Journal of Food, Agriculture and Environment

Sucrose and citric acid accumulations in melon genotypes with different sugar and acid contents

Author(s):

Mi Tang ^{1, 3}, Bao-cai Zhang ¹, Jun-jun Xie ¹, Zhi-long Bie ¹*, Ming-zhu Wu ², Hong-ping Yi ², Jong-xin Feng ²

Recieved Date: 2012-06-20, Accepted Date: 2012-09-24

Abstract:

‘Flavor No.4’, a novel Hami melon genotype with a distinct flavor, accumulates moderate sugar and acid contents in ripe fruits, enhancing its flavor and palatability. The patterns of sucrose and citric acid accumulation in ‘Flavor No.4’ and its parents during fruit development were investigated and compared in the present study. The outcomes reveal that the increase in total soluble solids and titratable acidity in ‘Flavor No.4’ fruit resulted from the accumulation of sucrose and citric acid, respectively. The sucrose concentration in ‘Flavor No.4’ was similar to that in the female parent ‘Shouxing’, a high-sugar genotype, and higher than that in the male parent ‘Suangua’, a high-acid genotype. The citric acid concentrations in mature fruits of ‘Flavor No.4’ and its male parent were significantly higher than those in the female parent. The expression of the sucrose phosphate synthase (SPS, EC 2.4.1.14) gene in the three genotypes increased as the fruit developed, but slightly decreased after a certain period. SPS activity continued to increase. Sucrose and SPS activity were significantly correlated in ‘Flavor No.4’ (r = 0.849**, P < 0.01) and ‘Suangua’ (r = 0.828*, P < 0.05), but not in ‘Shouxing’ (r = 0.482, P > 0.05). Therefore, sucrose accumulation may be related to the expression of the SPS gene and the SPS activities in the first two genotypes. However, sucrose accumulation in ‘Shouxing’ started when AI activity decreased beyond a threshold value. Interestingly, ‘Flavor No.4’ and ‘Suangua’ had higher enzyme activity in citric acid metabolism than ‘Shouxing’, which suggests that the operation of the Krebs cycle is elevated in acid-accumulating genotypes, which increases citric acid content. 

Keywords:

Melon, sucrose, citric acid, gene expression, enzyme activity

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 3&4
Category: Food and Health
Pages: 225-231

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