Pyramiding resistance genes for bacterial leaf blight (Xanthomonas oryzae pv. Oryzae) into the popular rice variety, Pratikshya through marker assisted backcrossing

Abstract

Background: Bacterial leaf blight (BLB) is one of the major biotic stress in rice cultivation. Management techniques, such as the development of BLB-resistant cultivars, are required to lessen the severity of the disease attack and yield losses. Pratikshya was selected in the present investigation as the recipient parent, as it is one of the popular high-yielding rice varieties of Odisha, India, which is having excellent grain as well as cooking quality. However, Pratikshya is highly susceptible to BLB which is prevalent in Eastern Indian region.

Methods and results: Three major BLB resistance genes xa5, xa13, and Xa21 from the donor source Swarna MAS (CR Dhan 800) were attempted to introduce into Pratikshya through a marker-assisted backcross breeding program. Those markers closely linked to the target genes were employed for foreground selection in the segregating generations till BC₂F₃. In each backcross generation, progenies containing all three targeted resistance genes and phenotypically more similar to the recipient parent, Pratikshya were selected and backcrossed. Screening of 1,598 plants of the BC₂F₂ population was conducted against BLB using Xoo inoculum and 35 resistant plants similar to Pratikshya were carried forward to the next generation. In the BC₂F₃ generation, 31 plants were found to possess all the three resistance genes. For background selection of plants carrying resistance genes 45 polymorphic SSR markers were employed. Evaluation of the pyramided lines at BC₂F₄ generation exhibited that, most pyramided lines were similar to Pratikshya in terms of morphological features and yield parameters, and some lines were superior to the recurrent parent in terms of morphological features and yield parameters.

Conclusion: The three-gene pyramided lines showed a high level of resistance to BLB infection and are anticipated to offer a significant yield advantage over the recipient parent Pratikshya. The pyramided lines can further be used for multi-location trial, so as to be released as a variety or can be used as a potential donor for BLB resistance genes.

Keywords: Bacterial leaf blight; Gene pyramiding; Marker-assisted backcrossing; Molecular markers; Rice.