Effect of Compound Treatment with Prochloraz and Chitosan on the Physicochemical Indexes of Refrigerated Citrus Gonggan

[Objectives]This study was conducted to investigate the synergized preservation effect of different concentrations of prochloraz and chitosan on citrus Gonggan,so as to prolong the sales period of Gonggan.[Methods]"Zhongshan Gonggan" was used as a material.The Gonggan fruit was soaked with prochloraz (250,300 and 350 mg/L) and then coated with different concentrations of chitosan (1.0% and 1.5%),respectively.The good fruit rate,weight loss rate and titratable acid (TA),reducing sugar,total soluble solids (TSS) and Vc contents were used as evaluation indexes to investigate the preservation effect of Gonggan during cold storage.[Results]The treatment of prochloraz plus chitosan can significantly prolong the shelf life of Gonggan as it can inhibit the decline of good fruit rate,reduce the weight loss rate,and slow down the degradation and loss of titratable acid,reducing sugar,soluble solids and Vc.The 350 mg/L prochloraz+1.0% chitosan treatment was superior to other treatments.[Conclusions]This study provides a theoretical basis for better prolonging the storage period of Gonggan.

Morphological,Molecular and Pathogenicity of Alternaria gaisen Associated with Leaf Brown-Spot on‘Gonggan’Mandarin in China

[Objective]This paper was to identify the pathogen of leaf brown-spot on‘gonggan’mandarin(Citrus reticulate var.gonggan)in Zhaoqing,Guangdong Province.[Method]The pathogen was determined based on sequence analysis of ITS,endoPG,tef1,gapdh,Alt a1,rpb2 and opa10-2 genes;the morphological characteristics were recorded on PDA and PCA;and its pathogenicity on excised and intact host leaves of citrus‘gonggan’was tested.[Result]A detailed description of Alternaria gaisen was obtained based on morphological,molecular and pathogenic characterization,which was the causal agent of brown-spot disease on leaves of‘gonggan’mandarin orchard trees in Zhaoqing,Guangdong,China.[Conclusion]This study provides a scientific basis for the effective control of leaf brown-spot on‘gonggan’mandarin.

Preservation Effect of Prochloraz-manganese Chloride Complex on ‘Gonggan’ (Citrus reticulata) Fruits

‘Gonggan’( Citrus reticulata) is a famous,high-quality and special citrus cultivar in the Xijiang River valley,Guangdong Province. However,it easily suffers from postharvest diseases,and thus is not tolerant to storage. Based on the preliminary test results,prochloraz-manganese chloride complex was selected as the disinfectant,and prepared into different concentrations for carrying out preservation test by dipping fruits. The fruit weight loss,soluble solids content and decay rate were analyzed,and the application security and sensory evaluation for fruit freshness and flavor were observed. The results showed that dipping fruits with prochloraz-manganese chloride complex solution had significant preservation effect on‘Gonggan’fruits in postharvest storage; the suitable concentration was 2. 0-3. 0 g/L,and the decay rates of fruits stored at room temperature for 30,60 and 90 d were below 5%,10% and 15%,respectively. Plate inoculation test further revealed that the pathogen of‘Gonggan’was sensitive to prochloraz-manganese chloride complex,and the concentration of 1. 0 g/L was enough to produce significant antimicrobial effect. Other technical links related to postharvest preservation of‘Gonggan’with prochloraz-manganese chloride complex were discussed.

Infection Characteristics and Interaction of Three Species of Penicillium in the Postharvest Storage of‘Gonggan'Mandarin(Citrus reticulata)

[Objectives]This study was conducted to understand the infection characteristics of Penicillium on‘Gonggan’mandarin(Citrus reticulata)and its effects on postharvest storage quality.[Methods]Nine inoculation treatments were designed and tested for the three identified Penicillium species,namely:three single inoculation experiments,four compound inoculation experiments,and two controls without inoculation.After treatment,the fruit was put into plastic film fresh-keeping bags and stored at a natural room temperature.The determined and analyzed indexes included fruit disease incidence,disease index,disease symptoms,disease spot expansion speed and weight loss rate,soluble solid content and organic acid content in different inoculation treatments.[Results]All‘Gonggan’fruit inoculated with Penicillium were diseased 2 d after inoculation,and completely rotted 14 d later.Of the three Penicillium species isolated and identified,Penicillium digitorum and its combinations were the most harmful to‘Gonggan’fruit.The hazard of Penicillium italicum was equal to or even weaker than that of Penicillium expansum.Eventually,P.digitorum dominated when coexisting on the same fruit.Different species of Penicillium obviously showed competition and antagonism in the process of growth and infection,especially for P.digitorum which was stronger,but other two species of Penicillium also had obvious self-protection ability.Low-temperature storage played a crucial role in the preservation of‘Gonggan’fruit,because it could significantly inhibit Penicillium infestation,and suppress fruit weight loss and the reduction of the contents of soluble solids and organic acids.[Conclusions]The infection characteristics and interaction relationship of Penicillium in the postharvest storage of‘Gonggan’fruit were revealed.

Effects of Storage and Preservation of Postharvest Gonggan Mandarin(Citrus reticulata)Fruit Immersion in Salicylic Acid Combined with Calcium Chloride

[Objectives]To investigate the effects and mechanism of fruit immersion treatment with salicylic acid(SA),calcium chloride(CaCl_(2))solutions at different concentrations or their combinations on post-harvest preservation of Gonggan Mandarin(Citrus reticulata)fruit.[Methods]13 experiments(2 storage temperatures,3 control treatments,3 concentrations of SA solution,4 concentrations of CaCl_(2) solution and 3 combinations of SA+CaCl_(2) solution for fruit immersion treatment)were conducted for 90 d.Gonggan fruit weight loss rate,rotting rate,disease index,disease type,soluble solids and organic acids content,and the differences in the activity of six enzymes(APX,PPO,CHI,CAT,SOD,PAL)related to fruit disease resistance were detected regularly.[Results]With the increase of storage days,the weight loss rate,rotting rate and disease index increased,the content of soluble solids and organic acids decreased,the activity of APX,PPO,CHI and SOD increased,and the activity of CAT and PAL decreased.However,the increase or decrease of fruit loss at low temperature was the smallest,and the increase or decrease of fruit at natural room temperature was the largest.Gonggan fruit cleaning before storage is an effective preservation and fresh-keeping technology,but its preservation and fresh-keeping effect is far less than that of fruit immersion by SA,CaCl_(2) and SA+CaCl_(2) compound solution.The effect of fruit immersion by SA solution was greater than that of fruit immersion by CaCl_(2) solution;the best concentration of SA alone was 6.0 mmol/L,which was not significantly different from 3.0 mmol/L,but the effect of 9.0 mmol/L decreased;the best concentration of CaCl_(2) alone was 6.0 mmol/L,which was significantly better than 3.0 and 9.0 mmol/L;the optimal concentration combination of SA+CaCl_(2) compound solution for fruit immersion treatment was 6.0 mmol/L SA+3.0 mmol/L CaCl_(2).[Conclusions]The fruit immersion by SA,CaCl_(2) and their compound solutions induced the increase of activity of six enzymes related to disease resistance in Gonggan fruit,and PPO and CHI were judged to be two key enzymes based on response intensity.

韶关贡柑园植株叶片矿质元素特征及其与土壤养分的相关性

研究韶关市贡柑叶片矿质元素以及果园土壤养分状况,为贡柑果园平衡施肥提供依据.2021年在广东省韶关市南雄贡柑果园布设20个采样点,采样测定贡柑叶片9种营养元素含量及土壤5种养分,同时分析两者的相关性.结果表明,贡柑叶片氮元素和磷元素均处于缺乏水平;钾、钙、镁元素以及微量元素铁、锰、铜、锌元素处于适量及适量以上水平,锌元素处于适量以下水平比例为85.71%.贡柑果园土壤pH介于4.00~4.69,均处于偏酸性状态;土壤有机质、碱解氮和速效钾含量较高,均值分别为53.58 g·kg^(-1)、286.41 mg·kg^(-1)和595.89 mg·kg^(-1),均处于过量状态;土壤有效磷含量均值为78.38 mg·kg^(-1),均高于适量状态.叶片钾元素与土壤碱解氮、有机质和速效钾呈显著正相关,叶片锰元素、锌元素与土壤pH均呈显著正相关;叶片铬、镉和汞元素与土壤碱解氮、有效磷和速效钾均呈显著正相关.贡柑果园整体土壤养分含量偏高,存在土壤养分和叶片元素需求不平衡问题,要注意科学合理施肥.

2022年钟山县气候条件及对贡柑生产的影响分析

对比钟山县国家基本气象站2022年逐日气象资料和钟山县近30年(1991年—2020年)的年平均值(以下统称为气候标准值),分析了2022年钟山县的气候特征及其对贡柑生长发育和品质产量的影响。结果表明:2022年钟山县年平均气温略偏低,年总降水量偏多,降水量主要集中在汛期4月—9月,年末10月—12月多干旱天气,年总日照时数偏多,年平均相对湿度偏高,总体气候条件对贡柑生产有利。

采前喷布水杨酸(SA)和赤霉素(GA_3)对采后贡柑果实生理及贮藏效果的影响

为探讨采前喷施SA和GA3影响贡柑采后果实贮藏品质的生理机制,于采前30d和20d分别对贡柑树冠进行清水和(1)20mg·L-1GA3、(2)400mg·L-1SA、(3)20mg·L-1GA3+0.5% CaCl2喷施处理。结果表明,20mg·L-1GA3、400mg·L-1SA和20mg·L-1GA3+0.5% CaCl2均能显著降低贮藏期果实的腐烂率、果皮细胞膜透性及膜脂过氧化作用产物丙二醛(MDA)的积累,延缓果实蔗糖、有机酸及维生素C的降解,从而抑制贡柑果实的衰老;20mg·L-1GA3+0.5%CaCl2的保鲜效果优于其他处理,表明Ca2+有促进GA3的保鲜作用。

贡柑采收期果肉颜色变化与果实成熟度的关系研究

以贡柑为试材,对5个不同采收期和成熟度果实的果肉颜色与果皮颜色的相关性以及果实品质的关系进行研究。结果表明:随着果实成熟度的增加,贡柑果肉色泽a/b值和果皮色泽a/b值的变化呈极显著正相关性(R=0.980>R0.01=0.959),表明贡柑果肉色泽变化和果皮色泽变化是一致的;贡柑果实的可溶性固形物、糖分等营养成分含量持续升高,而总酸含量逐渐被降解和减少。初步研究结果表明,贡柑果肉出现白色、黄色、红色的现象是由不同采收期成熟度和果实品质所决定的,而并非是自身遗传所致。

柑橘新品种——‘无籽贡柑’的选育

‘无籽贡柑’是从‘贡柑’的变异株中选出的优良柑橘新品种。该品种果实近圆球形,平均单果质量105 g,无子(平均每果种子≤3粒);可溶性固形物含量11.3%,果肉脆嫩化渣,清甜带香味。树势中等,适应性较强,早结果,丰产,综合性状优良。

贡柑与脐橙营养成分的分析与比较

对市售德庆贡柑的营养成分如水分、灰分、总糖、还原糖、总酸、果胶、蛋白质、脂肪、粗纤维、维生素C和矿质元素(Cu、Zn、Mn、Fe)进行了分析测定,并与江西脐橙进行了比较。结果表明,贡柑和脐橙各成分含量相差不太大,但贡柑中的水分含量比脐橙高,而粗纤维约为脐橙的一半,糖酸比则约是脐橙的两倍,贡柑与脐橙的VC以及Fe、Cu、Zn等矿质元素含量都较丰富。

二氧化氯处理对贡柑采后贮藏品质的影响

为探究二氧化氯(ClO 2)处理在贡柑果实采后贮藏中的防腐保鲜作用,设计不处理、水处理及5、10、15、20 mg/L ClO2溶液分别浸果处理5min,装入塑料薄膜保鲜袋中在自然室温下贮藏90d,期间于0、15、30、45、60、75、90d时分别测试分析了各处理果实贮藏品质的响应与差异。结果表明,不同浓度ClO2溶液浸果处理,均可不同程度地抑制贮藏期间贡柑果实可溶性糖、可滴定酸及维生素C(Vc)含量的下降,对贮藏中贡柑果实的失重和腐烂尤其具预防和抑制作用,其中ClO2浓度达15mg/L及其以上的处理,各项指标均与不处理、水处理有显著性差异(P<0.05)。该研究结果为贡柑果实绿色防腐保鲜提供了技术参考,可在采后商品化实践中应用。

贡柑砧木比较试验研究

以红柠檬、酸桔、江西红桔和小叶大花枳(简称枳)作贡柑的砧木,对不同砧穗组合贡柑的亲和力、树体生长情况、早结丰产性、产量和果实品质进行了系统研究。结果表明,4种砧木与贡柑接穗的亲和性无明显差异,均表现亲和力强;各砧木贡柑嫁接苗均能较早形成树冠,其中枳砧贡柑植株生势缓和,树冠矮化;枳砧和红柠檬砧贡柑表现早结丰产性好,初果期产量与酸桔砧和江西红桔砧贡柑的差异显著,而进入盛果期后各砧木贡柑的产量差异不大;枳、酸桔和江西红桔作贡柑砧木,果实的可溶性固形物、总糖和总酸含量较高,果实品质好,而红柠檬砧贡柑的可溶性固形物、总糖和总酸含量较低,果肉枯水严重,品质差。依据研究结果认为枳、酸桔和江西红桔是广东值得推广的优良贡柑砧木,而红柠檬一般不宜作贡柑砧木。

17种杀菌剂对贡柑炭疽病菌的生物活性测定研究

采用菌丝生长速率法测定了17种杀菌剂对发生于德庆的贡柑炭疽病菌的生物活性。结果表明,参测的12种新杀菌剂中,10种新杀菌剂[250 g/L施保克乳油、50%施保功可湿性粉剂、250 g/L势克乳油、250 g/L凯润乳油、250 g/L必扑尔乳油、300 g/L爱苗乳油、10%世高水分散粒剂、62%霜炭清(B)可湿性粉剂、75 g/L欧宝乳油和250 g/L富力库水乳剂]均对贡柑炭疽病菌表现出优异的抑制作用,EC50值介于0.0128～0.3637μg/mL之间,明显优于参测的250 g/L阿米西达悬浮剂(EC50=14.9902μg/mL)、50%翠贝水分散粒剂(EC50=114.7402μg/mL)和50%多菌灵可湿性粉剂(EC50=8.3998μg/mL)、40%达科宁悬浮剂(EC50=13.2340μg/mL)、62%双博可湿性粉剂(EC50=122.5649μg/mL)等5种常用杀菌剂、80%代森锰锌可湿性粉剂(EC50=400.9587μg/mL)、70%甲基托布津可湿性粉剂(EC50=131904.3068μg/mL)。

‘无核贡柑’的无核机理

以无核贡柑和普通有核贡柑为试验材料,对其花粉育性、成熟胚囊结构以及胚胎发育进行研究。结果表明:与有核贡柑相比,无核贡柑的花粉育性较低,但仍具有一定的生活力和发芽率,两者同属于中育型。无核贡柑成熟胚囊结构完整。无核贡柑授粉后3周,胚体开始败育;授粉后5周,胚乳退化;授粉后7、8周,没有种子的痕迹,最终发育成无核果实,说明胚胎败育是无核贡柑无核的主要原因。

采后加冰处理对德庆贡柑贮藏性能和果实品质的影响

[目的]探索保持贡柑果实品质的方法。[方法]在采后用冰果重量比1:1、1:2和1:3的比例加冰处理德庆贡柑,研究贡柑采后贮藏性能和果实品质变化特点。[结果]1:2加冰处理能保持果实TSS的含量;加冰处理可以较长时间保持果实总糖在高位水平;随加冰量的增加好蒂率也相应提高。从综合效果看,果实总糖、TSS、可滴定酸和Vc的含量和变化动态以冰果比1:2为优。加冰处理可以极显著降低果实霉蒂率,提高好果率,效果以1:1和1:2处理为佳。[结论]采后加冰能显著改善果实好蒂率、好果率及果实外观色泽,保持果实内含物含量和风味。

贡柑不同采收期果实可溶性糖红外光谱学研究

贡柑果实的可溶性糖主要包括果糖、葡萄糖和蔗糖,其红外光谱的吸收主峰在1637.6、1647.3 cm-1处属C=O的伸缩振动(峰位Ⅰ),1061.5、1033.0、1049.2 cm-1处则为C-O伸缩和O-H面内弯曲振动(峰位Ⅱ),994.7 cm-1处是属于环状的C-O伸缩振动。贡柑果实果汁红外光谱在峰位Ⅰ附近峰位差异性大,是可以直接用于可溶性糖组分定性分析的波数;在峰位Ⅱ附近峰位差异性小,可适用于定量分析蔗糖等可溶性糖总量的变化。贡柑不同采收期的果实可溶性糖红外光谱表现出差异,采收迟的果实呈现接近果糖的红外光谱特征。

不同保果处理对贡柑坐果及叶片营养的影响研究

针对广东贡柑自然着果率低及滥用生长调节剂保果等问题进行谢花后不同保果处理研究的结果显示,喷施GA31次+保果素1次的座果率显著高于连续喷施GA32次;喷施保果药剂+环割处理的座果率显著高于未环割处理,其中以喷施GA31次+保果素1次+环割处理的座果率和产量最高。同时指出,各种保果措施均能提高贡柑春梢叶片的氮、钾营养含量,但对贡柑的果实品质没有影响。

贡柑叶片的矿质营养及其对果实品质影响的研究

本研究从不同生产水平的贡柑果园取样,分析了叶片中不同矿质元素的含量变异,探讨叶片矿质元素营养生理及其与果实品质形成的关系。本研究发现,不同园区的贡柑叶片中不同矿质元素含量有显著的差异,变异系数在0.20~0.49之间,其中Mn、P、Mg和Zn变异系数较大,其次是Ca,Cu,N,Na,K,和Fe。贡柑品质综合评价指出,可溶性固形物含量、果汁量、酸含量、种子数、果形指数、风味,是影响贡柑品质独特性、提高经济价值的主要指标。相关分析指出,贡柑叶片含N量与果实可溶性固形物含量（0.642＊）,Mg含量与风味（0.607＊）和果汁含量（0.719＊＊）呈显著正相关。Mn含量与果形指数呈显著负相关（-0.673＊）。不同果园贡柑叶片中N、Mg、Mn含量对果实的品质有显著影响,在贡柑的高产优质栽培研究中应给予充分的注意。

贡柑果实采后可溶性糖代谢和风味品质变化的关系

研究德庆贡柑常温贮藏条件下果实蔗糖、葡萄糖和果糖等可溶性糖类含量、可溶性固形物含量、酸性转化酶活性等变化及其与风味品质变化的关系,探求贡柑果实风味品质变化的生理机制。结果表明,贡柑果实在贮藏后6~12 d先后出现可溶性固形物（TSS）、可滴定酸含量和酸性转化酶活性的增加,果实的风味品质则同期呈现变淡和出现异味等非正向变化;蔗糖等可溶性糖含量变化呈＂S＂型变化模式,其峰位的变化与TSS含量增加呈逆向变化关系,但和风味品质变甜变淡趋势相同。2,4-D处理贡柑后可显著增加好蒂率和好果率,可阻止果实异味产生,但不能延缓可溶性糖含量下降和果实风味品质变淡,蔗糖等可溶性糖含量变化没有呈现＂S＂型变化特征。