Abstract
Soybean cyst nematode (SCN, Heterodera glycine Ichinohe) is the most damaging soybean pest worldwide and management of SCN remains challenging. The current SCN resistant soybean cultivars, mainly developed from the cultivated soybean gene pool, are losing resistance due to SCN race shifts. The domestication process and modern breeding practices of soybean cultivars often involve strong selection for desired agronomic traits, and thus, decreased genetic variation in modern cultivars, which consequently resulted in limited sources of SCN resistance. Wild soybean (Glycine soja) is the wild ancestor of cultivated soybean (Glycine max) and it’s gene pool is indisputably more diverse than G. max. Our aim is to identify novel resistant genetic resources from wild soybean for the development of new SCN resistant cultivars. In this study, resistance response to HG type 2.5.7 (race 5) of SCN was investigated in a newly identified SCN resistant ecotype, NRS100. To understand the resistance mechanism in this ecotype, we compared RNA seq-based transcriptomes of NRS100 with two SCN-susceptible accessions of G. soja and G. max, as well as an extensively studied SCN resistant cultivar, Peking, under both control and nematode J2-treated conditions. The proposed mechanisms of resistance in NRS100 includes the suppression of the jasmonic acid (JA) signaling pathway in order to allow for salicylic acid (SA) signaling-activated resistance response and polyamine synthesis to promote structural integrity of root cell walls. Our study identifies a set of novel candidate genes and associated pathways involved in SCN resistance and the finding provides insight into the mechanism of SCN resistance in wild soybean, advancing the understanding of resistance and the use of wild soybean-sourced resistance for soybean improvement.
Highlights
The soybean (Glycine max (L.) Merr.), is an important legume crop that supplies more than half of the word’s vegetable fats, oils, and protein meal[1]
NRS100 showed high resistance to SCN race 5 with a Female Index (FI) of 3.3 and S-soja is highly susceptible with a FI of 14944,45
Peking-type resistance is conferred by SNAP gene at rhg[1] and SHMT at Rhg[4] each, and r espectively[18,20]
Summary
The soybean (Glycine max (L.) Merr.), is an important legume crop that supplies more than half of the word’s vegetable fats, oils, and protein meal[1]. Genetic isolation of environmental niches suggests that there is strong selection of environmentally tailored adaptations, such as nematode resistance, within the wild soybean gene pool[29,30]. Novel traits such as pest and disease resistance from wild relatives have been incorporated into major c rops[31,32,33,34,35,36,37,38,39,40], but progress of this sort is lacking in s oybeans[30,41,42,43]. SCN resistance is complex, and additional understanding of the mechanism in wild soybean is needed to benefit SCN resistance improvement
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