Genotype-Specific Responses of Common Bean to Meloidogyne incognita.

The root-knot nematode Meloidogyne incognita causes large galls on roots, interfering with the flow of water and nutrients to the plant. In the common bean, no major resistance (R) genes have been described. Instead, resistance is controlled by multiple genes, which have not proved effective so far. An RNA-seq approach was used to identify genes involved in common bean response to M. incognita at the stages of nematode invasion and root-galling. When comparing infected and uninfected treatments of a moderately resistant (MR) and a susceptible (S) genotype, several genes were identified as differentially expressed. Their functional annotation indicated that both genotypes underwent complex transcriptional reprogramming from early to later periods of the interaction, but defense-related genes were mostly upregulated in the MR genotype. At the early stage, a large set of genes was activated in both genotypes, including those involved in cell wall organization, signaling, hormonal pathways, transcription factors, oxidative stress and putative resistance gene analogs. Later, most of the previously activated defense mechanisms were no longer expressed in the S genotype. There was an increased expression of genes encoding proteins involved in hormonal signaling pathways (salicylic acid and gibberellin-related), protein kinases, transcription factors and oxidative stress in MR. However, a decreased expression of genes involved in signaling mediated by calcium and oxidative stress occurred in S, indicating susceptibility. The repertoire of genes identified herein will facilitate research in plant-nematode interactions, with possible applications for the improvement of the common bean.