Soybean stemcanker (SSC) is a destructive disease that can cause plant death, affecting crop yield and seed phytosanitary quality. SSC is caused by Diaporthe aspalathi (syn. Diaporthe phaseolorum var. meridionalis) and Diaporthe caulivora (syn. D. phaseolorum var. caulivora, Dc). SSC-Dc has emerged as one of the most prevalent soybean diseases in South America, and the Rdc1 gene represents the only reported source of resistance against D. caulivora. In this paper, inheritance studies were conducted to characterize the resistance to SSC-Dc in H32, a local soybean genotype that behaved consistently as resistant to Dc in different pathogenicity assays. After phenotyping several segregating populations and performing allelism tests under different environmental conditions, a novel and independent locus conferring resistance to SSC-Dc was identified, characterized as a major, dominant resistance gene, and proposed to be designed as Rdc2. Considering the potential damage caused by this disease, coupled with the absence of genetic resistance incorporated in Argentinian commercial varieties, the future strategy is to introgress Rdc2 and to stack the Rdc/Rdm genes into elite germplasm. The long-term goal is to achieve a broader and more durable resistance, and to mitigate the impact of SSC on crop performance, and consequently increase both yield and seed phytosanitary quality.
