Pericarp Pigment Changes and Correlations with Soluble Sugar and Titratable Acid Content in Plum Fruits with Different Colors During Maturation

Fruits from cultivars ‘Dahongli’ with red,‘Naili’with green and ‘Friar’with black skin were picked every 7 days from the beginning of maturation(June to Augest).The contents of anthocyanin,chlorophyll and carotenoid in peel and the contents of soluble sugar,titritable acid in flesh were measured,then the difference of pigment changes among different colour cultivar fruits and correlation with soluble sugar and titratable acid contents in flesh during maturation were compared.The results showed that during maturation,for 'Friar' and 'Dahongli'the contents of anthocyanin and chlorophyll showed the trend of constant rise and slightly drop respectively,but for ‘Nali’ were respectively very low and little change,and rise first then down.The carotenoid contents were slowly rising among three cultivars.The chlorophyll and carotenoid contents in ‘Naili’ were always significant or most significant higher than in the other two cultivars,but the anthocyanin content was significant or most significant lower than in them.For 'Dahongli'and 'Friar',anthocyanin content and soluble sugar content showed a significant and positive correlation,and titritable acid content was significant or very significant negative correlation;carotenoid content and soluble sugar content was a significant positive correlation,and the correlation between that and acid content showed not consistent;chlorophyll content and sugar or acid content no significant correlations were observed.For ‘Naili’,each kind of pigment content and sugar or acid content showed not significant correlation.These suggested that the fruit color for cultivars 'Dahongli'and 'Friar'may be determined by the concentration of anthocyanin,but for'Nali'by carotenoid and chlorophyll concentrations.