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Global warming is contributing to extreme weather events such as abnormally colder weather, but there is lack of information on the freezing tolerance of citrus grown in Korea. Therefore, it is necessary to prevent damage from the cold in advance, by acquiring information on the critical temperature at which 50% injury (LT50) occurs for citrus varieties grown in Korea. Electrolyte leakage (EL) and tetrazolium chloride (TTC) analyses were performed to determine LT50 values and estimate the freezing tolerance for citrus varieties cultivated in Korea. We also investigated which factors such as genotype, environmental condition (e.g., in vitro, in vivo), cultivation condition, and wind speed affect the LT50 value in citrus. The LT50 value measured in the EL and TTC analyses of the ‘Haryejosaeng’ mandarin indicated it had better resistance to the cold than the citrus hybrids. The LT50 value in the in vitro experiments was lower than for the in vivo experiments, but there was little difference among the genotypes. Some factors, such as cultivation condition and wind speed, affected the LT50 values. The flavonoid levels, total polyphenol content, and antioxidant activity were affected by exposure to freezing temperatures, which was not related to the change in freezing tolerance level.

This study investigated how the ploidy level of the kiwifruit pollinizer cultivars “CK3” (diploid), “T line” (tetraploid), “Pohwa” (hexaploid) and “Chieftain” (hexaploid) affected fruit set, fruit quality, and seed formation in the tetraploid kiwifruit cultivars “Halla Gold” and “Sweet Gold” cultivated in an unheated greenhouse in Jeju, Korea. Pollen tubes growing in the pistil reached and combined with the ovule 3 days after artificial pollination, and their patterns differed depending on the ploidy level of the pollen parent. The number of pollen tubes observed in “Halla Gold” and “Sweet Gold” pistils was significantly lower following pollination by “CK3” than with the other pollen donors. In all pollen treatments, the fruit set rates were > 90%. The fruit weight of both “Halla Gold” and “Sweet Gold” were high following pollination with “Chieftain” and “Pohwa”. The dry matter content, soluble solids, and acidity were not significantly different among all pollination treatments. Fruit firmness was higher following pollination with “Chieftain” and “Powha.” Colorimeter h˚ values for flesh of “Halla Gold” was low following pollination with “CK3,” but there were no differences for “Sweet Gold” among all pollinations. The number of seeds showed a similar trend to fruit weight, but the 100-seed weight was highest with “T line” as the pollinizer. The results indicate that the ploidy level of the pollen donor affects fruit quality more than fruit set. Also, the pollen most suitable for cultivation of “Halla Gold” and “Sweet Gold” is considered to be tetraploid “T line” and hexaploid “Pohwa” and “Chieftain,” which showed favorable effects on the weight and firmness of fruits, and the number and weight of seeds without adversely influencing fruit set and dry matter content.

In this study, we aimed to produce a citrus fruit with no seed and with edible peel. Therefore, the seedless Yoshida navel oranges (Citrus sinensis ‘Yoshida navel’) and Jangsil kumquat (Fortunella japonica) with edible peel were used as the starting materials. Since two varieties of different genera and different flowering periods would be difficult to crossbreed, protoplast fusion was conducted using the polyethylene glycol method. Yoshida navel orange and Jangsil kumquat were used as an embryogenic callus line and a mesophyll line, respectively. The regenerated plants were analyzed by flow cytometry to identify tetraploids, which were further evaluated by polymerase chain reaction, using simple sequence repeat markers specific for the nuclear and cytoplasmic organellar DNAs of the two parents, to confirm allotetraploids and cybrids. Sixteen allotetraploids were finally produced and characterized phenotypically for leaf morphology and fruit quality. All allotetraploids contained mitochondria originating from Yoshida navel orange; 12 contained chloroplasts derived from navel orange whereas four contained chloroplasts of kumquat origin. We investigated both plant and fruit characteristics of allotetraploids derived from the protoplast fusion of navel orange and kumquat. The sizes of the allotetraploid leaves were intermediate between those of both parents. However, in contrast to the spindle-shaped leaves of both parents, those of the allotetraploids were obovate. Petiole wings were absent in the allotetraploids, a known kumquat trait. Similar to navel oranges, flowering time was mid-May, and pollen was sterile, whereas fruit size, external shape, soluble solids content, and acidity were all intermediate between the two parents. Peel thickness and the number of segments were similar to those of kumquat, and flesh weight was similar to that of navel orange. Collectively, these results indicated that the intergeneric allotetraploids derived from navel orange and kumquat inherited favorable traits of both parents and could be produced and selected despite a lack of extensive parental variation. This is one of the first reports showing fruiting results of protoplast-fused citrus plants. The study reported characteristics of the fruits from both the original plants as well as from the protoplast-fused plant. Detailed characteristics of the allotetraploid fruit produced by protoplast fusion would be very helpful for future polyploid studies.

Intensive scion rooting in ‘Shiranuhi’ mandarin [(Citrus unshiu × C. sinensis) × C. reticulata] trees contributed to reduced flowering, yield, and fruit quality at commercial mandarin orchards. To elucidate the effect of a cultural technique on controlling the loss of fruit quality and yield, mandarin trees were grouped into three treatments as follows: no scion root (without scion roots), scion root intact, and scion root pruning in thirteen-year-old ‘Shiranuhi’ mandarin trees. Scion root pruning reduced leaf nitrogen (N) and enhanced leaf carbon (C), thereby increasing the leaf C/N ratio in scion root pruned trees, than those with intact scion roots. Physiological responses of flowering and fruiting were significantly enhanced by pruning scion roots in mandarin trees. Fruit size, fruit fresh weight, and soluble solids content (SSC) were considerably greater in scion root pruned trees than those with intact scion roots. Furthermore, pruning scion roots increased total fruit yield than that in mandarin trees with intact scion roots. Overall, the results indicated that scion root pruning should contribute to minimizing cultural problems, such as low yield and poor fruit quality, which have been caused by scion rooting in ‘Shiranuhi’ mandarin orchards.

Metaphase chromosomes of five Korean landrace citrus were analyzed to understand the phylogenetic relationship among them and to compare these characteristics with those of other Citrus species including previously reported six Korean landrace mandarins at a cytogenetic level using CMA banding patterns and rDNA loci. The CMA banding patterns of the five Korean landrace citrus were 1 A+2B+2C+6D+7E in dongjeongkyul (C. erythrosa), 3B+1C+7D+5E+2 F in hongkyul (C. tachibana), 2 A+1B+3C+4D+8E in sadoogam (C. pseudogulgul), 1 A+3B+1C+7D+6E in dangyooza (C. grandis), 1 A+1B+1C+9D+6E in jigak (C. aurantium). All types of chromosome bands were present in all accessions except in hongkyul, in which type A chromosome was absent but two of type F chromosomes were observed. The numbers of type A, B, and C chromosomes were lower in all accessions. In contrast, the type D and E chromosomes were remarkably constant and predominantly observed in all accession. The distributions of 5S and 45S rDNA loci by FISH were heterogeneous among them. All accessions possessed one 5S rDNA locus except for hongkyul, which displayed two 5S rDNA loci. And they always co-localized with 45S rDNA locus. All 45S rDNA loci were homotopic to CMA-positive regions. Every type A and B chromosomes possessed one 45S rDNA locus in the proximal region of the chromosomes. There was no type C and E chromosome with rDNA observed. Hierarchical cluster analysis and UPGMA phenogram based on CMA banding pattern combined with 5S and 45S rDNA loci of 11 Korean landrace citrus showed the strong karyotype dissimilarity in the invested taxa.

Tea is one of the most frequently consumed beverages across the world, second only to water, and it is known to have originated in China. As a natural...

In this study, genetic linkage maps were constructed for ‘Fina Sodea’ clementine (Citrus clementina) and Byungkyul (C. platymamma) using 152 F1 clones as a mapping population. Reference-guided whole-genome sequencing, using next-generation sequencing technology, along with 82 randomly amplified polymorphic DNA markers and seven genomic simple-sequence repeat (gSSR) loci, mined 41 polymorphic gSSR loci from the direct comparative analysis. The generated linkage map for ‘Fina Sodea’ clementine contained 22 markers distributed into 10 linkage groups, with a total length of 417.7 cM and an average interval of 19.0 cM. The map for Byungkyul contained 57 markers distributed into 10 linkage groups, with a total length of 684.9 cM and a smaller average interval of 12.0 cM. Comparison of shared gSSR markers between the two maps identified collinearities, such as linkage groups B3 and C7 and groups B9 and C7. The newly developed gSSR markers greatly enrich the limited amount of gSSR markers in Citrus, providing markers that can be useful for comparative mapping and other genetic studies.

Anthocyanins, one of the major plant pigments, are responsible for the coloration of various plant tissues and organs, including fruits. They are known to have significant health benefits. Anthocyanin biosynthesis is influenced by environmental factors such as cold temperature and is transcriptionally regulated by MYB/bHLH/WD40 complexes composed of R2R3-MYB, basic helix-loop-helix (bHLH), and WD40-type transcription factors (TFs). The Ruby locus, which encodes a MYB TF, controls anthocyanin production in the fruit of blood orange varieties in a dominant manner. For the marker-assisted selection of citrus breeding lines with high anthocyanin production, we established PCR-based molecular markers for robust genotyping of Ruby locus alleles. Two dominant Ruby alleles, RD-1 and RD-2, were specifically detected in the blood orange varieties with high anthocyanin contents in their fruit flesh, but not in the varieties rich in lycopene. For functional analysis of Ruby alleles, we generated transgenic Arabidopsis expressing a functional wild-type R, a non-functional r-1, or a dominant RD-2 allele. Expression levels of flavonoid/anthocyanin biosynthetic genes and anthocyanin production were highly increased in the transgenic plants expressing the dominant Ruby allele by its retrotransposon-mediated native promoter under cold treatment, suggesting that the retrotransposon may contain cis-regulatory elements that respond to cold temperature. Our results also support that the MYB TF encoded by Ruby could be a key component of regulatory complexes that control flavonoid/anthocyanin biosynthesis in citrus.

Mandarin is the major type of citrus grown in Jeju, Korea and has a long history of cultivation there. Landrace Citrus species represent broad and natural genetic variability, which are important and valuable as genetic material. In this study, metaphase chromosomes of six Korean landrace mandarins were analyzed to understand the phylogenetic relationship among them and to compare these characteristics with those of other Citrus species at a cytogenetic level using CMA banding patterns and rDNA loci. Chromosomes were categorized into five types according to the distribution and number of heterochromatic CMA-positive bands; type A chromosomes have two telomeric and one proximal bands, type B have one telomeric and one proximal bands, type C have two telomeric bands, type D have one telomeric band, and type E have no band. Gamza mandarin (C. benikoji) displayed the 1A/45S + 2B/45S + 2C + 5D + 1D/45S + 1D/5S-45S + 6E pattern, without a solitary 5S rDNA locus that differentiated the gamza mandarin from other accessions. A solitary 5S rDNA locus was observed in the chromosomes of byungkyul mandarin (C. platymamma) (1A/45S + 2B/45S + 1C + 6D + 1D/45S + 1D/5S-45S + 5E + 1E/5S) and cheongkyul mandarin (C. nippokoreana) (1A/45S + 1B/45S + 1C + 7D + 1D/5S + 1D/45S + 1D/5S-45S + 5E). The chromosome composition of byungkyul mandarin based on CMA banding pattern and rDNA loci suggests that byungkyul mandarin may be related to pummelo, sweet orange, and members of the Citrus subgenus Papeda during its evolution. Cheongkyul mandarin possessed a distinct marker chromosome (D/45S) that can be used to distinguish cheongkyul madrarin from the other Korean landrace mandarins. Jinkyul mandarin (C. sunki) (1A/45S + 1B/45S + 1C + 10D + 2D/5S-45S + 3E) may be related to pummelos. The karyotype of pyunkyul mandarin (C. tangerina) (3B/45S + 2C + 7D + 1D/5S-45S + 5E) suggests that the pyunkyul mandarin is a hybrid between C. grandis and C. reticulata. Binkyul mandarin (C. leiocarpa) (1A/45S + 1C + 6D + 2D/45S + 2D/5S-45S + 6E) seemed to be related to mandarins and pummelos. Heterozygous karyotypes of six accessions separated and differentiated each of the six Korean landrace mandarins and potential marker chromosomes were identified.

Many citrus cultivars have the polyembryony trait that develops many nucellar embryos alongside a single zygotic embryo in an individual seed by sporophytic apomixis. This unique botanical trait hinders citrus breeding by genetic hybridization and affects breeding efficiency and cost. Techniques to efficiently identify nucellar and zygotic individuals in citrus are still very limited. For a systematic and targeted citrus breeding program, we collected 101 citrus genetic resources and determined their embryo types, which revealed 22 monoembryo, 54 polyembryo, and 25 mixed types. We also developed 17 simple sequence repeat (SSR) markers showing polymorphism among the genetic resources from the public resources and our own comparative genome analysis. Seventeen SSR markers detected a total of 181 alleles, ranging from 5 to 16 alleles per locus. The average polymorphism information content value was 0.67, ranging from 0.43 to 0.84. Genetic cluster analysis based on similarity matrices of alleles revealed that several genetic resources of the genus Citrus were fragmented and/or scattered throughout the entire dendrogram, not forming unique groups, due to frequent natural or intended genetic crossings. Application of these polymorphic SSR markers to F1 individuals derived from several genetic crosses using polyembryonic citrus cultivars as a female parent revealed that the polyembryony trait decreased the breeding efficiency due to the poor occurrence rate of zygotic individuals. Therefore, our results suggest that identification of nucellar and zygotic embryo-derived F1 individuals using SSR markers as a genotyping technology may be a powerful tool for establishing a systematic molecular breeding program in citrus.

세계적인 과수작물로서의 경제적 중요성에도 불구하고, 감귤 생산은 주로 자연교잡 실생이나 눈 돌연변이로부터의 선발 또는 단순 품종 도입 등을 통해 이루어지고 있는 실정이다. 긴 유년기, 다배성, 자가불화합성과 같은 감귤 고유의 식물학적 특성, 주요 형질들(병저항성, 수량성, 품질 등)의 QTL에 의한 조절 등은 전통...

Abrupt and severe loss of leaves caused by a typhoon disrupts physiological development and metabolism in kiwifruit vines. The aim of this study was to evaluate the effects of time of defoliation on off-season flowering, vine regrowth, and fruit quality in ‘Jecy Gold’ kiwifruit. ‘Jecy Gold’ kiwifruit vines were subjected to artificial 100% defoliation on July 28 and August 29, 2014. In October, the occurrence of off-season flowering was observed only on vines that were defoliated on August 29. There was no significant difference in vine regrowth between defoliation on July 28 or August 29. However, defoliation on August 29 showed a significant reduction in soluble solid content in fruits at harvesting time. Furthermore, there was no significant difference in starch and sugar content of cane bark between the different times of defoliation. The results indicate that the floral evocation of ‘Jecy Gold’ kiwifruit might occur in August and that fruit maturation is delayed after defoliation on August 29 in comparison to defoliation on July 28.

Tea has long been a well-known crop for its economic value and widening the genetic variability of tea family is often necessitated. Hybridization programs at intraspecific level have been greatly fascinated as potential and useful methods in tea plant breeding to widening the genetic diversity. This comparative study was intended to explore a new avenue to develop the tea plant breeding programs through evaluating remote intraspecific cross-compatibility between Camellia sinensis var. sinensis (L.) O. Kuntze and C. sinensis var. assamica (Masters). Remote intraspecific cross-compatibility was assessed by comparing and contrasting the in-vivo pollen germination and pollen tube growth using fluorescence microscopy and the subsequent fruit set following controlled self- and cross-pollinations. In-vivo pollen germination and pollen tube growth was examined at 1 day, 3 days, and 14 days after pollination treatments, but disparity was not observed in pollen germination and pollen tube growth between self- and cross-pollinations. Early fruit set was evaluated at 3 months and 6 months after pollination. Fruit set was observed in cross-pollination except self-pollination. A late-acting self-incompatibility system or post-zygotic barriers and close intraspecific cross-compatibility were confirmed within C. sinensis var. sinensis (L.) O. Kuntze. Potential remote intraspecific cross-compatibility was recorded from cultivars crossed between China type and Assam type tea. The present findings bestow the significant contribution to develop the future tea breeding programs. Key words: Intraspecific cross, pollen germination, pollen quality, pollination, tea breeding.

Citrus is an economically important fruit tree with the largest amount of fruit production in the world. It provides important nutrition such as vitamin C and other health-promoting compounds including its unique flavonoids for human health. However, it is classified into the most difficult crops to develop new cultivars through conventional breeding approaches due to its long juvenility and some unique reproductive biological features such as gamete sterility, nucellar embryony, and high level of heterozygosity. Due to global warming and changes in consumer trends, establishing a systematic and efficient breeding programs is highly required for sustainable production of high quality fruits and diversification of cultivars. Recently, reference genome sequences of sweet orange and clementine mandarin have been released. Based on the reference whole-genome sequences, comparative genomics, reference-guided resequencing, and genotyping-by-sequencing for various citrus cultivars and crosses could be performed for the advance of functional genomics and development of traits-related molecular markers. In addition, a full understanding of gene function and gene co-expression networks can be provided through combined analysis of various transcriptome data. Analytic information on whole-genome and transcriptome will provide massive data on polymorphic molecular markers such as SNP, INDEL, and SSR, suggesting that it is possible to construct integrated maps and high-density genetic maps as well as physical maps. In the near future, integrated maps will be useful for map-based precise cloning of genes that are specific to citrus with major agronomic traits to facilitate rapid and efficient marker-assisted selection.

Kiwifruit is a new fruit crop that was commercialized in the late 1970s. Recently, its cultivation and consumption have increased rapidly worldwide. Kiwifruit is a dioecious, deciduous, and climbing plant having fruit with hairs and various flesh colors and a variation in ploidy level; however, the industry consists of very simple cultivars or genotypes. The need for efficient cultivar improvement together with the evolutional and biological perspectives based on unique plant characteristics, have recently encouraged genome analysis and bioinformatics application. The draft genome sequence and chloroplast genome sequence of kiwifruit were released in 2013 and 2015, respectively; and gene annotation has been in progress. Recently, transcriptome analysis has shifted from previous ESTs analysis to the RNA-seq platform for intensive exploration of controlled genetic expression and gene discovery involved in fruit ascorbic acid biosynthesis, flesh coloration, maturation, and vine bacterial canker tolerance. For improving conventional breeding efficiency, molecular marker development and genetic linkage map construction have advanced from basic approaches using RFLP, RAPD, and AFLP to the development of NGS-based SSR and SNP markers linked to agronomically important traits and the construction of highly saturated linkage maps. However, genome and transcriptome studies have been limited in Korea. In the near future, kiwifruit genome and transcriptome studies are expected to translate to the practical application of molecular breeding.

This study was conducted to investigate the seed formation potential by the evaluation of microspore development and self- and cross-compatibility through their pollen tube growth response to self and cross pollination in Jeju old local citrus species. Anther and pollen histological analyses were done to observe microspore development for three species including byungkyul, sadoogam, and dangyooza. Pollens of ten citrus species were tested for pollen viability by staining with Lugol’s solution and fluorescein diacetate. Flowers of all species were emasculated and self- and cross-pollinated just before anthesis. Pistils of nine pollinating combinations between the listed three species were collected at 1, 3, 5, 7, and 9 days after pollination for evaluation of a growth pattern of the pollen tube. Pistils of the other combinations were collected at 9 days after pollination for self- and cross-compatibility evaluation. Pistils were prepared by squashing and staining method with aniline blue. Eight pollen developmental stages were recognized and indicated normal development of microspore. These ten citrus species produced high percentage of viable pollens. Pollen tube behavior in compatible and incompatible pollination was distinguished. Pollen tube performance was largely depended on male-female combination. All of these Jeju old local citrus species were male fertile and have the ability to produce enough viable pollens for self- and cross-pollination. All evaluated citrus species were self- and cross-compatible to each other except dangyooza which was self-incompatible.

Leaves of kiwifruit have long petiole and large size, so that they are easily damaged by strong wind. This study was performed to evaluate the effect of leaves loss by typhoon damage on fruit quality and yield and new cane growth with artificial defoliation. Five-year-old ‘Jecy Gold’ kiwifruit vines grown in a plastic house were used in this study. Artificial defoliation was done on August 23 (100 days after anthesis) at the different defoliation levels, such as 0 (control), 50, 75, and 100%. Cane regrowth by axillary bud burst, cane bark carbohydrate reserve, and fruit quality and yield were investigated. Severe defoliation at 75 and 100% level showed significantly higher axillary budburst than the control and the 50% defoliation. Especially, the 100% defoliation induced a few abnormal off-season flowering. Starch and sucrose contents were significantly declined during the first 2 weeks after defoliation at the 75 and 100% defoliation. However, other soluble carbohydrate reserves including fructose, glucose, and myo-inositol were not affected significantly. Fruit drop was promoted and the mean fruit weight, firmness, and soluble solid concentrations were lower by the defoliation. Our results indicated that the loss of leaves above 50% would induce a transient shortage of assimilate supply and reduce fruit quality and yield significantly.

Based on double pseudo-testcross theory, a population of 79 F1 clones, which was derived from a crossing of two tea cultivars using a Japanese tea cultivar “Fushun” (Camellia sinensis) as female parent and a Korean tea cultivar “Kemsull” (C. sinensis) as male parent, was applied to construct a genetic linkage map with different molecular markers. Previously, 143 random amplified polymorphism DNA (RAPD) markers and 11 simple sequence repeat (SSR) loci developed from 41 decamer random primers and 60 published SSR primer pairs, respectively, were used into our mapping analysis. In the study of amplified fragment length polymorphism (AFLP), 2439 bands were generated from 27 primer combinations with an average number of 90.3 bands for each, of which 495 (20.3%) were polymorphic. The majority of those polymorphic markers segregated in accordance with Mendelian segregation ratios at p

Summary Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n-hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N-dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H-bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be

The study was conducted to investigate the effect of fruit bearing type with leafy (LY) and leafless (LS) fruits on fruit growth, sugar, and acid characteristics in satsuma mandarin. Fruit growth including fruit length, diameter, shape index (diameter/length), weight, and size distribution was not different between LY and LS fruits at ripening time. Total soluble solids (TSS) concentration of the fruit juice increased and acidity decreased continuously and then TSS:acidity ratio increased with fruit development from 100 days after anthesis to ripening time. Soluble sugar was continuously increased, whereas organic acid decreased. Theses tendencies were related to the increase of sucrose and decline of citric acid, respectively. However, there was no effect of fruit bearing type on TSS, acidity, and TSS:acidity ratio, and soluble sugar and organic acid composition in fruit juice. Also, photosynthetic rate and chlorophyll index with SPAD value were not different between leaves adjacent to LY and LS fruits. The results indicated that fruit growth and sugar and acid characteristics were not affected by fruit bearing type with leafy and leafless fruits in satsuma mandarin.

Polyploids are a potentially important germplasm source in seedless citrus breeding program. Seedlessness is one of the most promising traits of commercial mandarin breeds that mandarin triploid hybrids possess permanently. The formation of new constant triploid hybrids can be recovered through diploid species hybridization from the fusion of divalent gametes at low frequencyor intra-and inter-ploidy crosses. However, extensive breeding work based on small F1 hybrid seeds developed is impossible without a very effective aseptic methodology and ploidy event. In this study, in vitro embryo culture was employed to recover natural hybrids from monoembryonic diploid, open-pollinated mandarin. Flow cytometry was used to determine ploidy level. A total of 10,289 seeds were extracted from 792 fruits having approximately 13 seeds per fruit. Average frequency of small seeds developed was 7.1%, while the average frequency of small seeds per fruit were: 8.9% for ‘Clementine’ 10.2% for ‘Harehime’ 2.6% for ‘Kamja’ 3.1% for ‘Pyunkyool’ 2.8% for ‘Sadookam’ and 7.0% for ‘Wilking’ mandarin. Average size of a perfect seed was 49.52±0.07 mm2 (‘Clementine’) while the small seed measured 7.95±0.04 mm2 (‘Clementine’), which was about 1/6 smaller than the perfect seed. In total, 731 small seeds were obtained and all of them contained only one embryo per seed. The efficiency of ‘Clementine’ was 14 times higher than ‘Wilking’ and more than 109 times higher than ‘Pyunkyool’. The basic information on spontaneous polyploidy provides for the hybridization of constant triploids and increases the efficiency of conventional cross.

A new promising kiwifruit, 'Halla Gold' variety with yellow flesh and being harvested in October, was developed at the Agricultural Research Center for Climate Change, National Institute of Horticultural and Herbal Science, Rural Development Administration, Korea in 2007. This variety was derived from the seedling population crossed between Actinidia chinensis cv. Golden Yellow and A. chinensis cv. Songongu in 1997. It was selected out of 2,971 seedlings. Characteristic trials were carried out from 2001 to 2003. After the selection, adaptability test was also conducted at kiwifruit orchards in Jeju Island from 2003 to 2007. Shoots of 'Halla Gold' sprout slightly stronger than those of 'Jecy Gold' but weaker than 'Hort16A' and the color of leaf is green. Fruit shape is oblong and fruit skin color is yellowish-dark green without hair. The average weight of fruit is 106.3 g. Fruit has a moderate size soft core, yellow pericarp, and fragile and juicy flesh. Soluble solids content is Brix and acidity is 1.4%. The harvesting time is about 10 days earlier than 'Jecy Gold' and about 20 days ahead of 'Hort16A'. The storage life is about 90 days at . This variety can be recommended for cultivating at low land area bellow 100 m sea level in Jeju Island or under shelter to prevent disease and cold injury.

Arabidopsis thaliana dynamin-like protein 1E (ADL1E) is known to regulate mitochondrial elongation. The adl1e mutant has no morphological phenotype, and the growth and photosynthetic activity of the mutant are similar to those of the wild type. Leaf O2 uptake, which is supported by mitochondrial activity in the dark, is increased 1.7-fold by mutation in adl1e gene. The ATP content in the dark of guard and mesophyll cell protoplasts (GCPs and MCPs, respectively) was 2.5- to 4-fold higher in GCPs of the mutant and the wild type, and increased upon the addition of glucose in both genotypes. Oligomycin, an inhibitor of mitochondrial ATPase, suppressed ATP synthesis in both GCPs and MCPS isolated from adl1e plants, indicating that mutant had higher mitochondrial activity. The stomatal apertures of mutant and wild-type plants were then analyzed in vitro. In the light, the stomata of both genotypes showed similar patterns of opening. However, in the dark response, the stomata of the adl1e mutant closed faster than did those of the wild type. Oligomycin severely inhibited dark-induced stomatal closure in both cell types. The results suggest that stomatal closure in the dark is governed by cytosolic ATP concentration, which is stimulated by mitochondrial activity.

The paper reviewed research status and outlook of genetic transformation in fruit trees in Korea. Genetic transformation has been long considered as an alternative technique overcoming limitation of conventional breeding and conducted since early 1990’s. An efficient genetic transformation was established with major cultivars of apple, even in Fuji and Gamhong, and some transgenic apple plants have been transferred into the greenhouse for further analysis of gene expression. A few successes of genetic transformation have been reported and application to a variety of cultivars tried in citrus and kiwifruit. Successful genetic transformation has not been reported in the other fruit trees including grapevine, yet and it is considered being at the level of research. Those factors including replacement of antibiotics as a selective agent, use of transgenic rootstocks and manipulation of gene expression at proper parts and developmental stages have been prerequisites for the rapid commercialization of transgenic fruit plants.

Caffeine and catechins from the Yabukita, Yutakamidori, Saemidori, Okumidori, and Fushun varieties of tea leaves picked during different harvesting seasons from April to October were evaluated using HPLC. Total content of catechins increased greatly with the later harvesting time of tea leaves (i.e., picking the leaves in September versus in April) and decreased slightly after September. Yabukita tea leaves picked in August contained 43.1 mg% catechins including EGC, EC, ECG, and EGCG, with the ECGC levels constituting greater than 50% of those four compounds. Yutakamidori and Okumidori varieties picked in September contained the highest catechin values, at 43.6 mg% and 31.0 mg%, respectively. Fushun and Saemidori varieties contained lower catechin concentrations of 14.5 mg% (July) and 11.7 mg% (August) compared to other varieties. The EGCG levels gradually decreased in the late harvesting season, while levels of the other catechins, EC, EGC, and ECG, gradually increased. All varieties of green tea showed a gradual decrease in caffeine content toward the end of our harvesting efforts in October, with levels of 58～68 mg% in April and 28～57 mg% in October. Yabukita, Saemidori, and Okumidori varieties reached their highest caffeine levels in late spring/early summer, with Yabukita and Okumidori varieties reaching a high of 73.4% and 63.5% caffeine, respectively, in May, and Saemidori at 64.0% in June. In particular, Fushun still contained high caffeine of 66.8 mg% (September) during the late harvesting season.

Genetic transformation using a micro-cross section (MCS) technique was conducted to improve the carotenoid content in kiwifruit (Actinidia deliciosa cv. Hayward). The introduced carotenoid biosynthetic genes include geranylgeranyl diphosphate synthase (GGPS), phytoene desaturase (PDS), ζ-carotene desaturase (ZDS), β-carotene hydroxylase (CHX), and phytoene synthase (PSY). The transformed explants were selected on half-strength MS medium containing 0.001 mg l(-1) of 2,4-D and 0.1 mg l(-1) of zeatin, either 5 mg l(-1) hygromycin or 25 mg l(-1) kanamycin, and 500 mg l(-1) cefotaxime. The genomic PCR, genomic Southern blot analysis, and RT-PCR were performed to confirm the integration and expression of the transgenes. The transformation efficiencies of either kanamycin- or hygromycin-resistant shoots ranged from 2.9 to 22.1% depending on the target genes, and from 2.9 to 24.2% depending on the reporter genes. The selection efficiencies ranged from 66.7 to 100% for the target genes and from 95.8 to 100% for the reporter genes. Changes of carotenoid content in the several PCR-positive plants were determined by UPLC analysis. As a result, transgenic plants expressing either GGPS or PSY increased about 1.2- to 1.3-fold in lutein or β-carotene content compared to non-transgenic plants. Our results suggest that the Agrobacterium-mediated transformation efficiency of kiwifruit can be greatly increased by this MCS method and that the carotenoid biosynthetic pathway can be modified in kiwifruit by genetic transformation. Our results further suggest that GGPS and PSY genes could be major target genes to increase carotenoid contents in kiwifruit.

Kiwifruit shoots can be rapidly propagated through a micro-cross section (MCS) system we established here. Optimal culture conditions were determined for different expiant types, section sizes, and concentrations of inorganic salts and plant growth regulators. Rates of survival and callus formation were higher in half-strength MS salts than in full-strength MS media. Similar performance (i.e., survival and callus formation) was achieved with section sizes of either 800 μm or 1200 μm. Proliferation efficiency was greatest when expiants from stem tissue were cultured on 1/2 MS supplemented with 4.5x10-3 μM 2,4-dichlo-rophenoxyacetic acid and 4.6x10-1 μM zeatin. The number of shoots averaged 2.61 per expiant, representing an efficiency of 94%. RAPD analysis revealed that the regenerated plants from our MCS system were genetically stable. These results show that the culturing of micro-cross sections from stem tissue is a powerful method for kiwifruit propagation.

This study was conducted to determine the optimal transformation conditions during early gene transfer steps necessary to improve the efficiency of transformation mediated by Agrobacterium tumefaciens in Fuji apple plants. The use of 200 μM acetosyringone in the co-culture medium resulted in 4.7% transformation efficiency, compared with different concentrations of 0–400 μM. A 4-day co-culture period gave 1.9% transformation efficiency, compared with different co-culture periods of 1–5 days. There was no significant difference in transformation efficiency with different explant placement orientations on co-culture medium. A comparison of young leaves from plants cultured in rooting medium for 4 weeks with those cultured for 8 weeks showed that an 8-week culture period resulted in higher transformation efficiency. We therefore concluded that the efficiency of Fuji apple transformation depends on improving factors related to the gene transfer step.

In Fuji, the production of ethylene was increased with the addition of AgNO3 and inhibited with the addition of 10 μM aminoethoxyvinylglycine (AVG). The addition of 80 μM AgNO3 to transformed explants of ‘Fuji’ cultured on selection medium resulted in increased ethylene production (20 μl l−1) at 3 weeks. Under examining the effect of AgNO3 in ‘Fuji’, the 40 μM AgNO3 showed with higher 33.8% and 6.5% in the efficiency of regeneration and transformation. However, ethylene production in ‘Gala’ explants treated with 10μM AgNO3 (3 μl l−1) decreased after 2 weeks compared with the control (5 μl l−1). Although the regeneration efficiency of ‘Gala’ with 10 μM AgNO3 was higher (41.1%) than the control (20.1%), there was no significant difference in the transformation efficiency at the same concentration. Shoot regeneration of ‘Fuji’ and ‘Gala’ was completely inhibited with 10 μM AVG. These results suggest that the addition of AgNO3 affects the efficiency of Agrobacterium-mediated gene transfer in ‘Fuji’.

To develop a SCAR primer related to the hairy-fruit trait in the genusActinidia, we took a PCR-RAPD approach using arbitrary 10-mer primers. PCR with the UBC 376 primer generated specific fragments from three species with hairy fruit skin. Those fragments were then cloned to determine their nucleotide sequences. Two SCAR primers were designed from the UBC 376 primer and nucleotide sequences were obtained from the PCR fragments. A SCAR primer, OKC385, specifically amplified a 385-bp fragment from one clone ofActinidia eriantha, four ofActinidia chinensis, and four ofActinidia deliciosa. Deduced amino acid sequences of this fragment showed high sequence homology with plant cellulose synthases, which are involved in the biosynthesis of cellulose, a major cell wall component. The 385-bp fragment was specifically detected only in the seriesPerfectae C.F. Liang of sectionStellatae Li. This type has many hairs on the leaves, fruits, and stems, suggesting that the gene containing the PCR fragment is involved in hair formation in this phylogenetic group. Taken together, our results suggest that the SCAR primer, OKC385, can be used as a specific primer for early selection of the non-hair trait in breeding of the genusActinidia.