Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2006
Publication Date: 9/21/2006
Citation: Hill, C.B., Li, Y., Hartman, G.L. 2006. A single dominant gene for resistance to the soybean aphid in the soybean cultivar Dowling. Crop Science. Crop Science. 46:1606-1608 Interpretive Summary: Since its arrival from Asia, the soybean aphid has spread throughout soybean production areas in North America. High aphid populations reduce soybean production directly by causing severe plant damage during feeding, including leaf distortion, stunting, and desiccation. In 2003, extensive economic losses caused by the soybean aphid occurred in soybean in several Midwestern states with an estimated 1.6 million hectares damaged producing a loss of $80 million. Presently, the only means that soybean growers have to control the soybean aphid is with the application of registered insecticides. Plant resistance to the soybean aphid was recently discovered in soybean germplasm. Another cultivar found to have strong antibiosis-type of 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 in F2 and among F2-derived F3 (F2:3) families produced from crosses between Jackson and the susceptible soybean cultivar Loda was analyzed. Segregation of F2 plants was 247 resistant to 97 susceptible and fit a 3:1 genetic ratio (P=0.17). Segregation among F2:3 33 families derived from different F1 plants fit a 1 resistant:2 susceptible:1 susceptible monogenic 34 inheritance 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. This information will be used primarily by private industry in the development of soybean aphid resistant cultivars.
Technical Abstract: A new and serious pest, the soybean aphid (Aphis glycines Matsumara), of soybean, Glycine max (L.) Merr., first found in North America in 2000, rapidly spread throughout the continent, infesting millions of hectares of soybean, and has caused millions of dollars in economic losses. At present, the application of insecticides is the only means to control the soybean aphid; however, genetic resistance to the aphid was recently discovered. The old cultivar ‘Dowling’ was one of the soybean genotypes identified with strong antibiosis-type aphid resistance. The objective of this study was to determine the inheritance of resistance to the soybean aphid in Dowling. Resistance in F1, F2, and F2-derived F3 (F2:3) families produced from crosses between Dowling and the two susceptible soybean cultivars ‘Loda’ and ‘Williams 82’ was analyzed. All F1 plants were resistant to the aphid. Heterogeneity of segregation of F2 plants in 14 Dowling x Loda F2 families was non-significant (P=0.16) and pooled F2 data, with 132 resistant to 45 susceptible plants, fit a 3:1 pattern (P=0.90). Dowling x Williams 82 F2 plants segregated 135 resistant to 44 susceptible plants, also fitting a 3:1 pattern (P=0.89). Segregation among the F2:3 families fit a 1:2:1 monogenic inheritance pattern. These results indicated that resistance in Dowling was controlled by a single dominant gene that was named Rag1. The monogenic dominant resistance inheritance pattern will enable breeders to rapidly introgress Rag1 into existing cultivars by using back cross breeding procedures to produce new soybean aphid resistant cultivars.