【作者】 李雪莲；

【导师】 邓群仙； 陶炼；

【作者基本信息】 四川农业大学 ， 农业硕士（专业学位）， 2022， 硕士

【摘要】 有机酸是影响果实品质的重要指标,有机酸组分和含量的变化直接影响果实风味。本试验以秋冬开花普通枇杷品种黄肉系的‘大五星’、白肉系的‘白雪公主’及春天开花枇杷品种黄肉系的‘春花1号’为试验材料,分析了各品种枇杷果实发育过程中有机酸的积累规律及相关基因表达。主要研究结果如下:1.开花习性不同的枇杷品种果实发育规律存在差异,但果实可滴定酸含量均呈先上升后下降的趋势。‘大五星’和‘白雪公主’果实发育周期约为5个半月,果实生长曲线为“单S”形,‘春花1号’果实发育周期约为3个半月,果实生长曲线为非典型“单S”形;‘大五星’和‘白雪公主’果实可滴定酸含量均在花后135 d达最大值,‘春花1号’果实可滴定酸含量在花后70 d达最大值;在果实成熟期,‘春花1号’果实的可滴定酸含量最低,仅为0.11%,‘白雪公主’和‘大五星’果实的可滴定酸含量分别为0.50%和0.35%。2.在3个枇杷品种果实中共鉴定出6种有机酸,分别是苹果酸、酒石酸、琥珀酸、草酸、柠檬酸和α-酮戊二酸,品种间有机酸组分的变化规律存在一定差异,但3个品种果实苹果酸和总有机酸的变化规律均与可滴定酸一致。在果实发育早期,3个品种果实有机酸均以酒石酸为主;在果实成熟期,3个品种果实有机酸均以苹果酸为主。‘白雪公主’、‘大五星’和‘春花1号’成熟果实的苹果酸含量分别为3.28 mg·g^-1、2.28 mg·g^-1和0.95 mg·g^-1,分别占总有机酸的83.57%、77.51%和48.59%,苹果酸含量差异是3个品种果实总有机酸含量差异的主要原因。3.苹果酸合成和代谢相关酶活性及对应基因表达水平的差异是3个枇杷品种果实苹果酸含量出现差异的直接原因。‘春花1号’PEPC、NAD-MDH活性及对应酶基因的表达水平均最低,是其苹果酸含量最低的原因之一。NADP-ME主要受NADP-ME2的调控催化苹果酸降解;在果实成熟前,‘大五星’NADP-ME、NADP-ME2和NADP-ME4的表达水平均高于‘白雪公主’,NADP-ME活性表现一致,导致‘白雪公主’苹果酸降解速率慢于‘大五星’,是二者成熟果实中苹果酸含量差异的主要原因。4.CS和ATP-CSα2-1分别调控‘大五星’和‘白雪公主’柠檬酸的合成与降解,ACO通过抑制CS活性调控二者柠檬酸含量;‘春花1号’柠檬酸代谢与相关酶及基因的相关性较低。NAD-IDH酶调控3个枇杷品种果实柠檬酸降解及α-酮戊二酸合成,NAD-IDH5起主要调控作用。5.‘大五星’和‘白雪公主’在转运苹果酸时的跨膜电势差分别受不同VHAs调控,苹果酸跨膜转运分别受不同ALMTs调控;‘白雪公主’苹果酸的转运还受t DT2调控。‘春花1号’VHAs及ALMTs的表达水平整体低于‘大五星’和‘白雪公主’,且与其苹果酸和总有机酸含量的相关性较低,表明苹果酸转运效率低也是‘春花1号’酸含量的限制因子。更多还原

【Abstract】 Organic acid is one of the most important indicators of fruit quality,changes of organic acid components and contents directly affect fruit taste.In this experiment,loquat fruits of‘Dawuxing’（yellow flesh,flowering in autumn and winter）,‘Baixuegongzhu’（white flesh,flowering in autumn and winter）and‘Chunhua No.1’（yellow flesh,flowering in spring）at different developmental stages were used as experimental materials.The accumulation patterns of organic acids and related genes expression during fruit development of each loquat cultivar were analyzed.The main research results are as follows.1.Although there were differences in fruit development patterns among loquat cultivars with different flowering habits,the fruit titratable acid content of the three showed the same trend of increasing followed by decreasing.The fruit development period of‘Dawuxing’and‘Baixuegongzhu’was about 5.5 months,and their fruit growth curves were both“single S”shaped.The fruit development period of‘Chunhua No.1’was about3.5 months,its fruit growth curve was atypical“single S”shape.The titratable acid content of‘Dawuxing’and‘Baixuegongzhu’both reaching the maximum at 135 days after anthesis and‘Chunhua No.1’at 70 days after anthesis.At maturity,‘Chunhua No.1’fruits had the lowest titratable acid content of 0.11%,while the titratable acid content of‘Baixuegongzhu’and‘Dawuxing’fruits was 0.50%and 0.35%,respectively.2.A total of six organic acids were identified in the fruits of the three loquat cultivars,namely malic acid,tartaric acid,succinic acid,oxalic acid,citric acid andα-ketoglutaric acid.The variation patterns of each organic acid in each cultivar were somewhat different,but the variation patterns of malic acid and total organic acids in fruits of the three cultivars were consistent with titratable acid.At the early stage of fruit development,fruits of the three cultivars were dominated by tartaric acid;at maturity,all the three cultivars were dominated by malic acid.The malic acid content of‘Baixuegongzhu’,‘Dawuxing’and‘Chunhua No.1’fruits at maturity was 3.28 mg·g^-1,2.28 mg·g^-1 and 0.95 mg·g^-1,respectively,accounting for 83.57%,77.51%and 48.59%of the total organic acids,respectively.The difference in malic acid content was the main reason for the difference in total organic acid content of ripe fruits of the three cultivars.3.The differences in the activities of enzymes related to malic acid synthesis and metabolism and the expression levels of the corresponding genes in the fruits of the three cultivars were directly responsible for the differences in malic acid content.The activities of PEPC and NAD-MDH,and expression levels of the corresponding enzyme genes in‘Chunhua No.1’fruits were the lowest among the three cultivars,which was one of the reasons for its lowest malic acid content.NAPE-ME was mainly regulated by NADP-ME2to catalyzes malic acid degradation.Before fruits ripening,the expression levels of NADP-ME,NADP-ME2 and NADP-ME4 were higher in‘Dawuxing’than in‘Baixuegongzhu’,as was the activity of NADP-ME,resulting in a slower rate of malic acid degradation in‘Baixuegongzhu’than in‘Dawuxing’,which was responsible for the difference in malic acid content in ripe fruits between the two cultivars.4.In‘Dawuxing’and‘Baixuegongzhu’fruits,CS and ATP-CSα2-1 regulated citric acid synthesis and degradation,respectively;and ACO regulated citric acid content in both by inhibiting CS activity.While the citric acid metabolism of‘Chunhua No.1’fruit was less correlated with related enzymes and genes.NAD-IDH enzymes regulated citric acid degradation andα-ketoglutarate synthesis in fruits of the three loquat cultivars,with NAD-IDH5 playing a major regulatory role.5.In‘Dawuxing’and‘Baixuegongzhu’fruits,the transmembrane potential difference when transporting malic acid was regulated by multiple VHAs,and malic acid transport across the membrane was regulated by multiple ALMTs,respectively.t DT2 was also involved in regulating malic acid transport in‘Baixuegongzhu’.The overall expression levels of VHAs and ALMTs in‘Chunhua No.1’were lower than those in‘Dawuxing’and‘Baixuegongzhu’,and the correlations with malic acid and total organic acid content were low,indicating that the low efficiency of malic acid translocation was also a limiting factor for the acid content in‘Chunhua No.1’.更多还原