Confirmation of resistance in different soybean cultivars to Meloidogyne incognita using greenhouse screenings, enzymes and histopathology approaches

Abstract Greenhouse screenings evaluated soybean cultivars for genetic resistance to Meloidogyne incognita . For verification, cultivars identified with resistance were subjected to enzymatic assays, viz. lipoxygenase (LOX) and guaiacol peroxidase (GPX), as well as histopathological evaluations. Reproduction factor values were used as the main criterium to identify M. incognita resistance levels; it showed that cultivar LS 5995 and genotype GCI 7 contained the highest resistance levels while cultivars LS 6248 R and Dundee were highly susceptible. Significant differences in GPX levels in leaves and roots of inoculated GCI 7 plants versus uninoculated plants verified M. incognita resistance in this cultivar, while the same trend was only evident for GPX analyses from leaves of the resistant standard LS 5995. For LOX, the resistance trait was verified in roots of GCI 7 and LS 5995 48 h after J2 inoculation and in Egret 24 h after J2 inoculation. Histopathology evaluations confirmed the presence of resistance in both GCI 7 and LS 5995, attributed to the formation giant cells that were distinctly different from those observed in vascular cylinders of susceptible cultivars. Cultivar Egret, previously identified as resistant, showed susceptibility based on greenhouse screenings and histopathology investigations, but not according to LOX analysis. Greenhouse screenings proved to be an accurate strategy to identify resistance in local soybean cultivars, enzyme analyses confirming host status traits warrant further investigations to optimise such an approach. Histopathological studies ultimately indicated the mechanism of resistance at the cellular level, showing the presence of hypersensitivity as an additional resistance mechanism except for antibiosis.