Development of a molecular marker platform for the breeding of rice blast resistance multiline varieties

Rice blast, caused by Magnaporthe oryzae, is the most important disease commonly occurring in the first crop season in Taiwan. This disease can cause considerable damage in every rice-producing areas. Use of blast resistant varieties is an effective and environmental-friendly method for blast control. The emerging marker-assisted selection (MAS) approach, which can significantly reduce the time needed for the development of new resistant varieties, has become a new trend in rice resistance breeding. In Taiwan, most high-quality rice varieties are with good agronomic traits but lack of blast resistance. The resistance can be improved using this technology. In this study, we used 13 IRRI-bred blast-resistant lines (IRBLs, each carrying a known blast resistance gene effective against more local isolates of M. oryzae) and 20 high-quality rice varieties to develop a marker-assisted backcrossing platform, consisting of 11 polymorphic R gene markers and 95 background selection markers used in Fluidigm high-throughput genotyping. Two M. oryzae isolates were used to determine which Taiwan varieties would be suitable recipients for the 13 R alleles. The result showed that Taikeng 4, Taikeng 9, Taikeng 10, Taikeng 14, Taikeng 15, Tainung 71, Taiyuan 3, Tainan 11, Kaohsiung 145, and Kaohsiung 147 do not carry the R alleles at Pi9 (IRBL9-W), Piz5 [IRBLz5-CA, IRBLz5-CA (R)], Piz (IRBLz-Fu), Pi1 (IRBL1-CL), Pi7 (IRBL7-M), Pik (IRBLk-Ka), Pik-p (IRBLkp-K60), Pik-m (IRBLkm-Ts), Pik-h (IRBLkh-K3), Pi20 (IRBL20-IR24), and Pita-2 (IRBLta2-Pi, IRBLta2-Re). The 13 IRBLs and newly developed markers could be used to improve blast resistance of the 10 high-quality rice varieties. Meanwhile, the marker platform and backcross breeding strategy were utilized to introduce the resistance genes from 10 IRBL lines to Kaohsiung 145. To date, BC2F2 progenies were obtained from the crosses of “IRBLta2-Pi x KH145”, “IRBL9-W x KH145”, “IRBLkp-K60 x KH145”, and “IRBLkh-K3 x KH145”, with the highest background recovery rates of 80.51%, 94.08%, 97.27%, and 95.54%, respectively. For the crosses of “IRBL7-M x KH145”, “IRBLk-Ka x KH145”, “IRBLz5-CA x KH145”, “IRBLz5-CA(R) x KH145”, “IRBL20-IR24 x KH145”, and “IRBLta2-Rex KH145”, BC1F2 progenies were obtained. The work is expected to result in the development and deployment of a Kaohsiung 145 multiline variety carrying various blast resistant genes.