Journal of Heredity 2004:95(2):154-157
© 2004 The American Genetic Association
Genetics of Promiscuous Nodulation in Soybean: Nodule Dry Weight and Leaf Color Score
From the Department of Agronomy, University of Florida, P.O. Box 110300, Gainesville, FL 32611-0300. This research was supported by a grant from the Rockefeller Foundation. This is journal series paper no. R-09494, Florida Agricultural Experiment Stations. We are grateful to Dr. K. Dashiell and the staff at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, and Mrs. P. N. Nyakanda, Professor C. Keswani, and other staff at the Crop Breeding Institute (CBI), Harare, Zimbabwe, for supplying the seed of the parental lines. We are also indebted to Dr. P. Singleton, NifTAL, Paia, Hawaii, for providing the inoculant. We thank the Rockefeller Foundation for financial support of this research project.
Address correspondence to E. T. Gwata at the address above, or e-mail: egwata{at}ufl.edu.
The symbiotic relationship between the soybean plant and rhizobium results in fixation of atmospheric nitrogen (N2) in the root nodules, with the result that nitrogenous fertilization of the soybean is unnecessary. The effectiveness of nodule formation and N2 fixation with rhizobial strains is under genetic control with two general categories identified: (1) promiscuous, which produces functional nodules with cowpea-type rhizobial strains; and (2) nonpromiscuous, which forms no or nonfunctional nodules with these strains. The segregation pattern of this promiscuity trait was studied using nodule dry weight (NDW) and leaf color score (LCS) as indicators of N2 fixation effectiveness. Individual plants in each of six populations [P1 = nonpromiscuous, P2 = promiscuous, F1 = P1 x P2 (and the reciprocal cross), BC1(P1) = F1 (female) x P1, BC1(P2) = F1 (female) x P2, F2] were scored for these characters after inoculation with a rhizobial strain that would distinguish between both types. For NDW, nonpromiscuity was found to be partially dominant (h/d = 0.37), controlled by four loci. For LCS, nonpromiscuity was shown to be almost completely dominant (h/d = 0.74), controlled by two loci. LCS was a more meaningful estimate of N2 fixation because it represented the total effectiveness of nodulation to provide nitrogen for the plant.
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E. T. Gwata, D. S. Wofford, K. J. Boote, A. R. Blount, and P. L. Pfahler Inheritance of Promiscuous Nodulation in Soybean Crop Sci., February 23, 2005; 45(2): 635 - 638. [Abstract] [Full Text] [PDF] |
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