Changes in Meloidogyne incognita feeding sites in tomato roots associated to inoculum with Rizophagus intraradices and mild water stress

Biocontrol effects of arbuscular mycorrhizal fungi against nematodes have been reported in various plants. Literature data suggest that mycorrhizal symbiosis affects plant-water relationships as well. Moreover, it is well established that water deficit and infection with plant parasitic nematodes represent two environmental stresses with interacting effects under field conditions. Few data are available on the effect of combined mycorrhizae and water stress on the development of nematode feeding sites. We studied the impact of Rizophagus intraradices symbiosis on Meloidogyne incognita and tomato (cv San Marzano nano) interaction, with or without water stress. Plants inoculated or not with R. intraradices, maintained in growth chamber at 25°C, were exposed to mild water stress and subsequently infected with J2s of M. incognita. Galls hand-dissected at 7 and 14 days were processed for light microscopy observations. The analysis performed on cross sections of galls i) with or without mycorrhizae, ii) with water stress and iii) with mycorrhizae and water stress, showed changes in the morphology of galls and nematode feeding sites, affecting density and dimensions of nuclei. The symbiosis with R. intraradices and water stress hampered development and structure of giant cells, showing an effect on the modulation of host plant metabolism. NGS-based analysis of galls transcriptome is under study, to unravel the molecular pathways involved in this multiple interaction. Research partially funded by CNR, Progetto Premiale Aqua.