Effect of some biotic and abiotic factors on soft-rot bacteria (Pectobacterium carotovorum subsp. carotovorum) on Potato plants

Document Type : Original Article

Authors

1 Bacterial Diseases Research Department, Plant Pathology Research Institute, Agricultural Research Center, Giza, Egypt

2 Central Agricultural Pesticides Laboratory, Agricultural Research Center, Giza, Egypt

Abstract

The effectiveness of some biocontrol agents (Pseudomonas fluorescens and Trichoderma viride) and organic acids (acetic acid and boric acid) against soft rot bacteria Pectobacterium sp. were studied under laboratory and field conditions. Two soft rot bacterial isolates Pectobacterium carotovorum subsp. carotovorum Pcc and Pectobacterium carotovorum subsp. carotovorum Pcc160 (Acc. No. LN811442) were used in this study. Pcc isolate was isolated from Potato tuber (Burn variety), Pcc and Pcc160 isolates caused soft rot symptoms of potato. PCR was used to identify the Pcc isolate molecularly using universal primers for 16S rRNA. The PCR products' DNA sequence, BLAST analysis, and Genbank data revealed that the Pcc isolate belonged to Pectobacterium carotovorum sub sp. carotovorum. According to the phylogenetic tree based on the DNA nucleotide sequences of the 16s rRNA gene, the Egyptian isolate resembles the Chinese isolate (OQ727369) closely. In vitro acetic acid showed the strongest effect against Pcc and Pcc160 isolates with inhibition zones 41.33 and 33.67 mm and MIC 50 and 100 μg/mL respectively. Scanning electron microscope showed distinct inhibitory effect of acetic acid and T.viride on the growth and survival of P.c. subsp. carotovorum (Pcc). In vivo experiment T. viride treatment was the most effective, where it caused a reduction of disease severity index (DSI). Acetic acid and T. viride were evaluated for their efficacy in inducing defense enzymes, total soluble protein, phenols and salicylic acid (SA) content in potato against P. c. subsp. carotovorum (Pcc). The activity of defense enzymes [peroxidase (POD) and phenylalanine ammonia lyase (PAL)], total soluble protein content, polyphenols content and salicylic acid (SA) content were found to be increased in T. viride treated potato plants in both seasons compared to other treatments. The results of this study demonstrate that T. viride showed effective inhibitory activity against Pcc, thus T. viride could have potential application in controlling P. c. subsp. carotovorum.

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