水稻台農67號突變品系對褐飛蝨之反應及抗性遺傳之探討

Response and genetic analysis of brown planthopper resistance in rice mutants of the TNG67 variety

以疊氮化鈉（NaN_3）化學誘變所建立之水稻臺農67號（TNG67）突變庫之突變品系為試驗材料，利用秧苗集團檢定法篩檢其對褐飛蟲之反應，第一次誘變之突變品系，對褐飛蝨之生理小種1、2、3，分別有9.6-12.5%、3.4%及7.7%之突變品系，呈現3級以上之抗性反應，其中SA0006、SA0038、SA0080、SA0088、SA0159及SA0283等6個品系，對三個生理小種皆呈抗性;第二次誘變處理的突變品系，則有19.22-25.99%對生理小種1具有抗性，顯示以疊氮化鈉誘變可使不抗褐飛蝨的TNG67後裔產生抗虫性，且比率頗高。將抗性突變品系SA0006、SA0285與不抗褐飛蝨的TNG67、台硬2號（TK2）品種雜交，針對其F_2族群或BC_1 F_1進行抗性之遺傳分析，其抗、感分離比，經X^2分析皆呈3:1或1 : 1，符合一對顯性基因控制之擬說。以抗褐飛蝨之SA0006、SA0007、SA0236、SA0283、SA0284及SA0285等六個突變品系分別與同為抗性之Mudgo及Babawee品種雜交，檢定其F_2族群之表現，結果12個組合的F_2族群，皆呈現明顯抗、感分離;顯示，此6個突變品系之抗蟲基因型應與Mudgo（Bph1）或Babawee（bph4）不同。將上述六個抗褐飛蝨突變品系，分別與感蟲的TNG67及抗蟲的台農69號進行半互交，針對其F_3族群進行褐飛蝨抗性檢定，結果發現以TNG67為母本之組合除了TNG67 / SA0235組合的感蟲率達88%外，其餘組合的感蟲率約佔四分之一，近似由一對顯性基因所控制之性狀表現;在抗蟲品種（系）互交的組合中，有21個組合的F_3品系呈現抗、感分離現象，顯示二親本應具不同的抗性基因;而其中7個組合的F_3系統皆呈抗性，可能二親本的抗性基因型相同。這些抗褐飛蝨之水稻突變體將成為基因選殖及抗蟲育種之重要材料。

"Pure line mutants from the mutation pools of the TNG67 rice variety derived from seed mutagenesis using sodium azide were subjected to brown planthopper (BPH) challenge by the bulk-seedling method. About 9.6%.12.5%, 3.4%, and 7.7% of the mutants from the first mutation pool showed resistance (score ≦ 3) to Race 1, Race 2, and Race 3 of BPH, respectively. Among them, 6 mutants (SA0006, SA0038, SA0080, SA0088, SA0159, and SA0283) were resistant to all races of BPH tested. In the second mutation pool, about 19.2%-26.0% of mutants showed resistance to BPH Race 1. Our experiments demonstrated that sodium azide produced a significant mutagenesis effect on inducing resistance to TNG67, a BPH-susceptible variety, at a rather high rate. A genetic study of BPH resistance of mutants SA0006 and SA0285 was conducted by crossing to the susceptible varieties TNG67 and TK2; the segregation of resistant (R) to susceptible (S) progenies in F_2 or BC_1F_1 was 3:1 and 1:1, respectively, suggesting that the resistance was controlled by a single dominant gene. Significant segregations were observed in the F2 of crosses made between the resistant mutants (SA0006, SA0007, SA0236, SA0283, SA0284, and SA0285), Mudgo (Bph1), and Babawee (bph4) indicating that their resistant genes are distinct. BPH responses in F_3 of half-diallelic crosses made among 6 BPH-resistant mutants and 2 varieties, TNG67 (S) and TNG69 (R), showed that all crosses derived from TNG67 as their mother parents produced only 1/4 susceptible progeny, except that of SA0235 (88%), indicating that a single dominant gene was individually involved. Segregation of the BPH response was found in 21 F_3 populations of crosses made between the resistant lines suggesting that the resistant genes of parents differ; however, progeny of 7 populations were all resistant to BPH, indicating that parents have the same resistant genotype. The BPH-resistant mutants obtained in this experiment provide good resources for resistant gene cloning and for breeding BPH-resistant rice varieties."