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Reference Report for rootknotref_4
Title:A gene for resistance to the southern root-knot nematode in soybean
Authors:Luzzi, B.M., Boerma, H.R., Hussey, R.S.
Source:J. Hered. 1994, 85(6):484-486
Abstract:The inheritance of resistance in soybean [Glycine max (L.) Merrill] to the southern root-knot nematode [Meloldogyne incognita (Kofoid and White) Chitwood] was determined for a cross of Bossier (susceptible) √ó Forrest (resistant). The F1, F2, and F3 generations were screened in a greenhouse for resistance to gall formation by counting individual galls on the roots of plants inoculated with nematode eggs. The mean number of galls on F1 plants derived from reciprocal crosses of Bossier and Forrest were similar to each other and to the midparent mean, indicating that inheritance was not maternal and that neither resistance nor susceptibility was dominant. F2 plants which had fewer galls than the upper limit of the 95% confidence interval (Cl) about the mean of Forrest or more galls than the lower limit of the 95% Cl about the mean of Bossier were classified as resistant or susceptible, respectively. If an F2 plant had a gall number between the confidence intervals of Forrest and Bossier, It was classified as intermediate. These classifications were verified by family gall means and within-family variances of F3 progeny harvested from each F2 plant. Both the F2 and F3 populations segregated into distinct resistant, intermediate, and susceptible classes in a ratio of 1:2:1. In addition, low within-family variances Indicated that F3 families in the resistant and susceptible classes were derived from homozygous F2 plants. High within-family variances for F2 families in the intermediate class indicated they were derived from heterozygous F2 plants. These data indicate that Forrest contains a single additive gene for resistance to galling, designated Rmi1.






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