Abstract
Blast, a disease caused by Magnaporthe oryzae, is a major constraint for rice production worldwide. Introgression of durable blast resistance genes into high-yielding rice cultivars has been considered a priority to control the disease. The blast resistance Pik locus, located on chromosome 11, contains at least six important resistance genes, but these genes have not been widely employed in resistance breeding since existing markers hardly satisfy current breeding needs due to their limited scope of application. In this study, two PCR-based markers, Pikp-Del and Pi1-In, were developed to target the specific InDel (insertion/deletion) of the Pik-p and Pi-1 genes, respectively. The two markers precisely distinguished Pik-p, Pi-1, and the K-type alleles at the Pik locus, which is a necessary element for functional genes from rice varieties. Results also revealed that only several old varieties contain the two genes, of which nearly half carry the K-type alleles. Therefore, these identified varieties can serve as new gene sources for developing blast resistant rice. The two newly developed markers will be highly useful for the use of Pik-p, Pi-1 and other resistance genes at the Pik locus in marker-assisted selection (MAS) breeding programs.
Highlights
Rice blast disease, caused by Magnaporthe oryzae, is a major constraint for rice production in the world
PCR fragments corresponding to the two regions of Pi-1, Pik-p, Pi-k, Pik-m, Pik-h, Pik-s, and non-functional N-type alleles were amplified from rice monogenic lines IRBL1-CL-Pi1, IRBLkp-K60-Pik-p, IRBLk-Ka-Pik, IRBLkm-Ts-Pik-m, IRBLkh-K3-Pik-h, IRBLks-S-Pik-s, and Nipponbare with specific primers for the Pikp-Del and Pi1-In markers, respectively
Electrophoretic analysis showed that the band-type of Pik-p and Pi-1 were different from the others, and the N-type from Nipponbare had invisible PCR product (Fig. 1D)
Summary
Rice blast disease, caused by Magnaporthe oryzae, is a major constraint for rice production in the world. More than 100 resistance (R) genes have been found, and at least 28 of these genes have been successfully cloned (Deng et al 2017; of blast R genes that have been reported to confer durable and broad-spectrum resistance ( Chen et al 2016; Deng et al 2017; Wang et al 2017) One such cluster is the Pik locus on chromosome 11, which has been commonly considered to be the major locus in control of rice blast disease since it contains at least 6 identified blast R-genes, including Pi-1 (Hua et al 2012), Pik-h (Zhai et al 2014), Pi-k (Zhai et al 2011), Pik-m (Ashikawa et al 2008), Pik-s (Wang et al.2009), and Pik-p (Yuan et al 2011). Previous studies have shown that many R-genes from the
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