A total DNA clone bank of a strain of @entity17847 . malvacearum (Xcm) was constructed in the cosmid vector pSa747 and transfected into @entity526 . The Xcm strain carries at least nine identifiable avirulence (A) genes. Clones in @entity526 were mated individually into a recombination-proficient Xcm isolate carrying no known A genes. Screening was for incompatibility on congenic @entity2708 host lines that differ by single specific resistance (R) genes. Ten different cosmid clones conferring race-specific avirulence were recovered. In most cases, the same A gene clone was recovered independently several times. Using the congenic host lines and the merodiploid transconjugant pathogen strains, five of the A genes were shown to specifically interact, gene-for-gene, with individual R genes in the congenic @entity2708 lines. Some A/R gene interactions appeared qualitatively different from others, suggesting that the physiological mechanism(s) of gene-for-gene specified incompatibility may be unique to the interactive gene pair. All A genes appeared to be chromosomally determined, three were found linked on a single 32-kilobase clone, and the rest were spaced more than 31 kilobases apart. Colinearity of the cosmid inserts with the Xcm recipient (carrying no known A genes) chromosome was demonstrated in two of the three tested. This and other evidence suggests that at least some A genes in bacteria may have the equivalent of virulence (a) alleles. The genetics of race specificity in this phytopathogenic bacterium appeared in all respects to be identical to that found in phytopathogenic fungi.

Gene-for-gene interactions of five cloned avirulence genes from @entity17847 . malvacearum with specific resistance genes in XXXX .

@entity17847 :: ('339', 'Species') :: ['Xanthomonas campestris pv'] @entity2708 :: ('3635', 'Species') :: ['cotton'] @entity526 :: ('562', 'Species') :: ['Escherichia coli', 'E. coli']
@entity2708 :: (3635,Species) :: ['cotton']
