Effects Of Calcium Fertilizer Spraying On Blueberry Quality And Pectin Degradation

In this experiment,blueberry cv.‘O’Neal’ fruits were used as experimental materials to study the degradation of pulp pectin and related enzymes(polygalacturonase PG,pectin methyl esterase PME,beta-galactosidase β-gal)during the development and post-harvest stages.The effect of exogenous calcium fertilizer on fruit quality and pectin degradation was studied.The results are as follows:(1)To spray calcium fertilizer on blueberry plant and optimize the spraying scheme.First,the spray time was screened.The results showed that calcium fertilizer applying in all three stages showed better effect than any others.Based on the spraying scheme optimization result,the calcium fertilizer sources and the concentrations were investigated.The results showed that 1.5 g/L calcium nitrate had a prominent effect on increasing the size of ripe fruits and improving the firmness of pulp.The effect of 0.9 g/L saccharide alcohol chelating calcium on improving the size of ripe fruit and reducing the content of titratable acid was outstanding.The effect of 0.3 g/L amino acid chelating calcium on improving ascorbic acid content and reducing anthocyanin content of mature fruits was outstanding.EDTA chelated calcium 0.9 g/L had the best effect on improving the firmness of ripe blueberry pulp and reducing the content of titrable acid.(2)The degradation of pectin in blueberry fruits post-harvest treated by calcium was investigated.The results showed that the content of covalently bound pectin increased during fruit development.The PME activity,ion-bound pectin and NaCl-soluble calcium gradually increased from fruit coloration.When fruits were ripen and harvested,fruit firmness decreased,PG and beta-gal activity increased,PME activity reached a peak,water-soluble pectin and water-soluble calcium content increased gradually,and covalently bound pectin content decreased.In the calcium treatment,the fruit firmness post-harvest was delayed significantly.Meanwhile,the NaCl-soluble calcium content was higher than that of the control fruits during fruit developing,and the transformation of pectin morphology was delayed.PG,PME and ?-gal activity was inhibited to varying degrees by calcium.(3)The PG1/2,PME1/2 and GAL1/2 genes of blueberry pulp were cloned and the gene expression was analyzed.Gene expression results showed that exogenous calcium inhibited the expression levels of PG1/2 and GAL2 during fruit developing,and significantly inhibited the expression of PME1 and GAL1 when post-harvested.Calcium-spraying inhibited PGs expression and sequentially delayed pectin degradation.In addition,the expression of PG2 and PME1 was the dominant factor in the role of PG and PME in blueberry pulp.