Genetic Variability of Xanthomonas citri pv. citri in South Punjab, Pakistan

Abstract

Background. Citrus is an important nutritious fruit that belongs to the family Rutaceae, comprising a large group of trees and shrubs. Citrus constitutes about 40% of all fruits grown in Pakistan. The total contribution of kinnow, grown in Pakistan, in the international market is US$ 222 million. In Pakistan, citrus production has been recorded up to 2.0 million metric tons. There are multiple abiotic and biotic factors involved in the low productivity of citrus in the country. Moreover, citrus canker (caused by the pathogen Xanthomonas citri pv. citri) has been the major threat for citrus production in Pakistan for the last 10 years. The current study aims to document the disease incidence of citrus canker along with the characterization of citrus canker causal organism. Method. Samples exhibiting disease symptoms (such as small pimple-like spots about 1 mm in diameter and yellow in colour) were collected from the target areas. After isolation and purification, the samples were subjected to PCR analysis for molecular identification and characterization through SDT and MEGA11 software packages. Results. A total of 112 samples were collected from different sites in South Punjab, Pakistan. The bacterial colonies were small and yellow in color, which turned pink after staining. Bubble formation was also observed after conducting biochemical tests. Genetic analysis showed that Xanthomonas citri pv. citri Multan isolate has 98.91% nucleotide identity with Indian, Korean, Chinese, and South African isolates. Conclusion. The study underlines the emerging pathogen population of citrus canker that could help to manage this disease.