Investigation of interactions between Meloidogyne javanica and three soil‐borne fungi against susceptible plant hosts

Abstract

In the present study, combined interactions of the root‐knot nematode Meloidoyne javanica (M.j.) with the soil‐borne fungi Verticillium dahliae (V.d.), Fusarium oxysporum f.sp. radicis‐cucumerinum (F.o.r.c.) or Monosporascus cannonballus (M.c.) against susceptible plant hosts were evaluated. Direct and indirect interactions were tested by applying each pathogen (nematode or fungus) alone or together on the whole plant root system or on each of the two sides of a split‐root set‐up in all possible combinations. Plant–fungi–nematode interactions were estimated by measuring various disease and growth parameters on host plants. A significant increase of verticillium wilt symptoms was observed in eggplant when V.d. and M.j. were applied separately in split‐root plants compared with symptoms in whole root plants inoculated with both pathogens. Root and stem rot and root‐knot symptoms in cucumber were more severe when F.o.r.c. was combined with M.j. in a split‐root set‐up than when plants were only inoculated with a single pathogen on one part of the split‐root set‐up. No significant associations were observed in the case of melon‐M.c.‐M.j. interaction. Gene expression bioassays for cucumber‐F.o.r.c.‐M.j. interaction revealed increased transcriptomic activity for PAL1 gene in plants treated with F.o.r.c at 3 days postinoculation (d.p.i.), whereas high transcriptomic level for DEFENSIN gene was observed primarily in M.j.‐treated plants at 7 d.p.i. The possible interactions between the abovementioned pathosystems are presented and discussed for the first time in literature.