Genetic and molecular analysis of soybean cyst nematode virulence
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The soybean cyst nematode (SCN) Heterodera glycines is the most economically important pathogen of soybean, capable of causing large scale yield loss on a global scale. Current management practices utilize host resistance, but commercial resistance is limited to three main sources, the soybean plant introductions (PI) 54802 (Peking), 88788, and 437654. More than 95% of soybean grown in the north central United States have resistance derived from PI 88788 and repeated use of this resistance has led to the development of highly virulent nematode populations capable of infecting these resistant plants and causing yield losses. In order to identify the mode of inheritance for virulence on the three primary sources of resistance to SCN a controlled crossing study was performed, mating a highly virulent nematode (TN20) with an avirulent nematode (PA3). By monitoring the offspring of this cross it was found that depending on the source of host resistance, virulence is inherited in a dominant or a recessive manner except for virulence on PI 437654, which is likely a multigenic trait dependent on multiple recessive genes. A de novo transcriptome assembly was then generated for SCN and mined for novel stylet-secreted effectors, identifying a new pool of candidates that may play a role in virulence. Finally, a comparative transcriptomic analysis was performed across multiple SCN populations to identify conserved expression patterns and genes associated with virulence. Results from these studies will be used to improve current management practices for SCN and provide new potential targets for improving SCN resistance.
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