ABSTRACT
Bacterial blight of cotton is caused by Xanthomonas campestris pv malvacearum (X. m.), and affects all plant parts resulting in leaf defoliation and thus yield loss. Naturally infected plant tissues were collected from several regions in Texas, and X. m. was isolated and race identified. The identification of races of the pathogen are based an disease reactions of a set of ten host differentials. This study was conducted to determine the major races of X. m. in cotton under natural infestation. Race 18 was the predominant race isolated from tissues at Weslaco, Coastal Bend Counties and Hill County. Race 11 was identified from diseased tissues at Edroy and Stiles Farm. Earlier reports indicated that races 1 and 2 were the predominant ones. A shift has occurred in race distribution in Texas with the most virulent X. m. race 18 currently identified in several cotton growing regions in Texas.
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