脐橙晚熟突变体“奉晚”与原品种“奉节 72-1”的果实着色差异(英文)

Fruit Coloration Difference Between Fengwan, a Late-Maturing Mutant and Its Original Cultivar Fengjie72-1 of Navel Orange (Citrus sinensis Osbeck)

测定了果实成熟过程中“奉晚”和“奉节72．1”两个脐橙（Citrus sinensis L．Osbeck）品种果皮中叶绿素和总类胡萝卜素的含量，并采用RT-PCR技术研究了相关酶的基因表达。结果表明：“奉晚”脐橙果皮中叶绿素含量的显著降低发生在11月份，“奉节72．1”则发生存10月中下旬到11月上旬；“奉晚”脐橙果皮中的总类胡萝卜素含量显著积累始于12月中旬，而“奉节72.1”品种则始于11月初。另外，“奉晚”脐橙果皮中叶绿素含量在10～11月显著高于原品种，总类胡萝卜素含量在12-1月显著低于原品种。从基因表达分析结果看到，“奉晚”脐橙果皮中与类胡萝卜素合成酶相关的基因较强表达的时间也整体迟于“奉节72．1”脐橙；叶绿素水解酶基因表达在10～12月中旬表达较“奉节72—1”弱，翌年1月份则较“奉节72．1”强。

Fruit color is one of the most important external quality traits. Mutants with different color are useful for the study of regulating mechanism of coloration progress. A novel mutant, Fengwan, derived from Fengjie72-1 navel orange （Citrus sinensis L. Osbeck）, has the distinctive characteristic of the coloration delay of 30 d or so, with the change in total soluble solid （TSS） and the ratio of TSS/acidity. In order to understand the mechanism underlying the difference of coloration between the mutant and the parental variety, the chlorophyll and carotenoid contents in the peel of two cultivars at different maturation stages were analyzed. The expression of genes responsible for some carotenoid biosynthetic enzymes （phytoene synthase, phytoene desaturase, ξ-carotene desaturase, β-1ycopene cyclase, β-carotene hydroxylase） and chlorophyllase using the RT- PCR technique were also studied. The distinct decrease of chlorophyll in the peel of Fengwan navel orange occurred from early November to late November, about three weeks later than that of its original cultivar. Obvious accumulation of carotenoid in the peel of the mutant began on Dec. 12, while that of the original cultivar began on Nov. 3. Analysis of independent-samples t-test showed that the chlorophyll content of the peel of Fengwan navel orange from October to November was significantly higher, and the carotenoid content from December to January was significantly lower than that in the peel of the parental line, Fengjie72-1 navel orange. The expression of chlorophyllase gene in the peel of Fengwan navel orange reached a maximum in January and kept at a slightly lower level from October to December than that of Fengjie 72-1 orange, while the time of gene expression about some carotenoid biosynthetic enzymes reaching a maximum in the peel of the mutant were one month later than that of the original cultivar.