(32(3):201-208)Studies on the Improvement of Blast Disease Resistance of Japonica Rice, Tainung 67

為改良臺農67 號之稻熱病抵抗性，於民國68 年第二期作開始以抗稻熱病品種TKM-6 , Ml-48 , Dawn , Tetep , carreon , Shensho 及Dular 等為父本與臺農67 號雜交，後以臺農67 號為輪迴親本進行一系列之回交，以便將抗病基因導入於臺農67 號。其中Dawn , Tetep 及Carreon 有關三組合之BC1F1乃以磨傷法點接稻熱病菌4 個生理小種ID-14 , IE-2 , IF-3 及IG-2 於葉片上，檢驗其對4 小種之抵抗性。Dawn 組合BC1F1之分離比顯示，對IG-14 及IG-2 之抵抗性似各由一對基因所控制，而對IE-2 則有3 對，IF-3 有2 對基因參與。在Carreon 組合之BCIFI 對ID-14 及IG-2 似各有一對，對IE-2 及IF-3 似各有3 對基因參與。Tetep 組合的BC1F1則似乎比前兩組合有較多的抗病基因參與。對ID-14 及IG-2 之抗病性各有2 對，對IE-2 及IF-3 各有4 對基因參與。又Tetep 組合之BC2F1在病圃有較多的抗病系統出現，顯示Tetep 乃具有多數抗病基因之優良抗病種源。經人工接種選拔及病圃篩選選得之植株繼續回交至第3 、4 次，由其後代系統中，已選得多數抗病且株型優良之系統，其中部分已成立為品系參加產量比較試驗；同時亦進行BC4F1間之複交，再以花藥培養法做配偶子型之選拔，預期將可選育抗病性較廣且又高產之稉稻新品種。 Rice variety Tainung 67 which occupied 454,620 hectares of rice area in 1982 in Taiwan is known to have a lower degree of resistance to blast disease (Pyricularia oryzae Cav. ). In order to correct this defect, Tainung 67 was crossed to varieties, Tetep, Carreon, Dawn, M1-48, TKM-6, Shensho and Dular as the resistance source. The F1’s were then backcrossed to Tainung 67 three or four times. The BC1F1’s of three crosses, TNG 672 /Dawn, TNG 672 /Carreon and TNG 672/Tetep were inoculated with 4 races of the blast fungus that attacked Tainung 67, namely, ID-14, IE-2, IF-3 and IG-2 in the 2nd crop season, 1980. Based on the segregation patterns of bast disease resistance in the BC1F1’s, it is concluded that the resistance of Dawn to races ID-14 and IG-2 seems to be controlled by a single dominant gene, to race IE-2 by 3 pairs and to race IF-3 by 2 pairs of gene, while the resistance of Carreon to races ID-14 and IG-2 seems to be controlled by a single dominant gene and to IE-2 and IF-3 by 3 pairs of gene. However, Tetep’s resistance to races ID-14 and IG-2 seems to be controlled by 2 pairs of gene and to races IE-2 and IF-3 by 4 pairs of gene. The main purpose of this experiment was to introduce resisatnce genes of Tetep, Carreon, etc. into Tainung 67. To understand the mode inheritance of resistance in the early segregating generations of these crosses will facilitate our further efforts. The resistant BC1F1 plants selected from the above-mentioned test were again backcrossed to Tainung 67 three or four times and the BC2F1’s and BC4F1’s were grown in a blast disease nursery for continuous selection