Emergence of a new Xanthomonas oryzae pv. oryzae (Xoo) pathotype breaking the earlier resistance gene combination of improved Sambha Mahsuri
DOI:10.37992/2025.1602.025
Abstract
Bacterial Leaf Blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) continues to be a major threat to rice (Oryza sativa L.) production. The present study was conducted during Kharif seasons 2022-2024 to investigate the virulence of the Raipur Xoo isolate against a set of 28 Near Isogenic Lines (NILs) of IR24 introgressed with various combinations of BLB resistance gene along with local check Bamleshwari, resistant check Improved Sambha Mahsuri, and susceptible check TN-1. The results of artificial inoculation based BLB screening over the three years revealed that most single gene differentials (NILs) lines performed poorly against the Raipur Xoo isolate, where the most frequent resistance reactions ranged from susceptible to highly susceptible indicating the high virulence of the Raipur Xoo isolate. However, among the single gene NILs, the recessive gene xa5 showed relatively stable performance with moderate resistance across the three years. In contrast, NILs possessing two or more resistance genes exhibited improved and more stable resistance, particularly combinations involving xa5, xa13, Xa21, and Xa4. Notably, genotypes such as IRBB-60, IRBB-66, and IRBB-64 consistently displayed moderate to high resistance, emphasizing the advantage of gene pyramiding in conferring durable resistance. Interestingly, the susceptible reaction of the Improved Sambha Mahsuri having three major BLB resistance gene xa5+xa13+Xa21 during Kharif 2024 was against the resistance reaction during Kharif 2022 which further indicated the evolution of the pathogen towards virulence. This highlights the inherent dynamic nature of Xoo and its ability to overcome the existing BLB resistance genes. These findings substantiate the need for continuous monitoring of the pathogen virulence and search for new sources of BLB resistance gene.
Keywords: BLB; Marker Assisted Selection; Resistance breakdown; Artificial inoculation
Emergence of a new Xanthomonas oryzae pv. oryzae Xoo pathotype breaking the earlier resistance gene combination of improved Sambha Mahsuri
. 2025. Electronic Journal of Plant Breeding, 16 2, 197-205. Retrieved from https://ejplantbreeding.org/index.php/EJPB/article/view/5319It is certified that:
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