Variable suppression by mycorrhiza of root-lesion nematode Pratylenchus thornei reproduction among mung bean genotypes has implications for phenotyping.

Mung bean (Vigna radiata and Vigna mungo) is susceptible to the endoparasitic root-lesion nematode Pratylenchus thornei (Pt), which limits crop productivity. Mung bean roots host symbiotic arbuscular mycorrhizal fungi (AMF), which improve nutrient uptake and plant growth. The interaction of these organisms was previously reported in a single mung bean cultivar to increase P. thornei reproduction, suggesting potential consequences for phenotyping. Therefore, twelve diverse mung bean genotypes were evaluated to investigate the effect of AMF on P. thornei reproduction. A factorial design of genotypes, P. thornei and the AMF species Funneliformis mosseae (Fm) was evaluated in two glasshouse experiments. At 16 weeks after sowing, in mung bean inoculated with F. mosseae, there was a significant (P < 0.05) decrease in P. thornei population densities in nine genotypes whereas no significant effect on P. thornei population densities was observed in the remaining three genotypes. Root colonisation by F. mosseae was not affected by the presence or absence of P. thornei, with consistent root colonisation of ~ 26% across all genotypes. The widest range of P. thornei reproduction between genotypes, and hence the best discrimination of responses, occurred without F. mosseae inoculation. Consequently, it is recommended that mung bean germplasm should be screened for P. thornei resistance in the glasshouse in the absence of AMF for maximal differentiation between genotypes.