Bacterial diversity in potential cicadellids vectors of Xylella fastidiosa Wells et al. in coffee plants in Puerto Rico

Abstract

Bacteria from head and body tissues of three potential insect vectors of Xylella fastidiosa (Xf), Apogonalia spp., Hortensia similis and Caribovia coffeacola, were isolated in periwinkle wilt (PW) medium. They were characterized by fatty-acid methyl esters into 19 genera, which were divided into four groups according to insect tissue: Curtobacterium, Micrococcus and Pasteurella were identified only in the head; Brevundimonas, Paenibacillus, Pantoea, Providencia, Rhizobium and Vibrio were identified from internal tissues; Acinetobacter, Chryseobacterium, Clavibacter, Kluyvera, Kokuria, Nocardia, Pectobacterium and Pseudomonas were identified in the external tissues; Bacillus and Microbacterium were isolated from all tissues. The majority of these bacteria have been reported as biological control agents against many pests, and others as pathogenic bacteria in different hosts. The only genus previously reported antagonistic to Xf is Curtobacterium, which was isolated from the insect H. similis. Bacteria from coffee plants showing leaf curling and grown on the same farms where insects were collected, were isolated in periwinkle wilt medium. These isolates were identified into nine genera using BIOLOG®.The most frequent genera were Bacillus, Micrococcus and Staphylococcus. Less frequent were Arthrobacter, Chryseobacterium, Clavibacter, Enterobacter, Rhizobium and Sphingobacterium. Most of these genera have been reported as endophytic bacteria in other crops. Bacteria common in both insects and plants were Bacillus, Chryseobacterium, Clavibacter, Micrococcus and Rhizobium. All Gram negative bacteria were tested for the presence of Xf by the ELISA test. Four isolates from C. coffeacola and H. similis were positive to Xf when using ELISA, but it was not possible to isolate the bacterium in periwinkle wilt medium for final confirmation.