Soybean Cyst Nematode, Heterodera Glycines, Resistance Genes in PI 89772 and PI 209332 Soybean
Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is the most serious disease of soybean, Glycine max (L.) Merr., in the United States. Crop rotation plays an important role in controlling the nematode. Control also utilizes different cropping systems and resistant soybean cultivars to suppress yield loss caused by H. glycines. A race test was developed in early 1970's to classify variability in the nematode and was expanded in late 1980's to include 16 races. The number of resistance genes in PI 89772 and PI 209332 confering resistance to H. glycines race 3 is not well defined. Crosses of PI 89772 x 'Lee 68', PI 88788 x PI 89772, and Lee 68 x PI 209332 were made in the field and greenhouse. Several F1 and F2 families from each cross, 98 F3 families from cross PI 89772 x Lee 68, 74 F3 families from cross PI 88788 x PI 89772, and 80 F3 families from cross Lee 68 x PI 209332 were tested with an inbred line of H. glycines developed on PI 88788. Approximately 8,000 individual plants growing in pots containing 200 cm3 of sterilized soil were inoculated with 4,010 eggs and J2/pot. Thirty days after inoculation the number of females that developed on each plant was determined. Cluster analysis revealed sets of families with a low mean number of females and low variance, intermediate means and high variance, and high means with a low variance, indicating F3 plants came from, respectively, homozygous resistant, heterozygous or segregating, and homozygous susceptible F 2 Plants. The three H. glycines resistant parents have at least two genes that express resistance to H. glycines. One gene acts as a major gene (Rhgx) and the other a minor gene (Rhgy) in conferring resistance of the parents PI 89772 (Rhgx1?Rhgx1?Rhgy1? Rhgy1?), PI 88788 (Rhg x2?Rhgx2?Rhgy2?Rhgy2?), and PI 209332 (Rhgx3?Rhgx3?Rhgy3?Rhg y3?) to H. glycines race 3. The same major (Rhgx) and minor (Rhgy) genes occur in PI 89772 (Rhgx1?Rhgx1?Rhg y1?Rhgy1?) and PI 88788 (Rhgx2?Rhg x2?Rhgy2?Rhgy2?).
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign