Parallel transcriptome profiling of soybean cyst nematodes (SCN) during a three-way interaction among SCN, soybean aphids, and soybean

The soybean cyst nematode (SCN), Heterodera glycines (Ichinoe) (Rhabditida: Heteroderidae) is arguably the greatest yield-limiting factor for soybean (Glycine max [L.] Merr.) production in the United States. Previous research found that the impact of SCN infestation on yield is exacerbated during concurrent infestations with soybean aphids (SBA), Aphis glycines (Matsurmura) (Hemiptera: Aphididae). Although recent research has characterized the host root transcriptomic response during these infestations little is known about the corresponding in planta gene expression dynamics of either pest. This study examines the transcriptomic expression of SCN in soybean cultivars' roots under single or combined SBA infestations at two different time points: 5 and 30 days post-infestation (DPI). The SCN transcriptomics for SCN-susceptible (S) PI 518671 (Williams 82) cultivar reacted equivalently to both SCN and SCN + SBA treatments. However, transcriptomics in SCN-resistant (R) MN1806CN (H. glycines HG type 0/race 3 resistant) demonstrated an elevated significant expression pattern under the SCN + SBA combined treatment. During the early infestation period (i.e., sampled at 5 DPI), both S and R cultivars reacted similarly, irrespective of treatment conditions. The functional enrichment analysis of 1829 differentially expressed genes/transcripts showed that during the early co-infestation period (5 DPI), SCN genes were significant and mapped towards resistance breakage, whereas in the late stage (30 DPI), the gene flux oriented towards nematode dormancy. Together, these results suggest that SCN activity is amplified when combined with SBA, offering foundational data for molecular breeding to produce SCN resistant soybean cultivars.