Characterization of Pantoea agglomerans associated with shot hole, canker and gummosis in peaches and plums from the Northwestern Himalayan region of India

Abstract

Peaches and Plums are one of the most important stone fruit crops in the world and equally consequential in India. Surveys were carried out in peach and plum orchards during the years 2022 and 2023. Infected orchards of peach and plum trees showed an incidence of shot holes, cankers, and gummosis ranging from 51.25% to 88.95%. Typical symptoms included small yellow spots on the leaves that eventually turned purplish-brown and necrotic, leading to shot holes, as well as cankers and gummy exudates on the twigs. The associated bacterium was isolated that produced yellow, flat colonies with smooth margins on nutrient agar. Morphological and biochemical tests confirmed that the bacterium was Gram-negative and belonged to the Enterobacteriaceae family. After the screening of bacterial isolates by standard cultural and biochemical tests, the isolates were molecularly characterized by PCR amplification and sequencing of partial 16S rRNA, gyrB, and leuS. Pathogenicity tests by twig method and in vivo bacterial injection method, produced similar symptoms as observed in the field. Based on morphological, biochemical, molecular and pathogenicity studies the causal organism was identified as Pantoea agglomerans. To the best of our knowledge, this is the first report of P. agglomerans causing shot hole, canker, and gummosis on stone fruits in India. These findings will help in formulating effective management strategies against new emerging pathogens of stone fruits.