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- Author or Editor: Nicolas E. Valladares-Sanchez x
Abstract
A 6-parent Phaseolus vulgaris diallel cross was produced to determine the inheritance of leaf, external, and internal pod reactions to the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye = Xanthomonas phaseoli E.F.S. Dows (X.p.) Nebraska isolate EK-11. The parents and F1 generations were grown in the greenhouse, whereas the F2, along with parents, were also grown in the field at 2 locations (Lincoln and Scottsbluff, Neb.). The Gardner and Eberhart (1966) model, Analysis II, was used to obtain estimates of the genetic effects for the reactions to the pathogen in the different plant parts. Coefficients of variation were high in the greenhouse experiment and low in both field experiments. The increased precision of the field experiments allowed more genetic effects to be detected as being significant. The leaves of ‘Great Northern (GN) Nebraska #1 sel. 27’ and Plant Introduction (PI) 207262 were resistant, ‘Tacarigua’ moderately susceptible, and PI 163117, ‘GN 1140’, and ‘Guali’ were highly susceptible. The pods of the first 3 entries, along with ‘GN 1140’ showed moderate resistance, but the internal reaction of the pods of ‘GN Nebr. #1 sel. 27’ showed more susceptibility than the external reaction. The reaction to X.p. was quantitatively inherited in all experiments. Additive effects were primarily involved in the genetic control of the leaf, external, and internal pod reactions to X.p. Heterosis effects for leaf reaction were detected under field conditions. External and internal pod reactions were highly correlated, but little association between leaf and pod reaction was observed. It is, therefore, necessary to select for resistance simultaneously in both plant parts since correlated responses are not expected to be present. Large positive correlations were detected between the reactions of genotypes observed in the greenhouse with those in the field experiments and between the field experiments, indicating that greenhouse tests should adequately predict field performance. A significant genotype × location interaction for leaf reaction was detected, with ‘Guali’ and ‘Tacarigua’ being more susceptible at Lincoln, under higher night temperatures, than at Scottsbluff, indicating the importance of evaluating the reaction of germplasms to this pathogen in different environments.
Abstract
The leaf and pod reactions of greenhouse-grown plants of reportedly tolerant lines of P. vulgaris L.: Plant Introduction (PI) 169727, PI 197687, PI 163117, PI 207262, PI 325684, PI 325691, ‘Great Northern Nebr. #1 sel. 27’; P. coccineus: PI 165421 and P. acutifolius: Tepary (Nebr. Acc. 10) to Xanthomonas phaseoli (E. F. Smith) Dowson isolates [Xp-S and Xp 816 (Nebr.), Xp-15 (Michigan), Xp-Br (Brazil)], and X.p. fuscans (Burkh.) Starr & Burk. [Xpf-UI (Uganda)], were studied. The multiple needle method was used to inoculate leaves and a dissecting needle was used to inoculate pods of these plants. A differential reaction of lines to isolates was observed for each of the reactions on leaves and pods. All P. vulgaris lines were susceptible or moderately susceptible to the new virulent Xp-Br strain. Leaves and pods of P. acutifolius were highly tolerant to all isolates while P. coccineus PI-165421 showed a differential reaction to all isolates: leaves were highly tolerant and pods highly susceptible. The internal reaction for pods was more severe than the external reaction. P. vulgaris PI 207262 showed a uniform tolerance of leaf and pod to the USA isolates, while ‘GN Nebr. #1 sel. 27’ had a tolerant leaf and susceptible pod. These results suggested differential genetic control of pod and leaf reactions. Transgressive segregation for a high level of leaf tolerance to the virulent Xp-Br strain (water soaking method of inoculation) was observed in field-grown P. vulgaris F2 plants from the crosses ‘GN Nebr. #1 sel. 27’ × PI 163117 and ‘GN Nebr. #1 sel. 27’ × ‘Guali’. Transgressive segregation was confirmed in greenhouse-grown selected F3 families. High leaf tolerance was not associated with pod tolerance. Linkage was detected among the major genes controlling late maturity and indeterminate plant habit, and the polygenes controlling common blight tolerance.