بررسی تنوع ژنتیکی جدایه‌های باکتریایی عامل سوختگی باکتریایی شمعدانی به روش BOX-PCR

Bacterial blight and leaf spot caused by Xanthomonas hortorum pv. pelargonii is one of the most important pathogens in geranium plants. In 2020 and 2021, 22 bacterial strains were isolated from symptomatic geranium plants showing blight and leaf spot symptoms in Fars, Isfahan, Markazi, Tehran, Alborz, and Kohgiluyeh-Boyer-Ahmad provinces. Sequencing of housekeeping genes (gyrB and lepA) showed that these strains belong to X. hortorum pv. pelargonii. To investigate the genetic diversity of bacterial strains obtained in this study, they were subjected to BOX-PCR-based fingerprinting analyses using BOX-A1R primer. Reference strain of X. hortorum pv. pelargonii (ICMP 24701) and pathotype strain of X. hortorum pv. gardneri (ICMP 16689PT) were also included in the analyses. Ten microliters of PCR products were run on 1.5% agarose gel. Cluster analysis was performed by using the simple matching similarity coefficient, while unweighted pair group with arithmetic mean (UPGMA) was calculated using NTSYS-PC software v. 2.02e. The genetic diversity analysis with BOX-A1R primer produced four to eight fragments in size that ranged from 0.3 to 3 kb. Similarity coefficients ranged from 86% to 100%. Cluster analysis using a cutoff level at 86% of similarity yielded two major clusters I (IA and IB) and II. Cluster IA encompassed10 strains, four strains isolated in Fars Province, two strains eachf rom Isfahan and Kohgiluyeh-Boyer-Ahmad provinces, and one strain each from Alborz and Markazi provinces. Cluster IB consisted of two strains isolated from Fars and Tehran provinces. Ten strains were grouped within cluster II, five of which were isolated in Fars Province, two strains each from Alborz and Tehran, and one strain from Isfahan. The reference strain of X. hortorum pv. pelargonii (ICMP 24701) was grouped in cluster II. However, the pathotype strain of X. hortorum pv. gardneri (ICMP 16689PT) clustered separately from all X. hortorum pv. pelargonii strains, with 68% similarity coefficient. The use of the BOX-A1R primer in this research revealed that X. hortorum pv. pelargonii isolated from different provinces in the country exhibited a low genetic diversity. This finding suggests a possible homogeneity in the genetic makeup of the pathogen across geographical locations within the country.