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Studies on the Genetic Similarity and Heterosis of Chinese Cabbage (Brassica campestris L. ssp. pekinensis) Inbred Lines
|關鍵字:||Chinese cabbage;結球白菜;Genetic similarity;Genetic distance;Heterosis;Molecular markers;RAPD;AFLP;遺傳相似度;遺傳距離;雜種優勢;分子標誌||出版社:||園藝學系||摘要:||
本試驗利用園藝性狀及RAPDs與AFLPs二種分子標誌，分析結球白菜( Brassica campestris L. ssp pekinensis )自交系之遺傳相似度及探討結球白菜自交系之遺傳距離與雜種優勢之關係。
試驗調查19個結球白菜之園藝性狀；RAPDs以六組引子 (primers) 獲得69個標誌 (條帶)，其中52個條帶具多型性；AFLPs則利用六個引子組 (primer combination) 共獲得381個標誌 (條帶)，包括280個條帶具多型性。利用此三種方法分析結球白菜自交系之遺傳相似度及親緣關係，結果發現對於極相似之同群內的自交系，如C群之‘C2-7’及‘C2-9’、B群之‘B-11’及‘B-18’，E群之‘E-7’、‘E-9’及‘FL-9’ 及N群之‘N4-1’、‘N4-2’及“N5-3’等自交系，雖然遺傳相似度數值不同，但同群內自交系彼此間的關係卻頗為一致。但在遺傳相似度較低的自交系間，此種現象則較不明顯，則顯示出園藝性狀及不同分子標誌在分析遺傳相似度上的差異性。
利用‘C2-7’、‘C2-9’、 ‘N4-1’、‘N4-2’、‘E-9’與‘PL-1’等六個結球白菜之自交系，進行半互交法(methods of half-diallel cross)，分析組合力與雜種優勢，探討遺傳距離與雜種優勢之關係。結果顯示結球白菜自交系間具明顯的雜種優勢。進一步分析各組合親本間之遺傳距離與雜種優勢之相關性，得知適中的遺傳距離才能獲得最大的雜種優勢，而一般組合力之大小，無法完全決定雜種優勢之結果。如球重之平均值、特殊組合力、雜種優勢及雜種潛勢與三種遺傳距離與間皆呈現二次函數 (Y＝a＋bx＋cx2) 關係。其中除平均值外均以AFLP遺傳距離與相關介量之相關性最佳，如特殊組合力及雜種優勢與AFLP遺傳距離間均呈極顯著的二次關係，雜種潛勢則呈顯著二次關係。
Horticulture traits, RAPDs and AFLPs are used to analyzed the genetic similarity of Chinese cabbage (Brassica campestris L. ssp pekinensis) inbreds and their results are used to study the relationship between the genetic distance of inbreds and their heterosis (H1).
Nineteen horticulture traits were selected for characteristics analysis in genetic similarity. Sixty nine markers (bands) were obtained by using RAPDs with six primers of which fifty-two markers showed polymorphism. Three hundred eighty one markers were acquired by AFLPs from six set primer combination, including 280 polymorphic bands. The genetic similarity and genetic relationship among Chinese cabbage inbreds by using these genetic markers analysis, showed same kind of result which indicated that inbreds had high similarity should be grouped in the same group, such as ‘C2-7' and ‘C2-9' in group C, ‘B-11' and ‘B-18' in group B, ‘E-7', ‘E-9' and ‘FL-9' in group E, ‘N4-1', ‘N4-2' and ‘N5-3' in group N. The genetic distance among inbreds without consistence would be by using the three genetic markers analysis lower in their similarity.
Half-diallel corsses of six inbreds ‘C2-7', ‘C2-9', ‘N4-1', ‘N4-2' ‘E-9' and ‘PL-1' are used to study their combining ability and heterosis as well as the relationship between genetic distance and heterosis. Significant heterosis was observed in all cross combination. Further analysis of the relationship between genetic distance and heterosis among the parental combination, indicated that only the inbreds with appropriate genetic distance could be the best cross combination and generate the highest heterosis. A general combining ability could not completely decide the magnitude of heterosis. The relationship between average weight, SCA, heterosis and heterobeltiosis of cabbage head and the genetic distance showed quadratic curve (Y=a+bx+cx2). However, the genetic distance obtained AFLP markers was the most efficient compute the quadratic curve than other methods because of significant correlations with AFLP distance for SCA, heterosis (0.01) and heterobeltiosis (0.05) of cabbage head.
Evaluation of the relationship between heterosis force and the genetic similarity, found that genetic distance in between 0.624 to 0.626 in using horticulture traits lead to the largest heterosis. Genetic distance using RAPD and AFLP molecular markers indicated that the greatest heterosis would occurs between 0.171 to 0.177 and 0.304 to 0.337, respectively. Experimental result proved that genetic distance, general combining ability and specific combining ability would act together and influence the F1 occurrence of heterosis.
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