桃品種間同功異構酶變異性之研究

Study on Isozyme Variation in Malate Dehydrogenase and 6-phosphogluconate Dehydrogenase of Peach

本試驗利用澱粉膠體電泳探討56個桃品種之MDH及PGD同功異構酶變異性，其中MDH共有六種階型（A，A’，B，C，C’，D），低溫需求量高之品種中，有42.4%屬於MDH-B，而低溫需求量少之品種中，則有67%屬於MDH-A.分析MDH的遺傳顯示A和C是同一基因座上的兩個共顯性因子。MDH-D型品種之開放授粉後代分離為A，D及C型。MDH-B型（大久保，白鳳）和MDH-A型（Okinawa，Flordared）雜交可產生A,D,或A,C，或A,B型之後代，有些MDH的條帶可能是受某種修飾因子作用的結果。PGD在土用品種屬於一條型，其他調查過的16個品種均屬於兩條型，進一步分析MDH基因型可能有助於瞭解該酵素與低溫需求性狀的關係。

Isozyme variation in 56 peach varieties was investigated using starch gel electrophoresis. Malate dehydrogenase (MDH) and 6-phosphogluconate dehydrogenase (PGD) were found to be polymorphic. Six banding types (A,A',B,C,C’, and D) were observed in MDH. 42.4% of high chilling requirement varieties belonged to MDH-B type, while 67% of low chilling varieties belonged to MDH-A type. Genetic analysis of variable MDH types revealed that A (and probably A') anc C (and probably C') were two alleles of a single locus controlling MDH expression. MDH-D was a heterozygote which segregated into types A,D, and C. A cross between MDH-B (Okubo or White Phoenix) and MDH-A (Okinawa or Flordared) produced either A, D or A, C, or A, B types. Modification in some MDH isozymes of peach was suggested from this study. PGD showed less variable as compared to MDH. Further characterization of MDH gene(s)may be helpful in elucidating its relationship with chilling requirement in peach.