An xa5 Resistance Gene-Breaking Indian Strain of the Rice Bacterial Blight Pathogen Xanthomonas oryzae pv. oryzae Is Nearly Identical to a Thai Strain

Abstract

The rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo) constrains production in major rice growing countries of Asia. Xoo injects transcription activator-like effectors (TALEs) that bind to and activate host "susceptibility" (S) genes that are important for disease. The bacterial blight resistance gene xa5, which reduces TALE activity generally, has been widely deployed. However, strains defeating xa5 have been reported in India and recently also in Thailand. We completely sequenced and compared the genomes of one such strain from each country and examined the encoded TALEs. The two genomes are nearly identical, including the TALE genes, and belong to a previously identified, highly clonal lineage. Each strain harbors a TALE known to activate the major S gene SWEET11 strongly enough to be effective even when diminished by xa5. The findings suggest international migration of the xa5-compatible pathotype and highlight the utility of whole genome sequencing and TALE analysis for understanding and responding to breakdown of resistance.

Novel broad‐spectrum bacteriophages against Xanthomonas oryzae and their biocontrol potential in rice bacterial diseases

“…The rice cultivar Zhonghua 11 was used as the test material and was propagated in Hoagland's nutrient solution. Rice seedlings were grown in a growth chamber (BINGLIN ELEC-TRONIC CO., Ltd, ZRG-350C-L, Shanghai, China) maintained at 28 C, with an 85% relative humidity and a photoperiod of 12 h (Carpenter et al, 2020). Rice plants grown for 20-30 days up to more than five leaves were used for subsequent trials (Chen et al, 2010).…”

TALEs as double-edged swords in plant–pathogen interactions: Progress, challenges, and perspectives

“…Still, some strains can break through xa5 -mediated resistance in nature. An xa5 -compatible strain contains a PthXo1 homolog that can induce expression of OsSWEET11 even in the presence of xa5 ( Carpenter et al., 2020 ). Other studies showed that TFIIAγ1, the homolog of TFIIAγ5, is recruited by some TALEs to upregulate target genes in the host ( Ma et al., 2018b ).…”