| 摘要： 酸度為影響番石榴果實風味的重要因素之一，瞭解果實酸度在基因型間可能的變異範圍有助於果實相關性狀的育種應用。本研究的目的即在探討所收集之番石榴基因型及由一更年性紅肉品系66-90與一非更年性白肉品系M3雜交所衍生的F2後代在果實酸度相關性狀包括果汁pH值和可滴定酸的變異情形，並以SSR標記建構遺傳連鎖圖譜和定位果實酸度相關性狀之數量性狀基因座。結果顯示果實酸度相關性狀在番石榴基因型間有相當大的變異。所有測試的基因型中以Psidium acutangulum的酸度最高，而‘帝王拔’與其他測試的品種如‘珍珠拔’相比有相對較高的酸度。另外比較冬果和夏果果汁酸度，發現冬果的酸度一般高於夏果。而果實酸度在全年各月份間的變化，以‘西瓜拔’為例，酸度最高在十月到二月間，六至七月間則較低。至於F2族群，果實的pH值、可滴定酸含量以及糖酸比均呈常態分布，顯示這些性狀為數量遺傳，同時也找到超親表現的個體。此外，果汁pH值、可滴定酸含量和糖酸比彼此之間具有顯著的相關性。以176組具有多型性的SSR標記用於建構番石榴遺傳連鎖圖譜，共得到14條連鎖群，全長1263.5 cM，標記平均間隔為9.6 cM。進一步使用多數量性狀基因座定位(multiple QTL mapping)法，共定位到了4個數量性狀基因座，包含可滴定酸含量和維生素C含量相關數量性狀基因座各一個以及pH值相關數量性狀基因座二個，且酸度相關數量性狀基因座上的標記能區分高酸與低酸果實的基因型，維生素C含量相關數量性狀基因座上的標記也能區分維生素C含量高和低果實的基因型。Acidity is one of the important factors affecting the flavor of guava fruit. Understanding the possible variation of fruit acidity among genotypes is helpful in breeding for related fruit traits. The purpose of this study was to investigate the variations of fruit acidity-related traits including fruit juice pH value and titratable acid content among guava genotypes collected and the F2 progeny derived from the cross between a red-flesh, climacteric line, 66-90, and a white-flesh, non-climacteric line, M3. A genetic linkage map using SSR markers was also constructed to map QTLs for fruit acidity related traits. The results showed that the fruit acidity related traits had a considerable variation among the guava genotypes. Among all of the tested genotypes, Psidium acutangulum had the highest acidity, while ‘Diwang Ba’ had a relatively high acidity compared with other tested varieties such as ‘Jen-Ju Bar’. Comparing the juice acidity of winter fruits and summer fruits, the acidity of winter fruits is higher than that of summer fruits. Regarding the changes of fruit acidity during the year, taking ‘Shi Gua Ba’ as an example, the acidity is highest between October and February and relatively low between June and July. As for the F2 population, the pH value, titratable acid content and sugar-acid ratio of the fruits are normally distributed, indicating that these traits are quantitatively inherited. Individuals with transgressive performance were also found. In addition, the pH value, titratable acid content of the fruit juice and the sugar to acid ratio showed significant correlations with each other. A genetic linkage map of guava was constructed by 176 polymorphic SSR markers. The linkage map contains 14 linkage groups spanning a total length of 1,263.5 cM, with an average of 9.6 cM between markers. Furthermore, four QTLs were indentified using multiple QTL mapping method. These include one for titratable acid content, one for vitamin C content, and two for pH value. The markers from acidity-related QTLs were able to distinguish F2 progeny with different acidity levels by their genotypes. The marker from vitamin C-relatd QTL was also able to distinguish F2 progeny with different fruit vitamin C contents by their genotypes. |
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