect.
Highlights
The lethal bacterial wilt (BW) disease is caused by Ralstonia solanacearum, and the bacterial pathogen infects more than 400 plant species, especially plants belonging to the Solanaceae family (Hayward, 1991; Scott et al, 2005)
To verify the utility of Analysis System for Plant–Microbiome Interaction (ASPMI), thirteen physiochemical properties were comparatively evaluated between the four different field soils and sterilized commercial nursery soils treated with the microbial fraction (MF) isolated from the corresponding four field soils
These results suggest that the ASPMI method successfully eliminated the differential effect of physicochemical properties among the field soil samples, which enabled the evaluation of plant–microbiota interactions under controlled soil conditions using various soil MFs
Summary
The lethal bacterial wilt (BW) disease is caused by Ralstonia solanacearum, and the bacterial pathogen infects more than 400 plant species, especially plants belonging to the Solanaceae family (Hayward, 1991; Scott et al, 2005). R. solanacearum is a soil-borne pathogen that enters the plant through wounds or elongation zones and subsequently resides in the xylem vessels to block water transport (Vasse et al, 1995). One of the well-known BWresistant tomato cultivars is Hawaii 7996, which exerts the most stable resistance against R. solanacearum infection by several major and minor quantitative trait loci (QTL) (Thoquet et al, 1996; Wang et al, 1998). The quantitative resistance to BW is not completely understood, and the genes and functions of QTL have not been characterized in Hawaii 7996 and other major crops. It is known that the performance of quantitative resistance in Hawaii 7996 is frequently influenced by environmental conditions such as the pathogen strain, temperature, and soil conditions (Wang et al, 2013)
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