Comparative analysis of soybean transcriptional profiles reveals defense mechanisms involved in resistance against Diaporthe caulivora

Soybean stem canker (SSC) caused by the fungal pathogen Diaporthe caulivora is an important disease affecting soybean production. However, limited information related to the molecular mechanisms underlying soybean resistance to Diaporthe species is available. In the present work, the defense responses to D. caulivora in two contrasting soybean genotypes were analyzed. We showed that Genesis 5601 is more resistant to fungal infection than Williams, evidenced by significantly smaller lesion length, reduced disease severity and pathogen biomass. Transcriptional profiling was performed in untreated plants and in D. caulivora-inoculated and control-treated tissues at 8 and 48 hours post inoculation (hpi). In total, 2.322 and 1.855 genes were differentially expressed in Genesis 5601 and Williams, respectively. Interestingly, Genesis 5601 exhibited a significantly higher number of upregulated genes compared to Williams at 8 hpi, 1.028 versus 434 genes. Resistance to D. caulivora was associated with defense activation through transcriptional reprogramming mediating perception of the pathogen by receptors, biosynthesis of phenylpropanoids, hormones, small heat shock proteins and pathogenesis related (PR) genes. These findings provide novel insights into soybean defense molecular mechanisms used to control D. caulivora, and generate a foundation for development of resistant SSC varieties within soybean breeding programs.