The Quantitative Genetics of Prescutellar Bristles in Melon Fly, ＂Bactrocera cucurbitae＂ (Coquillett)

瓜實蠅［＂Bactrocera cucurbitae＂ (Coquillett)］中胸背板剛毛之數量遺傳機制

鄭允(Yun Cheng) ； 王志賢(Chih-Hsien Wang) ； 黃毓斌(Yu-Bing Huang) ； 江明耀(Ming-Yao Chiang)

《台灣農業研究》 63卷3期 (2014/09) Pp. 179-187

https://doi.org/10.6156/JTAR/2014.06303.01

摘要

野生瓜實蠅［＂Bactrocera cucurbitae＂ (Coquillett)］中胸背板之剛毛數（prescutellar bristles; ＂prsc＂）有95%個體為2，此外尚有少數個體為0-4隻剛毛，合計約5%。為瞭解此多型態（polymorphism）之控制機制，以室內汰選方式進行2-prsc及4-prsc單一形態型品系之純化，經過一百代以上，仍無法選出，反而在4-prsc汰選中觀察到有更多剛毛個體的出現。而2-prsc之汰選結果平均數為2.0 ± 0.7，範圍為1–3；4-prsc之結果平均數為4.0 ± 0.4，範圍為1-7，因此再汰選多剛毛品系，所得結果為平均數為12.7 ± 2.3，範圍為8-19。所有汰選均得到由一系列連續分布的多形態個體所組成之族群，此等多形態型組成有可能為數量遺傳（quantitative genetics）機制所造成。因此，進行遺傳測試求證，以2-prsc為父本，分別與12-prsc及14-prsc之母本雜交出F_1子代後再自交成F_2子代，計算其prsc不同數目型之個體數，求取平均值、標準誤差及分布範圍。F_1與F_2平均值以t-test進行差異顯著度測試，結果發現下列四項數量遺傳之佐證：（1）兩項測試之F_1平均剛毛數分別為4.7及5.0，均介於原父本及母本之間；（2）兩項測試之F_2平均剛毛數分別為4.7及5.1，在t-test顯示與F_1之平均值相同無顯著差異；（3）F_2子代剛毛數變異係數（Coefficient of variation）均較F_1子代者為大，分別為40.1% ＞ 19.5%及45.9% ＞ 21.7%；（4）F_2子代剛毛數分佈之兩端極端可達父本及母本之範圍，分別為2-15 prsc及1-17 prsc。本研究與1913年Emerson及East之玉米穗長度數量遺傳之經典測試結果均能吻合。因此，推論瓜實蠅中胸背板剛毛數之控制機制為數量遺傳，也與另一雙翅目之Drosophila屬剛毛數控制機制為數量遺傳相同。

關鍵字

瓜實蠅 ； 中胸背板剛毛 ； 數量遺傳分析 ； 數量策略

並列摘要

The polymorphism of prescutellar bristles (＂prsc＂) in melon fly, ＂Bactrocera cucurbitae＂ (Coquillett), was investigated by artificial selection of phenotypes and quantitative genetic analysis. In the wild strain, generally more than 95% population have 2 ＂prsc＂ while some may have 4 ＂prsc＂. By selection, however, a group of phenotypes was appeared with the number of ＂prsc＂ reach up to 14 and more. All multiplied bristles were randomly arranged in a region of posterior half of ＂scutum＂ and between the lateral ＂vita＂. The quantitative genetic analysis was conducted by crossing two strains of different phenotypes, one from each strain. In each cross only one virgin male and one virgin female were paired, with a total of 6 pairs in each experiment, and 200-500 offsprings from each experiment were examined for their phenotypes. For each cross, only one 2-＂prsc＂ individuals (the major component of the wild population) and one 12-＂prsc＂ or 14-＂prsc＂ individuals from the selected strains were interbred, and then inbred F_1 for the F_2 progeny. The results showed that for 2-＂prsc＂ × 12-＂prsc＂, the F_1 progeny constituted a group of phenotypes with different ＂prsc＂ numbers, and the mean was 4.7 ± 0.9 which was in-between two parental phenotypes. The mean of ＂prsc＂ in F_2 is 4.7 ± 1.9. The difference between the means of F_1 and F_2 is insignificant in the t-test (P ＞ 0.05). For 2-＂prsc＂ × 14-＂prsc＂, the F_1 progeny constituted a group of phenotypes, with the mean of 5.0 ± 1.0 which was in-between their parental phenotypes. The F_2 offsprings had their mean at 5.1 ± 2.3. The t-test indicated no significant difference between the means of F_1 and F_2 (P ＞ 0.05). Moreover, as the coefficients of variation of F_2 were higher than those of F_1 (40.1% ＞ 19.5% versus 45.9% ＞ 21.7%), it suggests that more variability around the mean of F_2 than that of F_1. The extreme values in ＂prsc＂ for F_2 were extended to the range of their parental values (2-15 ＂prsc＂ and 1-17 ＂prsc＂, respectively) than did the extreme values of F_1. Results of this study were similar to that reported by Emerson & East (1913), indicating that the ＂prsc＂ of melon fly is a continuous and quantitative trait in inheritance.

並列關鍵字

＂Bactrocera cucurbitae＂ ； Prescutellar bristles ； Quantitative genetic analysis ； Quantitative trait