Longan Cultivars Research Articles

Endogenous target mimics, microRNA167, and its targets ARF6 and ARF8 during somatic embryo development in Dimocarpus longan Lour.

microRNA167 regulates vegetative and reproductive growth by controlling expression patterns of auxin response factors 6 and 8 (ARF6/8) in plants. However, their mutual regulatory roles during plant embryo development are still unknown. Here, we first identified miR167 family members, isolated the primary miR167 and its promoter, predicted endogenous target mimics (eTMs), identified miR167 targets, and analyzed their accumulation in Dimocarpus longan (longan). Four variants of dlo-miR167a and one dlo-miR167f were identified; their accumulation at the cotyledonary embryo stage suggests they may be required for cotyledon-shaped embryo morphogenesis in longan. We then isolated the miR167 precursor, primary transcript, and promoter. The promoter contained cis-acting elements responsive to stimuli such as light, fungal elicitors, heat, low temperature, drought, methyl jasmonate, salicylic acid, gibberellic acid, and circadian control. Two eTM homologs of a phosphatidylinositol 3- and 4-kinase family protein containing a FAT domain and an unknown protein were predicted for miR167. miR167 mediates transcript degradation in longan somatic embryos for DlARF8 but not cleaves for DlARF6. Moreover, both the eTMs were barely detectable in incomplete compact pro-embryogenic cultures and torpedo-shaped embryos, but reached peaks at globular embryos, which was largely reciprocal to that of their corresponding miR167, indicating a potential role in the negative control of miR167 expression; increased DlARF6 is required for somatic embryo development; miR167a/DlARF8 pair is essential to globular embryo formation and subsequent conversion to cotyledonary embryos. In addition, eTM-miR167-ARF6-8 signal transduction was found to play a conserved role in root development of the longan cultivar ‘Sijimi.’ We conclude that eTM down-regulates miR167 via cleavage of DlARF8 mRNAs in longan somatic embryo development, especially during late developmental stages.

Identification of regulatory genes implicated in continuous flowering of longan (Dimocarpus longan L.).

Longan (Dimocarpus longan L.) is a tropical/subtropical fruit tree of significant economic importance in Southeast Asia. However, a lack of transcriptomic and genomic information hinders research on longan traits, such as the control of flowering. In this study, high-throughput RNA sequencing (RNA-Seq) was used to investigate differentially expressed genes between a unique longan cultivar ‘Sijimi’(S) which flowers throughout the year and a more typical cultivar ‘Lidongben’(L) which flowers only once in the season, with the aim of identifying candidate genes associated with continuous flowering. 36,527 and 40,982 unigenes were obtained by de novo assembly of the clean reads from cDNA libraries of L and S cultivars. Additionally 40,513 unigenes were assembled from combined reads of these libraries. A total of 32,475 unigenes were annotated by BLAST search to NCBI non-redundant protein (NR), Swiss-Prot, Clusters of Orthologous Groups (COGs) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Of these, almost fifteen thousand unigenes were identified as significantly differentially expressed genes (DEGs) by using Reads Per kb per Million reads (RPKM) method. A total of 6,415 DEGs were mapped to 128 KEGG pathways, and 8,743 DEGs were assigned to 54 Gene Ontology categories. After blasting the DEGs to public sequence databases, 539 potential flowering-related DEGs were identified. In addition, 107 flowering-time genes were identified in longan, their expression levels between two longan samples were compared by RPKM method, of which the expression levels of 15 were confirmed by real-time quantitative PCR. Our results suggest longan homologues of SHORT VEGETATIVE PHASE (SVP), GIGANTEA (GI), F-BOX 1 (FKF1) and EARLY FLOWERING 4 (ELF4) may be involved this flowering trait and ELF4 may be a key gene. The identification of candidate genes related to continuous flowering will provide new insight into the molecular process of regulating flowering time in woody plants.

A PRELIMINARY STUDY ON 'LIEYE' LONGAN

‘Lieye’ is a rare longan cultivar with split leaves first found in Guangxi Province in 2001. Young leaves from the grafted trees of ‘Lieye’ in Guangzhou were used to observe chromosome numbers by improved carbol fuchsin staining method and wall degradation hypotonic method. Some main fruit traits of ‘Lieye’ were also observed. The results showed that 23.53% of leaf cells contained 15 chromosomes, 17.65% contained 18 chromosomes, 45.10% contained 21 chromosomes and 13.73% contained 24 chromosomes, proving that ‘Lieye’ is a mixoploid. ‘Lieye’ only flowered once in ten years after grafting onto rootstocks and 20 fruits were obtained from 2 trees in 2011. The main fruit traits, including average mass (7.08 g), soluble solids content (19.30%), edible rate (63.22%) and seed germination rate (60.00%) were ordinary. Twelve seedlings survived and have integrifolious leaves except for one seedling with split leaves. The chromosome numbers (15, 18, 21, 24) of ‘Lieye’ are less than all the reported diploid cultivars (2n=2x=30) and this may explain the split leaf shape and low seed-setting rate.

Evaluation and Preservation of Some Longan Cultivars

Aims: This study was performedto choose or select the best cultivars of longan fruit (Wuyuan , Wu andKohala, Ko). Longan is an untraditional new crop fruits recently grown in new reclaimed areas. Besides, to investigate the possibility of preserving those aforementioned fruits Study Design: About 20Kg of longan cultivars namelyWuyuan (Wu) andKohala (Ko) were used in this study which has b

Comparison of Ultrasonic Extraction with Conventional Extraction Methods of Phenolic Compounds in Longan (Euphoria longana Lamk.) Seed

Three different extraction methods – hot water (HWE), ethanol (EE) and ultrasonic-assisted water extraction (UAE) – were evaluated for extraction of phenolic compounds in longan (cultivar Edor) seed. The findings indicated that longan seed extracts contained three major phenolic compounds, analyzed by HPLC, including gallic acid, corilagin and ellagic acid. The content of total polyphenolic compounds and antioxidant activities was determined using the Folin-Ciocalteu method and the DPPH assay, respectively. Longan seed extraction by HWE contained the highest yield, total polyphenol content and antioxidant activities (42.80%, 41.250mg gallic acid/g and IC50 = 0.017 mg/ ml, respectively). UAE produced a higher yield than EE, but lower than HWE, with the lowest extraction time. Moreover, gallic acid content (16.55 mg/g) and corilagin content (35.62 mg/g) extracted by UAE were higher than those of HWE and EE. Ellagic acid content obtained from UAE was significantly (P<0.05) higher than that from EE, but not significantly different from that of HWE. The application of UAE could provide an alternative method for extraction of photochemical from longan seeds.

Molecular cloning and development of RAPD-SCAR markers for Dimocarpus longan variety authentication

As an edible fruit and source of traditional medicine, D. longan is grown in most areas of Southern China. Identification of D. longan cultivars by using molecular markers is important genetically. In this study, we cloned fragments from improved randomly amplified polymorphic DNA (RAPD), and developed stably diagnostic sequence-characterized amplified region (SCAR) markers. The specific RAPD bands of D. longan cultivars from Guangxi, with size ranging from 500 bp to 900 bp were gel-purified, cloned and sequenced. Four clones named LY2-1, LY4-7, LY4-8 and LY5-2 were identified. In order to investigate whether the fragments were specific for the species, four pairs of SCAR primers were then designed. PCR amplifications were conducted to analyze 18 samples including different D. longan cultivars and other species. The specific bands with expected sizes were amplified in five D. longan samples but not in others. To identify and characterize the difference between D. longan and D. confinis, PCR amplifications were performed again. The specific bands with expected sizes were found in D. longan but not in D. confinis by SCAR markers LY2-1, LY4-7 and LY5-2, respectively. These results showed that our developed SCAR markers could be very useful as a specific D. longan variety authentication. Therefore, our study provides an effective and precise PCR-based diagnostic method and markers to identify D. longan species.

LATE MATURING LONGAN PERICARP COLOR AFFECTED BY THE CHANGES OF PIGMENT AND TOTAL PHENOLS CONTENTS IN THE PERIOD OF FRUIT KEEPING FRESH ON PLANT

ISHS III International Symposium on Longan, Lychee, and other Fruit Trees in Sapindaceae Family LATE MATURING LONGAN PERICARP COLOR AFFECTED BY THE CHANGES OF PIGMENT AND TOTAL PHENOLS CONTENTS IN THE PERIOD OF FRUIT KEEPING FRESH ON PLANT

Isolation and identification of polyphenolic compounds in longan pericarp

The phenol contents and the antioxidant activities of 12 Chinese longan cultivars were studied. The polyphenols of longan pericarp and seed demonstrated significantly higher antioxidant capacities than did the pulp. The ferric reducing antioxidant powers of longan fruits were closely correlated with the polyphenol contents ( r 2 = 0.8609, p < 0.001, n = 36). 52.9 mg g −1 (dry matter) polyphenols were extracted from the pericarp of cultivar Wulongling fruit with acetone aqueous along with ultrasonic treatment. Further fractionation was performed by Sephadex LH-20 chromatography. The results suggested that gallic acid (GA) and ellagic acid (EA) were not the major contributors to the antioxidant activity of longan pericarp. 15 other phenolic profiles in longan pericarp along with a number of unknown structures were revealed with high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC–ESI-MS) analysis. The rich array of phenolic compounds of several different types in longan pericarp extract might form a synergistic multilevel defence system against oxidation.

Ascorbic acid and mineral composition of longan ( Dimocarpus longan), lychee ( Litchi chinensis) and rambutan ( Nephelium lappaceum) cultivars grown in Hawaii

Longan ( Dimocarpus longan), lychee ( Litchi chinensis), and rambutan ( Nephelium lappaceum) cultivars were harvested from different locations in Hawaii and analyzed for vitamin C (ascorbic acid) and mineral content. Longan fruit had the highest vitamin C content (60.1 mg/100 g fresh weight) among the three specialty fruits tested. Average ascorbic acid content was 27.6 mg/100 g for lychees and 36.4 mg/100 g for rambutans. Vitamin C content was 63.3 and 55.3 mg/100 g for the longan cultivars, Biew Kiew and Sri Chompoo, respectively. For rambutans, vitamin C content ranged from 22.047.8 mg/100 g for the six cultivars tested. The early maturing lychee cultivar, Kaimana, had an average ascorbic acid content of 33.2 mg/100 g, and the later maturing Groff and Bosworth-3 cultivars had 21.2 and 22.5 mg/100 g, respectively. No correlation was found between ascorbic acid and total soluble solids (TSS) content. Longans were a good source of K (324.9 mg/100 g) and Cu (0.26 mg/100 g). Consumption of lychee fruit (100 g) would meet 2–4% of the daily recommended intake (DRI) for six minerals (P, K, Mg, Fe, Zn, Mn), and 22% of the DRI for Cu. Rambutan fruit had 20% of the DRI for Cu and 8–10% of the DRI for Mn. In general, fruit mineral content was not associated with soil mineral content.

Genetic diversity of Dimocarpus longan in China revealed by AFLP markers and partial rbcL gene sequences

Amplified fragment length polymorphism (AFLP) and partial rbcL gene sequencing were used to investigate genetic diversity among various longan ( Dimocarpus longan Lour) accessions as well as a presumed closely related species Dimocarpus confinis How et Ho and litchi ( Litchi chinensis Sonn). No significantly shared AFLP fragment was found between the three species, indicating that D. confinis and litchi are very far in genetic distance from any longan accession studied. Partial rbcL sequences of 501 bp from the first coding site in these species were obtained, which revealed several substitutes. One such DNA base pair substitute resulted in an amino acid difference between longan and litchi. Furthermore, another 4 bp resulted in a two amino acid difference between longan and D. confinis, which was consistent with AFLP results and indicated that D. confinis should be excluded from the longan genus, Dimocarpus. Within the longan species, no DNA substitute was found. Using nine primer combinations, a total of 66 AFLP markers were obtained from 41 longan accessions. One non-Chinese longan accession ‘Miaoqiao’ was distinctly different from all other longan cultivars collected in China, indicating that more genetic resources of longan might be collected also from longan production regions outside of China. AFLP markers might be developed to identify longan cultivars as well as expedite progeny screening in breeding programs of this perennial fruit tree.

Development, characterization and variability analysis of microsatellites in lychee (Litchi chinensis Sonn., Sapindaceae).

We report 12 microsatellites enriched in CT repeats obtained from a genomic library of the lychee ( Litchi chinensis Sonn.) cultivar Mauritius. The polymorphisms revealed by these microsatellites were evaluated in a collection of 21 lychee cultivars. A total of 59 fragments were detected with these 12 SSRs, with an average of 4.9 bands/SSR. Three primer pairs seem to amplify more than a single locus. The mean expected and observed heterozygosities over the 9 single-locus SSRs averaged 0.571 (range: 0.137-0.864) and 0.558 (range: 0.169-0.779) respectively. The total value for the probability of identity was 7.53 x 10(-5). In addition, the selected SSRs were used to amplify DNA from four longan cultivars. Eleven of the 12 SSRs produced amplification fragments in longan, and eight of these fragments were polymorphic. All except two of the products amplified from longan were the same size as those amplified from lychee, suggesting a close genetic proximity between the two species. The SSRs studied produced 22 different patterns, allowing the unambiguous identification of 16 lychee and the 4 longan cultivars studied. Discrimination was possible with just four selected microsatellites. Two groups with two and three undistinguishable cultivars were obtained, reflecting probable synonymies. Unweighted pair-group method of artimetic averages (UPGMA) cluster analysis divided the lychee cultivars studied into two main groups, one consisting of ancient cultivars and the other with more diverse recent cultivars. This is the first report of microsatellite development in the Sapindaceae, and the results demonstrate the usefulness of microsatellites for identification, similarity studies and germplasm conservation in lychee and related species.