| Summary: | 碩士 === 國立中興大學 === 園藝學系所 === 98 === The objective of this study was to compare differences in fruit characteristics and sugar metabolism during development between climacteric and non-climacteric guavas. Results indicated that all the guava cultivars analyzed had higher sucrose and fructose contents than glucose. Determination of activities of sugar metabolism related enzymes during fruit growth and development showed that with the raising of sucrose content, sucrose synthase and sucrose phosphate synthase activities also increased. The cumulative amount of fructose and glucose increased more rapidly during the late stage of fruit maturation and the neutral invertase activity also increased. However, the acid invertase activity showed non-significant difference. As a result, the sucrose synthase and sucrose phosphate synthase should be the key enzymes for sucrose accumulation in guava fruits during development, while neutral invertase may be related to the accumulation of hexoses.
With the treatment of ethephon, it resulted in the decrease in titratable acid and firmness of guava fruits and also turned the skin of fruit from dark green to yellow-green or white-green. However, fruit weights and total soluble solids were not affected by the ethephon treatment. The ethephon treatment on climacteric guava fruits, ''Huang Bar'' and ''Pakistani'', caused an increase in sucrose content, while on non-climacteric guava fruits, ''Jen-Ju Bar'' and ''Shy-Jii Bar'', the sucrose content had no significant difference. In addition, the hexose contents in non-climacteric guava fruits were increased by the ethephon treatment, which indicated that sugar metabolism mechanism may be different between climacteric and non-climacteric guava fruits during ripening stage.
After analyzing the climacteric guava cultivars, ''Huang Bar'', ''Pakistani'', ''Li Bar'', and non-climacteric cultivars, ''Jen-Ju Bar'', ''Shui-Jing Bar'', ''Shy-Jii Bar'', by RAPD (Random Amplified Polymorphism DNA), the dendrogram showed that non-climacteric cultivars was in the same cluster and ''Jen-Ju Bar'' and ''Shy-Jii Bar'' had the highest similarity of 0.90. In addition, OPN-15, OPR-11, OPW-7 and OPU-1 all generated a polymorphic band in climacteric cultivars, which was not found in non-climacteric cultivars. Those bands could be used to analyze the hybrid progenies from crosses between the alove cultivars.
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