Soybean Stem Canker: Molecular Markers Assisted Stacking of Rdm/Rdc genes.

MALDONADO, R; BIANCHI, J; PERUZZO, A.; ROJAS, A. ; PIOLI, R; CHIESA, M.A.

Viena

Conferencia; WSRC11; 2023

Soybean [Glycine max (L.) Merr.] crop is seriously affected worldwide by Stem Canker (SSC) disease, caused by Diaporthe aspalathi (ex D. phaseolorum var. meridionalis) (SSC-Da) and D. caulivora (SSC-Dc). Both Diaporthe spp. coexist in the core productive zone of Argentina and can infect stem and seed tissues. Furthermore, with the increased seed movement between northern and southern states in US and between US and South America, the development of resistant germplasm is determinant to reduce the impact of these pathogens on crop production and seed quality. Thus, the objectives of this work were (i) to analyze the resistance sources to SSC-Da (Rdm genes) and SSC-Dc (Rdc gene) present in the varieties currently sown in Argentina, as well as in germplasm from the University of Arkansas (US), by genotyping with molecular markers (MM) linked to Rdm3, Rdm4, Rdm5 and Rdc1 genes previously identified by our group; (ii) to stack Rdm3, Rdm4-5 and Rdc1 genes conferring resistance to SSC-Da and SSC-Dc, respectively, in order to confer a more durable and broader resistance to both causal agents. The results indicate that 55% of the genotypes have the Rdm4 gene incorporated, less than 5% have the Rdm3 gene, 21% have other alleles and the remaining do not present resistance alleles. Meanwhile, none of the tested genotypes have the MM linked to Rdc1 gene incorporated. These results suggest that most of currently cultivated soybean germplasm has the same resistance source to SSC-Da and does not present resistance to SSC-Dc. Finally, based on these results and assisted by the linked MM, the stacking of Rdm3, Rdm4 and Rdc1 genes in elite germplasm with good agronomic performance is in progress, to be used as donors in breeding programs aimed to incorporate a broader and more durable resistance to SSC.Keywords: Diaporthe spp., genetic resistance, genotyping, markers-assisted selection (MAS), stackingAcknowledgements: IICAR-CONICET/UNR PUE 22920160100043CO. Proyect-ASaCTeI PEICID-2021-119 (PI Chiesa, MA). Maldonado, R was awarded scholarship by ANPCyT; Pioli, RN is CIUNR Researcher; Bianchi J.S. and Chiesa M.A. are CONICET Career Researchers.