荔枝(Litchichinensis Sonn.)花芽分化过程的细胞超微结构观察

应用透射电镜对荔枝茎尖生长锥由营养生长转变为生殖生长过程的细胞超微结构进行观察 ,结果表明 ,荔枝圆锥花序发育前期细胞排列紧密 ,细胞质浓 ,液泡小 ,细胞核大并占据着细胞大部分位置 ;细胞质内有丰富的线粒体和膜状系统 ,整个膜状系统内连细胞核 ,外接胞间连丝 ;细胞内囊泡大量形成、融合与迁移 .这些均显示出细胞内结构物质在此期经历着活跃的周转和合成代谢 ,细胞内部在基因的控制下有序地表达 ,为发育过程质的转变积累足够的信息和物质 .生长锥由尖长变为宽平的花序原基时 ,其组织细胞结构也发生了相应的变化 ,最显著的特征是在此过程中 ,有一些细胞发生了程序性死亡 .正在凋亡的细胞核染色质固缩、趋边、核膜破裂或皱缩、细胞质囊泡化并将降解的物质运到周围细胞 。

Effects of saponin from the seed of Litchi chinensis Sonn on TGF-β1, FN and SOCS-1 in renal tubular epithelial cells under high glucose

Objective:To investigate the effect of saponin from the seed of Litchi chinensis Sonn(SLS)on the growth and apoptosis of human kidney epithelial cells(HKC)cultured in high glucose.Methods:HKC were cultured in DMEM/F12 medium supplemented with 30 mmol/L glucose and treated with or without SLS.In the normal group,isometric DMEM/F12 medium with 5.5mmol/L glucose was added.The secretion of TGF-β1 and fibronectin(FN)were detected by ELISA.Cell apoptosis was detected by the method of Annexin V-FITC/PI double staining.Western blot was used to detect the level of suppressor of cytokine signaling-1(SOCS-1).Results:The result of ELISA showed that the secretion of TGF-β1 and FN was decreased in SLS groups compared with those in 30 mmol/L glucose treated group(P<0.05).There were more cells apoptosis in 30 mmol/L glucose treated group than that in the normal group(P<0.01).Compared with the 30 mmol/L glucose treated group,the apoptosis of HKC were significantly decreased in SLS groups(P<0.01).Western blot showed that the level of SOCS-1 in high glucose+SLS group was decreased(P<0.01),compared with the high glucose group.Conclusion:SLS can reduce the secretion of TGF-β1 and FN in HKC by reducing the deposition of extracellular matrix.SLS also significantly reduced the apoptosis of HKC by inhibiting the level of SOCS-1.These results suggest the roles of SLS in preventing the progress of glomerular sclerosis.

Expression of SAMDC Gene for Enhancing the Shelf Life for Improvement of Fruit Quality Using Biotechnological Approaches into Litchi (Litchi chinensis Sonn.) Cultivars

Polyamines play an important role in plant response to abiotic stress. S-adenosyl-1-methionine decarboxylase (SAMDC) is one of the key regulatory enzymes in the biosynthesis of polyamines. In order to better understand the effect of regulation of polyamine biosynthesis on the shelf life improvement of litchi fruit, SAMDC cDNA isolated from Datura stramonium cloned in pBI121 was introduced into litchi genome by means of Agrobacterium tumefaciens through zygote disc transformation. Transgene and its expression are confirmed by Southern and Northern blot analyses, respectively. Transgenic plants expressing Datura SAMDC produced 1.7- to 2.4-fold higher levels of spermidine and spermine than wildtype plants under normal environmental condition, which indicated that the transgenic litchi presented an enhanced polyamines synthesis compared to wildtype plants. Our results demonstrated clearly that increasing polyamine biosynthesis in plants may be a means of creating improved fruit shelf life germplasm.

Cloning and Sequence Analysis of Expansin Genes from Litchi chinensis Fruit

Using PCR degenerate primers, designed with reference to the sequences of the conserved amino acids of known expansins, to amplify cDNA fragments in litchi fruit by RT-PCR, two different cDNA fragments , named as Lc-Exp1 and Lc-Exp2 , were cloned. Lc-Exp1 and Lc-Exp2 was respectively composed of 531 bp encoding 177 amino acids and 537 bp encoding 179 amino acids. Eight cysteine residues and three tryp-tophan residues, which is supposed to be the characteristics of expansins, are conserved in both Lc-Exp1 and c-Exp2. In addition, the homology between the two expansins is 71. 6% at nucleotide acid sequences and 76.3% at amino acid sequences. The homology of Lc-Exp1 with Fa-Exp2 or Pp-Exp1 was 92.7% or 92.1%, but that of Lc-Exp2 with Fa-Exp2 or Pp-Exp1 was only 77. 4% or 76.3% at amino acid sequences.

Agrobacterium tumefaciens-mediated transformation of embryogenic callus and CRISPR/Cas9-mediated genome editing in‘Feizixiao'litchi

Litchi(Litchi chinensis Sonn.)is a type of commercially prevalent subtropical and tropical fruit.Since litchi has a highly heterozygous genetic background and a long reproductive cycle,conventional breeding methods(such as hybridization)have limited ability to nurture new litchi cultivars.Here,an efficient and stable Agrobacterium tumefaciens-mediated genetic transformation of embryogenic callus was established in‘Feizixiao’litchi.Transgenic materials were verified using polymerase chain reaction(PCR)analysis,β-glucuronidase(GUS)assay,and green fluorescent protein(GFP)assay.To implement the technology of the Clustered Regularly Interspaced Short Palindromic Repeats(CRISPR)/associated protein 9(CRISPR/Cas9)technology in‘Feizixiao’litchi and verify the validity of these transformation systems,the litchi polyphenol oxidase gene(LcPPO,JF926153)was knocked out.Various categories of mutations,covering base insertions,deletions,and substitutions,were found in transgenic materials via sequence analysis.The transformation system achieved high feasibility and efficiency,and the system of CRISPR/Cas9 was successfully employed to edit genes in‘Feizixiao’litchi.This work provides an essential foundation for investigating the functions of genes and accelerating litchi genetic improvement.

荔枝种子发育过程中有机营养变化与萌发的关系

对比分析“妃子笑”和“紫娘喜”2个荔枝品种种子发育过程中的种子萌发规律,研究其淀粉、可溶性糖、有机酸和氨基酸组分及含量变化,探讨种子萌发与这些有机营养成分之间的相关性。结果表明,随着果实发育成熟,“妃子笑”荔枝种子萌发率呈先上升后下降的趋势,“紫娘喜”荔枝种子萌发率持续上升;盛花后45 d开始,“紫娘喜”荔枝种子萌发率持续高于“妃子笑”。果实发育过程中,“妃子笑”和“紫娘喜”荔枝种子中总可溶性糖含量分别呈“N”和“W”形变化,两者的淀粉含量均逐渐升高;果实完全成熟时,“紫娘喜”荔枝种子中淀粉含量显著高于“妃子笑”;两者种子中总有机酸含量均持续下降,但组分不同,“妃子笑”荔枝种子中含有8种有机酸,“紫娘喜”荔枝种子多了乳酸和琥珀酸。两个品种种子均含21种氨基酸,“妃子笑”荔枝种子总氨基酸含量呈先降低后上升至稳定水平的趋势;而“紫娘喜”种子中总氨基酸含量呈先短时降低后升高再降低的变化。相关性分析表明,两个荔枝品种的种子萌发率与淀粉含量呈极显著正相关,与总有机酸含量呈极显著负相关。说明淀粉和有机酸可能是影响种子发育与萌发的主要有机营养物质。

不同品种荔枝壳中原花青素的鉴定及其体外抗氧化活性研究

为筛选适合开发天然抗氧化产品的荔枝优良品种,本研究对7个不同品种荔枝壳中总酚、总原花青素、总黄酮含量及A型低聚原花青素组分进行了分析,采用DPPH、ABTS+自由基清除法及FRAP法测定其体外抗氧化活性。结果表明,褐毛荔果壳提取物中所含抗氧化活性成分如总酚、总原花青素、总黄酮以及总A型低聚原花青素含量均为最高。经电喷雾液质联用四级杆飞行时间质谱(HPLC-Q-TOF-MS/MS)分析鉴定,得到所含物质的一级及二级质谱。质谱结果显示荔枝壳中含有的低聚原花青素组分主要为表儿茶素、原花青素A2、原花青素A4、A型三聚体及四聚体,不同品种荔枝壳中原花青素含量具有差异性(P<0.05)。褐毛荔果壳提取物表现出较强的自由基清除活性(DPPH·:1144.60μmol Trolox/g DW,ABTS^(+)·:2905.56μmol Trolox/g DW,FRAP:868.84μmol Trolox/g DW)。经皮尔逊相关性分析,原花青素单体、二聚体、三聚体含量与抗氧化活性具有显著相关性(P<0.05)。综合分析,与其他品种相比,褐毛荔果壳提取物中A型低聚原花青素含量最高,体外抗氧化活性方面表现最佳,可作为开发天然抗氧化产品的新型潜在原料加以利用。

Physiological Changes during the Process of Pericarp Browning in the Postharvest Litchi

[Objective] Pericarp browning in the postharvest litchi significantly reduced its commercial value and limited the expanding of litchi markets. Physiological changes during the process of pericarp browning were determined in order to identify the underlying mechanisms. [Method] Matured Feizixiao fruits were stored at 25 ℃ and 70%±5% relative humidity. The physiological changes happened in pericarp during storage were tested at an 8-hour interval. [Result] The fruit of Feizixiao (Litchi chinensis Sonn. cv Feizixiao) turned completely brown within 72 h after being harvested under the experimental conditions. Sharp increase of the browning index occurred from 48 to 64 hours after harvest (HAH). With the browning of pericarp,water content of the whole fruit and pericarp decreased continuingly. In contrast,there were no significant changes in the water content of pulp during the same period. MDA content,pH value and relative leakage rate of pericarp were increased during storage. Most of pigment contents including anthocyanin,flavonoid,phenols,chlorophyll a and total chlorophyll decreased. POD activity was initially increased in 32 HAH and then decreased afterwards. PPO activity was decreased continuously,while the activities of catalase and superoxide dismutase exhibited the pattern of 'increasing-decreasing-increasing' as the storage time progressed. Correlation,stepwise regression and path analyses showed that water loss of pericarp was the major factor of pericarp browning. Principal and cluster analyses showed that there were two stages of pericarp browning during the course of litchi storage. [Conclusion] Water status of pericarp was the most important factor affecting pericarp browning. The pericarp browning happened by stages,which was mainly determined by the water loss of pericarp.

玉林市仙进奉荔枝高产栽培技术要点

为提升荔枝(Litchi chinensis Sonn.)果实的品质和产量,针对仙进奉荔枝在玉林市的物候期表现及果实变异的问题,主要从建园、种苗选择、秋梢培养、控梢促花、疏花保果、适时采摘、采后修剪及清园等方面描述其栽培技术要点,以期为仙进奉荔枝高质量生产提供参考。

荔枝(Litchi chinensis Sonn.)叶片白化变异体遗传和转录组分析

为了解荔枝叶片白化变异体遗传特点,本研究以白化变异体比例较高的‘玉谭蜜荔’白化变异体苗与正常苗为试验材料,测定叶片叶绿素含量,并观测叶绿体结构差异,最后通过高通量测序技术对苗期叶片进行转录组测序分析。结果表明:‘玉谭蜜荔’种子实生苗中白化变异体的比例约为8.59%;白化苗叶片色素含量极低,仅为正常苗的0.519%;叶绿体的结构松散,基粒片层结构较少或缺失。对高通量测序数据进行组装和注释,共获得Unigene 42782条,平均长度987 bp,比对到Nr、KOG、KEGG、Swiss-prot四大数据库中,超过64%的Unigene序列获得注释,差异分析表明在细胞色素合成、光系统亚基合成蛋白、采光复合物a/b结合蛋白相关序列表达显著下调。本研究为该变异体的基因定位鉴定提供了一定的遗传基因注释信息。

Effects of simulated acid rain on fertility of litchi

The regulatory role of calcium in fertility of pollen and pistil under simulated acid rain was investigated. The germination percentage of pollen treated with acid rain of pH 4.5 was 9.42% lower than that of control, and that of pH 3.5, pH 2.5 and pH 1.5 were 22.47%, 45.49% and 71.62%, respectively. Simultaneously, the injury character of pollen was obviously observed when flowers were treated with acid rain of pH 3.5. The difference in fruit setting rate between the female flower treated with acid rain of pH 4.0 and the control was significant at p 〈 0.05. Ca（NO3 ）5 of 0.2-0.4 mmol/L could promote pollen germination under the stress of acid rain. The beneficial function was reduced when calcium concentration surpassed 0.8 mmol/L. Spraying 2 mmol/L Ca（NO3 ）5 reduced the injury of acid rain to pistil and increased fruit-setting rate significantly. The physiological importance of calcium during pollen germination and pistil development was also discussed.

Flavonoids from Litchi(Litchi chinensis Sonn.) Seeds and Their Inhibitory Activities on α-Glucosidase

With the bioactivity-guided method,a new flavanone glycoside,together with nine known flavonoids were isolated from 50% aqueous ethanol of litchi（Litchi chinensis Sonn.） seeds.The chemical structure of the new compound was elucidated via 1D and 2D nuclear magnetic resonance（NMR） techniques and mass spectrometry to be （2S）-pinocembrin-7-O-（6＂-O-α-L-arabinosyl-β-D-glucopyranoside）（1）,and the nine known compounds were determined to be quercetin（2）,phlorhizin（3）,pinocembrin-7-O-glucoside（4）,kaempferol-7-O-β-D-glucopyranoside（5）,onychin（6）,nairutin（7）,narcissin（8）,pinocembrin-7-O-[（6＂-O-β-D-glucopyranoside）-β-D-glucopyranoside]（9） and pinocembrin-7-O-[（2＂,6＂-di-O-α-L-rhamnopyranosyl）-β-D-glucopyranoside]（10）.Some of the isolated flavonoids were tested for their inhibitory effects on α-glucosidase.And compounds 2 and 3 showed stronger inhibitory activity than positive control.

氨基酸对荔枝愈伤组织增殖及体胚发生体系优化的研究

【目的】探究氨基酸对荔枝愈伤组织增殖及体胚诱导的影响。【方法】采用L9(34)正交设计,分别在妃子笑荔枝愈伤组织继代及体胚诱导阶段添加不同氨基酸,比较其对愈伤组织增殖及体胚诱导的影响。【结果】在愈伤组织增殖阶段培养基中添加氨基酸均显著提高愈伤组织增殖率,最优处理为基础继代培养基添加0.1 g·L^(-1)γ-氨基丁酸+0.2 g·L^(-1)谷氨酰胺,愈伤组织增殖率为初始接种量的14.04倍。与对照相比,氨基酸处理组的胚性愈伤组织淡黄,颗粒较小,细胞呈椭圆形,细胞质浓厚,多为正在分裂状态;非胚性愈伤组织浅白,水渍严重,着生于顶部或者边缘,易于剔除。在愈伤组织增殖阶段培养基中添加γ-氨基丁酸、谷氨酰胺和丙氨酸对后续的体胚发生及萌发影响极显著(p<0.01),最优配方为基础继代培养基添加0.3 g·L^(-1)γ-氨基丁酸+0.4 g·L^(-1)谷氨酰胺+0.05 g·L^(-1)丙氨酸,每克愈伤组织可获得461个体胚,77株组培苗。在体胚发生阶段培养基中添加氨基酸,获得的体胚发生及萌发最优配方为基础诱导培养基添加0.3 g·L^(-1)γ-氨基丁酸+0.4 g·L^(-1)谷氨酰胺+0.05 g·L^(-1)丙氨酸,每克愈伤组织可获得270个体胚,72株组培苗。【结论】氨基酸可调节愈伤组织胚性,提高愈伤组织增殖率,促进体胚发生及萌发。

拉枝对仙进奉荔枝枝梢生长和成花坐果的影响

【目的】仙进奉荔枝是近年推出的优质晚熟新品种,在中晚熟荔枝产区经济效益和社会效益显著,其高效丰产栽培技术有待研发。拉枝是一种重要的果树整形修剪手段,能有效削弱顶端优势,利于开花结果。探究不同拉枝处理对仙进奉荔枝的影响,为仙进奉荔枝拉枝技术的应用和稳产丰产技术建立提供参考。【方法】以4年生仙进奉荔枝为材料,设置直立(不拉枝,CK)、水平(90°)和下垂(110°)3个处理,统计处理后枝梢生长量、成花率和座果率等指标。【结果】与直立处理(CK)相比,下垂和水平拉枝处理对第1次、第2次梢营养生长影响有限,但能延迟第3次梢(末次秋梢)萌芽7 d以上,同时显著减少末次秋梢萌芽数目,且以下垂处理的抑制效果最强。末次秋梢老熟时,拉枝处理枝条直径略低于直立处理(CK),各处理间差异不显著;下垂和水平拉枝处理均可有效将末次秋梢长度控制在15 cm左右,促生中短枝,利于开花坐果。翌年春季,下垂和水平处理枝组的成花率和座果率显著高于直立处理(CK),其中下垂处理枝组成花率达到100%,且全部为纯花穗、花穗质量高;直立处理(CK)枝组产生较多带叶花穗。各处理枝组的花穗长度无显著差异,但拉枝处理可显著降低花穗基部直径、抑制花穗旺长。雌花盛开后50 d,下垂和水平处理枝组座果率分别为9.81%和7.61%,显著高于直立处理(CK,5.54%)。【结论】下垂和水平拉枝可有效控制仙进奉荔枝结果母枝徒长,改善成花质量,显著提高座果率,以110°下垂拉枝效果最佳。

荔枝杂交F^(1)代群体部分枝叶性状的遗传变异分析

【目的】探究荔枝枝叶性状在杂交群体中的分离规律和遗传变异特征,为荔枝杂交育种的亲本选配提供参考。【方法】对三月红(♀)×紫娘喜(♂)杂交的258株F^(1)代的复叶主轴长、叶柄长、叶面积、叶长、叶宽、叶形指数、鲜重、干重、比叶重、枝皮率等10个枝叶性状指标进行鉴定,分析各性状变幅、分布频率、变异系数及广义遗传力等。【结果】10个表型数量性状变异系数的平均值为12.37%。叶面积的变异系数最大,为15.67%,其次是复叶主轴长(13.93%),最小为叶长(9.23%)。各指标测量值均呈正态分布。复叶主轴长、叶长、叶宽、鲜重、干重、叶面积、比叶重等F^(1)代平均值均高于亲中值,而叶柄长、叶形指数、枝皮率F^(1)代平均值均低于亲中值,说明基因重组可形成一定程度的非加性效应,导致超亲个体的出现。广义遗传力最高为叶柄长(0.87),其次是叶形指数(0.75),各指标广义遗传力平均值为0.45;叶宽性状在F^(1)代超高亲率最高,为99.22%;超低亲率最高为叶柄长,占比86.82%。【结论】荔枝枝叶性状在杂交群体中显示出较为广泛的变异,部分性状易受环境影响。

荔枝CDPK基因家族鉴定及其在霜疫病胁迫下的表达分析

【目的】鉴定荔枝(Litchi chinensis Sonn.)钙依赖蛋白激酶(CDPK)基因家族,并分析其在不同组织和荔枝霜疫病胁迫下的表达模式。【方法】基于荔枝基因组数据,利用生物信息学方法鉴定CDPK家族基因,并对其序列特征、基因结构、启动子顺式作用元件、染色体定位和进化关系等进行分析。依赖276份荔枝种质材料,筛选高抗霜疫病的优良荔枝品种。另外,通过RNA-Seq和qRT-PCR方法检测高抗病荔枝品种中LcCDPK基因家族成员在荔枝霜疫病胁迫处理下的表达模式。【结果】从276份荔枝自然群体材料中鉴定到荔枝高抗霜疫病品种裕荣1号(YR1)。从荔枝基因组中共鉴定出19个LcCDPK基因家族成员,分布于11条染色体上。根据保守结构域和系统发育分析将其分为4个亚家族。基因结构分析表明,LcCDPKs外显子数量为7~19。蛋白结构分析发现,所有LcCDPK蛋白均具有1~4个EF-hand结构域。顺式作用元件分析表明,LcCDPKs成员拥有大量的生物和非生物胁迫响应元件。组织表达分析发现,LcCDPK基因在荔枝不同组织存在组织特异性。另外,表达分析发现在高抗霜疫病荔枝裕荣1号(YR1)中,LcCDPK5、LcCDPK17和LcCDPK19在霜疫病胁迫后急剧上调表达,LcCDPK3和LcCDPK8急剧下调表达。【结论】裕荣1号(YR1)是一种高抗霜疫病的荔枝品种。荔枝基因组中共鉴定出19个CDPK基因家族成员,具有明显的组织特异性,LcCDPK5、LcCDPK17、LcCDPK19、LcCDPK3和LcCDPK8可能在荔枝抗霜疫病过程中发挥重要作用。研究结果为进一步探究荔枝CDPK基因家族提供了参考。

响应面法优化荔枝叶成分提取工艺及其抗炎作用研究

试验旨在采用响应面法优化提取荔枝叶成分的工艺并探究其抗炎作用。以液料比、提取时间、提取溶剂浓度为考察因素,以没食子酸、儿茶素、表儿茶素、芦丁、紫云英苷、槲皮素、山柰酚含量的综合评分为考察指标,结合响应面法中Box-Behnken设计原理,优化荔枝叶成分的提取工艺。采用脂多糖诱导RAW264.7细胞炎症模型评价荔枝叶的抗炎作用。结果表明,荔枝叶成分的最佳提取工艺参数为甲醇浓度72%、液料比18 mL/g、提取时间70 min。在此工艺条件下,荔枝叶成分的综合评分为88.99,与预测综合评分的84.53分相比误差较小。荔枝叶提取物可降低脂多糖(LPS)诱导RAW264.7细胞导致的一氧化氮(NO)、白细胞介素-1β(IL-1β)的释放量;对诱导型一氧化氮合酶(iNOS)蛋白的表达也具有抑制作用;荔枝叶提取物能够上调Toll样受体4(TLR4)mRNA的表达量与下调核因子κB(NF-κB)mRNA表达量。研究表明,此试验方法简单、稳定可靠,为荔枝叶成分的提取工艺研究提供了一定的参考依据。

荔枝果实性状多样性分析

为探究不同荔枝品种果实性状多样性,以期为高效利用荔枝种质资源提供参考依据,以120个荔枝品种为试材,对其果实形状、大小、果皮厚度、果皮质量、种子质量、单果质量、焦核率等形态和品质指标进行了鉴定评价。结果表明:供试品种果实形状从椭圆形到心形,果皮颜色从黄绿色到紫红色,龟裂片类型从平坦到尖突,果实风味从酸到甜,香气从无香到蜜香,肉质从粗糙到爽脆,汁液从少到多,果肉色泽从蜡黄到蜡白均有分布,单果质量13.36~56.04 g,焦核率0%~100%,果皮厚度0.74~3.13 mm,种子质量0.5~5.53 g,果实可食率59.18%~82.48%,可溶性固形物含量13.1%~21.7%。单果质量、焦核率、果皮厚度、种子质量、可食率、可溶性固形物6个数量性状的变异系数依次为31.71%、32.33%、48.94%、9.96%、7.92%、155.42%,其多样性指数(H')依次为1.8596、1.3017、1.9614、2.0206、2.0913、1.3017,荔枝品种之间果实品质性状表现出不同程度的变异和多样性。供试的120个荔枝品种果实的8个描述性状和6个数量性状均存在不同程度的多样性,后续荔枝品种选育、新种质收集等工作能以此作为参考依据开展。

荔枝果皮细胞壁组成与裂果发生关系的研究

【目的】通过比较裂果易感性不同的荔枝品种细胞壁组分的差异,研究外源喷施生长素类似物2,4-二氯苯氧乙酸(2,4-D)对裂果和果皮细胞壁组分的影响,探讨细胞壁组成与裂果发生的关系。【方法】比较2个易裂果荔枝品种(‘桂味’‘糯米糍’)和2个不易裂果荔枝品种(‘怀枝’‘岭丰糯’)花后75 d的果皮碳水化合物含量变化,并观察花后60~85 d果皮组织结构和木质素分布。利用2,4-D分别对2个果场的‘糯米糍’果穗进行浸泡处理,使用GC-MS测定裂果高发期的果皮可溶性糖含量,分光光度计法测定果皮淀粉和结构性碳水化合物含量,最后通过透射电镜、果皮组织木质素染色观察荔枝果皮组织结构。【结果】易裂果的‘糯米糍’果皮中己糖(果糖、葡萄糖、半乳糖)含量显著低于不易裂果的‘怀枝’和‘岭丰糯’。果胶含量与裂果易感性之间关系复杂,‘糯米糍’果皮果胶含量较低、仅1.7 mg/g,且果大、易裂果;‘桂味’果皮果胶含量高、为4.0 mg/g,果小、也易裂果。2,4-D处理后,前期暂时提高了座果率,但对最终座果率无显著影响;2,4-D处理可导致果皮细胞层数增多,内果皮细胞轮廓变模糊;与对照相比,40 mg/L 2,4-D处理后果皮果胶含量增多、细胞壁增厚、裂果率增加。【结论】裂果易感性不同的荔枝品种果皮中碳水化合物含量存在明显差异,其中果胶在荔枝裂果中可能扮演双重的角色,细胞膨大过程中果胶合成和降解呈动态变化,果胶含量过高则果皮延展性差,果实小易裂果,果胶含量过低则果皮延展性好,果实大但抗裂性低、也易裂果;2,4-D处理对‘糯米糍’最终座果率无影响但显著增加裂果风险。

多变量灰色预测模型在荔枝病虫害预测中的应用

荔枝病虫害易造成荔枝Litchi chinensis Sonn.产量少、品质劣、价格低,导致果农收益下跌,产业发展受制。因此,建立荔枝病虫害预测预报模型,开展病虫害发生程度预测,对荔枝产业高质量发展具有重要意义。基于2004—2020年广州市增城区第二代荔枝蒂蛀虫驻果率数据,以及前期气象要素数据,对影响蒂蛀虫驻果率的气象因子进行灰色关联分析,筛选出主要影响因子,采用多变量灰色预测模型GM(1,N)构建第二代蒂蛀虫驻果率预测模型。通过后验差以及小概率误差检验方法进行模型精度检验,并结合马尔科夫模型进行优化,以提高预测模型精度。研究结果表明,采用多变量灰色预测模型GM(1,N)进行荔枝蒂蛀虫驻果率预测,预测精度较高,可为荔枝病虫害预防提供决策参考。