Bacterial Spot of Tomato and Pepper on Four East Caribbean Islands: Races, Their Abundance, Distribution, Aggressiveness, and Prospects for Control
- Leonard W. O'Garro , Microbial Pathogenicity Research Group, Department of Biological and Chemical Sciences, University of the West Indies, Cave Hill Campus, P.O. Box 64, Bridgetown, Barbados
A total of 5,134 strains of Xanthomonas campestris pv. vesicatoria obtained from diseased pepper and tomato fruits at 22 diverse locations on the East Caribbean islands of Antigua, St. Christopher, St. Lucia, and Grenada were assessed for pathogenicity, taxonomic group phenotypes, and sensitivity to copper, zinc, and streptomycin. Altogether, 15 known races, namely T1, T2, P0T1, P0T2, P1T1, P1T2, P2T1, P2T2, P3T1, P3T2, P4T2, P5T2, P5T3, P6T2, and P6T3, were detected. Races T1, P0T1, P0T2, P1T2, P2T1, and P3T1 were common to all islands except St. Lucia. St. Lucia had races P2T2, P3T2, P4T2, and P6T2 in common with Grenada and two races each from among the four pathotypes in common with Antigua and St. Lucia. Races T1, P1T2, P3T1, and P3T2 were the most abundant strains of the bacterium in Antigua, whereas the two latter pathotypes, as well as races P0T1 and P2T1, were among the most prevalent strains in St. Christopher. In contrast, races P6T2 and P5T2 predominated in St. Lucia, and P6T2, P1T2, and P3T2 were the abundant pathotypes in Grenada. Generally, the largest bacterial spot fruit lesions were associated with the predominant races on each island, and the smallest lesions were generally linked to races capable of overcoming gene Bs2. Only these latter races were similar to group B strains of X. campestris pv. vesicatoria with respect to the presence of β-protein in their cellular protein profiles, ability to hydrolyze starch, and inability to oxidize cis-aconitate. Other race types tested resembled group A strains of the bacterium in their ability to utilize cis-aconitate, inability to hydrolyze starch and pectate, and the presence of the α-protein in profiles of cellular proteins. Copper-resistant strains of X. campestris pv. vesi-catoria constitute 8.7 to 10.6% of the pathogen collections from Antigua and St. Christopher and 44.4 and 66.7% of pathotypes from St. Lucia and Grenada, respectively. Almost all strains were sensitive to zinc. Streptomycin resistance was observed among 62% of the strains in St. Christopher and Grenada and 62.8 to 83.6% of those in Antigua and St. Lucia.