Characterization of <i><scp>B</scp>acillus altitudinis</i> as a New Causative Agent of Bacterial Soft Rot

Abstract

Abstract A total of 67 bacterial isolates were obtained from apple and pear fruits with signs of soft rot collected from E gyptian markets. Pathogenicity tests showed that 25 isolates (37%) were pathogenic to apple and pear fruits, with considerable variation of virulence. Among these isolates, 16 (64%) were Gram‐positive, motile, spore‐forming long rods and were identified as members of the genus B acillus based on an API test. In addition, five isolates (20%) were Gram‐negative, non‐spore‐forming, motile, oxidase and catalase‐positive short rods and were identified as members of the genus P seudomonas . Furthermore, four isolates (16%) were Gram‐negative, non‐spore‐forming, motile, catalase‐positive and oxidase negative short rods and were identified as belonging to the genus E rwinia . All selected isolates showed a wide host range and could cause soft rot of all representative fruits and vegetables tested. The three most virulent isolates, AB 4, AB 6 and PB 6, exhibited the highest soft rot severity on different apple and pear cultivars, and apple cv. A nna (116) was the most susceptible to infection by isolates AB 4 and AB 6, with soft rot severities of 63.33 and 60.67%, respectively. Also, pear cv. L e‐ C onte was most susceptible to infection by isolate AB 6, with a soft rot severity of 89.9%. A phylogenetic tree based on 16 S r RNA gene sequences indicated that strains AB 4 and AB 6 were very similar to one another and also showed a similarity of 99% to B acillus altitudinis , and strain PB 6 revealed a similarity of 99% to B acillus pumilus . To our knowledge, this is the first report of B . altitudinis as a soft rot pathogen for both apple and pear fruits.