A Single Dominant Gene Controlling Resistance to Soil Zinc Deficiency in Common Bean

Cultivated soils often are either deficient or possess toxic concentrations of one or more mineral elements that adversely affect emergence, growth, maturity, production potential, and/or nutritional quality of common bean (Phaseolus vulgaris L.). Our objective was to study the inheritance of resistance to soil Zn deficiency. The resistant `Matterhorn' was crossed with the susceptible 'T-39'. The F1 was backcrossed to Matterhorn (BC 1 ) and T-39 (BC 2 ), and advanced to the F2. The two parents, F 1, F2, BC 1, and BC2 were evaluated in a Zn deficient field trial at Kimberly, Idaho in 2001. Plants were classified as tall-healthy or stunted with chlorotic leaves. Leaves were sampled from the two types of plants at flowering and analyzed for Zn concentration. The tall plants had an average leaf Zn concentration of 22.5 mg kg1. In contrast, stunted plants had a Zn concentration of 15.0 mg kg1. All F1 plants were tall resembling Matterhorn, except that unlike Matterhorn (white flowers and seeds) they had purple flowers and black shiny seeds. Thus, the resistance to Zn deficiency was dominant. A segregation of 45 resistant (R) to 20 susceptible (S) plants was observed in the F2, giving a good fit to 3 R:1 S (x 2 = 1.1538, P = 0.28). All plants in BC 1 were resistant. In BC 2, 142 It and 139 S plants were observed, giving a ratio of 1 R to 1 S (x2 = 0.032, P = 0.86). This supports a single dominant gene controlling soil Zn deficiency resistance. The symbol Znd is proposed for the dominant allele controlling resistance to soil Zn deficiency, and znd for its susceptible