Subtropical Fruit Tree Research Articles

Reuse of Pruning Waste from Subtropical Fruit Trees and Urban Gardens as a Source of Nutrients: Changes in the Physical, Chemical, and Biological Properties of the Soil

A field experiment was conducted on the Andalusian coast (Granada, Southern Spain) to study the time course of nutrient release into the soil after the addition of bagged pruning waste from subtropical orchard trees (avocado, cherimoya, and mango) and urban garden waste over three two-year periods. N, P, and K concentrations were greater in the garden waste, whilst avocado and cherimoya pruning waste registered the highest values for Mg. In general, micronutrient contents were low in all waste, especially Cu. Macronutrient release followed a three-phase dynamic: fast initial release, intermediate stabilization, and final increase. Garden waste showed a similar time course in all three trees and released greater concentrations of K and P. The annual decomposition rate factor k was negative for N and Ca in the avocado tree, indicating strong biological activity in this plot. Avocado, cherimoya, and garden waste showed a good microbial degradation, improving soil quality by increasing carbon and nitrogen contents as well as soil microbial activity. As for the mango tree, its special microclimatic conditions appeared to favor waste photodegradation, thus eliminating nutrients that were not incorporated into the soil. Soil enzymatic activities increased in the avocado and cherimoya trees with the addition of all waste. In the mango tree, only an increase in urease was detected after the addition of garden waste. Our results suggest that the time course of organic waste in different subtropical trees grown on similar soils is significantly conditioned by the microclimatic characteristics.

Transcriptional analysis of the response of nectarine fruit to low-temperature stress in cold storage

ABSTRACT Nectarine (Prunus persica var. nectarina) is a sub-tropical fruit tree with strong cold sensitivity. In this study, flesh of nectarine (Shuguang) was used to determine the difference in transcriptional data before and after chilling injury under storage. In addition, genes responses involved in nectarine acclimation to cold stress were also explored. Results of the current study showed that nectarine was found to be more susceptible to chilling injury during storage at 5°C than at 0°C, and differentially expressed genes (DEGs) were concentrated in the late stage of low-temperature storage where chilling injury symptoms appeared at the end of the experiment. The key genes related to low-temperature response were associated with post-harvest biological processes. DEGs were annotated on the metabolic pathways of cold regulation signal transduction, cold resistance physiological metabolism and cold resistance-related protein synthesis. Moreover, the expression of genes related to cold stress such as plant hormone signal transduction element such as Auxin-responsive protein, transcription factors responding to cold stress such as WRKY transcription factor and genes related to maintaining membrane stability and regulating physiological metabolism such as proline dehydrogenase was more pronounced when nectarine was stored at 5°C than at 0°C. Overall, these findings showed that alteration in chilling temperature has substantial impact on the transcription levels associated with cold resistance pathway during the low-temperature storage of nectarine and thus promotes chilling injury disorders in nectarine.

A review on Active Constituents and Pharmacological Effects of Eriobotrya Japonica Lindl. (Loquat)

Eriobotrya japonica Lindl., named as loquat, is a subtropical fruit tree of the family Rosaceae which is well known medical plant originated in Japan and China. Loquat portions, like leaves, peels and fruits have been shown to possess various health usefulnesses. In Chinese classical medicine, it is vastly utilized in many illnesses, like gastroenteric disorders, diabetes mellitus, pulmonary inflammatory diseases and chronic bronchitis. Loquat plant contain many active constituents, such as flavonoids, carotenoids, vitamins, polyphenolic compounds, other that have many biological effects like anti-tumor, anti-diabetic, anti-inflammatory, anti-mutagenic, antioxidant, antiviral, antitussive, hepatoprotective and hypolipidemic activity.

Studies on Cultivation Managements for Stable Fruit Set in Subtropical Fruit Trees:

Studies on Cultivation Managements for Stable Fruit Set in Subtropical Fruit Trees:

Total Sesquiterpene Glycosides from Loquat Leaves Ameliorate HFD-Induced Insulin Resistance by Modulating IRS-1/GLUT4, TRPV1, and SIRT6/Nrf2 Signaling Pathways.

Loquat (Eriobotrya japonica Lindl.), a subtropical fruit tree native to Asia, is not only known to be nutritive but also beneficial for the treatment of diabetes in the south of China. To expand its development, this study was undertaken concerning the potential therapeutic role of total sesquiterpene glycosides (TSGs) from loquat leaves in insulin resistance (IR), the major causative factor of type 2 diabetes mellitus (T2DM). Male C57BL/6 mice were fed on high-fat diet (HFD) to induce IR and then were given TSG by oral administration at 25 and 100 mg/kg/day, respectively. TSG notably improved metabolic parameters including body weight, serum glucose, and insulin levels and prevented hepatic injury. Moreover, inflammatory response and oxidative stress were found to be remarkably alleviated in IR mice with TSG supplement. Further research in liver of IR mice demonstrated that TSG repaired the signalings of insulin receptor substrate-1 (IRS-1)/glucose transporter member 4 (GLUT4) and AMP-activated protein kinase (AMPK), which improved glucose and lipid metabolism and prevented lipid accumulation in liver. It was also observed that TSG suppressed the expression of transient receptor potential vanilloid 1 (TRPV1), whereas the signaling pathway of sirtuin-6 (SIRT6)/nuclear factor erythroid 2-related factor 2 (Nrf2) was significantly promoted. Based on the results, the current study demonstrated that TSG from loquat leaves potentially ameliorated IR in vivo by enhancing IRS-1/GLUT4 signaling and AMPK activation and modulating TRPV1 and SIRT6/Nrf2 signaling pathways.

Hand Pruning and Training of Tropical and Subtropical Fruit Trees

This new 6-page document explains the proper way to prune fruit trees using hand tools. An important aspect of growing tropical and subtropical fruit trees is size control through pruning. In addition to size control, pruning also makes it easier to spray the tree and harvest fruit from the tree. Pruning also makes the tree more hardy to wind events and healthier in general because you can remove damaged or unhealthy parts of the tree. Written by Jeff Wasielewski, Jonathan Crane, and Carlos Balerdi, and published by the UF/IFAS Horticultural Sciences Department.https://edis.ifas.ufl.edu/hs1372

Impacts of climate change on potential geographical cultivation areas of longan (Dimocarpus longan) in China

AbstractLongan is an economically important sub-tropical fruit tree native to southern China and southeast Asia. Its production has been affected significantly by climate change, but the underlying reasons remain unclear. Herein, the potential growing areas of longan were simulated by the Maxent model under current and future conditions. The results showed excellent prediction performance, with an area under curve of >0.9 for model training and validation. The key environmental variables identified were mean temperature of the coldest quarter, minimum temperature of the coldest month, annual mean temperature and mean temperature of the driest quarter. The optimum suitable areas of longan were found to be concentrated mainly in south-western, southern and eastern China, with a slight increase in optimum suitable areas under two different emission scenarios of three global climatic models. However, its future potential growing areas were predicted to differ among provinces or cities. Suitable growing areas in Sichuan, Jiangxi, Guangxi and Chongqing will first increase and then remain approximately unchanged between the 2050s and 2070s; those in Yunnan, Guangdong and Hainan will remain approximately unchanged from the present to the 2070s; those in Fujian and Guizhou will fluctuate slightly from the present to the 2050s and then increase to the 2070s; those in Taiwan will first decrease and then increase. In summary, the major future production areas of longan will be Guangdong, Hainan and Guangxi provinces, followed by Chongqing, Yunnan, Fujian and Taiwan. Thus, this study serves as a useful guide for the management of longan.

Three Novel C-Repeat Binding Factor Genes of Dimocarpus longan Regulate Cold Stress Response in Arabidopsis.

Longan (Dimocarpus longan) is a typical southern subtropical fruit tree species that is sensitive to cold stress. C-repeat binding factors (CBFs), as transcription factors, are crucial components involved in the molecular regulation of the plant response to cold stress. However, the role of CBF homologs in the cold response regulation of longan remains largely unknown. Here, three novel CBF genes, DlCBF1, DlCBF2, and DlCBF3, were cloned from longan. DlCBF1 and DlCBF2 contain an AP2 domain and PKKPAGR and DSAWR CBF signature motifs, while DlCBF3 has mutations within these conserved signature motifs. DlCBF1/2/3 were mainly localized in the nucleus and specifically bound to CRT/DRE cis-elements, resulting in strong transcriptional activation. DlCBF1/2 exhibited tissue expression specificity, and their expression was induced by low temperature, while DlCBF3 had no tissue specificity and barely responded to low temperature. DlCBF1, DlCBF2, and DlCBF3 overexpression in Arabidopsis-enhanced cold tolerance by increasing proline accumulation and reducing reactive oxygen species (ROS) content, accompanied by upregulated expression of cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47, and AtKIN1) in the CBF cold stress response signaling pathway. In conclusion, the biological functions of DlCBF1/2/3 were somewhat conserved, but slow expression of DlCBF1/2 and low expression of DlCBF3 may partly cause the cold sensitivity of longan. Collectively, these results indicated that differences exist in the expression and function of CBF orthologs in the cold-sensitive plant species longan, and these findings may help to improve the understanding of the cold response regulation mechanism and provide important theoretical support for cold-tolerant breeding of longan.

Genome-Wide Transcriptomic Analysis Reveals a Regulatory Network of Oxidative Stress-Induced Flowering Signals Produced in Litchi Leaves.

Litchi is an important subtropical fruit tree that requires an appropriately low temperature to trigger floral initiation. Our previous studies have shown that reactive oxygen species (ROS) are involved in litchi flowering. To identify oxidative stress-induced flowering related genes in leaves, ‘Nuomici’ potted trees were grown at medium low-temperature conditions (18/13 °C for day/night, medium-temperature). The trees were treated with the ROS generator methyl viologen dichloride hydrate (MV) as the MV-generated ROS treatment (MM, medium-temperature plus MV) and water as the control treatment (M, medium-temperature plus water). Sixteen RNA-sequencing libraries were constructed, and each library generated more than 5,000,000 clean reads. A total of 517 differentially expressed genes (DEGs) were obtained. Among those DEGs, plant hormone biosynthesis and signal transduction genes, ROS-specific transcription factors, such as AP2/ERF and WRKY genes, stress response genes, and flowering-related genes FLOWERING LOCUS T1 (FT1) and FLOWERING LOCUS T2 (FT2) were significantly enriched. Then, as a confirmatory experiment, the potted trees were uniformly sprayed with MV, N,N’-dimethylthiourea (DMTU, ROS scavenger) plus MV, and water at medium-temperature. The results showed that the MV-generated ROS promoted flowering and changed related gene expression, but these effects were repressed by DMTU treatment. The results of our studies indicate that ROS could promote flowering and partly bypass chilling for litchi flowering.

Creation of an avocado unambiguous genotype SNP database for germplasm curation and as an aid to breeders

Avocado (Persea americana) is an important tropical and subtropical fruit tree crop. Traditional tree breeding programs face the challenges of long generation times and significant expense in land and personnel resources. Avocado selection and breeding can be more efficient and less expensive through the development and application of molecular markers. A total of 1524 individuals were genotyped with 384 SNPs creating the largest SNP genotype database for avocado. These individuals correspond to four extensive germplasm collections including two housed in Florida and two in California. In addition, hybrids and selections from two rootstock breeding programs have been genotyped. Genotype data were analyzed using an affinity propagation method to define 155 groups. The 384 SNP markers provided accurate genotype data for individuals from different Persea species as well as half-siblings. Therefore, the majority of the genetic diversity of the avocado germplasm and related species that were genotyped has been captured. A simple visual method can also be used to identify self-pollinated individuals among the half-siblings of known maternal parents and, in some cases, to infer likely candidates for the paternal parent. Finally, this dataset is unambiguous so breeders can determine the genetic diversity of their breeding stock to optimize avocado breeding and selection programs by identifying outcrossed individuals at the seedling stage, thus increasing the efficiency of avocado genetic improvement.

Occurrence of algal leaf spot on longan (Dimocarpus longan ) caused by Cephaleuros virescens in India

Longan (Dimocarpus longan Lour. ) is an evergreen subtropical fruit tree species of Sapindaceae family with a long cultivation tradition in South East Asia. Between July to September of 2014 and 2015, leaves of longan trees were found infected by green algae at experimental farm of National Research Centre on Litchi, Muzaffarpur, Bihar (India). The symptoms of the disease appeared on the upper leaf surface as dark gray to reddish-rust coloured lesions, slightly raised with a velvet-like appearance. The disease incidence among leaves was 28. 4-57. 3% while percent disease severity index was 13. 3 to 20. 2. The algal thalli were isolated and cultured successfully on potato dextrose agar and Bold's basal medium but there was no development of sporangiophores and sporangia in culture. In pathogenicity test, inoculums either from naturally infected leaves or from pure culture of algal filaments could not reproduce typical symptom of the disease even up to three months of inoculation. Based on the leaf symptom and morphological characteristics, the pathogen was identified as Cephaleuros virescens Kunze. To our knowledge, this is the first report of leaf spots caused by Cephaleuros virescens on longan trees in India.

DlICE1, a stress-responsive gene from Dimocarpus longan, enhances cold tolerance in transgenic Arabidopsis

ICE1 (inducer of CBF expression 1) encodes a typical MYC-like basic helix-loop- helix (bHLH) transcription factor that acts as a pivotal component in the cold signalling pathway. In this study, DlICE1, a novel ICE1-like gene, was isolated from the southern subtropical fruit tree longan (Dimocarpus longan Lour.). DlICE1 encodes a nuclear protein with a highly conserved bHLH domain. DlICE1 expression was slightly upregulated under cold stress. Overexpression of DlICE1 in Arabidopsis conferred enhanced cold tolerance via increased proline content, decreased ion leakage, and reduced malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. Expression of the ICE1-CBF cold signalling pathway genes, including AtCBF1/2/3 and cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47 and AtKIN1), was also significantly higher in DlICE1-overexpressing lines than in wild-type (WT) plants under cold stress. In conclusion, these findings indicate that DlICE1 is a member of the bHLH gene family and positively regulates cold tolerance in D. longan.

Field application of entomopathogenic nematodes against Thaumatotibia leucotreta in South African avocado, litchi and macadamia orchards

False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is an important pest of fruit trees in South Africa. The subtropical fruit tree crop industries use a combination of techniques for T. leucotreta suppression. Semi-field trials were conducted in avocado, litchi and macadamia orchards, using four entomopathogenic nematode (EPN) species. The effect on T. leucotreta mortality, directly after application (two days), as well as on persistence for 7, 14, 21, 28, 35, and 42 days post-application, was determined. Results from the field trials, using 30 IJs cm2 of Steinernema yirgalemense, showed the highest mortality of 86% directly after application, with Steinernema litchii being the least effective of the four EPN species, with 63% mortality. High persistence was found until day 14, with a steep decline thereafter until day 28. Local South African EPN species showed great potential for the future control of the late instar T. leucotreta, with the added advantage of persistence.

Genome-wide characterization of the auxin response factor (ARF) gene family of litchi (Litchi chinensisSonn.): phylogenetic analysis, miRNA regulation and expression changes during fruit abscission

Auxin response factors (ARFs) play fundamental roles in modulating various biological processes including fruit development and abscission via regulating the expression of auxin response genes. Currently, little is known about roles of ARFs in litchi (Litchi chinensis Sonn.), an economically important subtropical fruit tree whose production is suffering from fruit abscission. In this study, a genome-wide analysis of ARFs was conducted for litchi, 39 ARF genes (LcARFs) were identified. Conserved domain analysis showed that all the LcARFs identified have the signature B3 DNA-binding (B3) and ARF (Aux_rep) domains, with only 23 members having the dimerization domain (Aux_IAA). The number of exons in LcARF genes ranges from 2 to 16, suggesting a large variation for the gene structure of LcARFs. Phylogenetic analysis showed that the 39 LcARFs could be divided into three main groups: class I, II, and III. In total, 23 LcARFs were found to be potential targets of small RNAs, with three conserved and one novel miRNA-ARF (miRN43-ARF9) regulatory pathways discovered in litchi. Expression patterns were used to evaluate candidate LcARFs involved in various developmental processes, especially in flower formation and organ abscission. The results revealed that most ARF genes likely acted as repressors in litchi fruit abscission, that is, ARF2D/2E, 7A/7B, 9A/9B, 16A/16B, while a few LcARFs, such as LcARF5A/B, might be positively involved in this process. These findings provide useful information and resources for further studies on the roles of ARF genes in litchi growth and development, especially in the process of fruit abscission.

Reproductive biology of avocado (Persea americana)

Avocado is a subtropical fruit tree that shows protogynous dichogamy. As a consequence, each bisexual flower opens twice: first functionally as female (stigmatic surface receptive), then the flower closes and reopens the next day functionally as male (dehiscence of anthers). In avocado, more that 99% of the flowers produced at anthesis are not able to set fruits. In order to study why most flowers prematurely abscise while some of them remain in the tree, we analyzed the progamic phase (from pollination to fertilization) under the environmental conditions of southern Spain. Our results showed that pollination is a critical step in avocado fruit set since most of the flowers had received no pollen at the time of closing in the female stage. Although the probability of a flower developing into a fruit was significantly affected by the number of pollen grains adhered to the stigma, fertilization and subsequent fruit set can take place with a low number of pollen grains on the stigma. Moreover, a high pollen adhesion also occurs during the male stage, and, although the stigma maintains the capacity to support pollen germination, no fertilization was observed in flowers pollinated during the male stage. Even after hand-pollination and, in spite of the higher fruit retention observed, fruit set rate was still very low. This suggests that additional factors might be involved in fruit set. The results are discussed in terms of the implications of the environmental conditions on reproductive success and fruit set in avocado.

Comprehensive tissue-specific transcriptome profiling of pineapple (Ananas comosus) and building an eFP-browser for further study.

Pineapple is one of the most economically important tropical or subtropical fruit trees. However, few studies focus on the development of its unique collective fruit. In this study, we generated a genome-wide developmental transcriptomic profile of 14 different tissues of the collective fruit of the pineapple covering each of the three major fruit developmental stages. In total, 273 tissue-specific and 1,051 constitutively expressed genes were detected. We also performed gene co-expression analysis and 18 gene modules were classified. Among these, we found three interesting gene modules; one was preferentially expressed in bracts and sepals and was likely involved in plant defense; one was highly expressed at the beginning of fruit expansion and faded afterward and was probably involved in endocytosis; Another gene module increased expression level with pineapple fruit development and was involved in terpenoid and polyketide metabolism. In addition, we built a pineapple electronic fluorescent pictograph (eFP) browser to facilitate exploration of gene expression during pineapple fruit development. With this tool, users can visualize expression data in this study in an intuitive way. Together, the transcriptome profile generated in this work and the corresponding eFP browser will facilitate further study of fruit development in pineapple.

Application of genomic tools to avocado (Persea americana) breeding: SNP discovery for genotyping and germplasm characterization

Avocado (Persea americana) is an important tropical and subtropical fruit tree crop. Traditional tree breeding programs face the challenges of long generation time and significant expense in land and personnel resources. Avocado selection and breeding can be more efficient and less expensive through the development of molecular markers for the estimation of germplasm genetic diversity, marker-assisted selection (MAS), and creation of linkage maps. Two important breeding resources, the world's two largest avocado mapping populations and an extensive germplasm collection, are housed at the USDA-ARS Subtropical Horticulture Research Station (SHRS) in Miami, Florida. However, to use these resources to their greatest advantage, many thousands of genetic markers are necessary. Here, we describe the development of the first set of avocado genetic markers based on single-nucleotide polymorphism (SNP) variation in expressed genes. RNA sequencing was used both to build a reference transcriptome from 'Hass', the most widely grown avocado cultivar worldwide, and to identify SNPs by alignment of RNA sequences from the mapping population parents to the ˈHassˈ transcriptome. This study provides a new genomic tool for the avocado community that can be used to assess the genetic diversity of avocado germplasm worldwide and to optimize avocado breeding and selection programs by complementing traditional breeding methods with molecular approaches, thus increasing the efficiency of avocado genetic improvement.

Cloning and Characterization of a Flavonol Synthase Gene From Litchi chinensis and Its Variation Among Litchi Cultivars With Different Fruit Maturation Periods.

Litchi (Litchi chinensis) is an important subtropical fruit tree with high commercial value. However, the short and centralized fruit maturation period of litchi cultivars represents a bottleneck for litchi production. Therefore, the development of novel cultivars with extremely early fruit maturation period is critical. Previously, we showed that the genotypes of extremely early-maturing (EEM), early-maturing (EM), and middle-to-late-maturing (MLM) cultivars at a specific locus SNP51 (substitution type C/T) were consistent with their respective genetic background at the whole-genome level; a homozygous C/C genotype at SNP51 systematically differentiated EEM cultivars from others. The litchi gene on which SNP51 was located was annotated as flavonol synthase (FLS), which catalyzes the formation of flavonols. Here, we further elucidate the variation of the FLS gene from L. chinensis (LcFLS) among EEM, EM, and MLM cultivars. EEM cultivars with a homozygous C/C genotype at SNP51 all contained the same 2,199-bp sequence of the LcFLS gene. For MLM cultivars with a homozygous T/T genotype at SNP51, the sequence lengths of the LcFLS gene were 2,202–2,222 bp. EM cultivars with heterozygous C/T genotypes at SNP51 contained two different alleles of the LcFLS gene: a 2,199-bp sequence identical to that in EEM cultivars and a 2,205-bp sequence identical to that in MLM cultivar ‘Heiye.’ Moreover, the coding regions of LcFLS genes of other MLM cultivars were almost identical to that of ‘Heiye.’ Therefore, the LcFLS gene coding region may be used as a source of diagnostic SNP markers to discriminate or identify genotypes with the EEM trait. The expression pattern of the LcFLS gene and accumulation pattern of flavonol from EEM, EM, and MLM cultivars were analyzed and compared using quantitative real-time PCR (qRT-PCR) and high-performance liquid chromatography (HPLC) for mature leaves, flower buds, and fruits, 15, 30, 45, and 60 days after anthesis. Flavonol content and LcFLS gene expression levels were positively correlated in all three cultivars: both decreased from the EEM to MLM cultivars, with moderate levels in the EM cultivars. LcFLS gene function could be further analyzed to elucidate its correlation with phenotype variation among litchi cultivars with different fruit maturation periods.

Characterization of soursop population (Annona muricata) from the central region of ecuadorian littoral using ISSR markers

Soursop (Annona muricata L.) is a subtropical fruit tree very desirable for the flavor of its fruit and its nutritional value. In Ecuador, this fruit species grows endemically in the south of Manabi. For this reason the aim of this research was to characterize molecularly a population of 60 individuals distributed in four counties (Jipijapa, Pajan, 24 de Mayo and Olmedo) of this province. Plant DNA was extracted and amplified using 8 ISSR molecular markers. All the markers were informative; however, ISSR 824 and ISSR 873 stood out because they obtained the highest PIC value (0.29). Four groups were formed, with group 2 involving the largest number of individuals, including the entire population of Jipijapa and the highest proportion of the population of 24 de Mayo. Results showed a moderate genetic variability of the study population. This research provides information on the diversity of A. muricata in order to promote future advances in fruit breeding in Ecuador.

Entomopathogenic nematodes from north-eastern South Africa and their virulence against false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae)

ABSTRACTA survey was undertaken to determine the diversity and frequency of endemic entomopathogenic nematodes (EPN) in subtropical regions in the Mpumalanga, Limpopo and KwaZulu-Natal provinces of South Africa. A total of 136 soil samples were randomly taken from cultivated and uncultivated habitats, including subtropical fruit tree orchards (avocado, litchi, macadamia, mango and guava) and adjoining natural vegetation. EPNs were isolated from 14 samples (10.3%) by means of baiting with Tenebrio molitor larvae. Heterorhabditis was the most common genus isolated from 12 samples, whereas only two Steinernema species were isolated. The most common Heterorhabditis isolated were Heterorhabditis noenieputensis and H. zealandica, which were both isolated from four samples each. The present report is the first occurrence of H. taysearae and H. baujardi in South Africa. The two Steinernema species are both unknown species. Laboratory bioassays were conducted to determine the potential of seven native EPN isolates to control the false codling moth (Thaumatotibia leucotreta) (FCM). Last instar FCM larvae were found to be most susceptible to S. yirgalemense (157-C), H. zealandica (WS 23) and Steinernema litchii (WS9), when exposed to 50 IJs/50 µℓ water for 48 h, causing 100%, 94.2% and 93.5% mortality, respectively.