• Horticultural Science & Technology
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• v.34 no.6
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• pp.830-839
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• 2016

Germination of Hemerocallis seeds as influenced by cold stratification at $5^{\circ}C$ (CS) and maturity of seeds evaluated using X-ray imaging has not been well investigated. Seeds of H. lilioasphodelus, H. citrina, H. citrina 'April Flower', and H. minor collected from China and H. thunbergii collected from Korea were germinated at $20^{\circ}C$ without pre-temperature treatment, while H. hongdoensis, H. dumortieri, H. minor, and H. vespertina seeds were treated with CS. Harvesting 'Stella de Oro' capsules at 35-40 days after anthesis yielded mature seeds with well-developed embryo and cotyledons analyzed by X-ray images with a 92% germination in 17 days after sowing. Seeds of H. thunbergii and H. citrina germinated in less than 13 days without CS; two weeks of CS did not accelerate seed germination. Seeds of H. hongdoensis germinated in 24 days when seeds were stored at $25^{\circ}C$ without CS and in less than 27 days when cold stratified. Therefore, 'Stella de Oro' capsules should be harvested at 35-40 days after anthesis to harvest mature seeds. Cold stratification is not required to accelerate seed germination in the Hemerocallis taxa evaluated in this study.

• Horticultural Science & Technology
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• v.34 no.6
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• pp.898-911
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• 2016

Sugars play many important roles in plant metabolism and directly influence fruit quality. The effects of two edible coatings, 2% calcium chloride and 1% pullulan, on sugar metabolism in postharvest Huangguan pear fruit were investigated during cold storage. The respiration rate, sugar content and composition, sucrose metabolism enzyme activities [acid invertase (AIV), neutral invertase (NI), sucrose synthase (SS), and sucrose phosphate synthase (SPS)] and expression of the AIV gene were analyzed during storage at $0^{\circ}C$ for 210 days. Coating treatments slowed the decrease of sucrose and hexose, the respiration rate, and the activities of AIV, NI, SS and SPS, thus maintaining high total soluble solids (TSS) and titratable acid (TA) contents in the fruit. There were no significant differences in AIV expression or activity between the treated and control groups of fruits. Both of the coatings could inhibit the activities of sucrose-cleaving enzymes, thus slowing the decrease of sugar content and maintaining high fruit quality during cold storage.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.363-371
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• 2016

Tabulis [Astilboides tabularis (Hemsl.) Engl.] has the potential for becoming a useful horticultural crop. This study was conducted to classify the seed dormancy types and to identify the germination conditions that improve the horticultural usefulness of this plant. We found that A. tabularis (Hemsl.) Engl. produced undifferentiated embryos and had a low germination rate of under 50%. In addition, water submersion led to moisture absorption. Therefore, A. tabularis seeds were designated as morphologically dormant. The germination rate was highest (86.3%) at $30^{\circ}C$ under light conditions. Higher temperatures generally led to an acceleration of the germination process, regardless of light condition. To improve the germination rate, seeds were submerged in various concentrations of growth regulators, such as $GA_3$ and kinetin, as well as minerals such as $KNO_3$ and KCl. An analysis of germination characteristics at $30^{\circ}C$ under light conditions revealed that treatment with 200 and $500mg{\cdot}L^{-1}GA_3$ led to an excellent germination rate of 97.0%. Treatment with $100mg{\cdot}L^{-1}GA_3$ led to a better germination rate than the control as well. However, treatment with kinetin, $KNO_3$, and KCl had no effect on germination, regardless of concentration.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.396-404
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• 2016

In this study, four cultivars of strawberry commonly grown in South Korea, 'Daewang', 'Seolhyang', 'Maehyang', and 'Ssanta', were evaluated for several qualities, including the presence of phytochemicals, sugar content, organic acids, and fruit hardness. The plants were cultivated on a high-bench bed system in a plastic greenhouse and drip irrigated. Fruit samples were collected three times in February 2013 to analyze the fruit characteristics. We found that the fruit hardness of the 'Daewang', 'Maehyang', and 'Ssanta' cultivars was greater than that of 'Seolhyang', however 'Seolhyang' showed the highest moisture content of all the cultivars, indicating that fruit hardness was negatively associated with moisture content. Furthermore, 'Seolhyang' was found to have the highest levels of phenolic compounds and anthocyanins compared to the other cultivars. 'Maehyang' had the highest amount of total sugars. 'Seolhyang' and 'Maehyang' accumulated higher amounts of total organic acids. As a result, 'Daewang' and 'Maehyang' were expected to be preferred by consumers because they had the highest ratio of sugar to total acid in their fruit.

• Horticultural Science & Technology
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• v.34 no.1
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• pp.1-14
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• 2016

Heat stress is an agricultural problem for Gerbera jamesonii, and it often causes poor seedling growth, reduced flower yield and undesirable ornamental characteristics of flowers. However, little is known about the effect of heat stress on the morphological, physiological and biochemical characteristics of gerbera plants. Here, the responses of six cultivars of Gerbera jamesonii to heat stress were investigated. Under a 1-d heat treatment at $45^{\circ}C$, the leaves of gerbera cultivars showed yellowing, wilting, drying and death to varying degrees. The heat treatment also resulted in increased electrical conductivity, decreased soluble protein and chlorophyll contents, and the accumulation of malondialdehyde (MDA) and proline in leaves. Moreover, heat tolerance differed among the six tested gerbera cultivars. Our results demonstrated that among the six gerbera cultivars, 'Meihongheixin' is a heat-resistant cultivar, whereas 'Beijixing' is a heat-sensitive one. 'Shijihong' and 'Linglong' are relatively heat-resistant cultivars, and 'Dadifen' and 'Taiyangfengbao' are relatively heat sensitive.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.453-460
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• 2016

The parentage of the horticulturally important pear cultivar 'Niitaka' was confirmed by determining its S-genotypes based on the S-RNase and $PpSFBB^{-{\gamma}}$ genes, and genotyping using simple sequence repeat (SSR) markers. Previous reports suggested that the cultivars 'Amanogawa' and 'Imamuraaki' were the parents of 'Niitaka', although the cultivars 'Chojuro' and 'Shinchu' were also examined as candidate parents, along with two other cultivars. In the present study, the S-genotype of 'Niitaka' was determined to be $S^3S^9$. The $S^9$-RNase of 'Niitaka' was found to be likely inherited from the parent 'Amanogawa' ($S^1S^9$) and the $S^3$-RNase from 'Chojuro' ($S^3S^5$) or 'Shinchu' ($S^3S^5$). Based on the S-genotypes, the cultivar 'Imamuraaki' ($S^1S^6$) had no contribution to the parentage of 'Niitaka' ($S^3S^9$). A total of 67 polymorphic SSR markers were used to further confirm the parentage of 'Niitaka'. Discrepancies were found at several SSR loci between 'Niitaka' and the cultivars 'Imamuraaki' and 'Shinchu', whereas 'Niitaka' inherited alleles from 'Amanogawa' and 'Chojuro' at all SSR loci. Therefore, our findings established that 'Amanogawa' and 'Chojuro' are the parents of pear cultivar 'Niitaka', and not 'Imamuraaki' as previously reported.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.383-395
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• 2016

This study investigated the effect of exogenous hydrogen peroxide ($H_2O_2$) on the antioxidant responses and growth of warm-season turfgrass (Zoysia japonica Steud.) and cool-season turfgrass (Poa pratensis L.) subjected to drought stress. Compared with control plants that were not pretreated with $H_2O_2$, plants pretreated with $H_2O_2$ had significantly greater fresh and dry weights of shoots and roots, and increased water content. $H_2O_2$ pretreatments before drought stress significantly decreased the concentrations of malondialdehyde and $H_2O_2$. DPPH radical scavenging and glutathione activities were significantly increased. The responsive activities of the antioxidant enzymes superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase were also significantly enhanced. Our results suggest that exogenous $H_2O_2$ could improve the growth of warm-season and cool-season turfgrass under drought stress by increasing the activity of their antioxidant enzymes, while decreasing lipid peroxidation.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.294-304
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• 2016

Members of the genus Brassica, which are known as oil crops or cruciferous vegetables, are widely cultivated in Canada, Australia, Asian and Europe. Because Brassica species have high yields, are well adapted to their environments, and are self-incompatible, the germplasm is abundant. Previous studies have reported abundant genetic diversity even within Brassica subspecies. In Korea, fresh cabbage leaves are eaten with roast meat, and to meet the current popular demand, new varieties are being increasingly bred. To determine the genetic diversity and relationships among the cabbage vegetables in Korea, we evaluated the genetic variation of 18 accessions based on 5S and 18S ribosomal RNA (rRNA) gene sequences. We detected many variable nucleotide sites, especially in the 5S rRNA gene sequences. Because the length of the 18S rRNA gene might influence the dissimilarity rate statistics, we used both the 5S and 18S sequences to analyze the phylogenetic relationships. S7 (B. oleracea) showed the most distant phylogenetic relationship with the other Brassica species. Interestingly, B2 (B. oleracea), B15, and B18 (B. campestris) have three different types of leaf profiles, and were divided into one group, and the other Brassica species formed another group. Statistical analysis of interspecies and intraspecies genetic distances revealed that B. campestris L. showed higher genetic diversity than B. oleracea L. This work provides additional data that facilitates the evaluation of the genetic variation and relationships among Brassica species. The results could be used in functional plant breeding programs to improve Brassica crops.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.257-268
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• 2016

Physiological characteristics of five new apple cultivars from the Korean apple breeding program were evaluated as a function of harvest time and storage after harvest. Internal ethylene concentration (IEC), flesh firmness, soluble solids concentration (SSC), and titratable acidity (TA) were measured in 'Summer Dream', 'Summer King', 'Green Ball', 'Picnic', and 'Hwangok' apples at harvest, during shelf life at $20^{\circ}C$, and one day after cold storage at $0.5^{\circ}C$ in air. IEC increased during shelf life in 'Summer Dream', 'Summer King', and 'Green Ball' but not in 'Picnic' or 'Hwangok', regardless of harvest time. Flesh firmness decreased towards harvest time and decreased gradually with time in cold storage only in the former three cultivars. In turn, IEC increased during cold storage in the first three cultivars but not for the last two cultivars, irrespective of harvest time. Changes in SSC and TA did not consistently relate to harvest time or storage period but TA tended to decrease as IEC increased. Furthermore, IEC was negatively correlated with flesh firmness except in the 'Green Ball' cultivar but the significance level was much greater in 'Summer Dream' and 'Summer King' (p < 0.0001) than in 'Picnic' (p < 0.01) or 'Hwangok' (p < 0.05) cultivars. Flesh firmness was positively correlated with TA in the first three cultivars but not in the last two cultivars. Overall, the results indicate that cultivars for which IEC increased after harvest had reduced flesh firmness and TA after storage.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.314-323
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• 2016

A transient ihpRNA-induced gene silencing system based on Agrobacterium-mediated injection infiltration has been established to evaluate candidate genes involved in proanthocyanidin (PAs) biosynthesis in persimmon (Diospyros kaki Thunb.). We chose DkPDS (phytoene desaturase) as a gene-silencing target to evaluate the newly developed transient gene silencing system. Our qRT-PCR analysis indicated that two ihpRNA constructs (pHG-PDS5' and pHG-PDS3') targeted DkPDS, which also led to significantly reduce expression of DkPDS in 'Mopanshi' persimmon leaves. To further confirm the reliability of the system, we successfully utilized it for DkLAR (leucoanthocyanidin reductase) gene silencing. The expression levels of DkLAR in 'Mopanshi' and 'Eshi 1' leaves were ca. 6-fold and ca. 5-fold lower than those in leaves harboring empty vector (pHG-GFP), respectively. DMACA (4-dimethylaminocinnamaldehyde) staining and the Folin-Ciocalteau assay showed that the accumulation of PAs was markedly inhibited in 'Mopanshi', 'Eshi 1' and 'Youhou' leaves. These results indicate that DkLAR plays an important role in the accumulation of PAs in persimmon. The transient ihpRNA-induced gene silencing method developed in this study is a highly efficient and useful tool for functional analysis of persimmon genes involved in PA biosynthesis.