Stability of Four New Sources of Bacterial Leaf Blight Resistance in Thailand Obtained from Indigenous Rice Varieties

Abstract

Bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious diseases in rice production. Breeding varieties specifically for their resistance to BLB disease is therefore an efficient and cost-effective strategy. However, the resistance gene for BLB can be race and non-race specific, meaning it is often overcome by the pathogen. The identification of new sources of resistance genes for Xoo is crucial in rice breeding programmes. In this study, six rice varieties were assessed using six Xoo isolates in multiple screening conditions. The GGE biplot analysis considers both genotype (G) and genotype environment (GE) interaction effects and demonstrates GE interaction. The first two principal components (PCs) accounted for 95.46% of the total GE variation in the data. Based on lesion length and stability performance, Phaladum was the most ideal genotype against all Xoo isolates in the four screening conditions. The results relayed that Phaladum indigenous rice varieties could be considered as new sources of bacterial leaf blight resistance in Thailand. In the future, the BLB resistance gene in this variety will be identified in regard to mode of inheritance and used as parental line in rice breeding programmes for resistance to BLB.

Phenotypic Broad Spectrum of Bacterial Blight Disease Resistance from Thai Indigenous Upland Rice Germplasms Implies Novel Genetic Resource for Breeding Program

“…The results indicated a positive correlation between the resistance scores from mixed inoculation and natural infection (Table 2). In addition to the plant-pathogen interaction, environmental factors, such as relative humidity [26,30,58] and temperature [59,60], play a part in BB disease incidence and epidemiology, referred to as the disease triangle (Figure S1), [61]. These results follow the influence of environmental factors on optimal conditions for BB disease incidence reported by Sribunrueang et al [26].…”

“…In this study, the screening of BB resistance in the single Xoo strain inoculation experiment under greenhouse conditions, with the MS1-2 or NY1-1 isolate, revealed the BB resistance in more than 150 cultivars among 256 tested indigenous upland rice cultivars (Figure 3). Moreover, there was the positive correlation between the lesion lengths of individual cultivars in response to the MS1-2 and NY1-1 isolate (Figure 4), demonstrating the correspondence of host plants' reactions to two different virulent Xoo isolates as investigated on indigenous lowland rice cultivars by Sombunjitt et al [36] and Sribunrueang et al [26]. This presumably suggests whether the individual host plants possess the analogous resistance genes [37,38] or that the two examined Xoo isolates own the analogous avirulence genes [39], resulting in greater similarities in the physiological and morphological responses [31,40].…”

“…The Xoo inoculum was prepared as suspension by mixing bacterial colonies grown on nutrient agar with sterile distilled water. The final concentration of Xoo suspension was adjusted into OD 600 = 0.60 using a spectrophotometer [26]. Inoculated plants were further grown in the greenhouse under a mist nozzle.…”