套袋对富士芽变优系果皮色泽及花青苷合成相关酶活性的影响

Effects of bagging on peel color and activities of enzymes related to anthocyanin synthesis of Fuji bud mutation

【目的】研究富士芽变优系果皮色泽、花青苷及相关酶活性的关系,分析果皮着色的变化规律及生理差异,为苹果品种选育和栽培提供理论依据。【方法】以长富2号及其芽变优系为试材,分别于解袋日(9月20日)后0(即解袋日当天)、2、4、6、8、10、15、20、30 d采集套袋和未套袋的果实,测定果皮色泽参数L*、a*、b*、C*和h°值,叶绿素、花青苷的含量,苯丙氨酸解氨酶(PAL)、查尔酮异构酶(CHI)、二氢类黄酮还原酶(DFR)、类黄酮3,5-糖苷转移酶(UFGT)4种花青苷合成相关酶的活性。【结果】随着果实解袋时间的延长,套袋和未套袋的果皮色泽参数L*、b*和h°值均呈下降趋势;而其a*值却均呈上升趋势;其C*值在解袋后0~6 d均呈下降趋势,8~30 d却均呈上升趋势。果皮花青苷的含量在形成第1个峰值后短暂下降,此后又急速上升,解袋后30 d花青苷的含量最高。套袋和未套袋的果皮叶绿素含量均较低且无明显波动,但套袋的芽变优系和长富2号果皮叶绿素含量均明显低于未套袋的(P<0.01);叶绿素含量下降的时间与花青苷大量合成的时间相近。套袋和未套袋的芽变优系和长富2号果皮苯丙氨酸解氨酶(PAL)的活性为7~10 U/g,其活性变化趋势一致;解袋后0~30 d,套袋和未套袋的芽变优系和长富2号果皮的查尔酮异构酶(CHI)活性均呈上升趋势,但套袋的芽变优系与长富2号果皮的CHI活性均明显低于未套袋的;套袋和未套袋的芽变优系和长富2号果皮二氢类黄酮还原酶(DFR)活性变化趋势与其CHI活性变化趋势相似,但套袋的芽变优系和长富2号果皮DFR的活性均呈上升趋势,而未套袋的芽变优系和长富2号果皮的DFR活性均呈下降趋势;套袋和未套袋的芽变优系果皮的类黄酮3,5-糖苷转移酶活性(UFGT)活性均呈上升趋势,而套袋和未套袋的长富2号果皮的UFGT活性却平缓波动。【结论】套袋可显著提高芽变优系和长富2号苹果果面的光洁度,增加果皮花青苷含量,降低叶绿素含量。PAL并非花青苷合成的关键酶,CHI和UFGT的活性与果实花青苷的合成均密切相关,芽变优系和长富2号均通过增强CHI与UFGT的活性来促进花青苷的合成。果皮红色产生的主要原因可能是花青苷含量的明显增加及UFGT活性较高,而与叶绿素含量不相关。

【Objective】To study the relationship between peel color,anthocyanin and related enzyme activities of Fuji bud mutation,analyze the change pattern of peel coloration and physiological differences,and provide theoretical basis for apple variety selection and cultivation.【Method】Nagafu No.2 and its bud mutation were used as test materials.The bagged and unbagged fruits were collected at 0(that is,the day of bagging),2,4,6,8,10,15,20 and 30 days after the bagging day(September 20),determine the peel color parameters L*,a*,b*,C*and h°,chlorophyll content,anthocyanin content and activities of four enzymes including phenylalanine ammonia-lyase(PAL),chalcone isomerase(CHI),dihydroflavonoid reductase(DFR),and flavonoid 3,5-glycosidic transferase(UFGT),related to anthocyanin synthesis.【Result】With the prolongation of fruit bagging time,the values of L*,b*and h°of the bagged and unbagged fruits showed a downward trend,while the values of a*showed an upward trend,and the values of C*showed a downward trend from 0 to 6 days after bagging and an upward trend from 8 to 30 days after bagging.The content of pericarp anthocyanin decreased briefly after the first peak,and then increased sharply,and it was the highest after 30 days of bagging.The pericarp chlorophyll content of bagged and unbagged was low and did not fluctuate significantly,but the pericarp chlorophyll content of the bagged fruits both in bud mutation and Nagafu No.2 were significantly lower than that of the unbagged ones(P<0.01).The decrease time of chlorophyll content was similar to the time of anthocyanin synthesis.The activity of phenylalanine ammonia-lyase(PAL)in the bagged and unbagged pericarp of both bud mutation and Nagafu No.2 was 7-10U/g,with the same trend.From 0 to 30 d after the September 20th,the CHI activity of the bud mutation and Nagafu No.2 peel showed an increasing trend,but the CHI activity of the bagged bud mutation and Nagafu No.2 peel was significantly lower than that of the unbagged.The trends of dihydroflavonoid reductase(DFR)activity of the bagged and unbagged bud mutation and Nagafu No.2 peels were similar to those of CHI activity,but the DFR activity of the bagged bud mutation and Nagafu No.2 peels showed an increasing trend,while the DFR activity of the unbagged bud mutation and Nagafu No.2 peels showed a decreasing trend.The UFGT activity in the pericarps of the bagged and unbagged bud mutation showed an increasing trend,while it showed an flat fluctuation in the pericarp of the bagged and unbagged Nagafu No.2.【Conclusion】Bagging can significantly improve the smoothness of the apple surface,increase the anthocyanin content and reduce the chlorophyll content for both Nagafu No.2 and its bud mutation,PAL is not the key enzyme of anthocyanin synthesis,and the activities of CHI and UFGT are closely related to the synthesis of anthocyanin in fruit.Both bud mutation and Nagafu No.2 promote anthocyanin synthesis by enhancing the activities of CHI and UFGT.The main reason for the red color of the peel may be the significant increase of anthocyanin content and higher UFGT activity,but not related to chlorophyll content.