An apple (Malus × domestica Borkh.) core collection was established using 19 SSR markers in 1,344 apple germplasm samples using the PowerCore program. For this, 166 accessions were selected using a heuristic strategy, accounting for about 12.4% of the entire collection. The core collection had an allelic loci retention ratio of 100%, and no significant differences were observed in the number of alleles, Shannon’s information index, observed heterozygosity, expected heterozygosity, major allele frequency, or polymorphic information content between the core and the entire collection, as indicated by t-tests and Levene’s test. Analysis of molecular variance also revealed no significant genetic variation between the core and the entire collection. For all apple accessions, the genetic relationship, assessed using neighbor-joining analysis, was divided into five clusters, and the population structure had the highest value at k = 2. The first two axes in the principal coordinate analysis accounted for 14.00% and 9.85% of the total variance, and the core collection was distributed in a scattered pattern across the plot of the entire collection. The 166-apple core set constructed here is recommended for use as the core collection for the Korean apple germplasm.
This study aimed to reveal the effect of silver nitrate on sex modification in dioecious pointed gourd (Trichosanthes dioica Roxb.) originated in South Asia, and to explore the possibility of crossing among female plants. Three concentrations (50, 100, and 200 ppm) of silver nitrate were applied as foliar spray on female vines of three pointed gourd accessions. Application of 50 ppm silver nitrate found as effect to induce maximum proportion of hermaphrodite flowers with expanded duration irrespective of genotypes. The percentage of hermaphrodite flower induction was decreased with the increase of silver nitrate concentration. Viability of pollen grain (92.6–94.0%) in 100 ppm silver nitrate induced hermaphrodite flowers were as similar as that of normal male flowers (95.3%). Crossing among different female genotypes with pollen taken from the induced hermaphrodite flowers, produced same size of fruits of normal crossing. Seeds obtained from such crossing germinated successfully and seedlings grew vigorously as that of normal seeds. This technique seems to be useful for crossings among female plants that have suitable characters and facilitate a breeding of new variety in pointed gourd.
The branching habit and stalk proportion of heading type broccoli (Brassica oleracea L. var. italica) differs based on the cultivar, but the extent of the effects of these factors on the apical head weight is unknown. The main objectives of this study were to elucidate the relationships between the apical head weight and the branching habit or the stalk proportion. Firstly, the shoots of broccoli from six cultivars were divided into four parts (apical head, leaves on the main stem, lateral branches, and the rest of the main stem), and the weight proportions of each part were investigated. The results showed that the cultivars showing higher branching tended to produce smaller apical heads. Furthermore, apical head weights showed a positive relationship with the area of the leaves on the main stem, but a negative relationship with those on the branches. Secondly, four cultivars were grown with lateral bud nipping. This significantly increased the apical head weight in the cultivars showing higher lateral branching, but did not significantly change the weight of the whole shoot. These results suggest competitive biomass allocation between the main shoot and lateral branches. The difference in the weight of lateral branches depended on the probability of axillary bud presence rather than on the number of internodes or weight per branch. Finally, a strong correlation between the apical head weights and the square of the stalk diameter was demonstrated by generalized linear models (R2 = 0.95). These findings will contribute to the knowledge base on diverse methods of broccoli cultivation.
As a major growth limitation, low temperature-induced injuries may adversely affect grape production in many areas. Ten-year-old grapevines ‘Thompson Seedless’ were sprayed with calcium chloride (CaCl2) three times at 10-day intervals from 19th September to 8th October 2015 and again in 2016 in a commercial vineyard. Bud samples were collected in December 2015 and 2016, January 2015 and 2016 and February 2016 and 2017. The buds were exposed to freezing treatments: −12, −16, −20, −24, and −28°C for 3 hours, to assess their low temperature tolerance. Moreover, the relationships among freezing tolerance and changes in antioxidant enzyme activity, soluble carbohydrates, proline and total proteins were investigated. Irrespective of foliar spray treatments, the freezing tolerance of buds increased from December to January and decreased in February. Application of CaCl2 at a 1% concentration resulted in increased bud freezing tolerance compared to the control plants. Application of 1% CaCl2 considerably increased the concentrations of soluble carbohydrates and total proteins in buds, but had subtle and inconsistent effects on proline. Activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) were increased in response to foliar application of CaCl2; however, inconsistent changes were found in the activities of catalase and peroxidase following CaCl2 application. The results showed that application of 1% CaCl2 increased freezing tolerance of grapevines predominantly via upregulating soluble carbohydrates and total proteins.
To clarify the effect of ultrafine bubbles (UFBs) on the growth of tomato seedlings, we investigated elongation growth and dry matter production by analysing growth under different assimilation conditions and by modelling. The leaf area enlargement rate of plants grown with UFB nutrient solution increased and the specific leaf area (SLA) decreased at 18 days after sowing (DAS) relative to those grown without UFB solution. Thus, UFBs increased both leaf area and leaf thickness. UFB significantly increased the relative growth rate (RGR) and net assimilation rate (NAR) at 18 DAS, but there was no significant difference in SLA, RGR, and NAR between treatments at 25 DAS. These results were used to model plant growth with and without UFB treatment. In a second experiment, UFB treatment increased aboveground dry weight under a low-assimilation condition, but had no significant effect under a high-assimilation condition. Our model supported these results. It was also implied that UFB treatment affected leaf area expansion, but not dry matter production. Although the values predicted by the model were slightly lower than observed, it was possible to predict the effect of UFB treatment on plant growth with high accuracy.
Uniform temperature throughout a greenhouse is recommended, as the present climate control method and many other studies have shown that the temperature gradient decreases vertically and horizontally in a greenhouse. However, recent research revealed that roots, fruits, flowers, and shoot-tips are more sensitive to temperature changes than leaves and stems, indicating that uniform temperature control may not be necessary. In addition, energy-saving techniques that do not lead to yield loss are desirable to reduce energy costs and ensure sustainable greenhouse production. In this paper, we review current studies on local temperature control methods in greenhouse vegetable production, primarily focusing on the tomato, and compare them with novel climate-control techniques. Roots, fruits, shoot-tips and flowers are sensitive to temperature changes, showing negative symptoms under extreme temperature conditions. Therefore, the temperature of these plant organs should be controlled locally. Root zone temperature control enhances root growth and its associated physiological activities, promoting uptake of water and mineral nutrients. This subsequently leads to enhanced growth of shoots. Fruit temperature control may not be effective for tomato plants, but it promotes fruit growth and fruit sugar accumulation in melons and watermelons. Shoot-tip temperature control promotes the differentiation of leaf and flower buds. Flower temperature control enhances pollen viability and promotes fruit set. The combination of shoot-tip and flower heating enables low energy consumption compared with conventional heating, without loss of yield. Local temperature control techniques (except roots) have been studied in recent years; however, there is a distinct lack of research on the physiological mechanisms and practical approaches to develop a better local temperature control system. Thus, further studies are required on this area in the future.
Strawberry (Fragaria × ananassa) contains a major allergen, Fra a 1, which causes oral allergic syndrome. Fra a 1 is a PR-10 homolog that is regulated by environmental conditions. The allergenicity of fruit caused by Fra a 1 may depend on the genotype or growing conditions. We analyzed the Fra a 1.01 transcript levels and Fra a 1.01 protein levels in strawberry fruits of several genotypes across all seasons. In the preliminary rough screening, we selected the line WH1 bearing white fruit and the red-fruited cultivar ‘Akihime’. Under the same environmental conditions, there was no significant difference in Fra a 1.01 levels between the two cultivars over several months, suggesting that receptacle color was not indicative of allergenicity caused by Fra a 1.01. Fruits cultivated under the same environmental conditions should be used for comparisons of the allergenicity among genotypes. Both ‘Akihime’ and WH1 accumulated significantly higher levels of Fra a 1.01 protein in winter than in spring. We investigated the effects of irradiation and low temperature as environmental factors controlling the accumulation of Fra a 1.01 in winter. A shading treatment on fruit did not significantly affect Fra a 1.01 protein accumulation in strawberry fruits. Regarding variations over time, the Fra a 1.01 protein content was higher in fruits harvested at midnight in January than in those harvested at other times and in other months. These findings suggested that the Fra a 1.01 protein accumulates in response to environmental factors such as cold stress.
In this study, we cultivated 32 major citrus cultivars and local accessions of Kagoshima and one control accession to elucidate the polymethoxylated flavone contents with the purpose of providing information for citrus consumers to promote citrus production in the region. All trees were grafted on trifoliate orange rootstock and cultivated in Kagoshima City, Japan. In general, the Brix values and fruit weights of the major cultivars were higher and heavier than those of the local accessions. The ascorbic acid content of Tankan and Rokugatsu Mikan was high and that of Shiikuwasha, Kabuchii, and Shiikuu was very low. For analysis of polymethoxylated flavones (PMF), important health-promoting components sinensetin, nobiletin, heptamethoxyflavone, and tangeretin were quantified. Cultivar and accession differences in the PMF content were also observed. Nobiletin and tangeretin were found to be major PMF in most accessions, and heptamethoxyflavone was not detected in some species such as Kishu Mikan, Ponkan, Shiikuwasha, and Kuroshima Mikan. In the major cultivars, the PMF contents of Kishu Mikan, Ponkan, and Tankan were found to be high. In the local citrus accessions, Shiikuwasha, its relative, and Kishu Mikan were found to have the highest PMF content, and those of Kabuchii and Kuroshima Mikan were also high. Major cultivars Satsuma mandarin, pummelo, and its relative and the local accession Kunenbo contained little PMF.
Moderately vigorous shoots of mature rabbiteye blueberry ‘Tifblue’ bushes were pruned in summer to clarify the effects on vegetative and reproductive traits. Treatments included un-pruned, 25% pruned (removing 25% of the shoot length), 50% pruned (removing 50% of the shoot length) and 75% pruned (removing 75% of the shoot length). Vegetative and flower bud number per shoot decreased with increasing pruning severity. Consequently, the number of laterals per shoot dropped. However, lateral length increased with increasing pruning severity. Shoots pruned at 75% produced a small number of laterals, but they were the most vigorous. Pruning severity induced the transition of vegetative buds to reproductive buds in areas lower than the cut position. The flower bud number per shoot decreased with increasing pruning severity. However, yield per shoot was not affected due to a compensatory increase in berry weight. Total soluble solids content and titratable acidity of the berry juice, as well as, the number of berries per flower bud were not affected. Hence, to reduce the unproductive parts of the plant, and to produce bigger berries, September removal of either 50% or 75% of the length of mature rabbiteye blueberry shoots under conditions similar to the Kanto region of Japan is recommended.
Axillary buds of broccoli (Brassica oleracea L. var. Italica) develop and produce lateral heads after the apical heads have been harvested; however, lateral heads are not used because of their small size, and only one apical head is generally harvested from one plant. In this study, we aimed to establish a new method to harvest two heads of 12 cm diameter from a plant by pinching the apical bud and growing two axillary buds (“V-shaping” process) in autumn cropping. First, we measured the probability of axillary bud generation (PA) at each leaf axil and calculated the integration of the PA (IPA). The PA from the 5th to 8th true leaves was especially high, and the IPA reached 4.7. Next, we investigated the period of harvest and yield of heads at different times (3rd, 5th, 7th, 9th, 11th, 13th, and 15th leaf stage) of V-shaping in Field 1 (Ibaraki Prefecture, Tsukuba City). In V-shaped plots from the 7th to 11th leaf stages, the number of marketable heads significantly increased in comparison to that of the control. It increased by 61% of that of the control at the 11th leaf stage. However, the period of harvest was delayed, and the quality of heads deteriorated by cold injury when V-shaping was conducted from the 11th stage onward. Finally, we assessed the applicability of V-shaping cultivation in other fields. V-shaping was conducted from the 9th to 11th leaf stage. The number of marketable heads increased by 69 and 62% in Field 2 (Ibaraki Prefecture, Tsukubamirai City) and Field 3 (Nara Prefecture, Uda City), respectively. However, it only slightly increased in Field 4 (Mie Prefecture, Tsu City). Comparison of cultivation conditions at these 4 fields revealed that early transplantation, to allow an approximate 300°C day increase in effective heat unit summation for harvesting before the daily minimum temperature fell below approximately 0°C, was important. In addition, improving the drainage of the field seems important, and the input of manure compost (long-term fertilizer effect) may improve the quality and yield of heads. Thus, we concluded that V-shaping cultivation enabled the harvesting of two heads by V-shaping and increased the number of marketable heads by more than 60% in a wide area.