Figure 1.

The Phaseolus bean halo‐blight disease gene‐for‐gene matrix proposed by Taylor et al. (1996) to explain race specificity in the Phaseolus syringae pv. phaseolicola (Pph)–Phaseolus vulgaris interaction. The avr genes cloned by function from Pph include avrPphB, avrPphE and avrPphF, which correspond to avr genes 3, 2 and 1 indicated in the matrix. Stab inoculation assays for virulence in bean pods are also illustrated, comparing susceptible water‐soaked lesions with the hypersensitive resistance reaction. Despite the application of targeted cloning and selection strategies, the avr gene matching R4 has not been identified. Other avr genes recovered from Pph by the exchange of genomic libraries between pathovars and assays in soybean and pea include avrPphC and avrPphD, respectively (Arnold et al., 2001a; Yucel et al., 1994).