栽培稻台稉14號帶抗稻熱病基因Piz-t之探討

Identification of blast resistance gene Piz-t in a rice cultivar Taikeng 14

栽培稻台稉14號於1996年由桃園區農業改良場推出，在臺灣各地對稻熱病呈現中等抗性。為探討台稉14號所帶抗病基因，本研究以台稉14號與感病水稻LTH雜交所得之450個F2子代，透過接種本土稻熱病菌菌株12YL-TT4-1評估抗性，並針對主要抗稻熱病基因座Pi2/9、Pik與Pita/Pita-2設計分子標誌，進行基因型鑑定與連鎖分析，結果顯示台稉14號帶有Pi2/9基因座的顯性單基因抗性；進一步以該基因座上已發表的抗病基因序列設計引子對進行定序，定序結果顯示台稉14號帶有Pi2的等位基因Piz-t。此外，分別以稻熱病菌12CY-MS1-2、12YLTT4-1及13TN-HB1-3等菌株，接種帶Pi2/9基因座內單一抗病基因的LTH單基因系判別品系：IRBLz5-CA（R）（Piz5=Pi2）、IRBLz5-CA（Piz5=Pi2）、IRBL9-W（Pi9）、IRBLzt-T（Piz-t）與IRBLz-Fu（Piz），確認台稉14號在Pi2/9基因座之抗性係來自Piz-t，而非Pi2、Pi9或Piz。然IRBLzt-T（Piz-t）在各地區稻熱病圃的抗性檢測結果為感病，顯示Piz-t對台灣主要稻熱病菌群之抗性已失效，故推測台稉14號的田間抗性應來自Piz-t以外之基因。

"The rice cultivar Taikeng 14, released by Taoyuan District Agricultural Research and Extension Station in 1996, has exhibited moderate resistance to rice blast in many areas around Taiwan. To identify the resistance gene, a population of 450 F2 progeny from the cross of Taikeng 14 and the susceptible cultivar LTH was developed and used for linkage analysis. The F2 plants were inoculated with a local Magnaporthe oryzae isolate 12YL-TT4-1, and genotyped with newly developed markers targeting three major blast resistance gene loci Pi2/9, Pik, and Pita/Pita-2. Trait-marker association suggested a single dominant resistance gene at Pi2/9. Sequencing analysis by the primers designed based on known R genes at Pi2/9 revealed that Taikeng 14 carries Piz-t. Inoculations of M. oryzae isolates 12CYMS12, 12YL-TT4-1, and 13TN-HB1-3 on the LTH monogenic lines each carrying a single R gene at Pi2/9, including IRBLz5-CA(R) (Piz5=Pi2), IRBLz5-CA (Piz5=Pi2), IRBL9-W (Pi9), IRBLzt-T (Piz-t), and IRBLz-Fu (Piz), further confirmed that the resistance of Taikeng 14 comes from Piz-t, but not Pi2, Pi9, or Piz. However, IRBLzt-T (Piz-t) showed susceptible phenotype in different blast nurseries, indicating that Piz-t is ineffective against the M. oryzae population in Taiwan. In Taikeng 14, field performance of moderate resistance is likely due to gene(s) other than Piz-t."