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.