Abstract:

【Objective】 The characteristics of soluble sugar content of 70 varieties of sand pear mature fruit (including 47 local species and 23 cultivars) and the dynamic changes during the fruit development period (4 varieties) were studied and the differences and characteristics among sand pear varieties were compared. 【Method】Capillary GC-FID was used to detect the constitution of soluble sugar in sand pears. 【Result】 The major parts of organic acids in sand pears are malic acid and citric acid, which induce two types, malic acid dominant and citric acid dominant. The content of malic acid ranges from 1.30 mg?ml-1 to 4.16 mg?ml-1, with a mean value of 2.32 mg?ml-1. Compared with the local cultivars, the extent of variation is narrower and the quantity is bigger in cultivars. Citric acid ranges from 0.43 mg?ml-1 to 6.20 mg?ml-1, with a mean of 2.03 mg?ml-1; on the contrary, the concentration in cultivars is lower than that in local cultivars. Quinic acid in mature sand pears is as low as 0.74 mg?ml-1 (mean), with no difference between cultivars and local ones. The total content of organic acids in sand pear fruits is coming down with the development of fruit. Especially, the quinic acid drops significantly in any breed. The accumulation process of malic acid shows a parabola-like rise-and-fall motif. In the two kinds of acid dominant breeds being investigated, the content of citric acid remains low in early development. In citric acid dominant breeds, the content of citric deposits rapidly in 8 weeks after blossom fall, while in malic acid dominant breeds, it keeps in a low concentration, both of the two kinds of breeds have a great content diversity during fruit maturation.【Conclusion】There are two types of sand pears, malic acid dominant and citric acid dominant. Almost exclusively, cultivars are malic acid dominant, while local cultivars are citric acid dominant. The concentration of citric acid rises when that of malic acid drops.

Key words: sand pear(Pyrus pyrifolia), germplasm resource, organic acids