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Rice growing in Russia has some peculiarities, e.g. cultivation of a single crop per year and application of multiannual crop rotation cycles. Phytoparasitic nematodes were previously found on rice crops in Russia: Aphelenchoides besseyi, as well as Hirschmanniella sp., Longidorus sp., Paratylenchus spp., Paraphelenchus, Aphelenchus, Aphelenchoides. Nematodes in rice agroecosystems are known to damage crops by feeding on roots and shoots. It is, however, unknown, how nematodes react to crop rotation and across different soil types. To shed some light on this issue we performed a field study and collected soil samples using standard methods  in the four habitat types: flooded rice paddies, drained rice fields with upland crops, paddy bunds and seminatural grasslands across three major rice-growing regions of Russia: Krasnodar, Kalmykia and Primorye.

In flooded rice relative abundance of soil nematode feeding groups was significantly modified. Plant feeders’ density increased in particular. Specifically representatives of Pratylenchus, Ditylenchus, Rotylenchus and Helicotylenchus genera known for the high ecological plasticity and low selectivity of host taxa (weeds and agricultural crops: wheat, soybeans and corn) dominated. Their density was independent of edaphic parameters (pH, bioavailable biogenic elements and litter depth). Simultaneously, increased abundance of plant feeders in Krasnodar and Primorye and decreased one in Kalmykia reflected phytomass fluctuations across regions due to aridity of the latter region. We conclude that in Russia climate and habitat type as a proxy of a plant community characteristics act as leading drivers explaining plant feeding nematode abundance. This opens ground for developing optimized regional strategies for plant protection in temperate rice agroecosystems. The study was supported by RSF (grant #16-14-00096).