Soybean cyst nematode (SCN) is one of the pests that most affect soybean yields per hectare. An effective method of controlling the disease that still ensures satisfactory yields is the use of soybean varieties resistant to soybean cyst nematode. Due to the long and frequent use of soybean varieties derived from the PI 88788 and Peking lines, the pest has managed to adapt to these two genetic sources of resistance. The rhg1 and Rhg4 loci are in several allelic variants, as they carry different numbers of copies of the genes conferring resistance to SCN. The allelic variants are rhg1-a, rhg1-b, Rhg4-a. It is for this reason that the characterisation of the different genetic sources of resistance to SCN has received particular attention in science. Knowing the copy number of genes at loci associated with resistance to SCN in different soybean lines allows us to use different genetic sources in breeding programmes. By genetically diversifying resistant varieties, it is possible to reduce the selection pressure on the pest and to ensure the production of soybean with satisfactory agricultural yields in the long term.
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