Effects of intraspecific variation in rice resistance to aboveground herbivore, brown planthopper, and rice root nematodes on plant yield, labile pools of plant, and rhizosphere soil.

In agricultural ecosystems, most crop cultivars are bred for pest resistance with the aim of resisting aboveground herbivores, but it is unclear if this resistance also affects abundance, composition, and activity of underground pests and content of soil labile pools. A fully factorial greenhouse experiment was carried out, using four rice cultivars with distinct resistance to shoot herbivore brown planthopper, Nilaparvata lugens, with and without rice root nematodes, Hirschmanniella spp., to test two hypotheses: (1) rice cultivars resistant to brown planthopper are more susceptible to rice root nematodes and (2) rice root nematodes of resistant cultivars cause greater modification of labile pools of rhizosphere soil than those of susceptible cultivars by inducing more leakage of plant metabolites. Nematode abundance, soluble sugar and soluble amino acid contents of plant, and microbial biomass C and N, dissolved organic C and N, and soluble sugar and amino acid contents of rhizosphere soil were analyzed. The abundance of rice root nematodes substantially increased under all rice cultivars following root nematode inoculation. Rice cultivar resistance to brown planthopper did not affect the numbers of rice root nematodes but decreased negative effects of nematodes on root growth, shoot soluble sugar and amino acid contents, and labile pools of rhizosphere soil, probably implying that integrated complex mechanisms other than only resource allocation were involved in rice resistance to aboveground and belowground herbivores. Our study will contribute to a better understanding of aboveground-belowground interactions and to the development of integrated pest managements by considering belowground ecosystem responses in crop systems. [ABSTRACT FROM AUTHOR]