Litchi Cultivars Research Articles

Determination of α-methylenecyclopropylglycine in Shahi and China litchi cultivars at three different maturity stages: A quantitative study using liquid chromatography tandem mass spectrometry

This study presents the contents of α-methylenecyclopropylglycine, a potentially toxic amino acid, in the peel, pulp and seed fractions of two well-known litchi varieties, namely Shahi and China, over a span of three harvest-seasons. For analysing α-methylenecyclopropylglycine, an LC-MS/MS-based method was validated. The method-accuracies fell within 75–110 % (RSD, <15 %) at 0.1 mg/kg (LOQ) and higher levels. A comparative evaluation of the results in peel, pulp and seed at 30 days before harvest (DBH), 15-DBH, and edible-ripe stage revealed that α-methylenecyclopropylglycine content increased as the litchi seeds grew towards maturity, regardless of the cultivar. In arils, at maturity, the concentration of α-methylenecyclopropylglycine ranged from not-detected to 11.7 μg/g dry weight. The Shahi cultivar showed slightly higher α-methylenecyclopropylglycine content in comparison to China litchi. This paper presents the first known analysis of combined seasonal data on different fruit components at various growth stages for the two chosen litchi cultivars grown in India.

Effects of Foliar Ca and Mg Nutrients on the Respiration of ‘Feizixiao’ Litchi Pulp and Identification of Differential Expression Genes Associated with Respiration

The ‘Feizixiao’ litchi cultivar, predominantly grown in Hainan Province, faces the issue of “sugar receding” during fruit ripening. The application of mixed foliar nutrients containing calcium and magnesium (Ca+Mg) during the fruit pericarp’s full coloring stage was investigated to overcome this issue. Experimental trials unveiled significant alterations in litchi pulp physiochemical properties, including the main nutrient and flavor quality, the total respiration rates of the main respiratory pathways, and the activities of some important enzymes associated with Embden–Meyerhof–Parnas (EMP), the tricarboxylic acid cycle (TCA) and the pentose phosphate pathway (PPP). The Ca+Mg treatment showed higher sugar levels than the control (CK) during ripening. Notably, the application of Ca+Mg in litchi pulp inhibited respiration rates through the EMP, TCA, and PPP pathways, resulting in a strong effect. RNA sequencing analysis revealed the impact of Ca+Mg treatment on respiratory pathways, revealing differentially expressed genes (DEGs) such as pyruvate PK1, PK2 (pyruvate kinase), and PDC (pyruvate dehydrogenase complex), validated through qRT-PCR with a significant correlation to RNA-seq results. In general, Ca+Mg treatment during litchi fruit ripening overcame “sugar receding” by inhibiting the expression of respiration key metabolic pathway genes. These findings provide insights for enhancing cultivation management strategies.

Impact of flowering temperature on litchi yield under climate change: A case study in Taiwan

Litchi is a subtropical fruit tree that undergoes flower bud differentiation under low-temperature conditions. However, climate change has affected litchi production in Taiwan, causing litchi farmers to experience economic losses. This study explored the influence of flowering temperature on litchi yield under climate change in Taiwan by analyzing litchi production data from 2001 to 2020 and observation data from meteorological stations in litchi-producing areas. Historical observed data were used to construct several regression models relating temperature to yield, with the performance of the models used to determine critical temperature thresholds for litchi flower bud differentiation. Analytical climate data (CMIP5) were used to project yield changes in Taiwan’s litchi-producing regions under anticipated low-temperature conditions for the mid- (2036–2065) and late- (2071–2100) 21st century. The variable that exhibited the highest correlation with yield changes was the number of days with an average flowering temperature below 16 °C. The production yield, in terms of yield variation per hectare, is expected to decrease by 12 % to 35 % by the end of the 21st century (2071–2100). Given the projected decline in the number of cooler days due to climate change, existing litchi cultivars may become unsuitable for cultivation in production areas in southern Taiwan. Practical ImplicationsSome fruit trees require a period of low temperature before their flowering stage. Climate change is expected to cause warming of winter temperatures in Taiwan, which is likely to lead to reduced litchi flowering. The current study assessed the potential effects of climate change on litchi flowering in the future.Historical observed data were used to establish models, and critical temperature thresholds for litchi flowering were determined on the basis of model performance. Days with average temperatures below 16 °C exhibited the highest correlation with litchi yield among the tested thresholds. According to our results, farmers can use this 16 °C threshold to evaluate the potential effects of future climate change at their current farm locations and to identify other areas with similar or more favorable conditions for litchi cultivation. For agricultural researchers, this temperature threshold could provide a target for new litchi variety breeding and a reference basis for research on optimal cultivation methods.Notably, because climate change projection data have a high degree of uncertainty, the results of this study may differ from those of studies using different databases. In this study, we used an ensemble of CMIP5 projections incorporating data from models from various research centers around the world, which can provide more robust results based on an ensemble mean than those obtainable from a single model or a few models. In addition, rainfall is a crucial factor during the flowering growth stage. Future studies should consider the effects of rainfall and temperature on yield and should consider using a model with yield being considered a function of both of these variables to improve model accuracy.To conclude, the present study provides researchers, policymakers, and other stakeholders with insights into the primary effects of climate change on litchi production. It also lays the groundwork for future climate adaptation strategies in Taiwan’s litchi industry.

Metabolome and Transcriptome Analysis Provide Insights into Flower Bud Color Variation in the Adaptation to UV-B Radiation of Litchi

Flower color variations have increasingly been recognized as playing an important role in the adaptation to UV-B radiation; however, the underlying mechanism is poorly understood in perennial fruit trees. Litchi is an important fruit tree, and extremely early maturing (EEM) and middle-to-late-maturing (MLM) cultivars that originated from regions with high and low UV-B radiation have dark brown and light yellow flower buds, respectively, while their hybrid early-maturing (EM) cultivars have an intermediate brown flower bud. This study comprehensively analyzed the metabolome and transcriptome of flower buds of litchi EEM, EM and MLM cultivars to explore the mechanism underlying flower color variation during the adaptation to UV-B radiation for the first time. Metabolomic analysis identified 72 flavonoids in litchi flower buds, among which a higher accumulation of flavonol glycosides was responsible for darker flower buds of EEM cultivars. And transcriptome analysis revealed key structural genes, including LcCHI, LcFLS and seven UGTs, together with two transcription factors (LcMYB12 and LcMYB111), which could be directly up-regulated by UV-B radiation, playing critical roles in regulating the differential accumulation of flavonol glycosides. These results provide new insights into the molecular mechanism underlying adaptation to UV-B radiation and provide a genetic basis for future breeding of stress-tolerant cultivars of litchi.

An LcMYB111-LcHY5 Module Differentially Activates an LcFLS Promoter in Different Litchi Cultivars

Flavonol synthase (FLS) is the crucial enzyme of the flavonol biosynthetic pathways, and its expression is tightly regulated in plants. In our previous study, two alleles of LcFLS, LcFLS-A and LcFLS-B, have been identified in litchi, with extremely early-maturing (EEM) cultivars only harboring LcFLS-A, while middle-to-late-maturing (MLM) cultivars only harbor LcFLS-B. Here, we overexpressed both LcFLS alleles in tobacco, and transgenic tobacco produced lighter-pink flowers and showed increased flavonol levels while it decreased anthocyanin levels compared to WT. Two allelic promoters of LcFLS were identified, with EEM cultivars only harboring proLcFLS-A, while MLM cultivars only harbor proLcFLS-B. One positive and three negative R2R3-MYB transcription regulators of LcFLS expression were identified, among which only positive regulator LcMYB111 showed a consistent expression pattern with LcFLS, which both have higher expression in EEM than that of MLM cultivars. LcMYB111 were further confirmed to specifically activate proLcFLS-A with MYB-binding element (MBE) while being unable to activate proLcFLS-B with mutated MBE (MBEm). LcHY5 were also identified and can interact with LcMYB111 to promote LcFLS expression. Our study elucidates the function of LcFLS and its differential regulation in different litchi cultivars for the first time.

Increased DNA methylation of the splicing regulator SR45 suppresses seed abortion in litchi.

The gene regulatory networks that govern seed development are complex, yet very little is known about the genes and processes that are controlled by DNA methylation. Here, we performed single-base resolution DNA methylome analysis and found that CHH methylation increased significantly throughout seed development in litchi. Based on the association analysis of differentially methylated regions and weighted gene co-expression network analysis (WGCNA), 46 genes were identified as essential DNA methylation-regulated candidate genes involved in litchi seed development, including LcSR45, a homolog of the serine/arginine-rich (SR) splicing regulator SR45. LcSR45 is predominately expressed in the funicle, embryo, and seed integument, and displayed increased CHH methylation in the promoter during seed development. Notably, silencing of LcSR45 in a seed-aborted litchi cultivar significantly improved normal seed development, whereas the ectopic expression of LcSR45 in Arabidopsis caused seed abortion. Furthermore, LcSR45-dependent alternative splicing events were found to regulate genes involved in seed development. Together, our findings demonstrate that LcSR45 is hypermethylated, and plays a detrimental role in litchi seed development, indicating a global increase in DNA methylation at this stage.

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.

Aroma Volatiles in Litchi Fruit: A Mini-Review

Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with unique aromas have emerged during the past 2000 years of cultivation. In this review, our aim is to collect, compare, integrate, and summarize the available literature on the profiles of VOCs of 25 litchi cultivars. We showed that a total of 556 VOCs were reported from litchi fruit, and the aroma of litchi is mainly determined from the content and composition of monoterpenoids and alcohols, including linalool, geraniol, limonene, terpinolene, β-citronellol, p-cymene, nerol, α-terpineol, cis-rose oxide, β-myrcene, 4-terpineol, citral, and neral (cis-citral), which might contribute to the rose-like or citrus-like aroma of litchi fruit. Moreover, sulfur-containing volatile compounds (VSCs) possibly impart a special flavor to litchi fruit. This review would be a valuable resource for researchers aiming to improve litchi aroma quality by elucidating the possible mechanisms underlying VOC biosynthesis and their metabolism in litchi fruit.

Growth and Nutrient Concentration of Lychee Grown on an Acid Ultisol

Little is known about the adaptability of lychee (Litchi chinensis) to acidic soils high in aluminum (Al). A 2-year greenhouse study was conducted to determine the effects of various levels of soil Al on dry matter production, plant growth, and nutrient concentration in shoots of lychee cultivar rootstock seedlings (maternal half-sibs) of cultivars Brewster, Bostworth-3 (Kwai May Pink), and Kaimana. Soil Al treatments were statistically different for all variables measured in the study but not rootstock seedlings. Total leaf, stem, and root dry weights significantly decreased at soil Al concentrations ranging from 0.42 to 12.69 cmol·kg−1. Increments in soil Al resulted in a significant reduction in the concentration of leaf calcium and phosphorus and a significant increase in leaf Al in cultivar rootstock seedlings. The concentration of leaf potassium, magnesium, iron, zinc, and boron were in the optimum range for lychee, whereas leaf nitrogen and manganese concentrations were above optimum. The results of this study demonstrated no cultivar rootstock seedlings differences for dry matter production in lychee trees grown under Al stress and demonstrate that lychee is highly susceptible to acid soils.

Characterization and bioactivity of A-type procyanidins from litchi fruitlets at different degrees of development

Characterization and bioactivity of A-type procyanidins was investigated in litchi fruitlet (LF) at different stages and mature pericarp (MP) of 5 litchi cultivars. The content of total phenols in LFs was higher than that of MP and showed good antioxidant activity. Eleven procyanidins were identified in samples, including procyanidin A2, procyanidin A4, and 1 dimer, 2 trimers, and 1 tetramer of A-type procyanidin. Also, A-type procyanidin could stably exist in LFs stage, but declined substantially after maturity, which was about 1.45 – 3.56 times than mature pericarp. In addition, the second stage of LFs showed strong anti-inflammatory and anti-proliferative activities, in which monomer and A-type procyanidin trimers in LFs were significantly correlated with antioxidant (r > 0.72; p < 0.01) and anti-inflammatory (r = 0.53; p < 0.05) activities, respectively. Therefore, litchi in LF stage could be a good source of A-type oligomer procyanidins which had good application value.

Identification of Chilling-Responsive Genes in Litchi chinensis by Transcriptomic Analysis Underlying Phytohormones and Antioxidant Systems.

Litchi (Litchi chinensis Sonn.) is an important subtropical and tropical evergreen fruit tree that is seriously affected by chilling stress. In order to identify genes that may be involved in the response to chilling in litchi, we investigate the physiological and biochemical changes under chilling stress and construct 12 RNA-Seq libraries of leaf samples at 0, 4, 8, and 12 days of chilling. The results show that antioxidant enzymes are activated by chilling treatments. Comparing the transcriptome data of the four time points, we screen 2496 chilling-responsive genes (CRGs), from which we identify 63 genes related to the antioxidant system (AO-CRGs) and 54 ABA, 40 IAA, 37 CTK, 27 ETH, 21 BR, 13 GA, 35 JA, 29 SA, and 4 SL signal transduction-related genes. Expression pattern analysis shows that the expression trends of the 28 candidate genes detected by qRT-PCR are similar to those detected by RNA-Seq, indicating the reliability of our RNA-Seq data. Partial Least Squares Structural Equation Modeling (PLS-SEM) analysis of the RNA-Seq data suggests a model for the litchi plants in response to chilling stress that alters the expression of the plant hormone signaling-related genes, the transcription factor-encoding genes LcICE1, LcCBFs, and LcbZIPs, and the antioxidant system-related genes. This study provides candidate genes for the future breeding of litchi cultivars with high chilling resistance, and elucidates possible pathways for litchi in response to chilling using transcriptomic data.

Two divergent haplotypes from a highly heterozygous lychee genome suggest independent domestication events for early and late-maturing cultivars

Lychee is an exotic tropical fruit with a distinct flavor. The genome of cultivar ‘Feizixiao’ was assembled into 15 pseudochromosomes, totaling ~470 Mb. High heterozygosity (2.27%) resulted in two complete haplotypic assemblies. A total of 13,517 allelic genes (42.4%) were differentially expressed in diverse tissues. Analyses of 72 resequenced lychee accessions revealed two independent domestication events. The extremely early maturing cultivars preferentially aligned to one haplotype were domesticated from a wild population in Yunnan, whereas the late-maturing cultivars that mapped mostly to the second haplotype were domesticated independently from a wild population in Hainan. Early maturing cultivars were probably developed in Guangdong via hybridization between extremely early maturing cultivar and late-maturing cultivar individuals. Variable deletions of a 3.7 kb region encompassed by a pair of CONSTANS-like genes probably regulate fruit maturation differences among lychee cultivars. These genomic resources provide insights into the natural history of lychee domestication and will accelerate the improvement of lychee and related crops.

Physical Characterization, Nutrient, Phenolic Profiles and Antioxidant Activities of 16 litchi Cultivars Grown in the Upper Yangtze River Region.

Litchi grown in the upper Yangtze River region have the advantage of being late-maturing owing to the geographical location. This study aimed to evaluate the physical characteristics, nutritional values, phenolic composition and antioxidant activities of 16 litchi cultivars grown in the upper Yangtze River region. Litchi grown in this region had total soluble solid and ascorbic acid contents comparable with those of cultivars grown in other locations. The total polyphenol contents were determined using the Folin-Ciocalteu assay, and the phenolic profiles were determined using UPLC-QqQ-MS/MS. Nine phenolic compounds were identified and quantified in this study. Naringin, rutin and p-coumaric acid were the major phenolic compounds in all the litchi cultivars. Statistical analysis of all the physiochemical results was performed using principal component analysis. Our results indicated that litchi grown in the upper Yangtze River region not only showed the late-maturity characteristic but were also good dietary sources of phenolic compounds and antioxidants. In particular, 'Fei Zi Xiao' and 'Jing Gang Hong Nuo', characterized by high polyphenol contents and high antioxidant capacities, were of superior comprehensive quality. This study provides important information for the development of late-maturing litchi industry.

Assessment of Fruit Drop in Different Cultivars of Litchi

Individual panicles produce hundreds of pistillate flowers but only a small proportion of these bear fruit and reach maturity. There are some stages of fruit drop during growth and development caused by different factors. An experimental trial was conducted in National Active Germplasm Site (NAGS) at ICAR-NRC on Litchi, Muzaffarpur, to assess the fruit drop due to different factors during 2014–2015. The result revealed that four factors viz., improper pollination and fertilization, embryo abortion, seed and fruit borer, and normal fruit abscission were associated with fruit drop in litchi and fruit drop varied from 23.53–77.54% with a maximum in Shahi and lowest in Elaichi during the first week of flowering. Fruit drop increased to 92.65–97.86% during the third week of flowering because of improper pollination and fertilization, and it reached a maximum level of 98.51–99.70% at the time of ripening stage with the lowest in Deshi. Embryo abortion was one primary cause of fruit drop during the 4th week whereas infestation of seed and fruit borer was the major factor for fruit drop during the 5–7th week. Such fruit drop can be controlled by managing the infestation of borer. Abscission due to ethylene production and heat stress during the maturity of fruit was yet another cause of fruit drop. This study will help to researcher to find out the time of infestation of seed and fruit borer which causes heavy fruit drop and it can be controlled with pest management option.

Development of molecular markers based on the promoter difference of LcFT1 to discriminate easy- and difficult-flowering litchi germplasm resources and its application in crossbreeding

BackgroundLitchi is a well-known subtropical fruit crop. However, irregular bearing attributed to unstable flowering is a major ongoing problem for the development of the litchi industry. In a previous study, our laboratory proved that litchi flowering was induced by low temperature and that a FLOWERING LOCUS T (FT) homologue gene named LcFT1 played a pivotal role in this process. The present study aimed to understand the natural variation in FT among litchi germplasm resources and designed markers to verify easy- and difficult-flowering litchi germplasms. A grafting experiment was also carried out to explore whether it could shorten the seedling stage of litchi seedlings.ResultsTwo types of LcFT1 promoter existed in different litchi germplasm resources, and we named them the ‘easy-flowering type of LcFT1 promoter’ and ‘difficult-flowering type of LcFT1 promoter’, which resulted in three different LcFT1 genotypes of litchi germplasm resources, including the homozygous easy-flowering type of the LcFT1 genotype, homozygous difficult-flowering type of the LcFT1 genotype and heterozygous LcFT1 genotype of litchi germplasm resources. The homozygous easy-flowering type of the LcFT1 genotype and heterozygous LcFT1 genotype of the litchi germplasm resources completed their floral induction more easily than the homozygous difficult-flowering type of the LcFT1 genotype of litchi germplasm resources. Herein, we designed two kinds of efficient molecular markers based on the difference in LcFT1 promoter sequences and applied them to identify of the easy- and difficult-flowering litchi germplasm resources. These two kinds of molecular markers were capable of clearly distinguishing the easy- from difficult-flowering litchi germplasm resources at the seedling stage and provided the same results. Meanwhile, grafting the scion of seedlings to the annual branches of adult litchi trees could significantly shorten the seedling stage.ConclusionsUnderstanding the flowering characteristics of litchi germplasm resources is essential for easy-flowering litchi breeding. In the present study, molecular markers provide a rapid and accurate approach for identifying the flowering characteristics. The application of these molecular markers not only significantly shortened the artificial crossbreeding cycle of easy-flowering litchi cultivars but also greatly saved manpower, material resources and land.

Construction of high-density SNP genetic maps and QTL mapping for dwarf-related traits in Litchi chinensis Sonn

Litchi chinensis Sonn is widely cultivated in subtropical regions and has an important economic value. A high-density genetic map is a valuable tool for mapping quantitative trait loci (QTL) and marker-assisted breeding programs. In this study, a single nucleotide polymorphism (SNP)-based high-density linkage map was constructed by a genotyping-by-sequencing (GBS) protocol using an F1 population of 178 progenies between two commercial litchi cultivars, ‘Ziniangxi’ (dwarf) and ‘Feizixiao’ (vigorous). The genetic map consisted of 3027 SNP markers with a total length of 1711.97 cM in 15 linkage groups (LGs) and an average marker distance of 0.57 cM. Based on this high-density linkage map and three years of phenotyping, a total of 37 QTLs were detected for eight dwarf-related traits, including length of new branch (LNB), diameter of new branch (DNB), length of common petiole (LCP), diameter of common petiole (DCP), length of internode (LI), length of single leaf (LSL), width of single leaf (WSL), and plant height (PH). These QTLs could explain 8.0 to 14.7% (mean=9.7%) of the phenotypic variation. Among them, several QTL clusters were observed, particularly on LG04 and LG11, which might show enrichment for genes regulating the dwarf-related traits in litchi. There were 126 candidate genes identified within the QTL regions, 55 of which are differentially expressed genes by RNA-seq analysis between ‘Ziniangxi’ and ‘Feizixiao’. These DEGs were found to participate in the regulation of cell development, material transportation, signal transduction, and plant morphogenesis, so they might play important roles in regulating plant dwarf-related traits. The high-density genetic map and QTLs identification related to dwarf traits can provide a valuable genetic resource and a basis for marker-assisted selection and genomic studies of litchi.

FRUIT ORIENTATION ALTERS THE QUALITY OF LITCHI (LITCHI CHINENSIS SONN.) UNDER THE AGRO-CLIMATIC CONDITIONS OF EASTERN INDIA

Objective: The experiment was conducted on ten litchi cultivars, namely; Purbi, Bedana, Lal Bombay, Mandaraji, Calcuttia, Late Bedana, Trikolia, Dehradoon, Dehrarose, and Seedless No. 2 to assess the physical and chemical composition of fruit as affected by fruit orientation on the tree.&#x0D; Methods: Fruits were picked both from the lower and upper half portion of the tree at fully ripened stage and physio-chemical attributes were analyzed.&#x0D; Results: The result indicated that fruits at lower half portion were not only heavy in weight but also had more percentage of total acidity. However, stone weight, ascorbic acid content, and total sugars were found to be more in fruits collected from the upper half portion of the tree.&#x0D; Conclusion: It can be suggested that picking should be started from those fruits which are positioned at the lower half portion of the tree to collect fruits of superior quality.

Effect of Mode of Pollination on Fruit Set and Fruit Characteristics in Litchi

An experiment was conducted during 2017 and 2018 at active field gene bank of ICAR-National Research Centre on Litchi to assess the effect of open cross pollination and self-pollination on fruit set and fruit characteristics in litchi. Nine cultivars of litchi were selected for study and result indicated that fruit set ranged from 17.41 to 68.14 per cent with maximum in ‘Ellaichi’ and minimum in ‘Shahi’. The only three cultivars ‘Ajhauli’, ‘Dehradoon’ and ‘Rose Scented’ carried out fruit (0.28, 0.41 and 2.11%, respectively) at harvest under self-pollination condition while all nine cultivars carried out fruit at harvest ranged from 1.23 to 3.16 with maximum in ‘Rose Scented’ and minimum in ‘Dehradoon’ under open cross pollination. ‘Dehradoon’ had shown 3.23 fold more fruit set at harvest under open cross pollination as compare to self-pollination, similarly ‘Rose Scented’ and ‘Ajhauli’ has shown 2.98 fold and 10.5 fold, respectively more fruit set at harvest compare to self-pollination. The fruit weight was heavier in all three cultivars ‘Dehradoon’ (21.46 g), ‘Rose Scented’ (20.37 g) and ‘Ajhauli’ (18.95 g) in open cross pollination as compare to self-pollinated ‘Dehradoon’ (19.67 g), ‘Rose Scented’ (18.89 g) and ‘Ajhauli’ (17.35 g). The relatively self-incompatible was observed in ’Late Large Red’, ‘Ellaichi’, ‘Dehradoon’, ‘Rose Scented’ whereas severely self-incompatible was found in ‘Shahi’ and ‘Ajhauli’. The completely self-incompatibility was observed in ‘Trikolia’, ‘Dehra Rose’ and ‘Deshi’.

Improved prediction of litchi impact characteristics with an energy dissipation model

A model of elastic impact (EI) and a model that considers energy dissipation (CED model) were developed to describe the deformation behavior during litchi impact. In the CED model, dissipation energy is due to damping effect and the change of elastic modulus after impact. Drop tests of fruit onto a fixed plate were conducted with a pendulum device for three litchi cultivars (‘Nuomci’, ‘Guiwei’, and ‘Lvhebao’) to test the accuracy of the two models. The results show that the CED model better simulated the change of fruit velocity during impact and better predicted the occurrence time of maximum impact force and maximum deformation compared to the EI model. Both models accurately predicted the maximum impact force of ‘Guiwei’ litchi with all errors less than 5 %, but had errors up to 24.8 % for the prediction of the maximum impact force of ‘Nuomici’ and ‘Lvhebao’ litchis at high drop heights (drop height ≥ 400 mm). The CED model accurately predicted maximum deformation (errors less than 8 %) but the EI model over-predicted maximum deformation with errors range from 12.2 % to 39.2 % at all drop heights for the three tested cultivars. Both models predicted the contact time with low-level errors (<10 %). With a reliable theoretical model, the impact characteristics of litchis can be calculated and then applied to assess the fruit damage degree.

Metabolite Differences of Polyphenols in Different Litchi Cultivars (Litchi chinensis Sonn.) Based on Extensive Targeted Metabonomics.

Litchi is an important fruit cultivated in tropical and subtropical areas with high nutritious and delicious flavor and the pulp is the main part of the fruit consumed. Previous studies found that litchi had high total phenol content and antioxidant activity, but most of them focused on the identification of single or a few phenolic components with a low throughput test, and the metabolic differences of cultivars are still unknown to a some extent. In this study we used widely targeted metabolome based on ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS/MS) to analyze the polyphenol metabolites of five different genotypes of mature litchi fruit. A total of 126 polyphenol metabolites in eight categories were identified to reveal the composition and differences of polyphenol; 15 common differential metabolites and 20 specific differential metabolites to each cultivar were found for the first time. The results infer that flavonoids, flavonols, hydroxycinnamoyls and catechins are the main polyphenol metabolites of litchi pulp. Cluster analysis showed that there were three groups of polyphenols from high to low; early maturing Feizhixiao is a kind of high polyphenol content cultivars, especially in catechins, anthocyanins, flavonols, quinic acids and hydroxycinnamoyls. The polyphenols in the flesh of mature litchi are rich, and there are significant differences among cultivars; there was a level of correlation between the contents of phenolics and the maturity of litchi cultivars; the content of phenolics in early maturing litchi cultivars appeared higher than those of mid- to late-maturing cultivars. This experiment will provide significant reference information for cultivation, breeding, processing and consumption.