Soybean Rhg1 resistance to Heterodera glycines hinders theparasitism of Pratylenchus penetrans

Abstract

Rhg1 has been the most effective QTL deployed in soybeans (Glycine max) to control soybean cyst nematode (Heterodera glycines; SCN). However, the resistance mechanisms and specificity of Rhg1 towards SCN as opposed to other plant parasitic nematodes are not well known. In this study we report that Rhg1 can hinder the parasitism of the root lesion nematode Pratylenchus penetrans (Pp), which is commonly found along with SCN in northern U.S. soybean fields. Two elite public soybean varieties, carrying either rhg1-a + Rhg4 or rhg1-b, negatively impacted Pp populations measured at 30 dpi. This contribution of Rhg1 was more rigorously demonstrated using near isogenic lines for rhg1-b. Additionally, in three of the four soybean genetic backgrounds tested we observed significantly more Pp at 30 dpi when Pp were co-inoculated with SCN, consistent with a previous study. No significant changes in SCN cyst numbers upon co-inoculation with Pp were observed for any of the SCN-resistant rhg1 lines. No nematode-induced changes in Rhg1 transcript abundances were observed when sampling infected root sections in any of the plant genotypes, and no changes in a jasmonate response indicator were observed. However, the 3 dpi salicylate-mediated response to SCN or Pp became more robust during SCN + Pp co-infection. Multiple hypotheses for further dissection and manipulation of soybean resistance to Pratylenchus root lesion nematodes are suggested based on the present findings.