Identification and Characterization of Xanthomonas axonopodis pv. dieffenbachiae: The Causal Agent of Bacterial Blight in Taro

Abstract

Taro, a versatile crop grown under diverse and adverse climatic conditions, is susceptible to several fungal, bacterial, and viral pathogens. Among these, bacterial leaf blight caused by Xanthomonas axonopodis pv. dieffenbachiae (Xad) is a major disease, leading to severe damage and significant losses to crop growth and yield. The disease primarily affects the foliage, resulting in reduced productivity.  Initial disease symptoms appear as small, star-shaped, water-soaked spots that later expand into V-shaped, irregular brown necrotic patches surrounded by a yellow margin, especially in dry weather. The bacterial isolates were Gram-negative, small rod-shaped cells and exhibited close similarity to Florida strains of Xad, as confirmed through morphological characterization, biochemical tests, pathogenicity assays and molecular analysis, and field emission scanning electron microscopy (FESEM). FESEM imaging revealed the isolates as short rod-shaped cells measuring 572.26–614.21 nm in width and 1071.05–1275.23 nm in length. Timely and accurate identification of the pathogen is critical for implementing effective management strategies and enabling prompt application of control measures for sustainable and profitable cultivation of Taro.