Marker Assisted Introgression of Resistance Genes and Phenotypic Evaluation Enabled Identification of Durable and Broad-Spectrum Blast Resistance in Elite Rice Cultivar, CO 51

Abstract

Across the globe, rice cultivation is seriously affected by blast disease, caused by Magnaporthe oryzae. This disease has caused heavy yield loss to farmers over the past few years. In this background, the most affordable and eco-friendly strategy is to introgress blast-resistant genes from donors into elite rice cultivars. However, it is not only challenging to evolve such resistance lines using conventional breeding approaches, but also a time-consuming process. Therefore, the marker-assisted introduction of resistance genes has been proposed as a rapid strategy to develop durable and broad-spectrum resistance in rice cultivars. The current study highlights the successful introgression of a blast resistance gene, i.e., Pi9, into CO 51, an elite rice cultivar which already has another resistance gene named Pi54. The presence of two blast resistance genes in the advanced backcross breeding materials (BC2F2:3) was confirmed in this study through a foreground selection method using functional markers such as NBS4 and Pi54MAS. The selected positive introgressed lines were further genotyped for background selection with 55 SSR markers that are specific to CO 51. Consequently, both Pi9 as well as Pi54 pyramided lines, with 82.7% to 88.1% of the recurrent parent genome recovery, were identified and the selected lines were evaluated under hotspot. The analysis outcomes found that both the lines possessed a high level of resistance against blast disease during the seedling stage itself. In addition to this, it was also noticed that the advanced breeding rice lines that carry Pi9 + Pi54 were effective in nature and exhibited a higher degree of resistance against blast disease compared to the lines that were introgressed with a single blast resistance gene. Thus, the current study demonstrates a rapid and a successful introgression and pyramiding of two blast resistance genes, with the help of markers, into a susceptible yet high-yielding elite rice cultivar within a short period of time. Those gene pyramided rice lines can be employed as donors to introgress the blast-resistant genes in other popular susceptible cultivars.