Distribution and pathotype identification of Xanthomonas citri subsp. citri recovered from south-western region of Saudi Arabia

Abstract

We investigated the distribution of Xanthomonas citri subsp. citri (Xcc) pathotypes in southwestern region of Saudi Arabia. A total of 76 Xanthomonas like strains were isolated from different citrus species showing bacterial canker symptoms from citrus commercial farms, backyard orchards and nurseries. These strains were subjected to biochemical, molecular and pathogenicity tests on leaves of grapefruit (Citrus paradisi). Based on symptoms induced on leaves of grapefruit, these strains were divided into two groups. There were 21 strains that induced typical erumpent canker lesions with watersoaked margin, belonging to Xcc type A. On the other hand, strains that produced flat necrotic lesions with water-soaked margin on grapefruit leaves belonged to Xcc A* type (55 strains). The physiological and biochemical tests, ImmuneStrip ® assays and 16S rDNA analysis confirmed the identity of the two Xcc pathotypes: A and A*. Our results indicate that, the two pathogenic variants co-exist in southwestern region of Saudi Arabia and this could further favour the generation of new genetic variants through recombination and horizontal genetic exchange. The generation of new aggressive pathotypes may threaten the citrus plantation in Saudi Arabia.

Characterization of Xanthomonas citri pv. citri from the western and south‐western regions of Saudi Arabia based on CRISPR typing

“…Our recent findings (Pruvost et al, 2022) confirmed the first report by Al Saleh et al (2014) regarding the presence of Pathotype A in Saudi Arabia. On the contrary, spoligotypes of Pathotype A Lineage 2 in Saudi Arabia may indicate that this lineage has been well adapted to the environmental conditions in Saudi Arabia.…”

“…Since the first report of Xcc in the Jazan region of Saudi Arabia in the 1980s (FAO, 1983), several studies regarding the aetiology of the disease have been conducted (Al Saleh et al, 2014; Vernière et al, 1998). The occurrence of Pathotypes A and A* in Saudi Arabia was previously suggested by Al Saleh et al (2014). However, Ibrahim et al (2019) indicated that accurate genotyping data were needed to determine whether or not Pathotype A occurs in Saudi Arabia.…”

“…The second pathotype of Xcc in Saudi Arabia is Pathotype A*. This pathotype is well known to be present in the Middle East and Saudi Arabia (Al Saleh et al, 2014) and some other countries, including South‐west Asia, Thailand, Cambodia (Bui Thi Ngoc et al, 2007, 2008) and Ethiopia (Derso et al, 2009). In Saudi Arabia, the distribution of Pathotype A* is wider than Pathotype A.…”

“…Citrus bacterial canker (CBC) is considered one of the most severe diseases harming the citrus industry. It is now prevalent in many hot, humid citrus‐growing locations worldwide, including Saudi Arabia (Al Saleh et al, 2014; Graham et al, 2004). CBC has a broad host set, including citrus species and relatives in commercial groves and nurseries and also backyard trees found in private properties (Gottwald et al, 1993).…”

“…To date, Oman is the only country in the Arabian Peninsula with all three pathotypes of Xcc. Meanwhile, Al Saleh et al (2014) suggested that both Pathotypes A and A* occur in Saudi Arabia. A recent study used a detached leaf assay to confirm some diversity in pathogenicity on grapefruit among Saudi Arabian strains.…”