Development of near-isogenic lines of Japonica-type rice variety Lijiangxintuanheigu as differentials for blast resistance

Abstract

Twenty near-isogenic lines (NILs) of rice (Oryza sativa L.) containing 11 blast resistance genes (Pib, Piz-5, Pi9, Pi3, Pia, Pik-s, Pik, Pik-h, Pi7(t), Pita and Pita-2) were developed by recurrent backcrossing of 19 donor varieties to a susceptible Japonica-type variety, Lijiangxintuanheigu (LTH). The resistant plants were selected in each backcross generation using a specific avirulent blast isolate for each targeted resistance gene. The NILs showed similar reaction patterns to those of the corresponding resistance-containing monogenic lines (MLs) when challenged with 20 standard blast isolates from the Philippines, suggesting that the target resistance genes were successfully introduced. The introgression of the targeted resistance genes was further confirmed by SSR markers that were located within the chromosome regions where the resistance genes had previously been mapped. Genome surveys using SSR markers showed that the NILs had genetic compositions more similar to that of the recurrent parent LTH than did the MLs, which had been derived using fewer backcrosses to LTH. The morphological characteristics of each NIL were generally similar to those of LTH. These NILs, with the genetic background of a Japonica-type variety, are expected to be valuable genetic tools for research and breeding programs for blast resistance.