Soybean aphid resistance in soybean Jackson is controlled by a single dominant gene

The soybean aphid, Aphis glycines Matsumura, has become established as a serious pest of soybean, Glycine mar (L.) Merr., since it was first found in North America in 2000 and has caused millions of dollars in economic losses. While the application of chemical insecticides is the only means to control the soybean aphid at present, genetic resistance to the aphid was recently discovered in soybean. A single dominant gene named Rag1 that controls resistance to the soybean aphid was found in the cultivar Dowling. Another cultivar found to have strong antibiosis-type resistance to the soybean aphid was Jackson. The primary objective of this study was to determine the inheritance of resistance to the soybean aphid in Jackson. Segregation of resistance was analyzed in F-2 and among F-2-derived F-3 (F-2:3) families produced from crosses between Jackson and the susceptible soybean cultivar Loda. Segregation of F-2 plants was 247 resistant to 97 susceptible and fit a 3:1 genetic ratio (P = 0.17). Segregation among F-2:3 families was not clear because a number of susceptible F-2 plants did not produce a sufficient amount of seed for progeny testing. Ignoring the susceptible class, the segregation of F-2:3 families fit a 1:2 (all resistant/segregating) ratio. These results indicated that a single dominant gene controlled resistance in Jackson. There is no known genetic relationship between Jackson and Dowling. The genetic relationship between Rag1 in Dowling and the gene in Jackson is unknown.