Fruit Section-drying Regulating Techniques Of Late-maturing Navel Orange And Analysis Of Related Genes’ Expression

Section-drying phenomenon in citrus fruits has a strong impact on fruits’ edible and economic value, therefore, to find the mechanism of fruit section-drying and the effective solution is imperative. In this study, Lane Late navel orange(Citrus sinensis Osbeck ‘Lane Late’)and Cara cara navel orange(Citrus sinensis Osbeck ‘Cara Cara’) were used as materials to be conducted by some regulating techniques, such as bagging, canopy-film-covering, quantitative spraying hormones by installments and irrigating in flower-fruit contemporary period, discussing these techniques’ influence on fruit section-drying situation and fruit quality; Furthermore, the expression of some genes related to Section-drying, such as gene PME, PG, Cx, PAL, CAD and POD were analyzed by Semi-quantitative PCR. The mechanism of fruit section-drying phenomenon was preliminary analyzed and the main results showed as follow:1.The quality and section-drying status of late-maturing navel orange collected from different altitudes were studied, the result showed that when altitude was higher than 300 meter, the fruit section-drying phenomenon was very obvious and it became worse. Moreover, the content of Vc and titratable acid was decreased distinctly and some fruits dropped. It is clear that altitude(low temperate) has direct impact on section-drying phenomenon and fruit quality and it’s the main factor for section-drying phenomenon.2.It was clear that the fruit drop rate and the degree of section-drying of late-maturing navel orange processed by bagging, canopy-film-covering, 2,4-D and irrigating reduce effectively. The fruit quality was improved, it could be promoted to improve quality and yield.3.The results of Semi-quantitative PCR revealed that the expression of gene PME gradually increased and gene PG and Cx decreased gradually as the growth of processing time. These genes all related to cell wall degradation. Gene PAL, CAD and POD increased. Preliminary ascertain the expression of related genes under drought and cold stress4.The results of Semi-quantitative PCR displayed that the expression model of related gene as section-drying accentuated was very similar to the situation of water and cold stress. That is, the expression of PME increased, PG decreased; Cx decreased; PAL, CAD and POD decreased. It made the expression of related genes under different section-drying degree more explicit, moreover, it confirmed that water and cold stress were the main factors for section-drying, applying reference to regulating techniques.5.Results from comprehensive analysis for section-drying of late-maturing navel orange according to the function of related genes, find that the expression of had been changed under the water and cold stress, one hand, accumulating high molecular weight de-methyl ester poly galacturonic acid, When there was a certain amount of de-methyl ester poly galacturonic acid and Ca2+, it would become gel. On the other hand, it will slow the decomposition speed of cellulose and hemicellulose, and thicken cytoderm secondary wall’s secondary growth continuously. Meanwhile, when the speed of synthesizing lignin was faster than breaking down lignin, lignin would accumulate in the cell wall, leading to cell wall lignification, harden and section-drying.