Exploration of local citrus genetic resources grown in the Kingdom of Bhutan was conducted in September 2007, Mongar and Trashigang in the east region, Wangdue Phodrang and Thimphu in the west region, and Tsirang in the south region. Among 14 accessions investigated, all accessions belonged to genus Citrus except one Bael (Aegle marmelos). Among them, eleven accessions were native and/or local Citrus genetic resources; one Ichang papeda relative, four Lime relatives, two Acidless limes, two Citron relatives, one Rough lemon relative, and one unidentified accession. Ichang papeda relative was found at elevations of around 2,000 m. In Bhutan, places at that altitude are normally too cold for any citrus tree to survive especially in winter where the temperature drops to below freezing, occasionally with snowfalls. Analysis of matK sequences revealed that chloroplast DNA of Bhutanese Ichang papeda relative and a preserved tree of Ichang papeda in Faculty of Agriculture, Saga University was different. MatK sequence of Bhutanese Ichang papeda relative was identical with that of a preserved tree of Khasi papeda in Saga University. Diversity was found in matK sequence among lime relatives. Precise accession identification could be conducted from the results of matK sequences in conjunction with morphological traits.
To breed varieties with the parthenocarpic trait for laborsaving of tomato cultivation, we investigated an efficient selection method for the trait. In spring and autumn when self-fertilization occurs, working hours of stigma excision were shorter than those of emasculation. The decisions of the parthenocarpic trait in each treatment generally corresponded. These findings show that stigma excision is effective in actual breeding. In winter when self-fertilization is difficult, it is important to control night temperature to the lowest of 8°C or higher and select individuals with seedless fruits enlarging normally from ones flowering after the start of night temperature control. Parthenocarpy can be selected efficiently by stigma excision in spring and autumn, or by the method using low temperature in winter.
We attempted to produce intersectional hybrids between Vaccinium uliginosum L. (2 n = 6 x = 72) of the section Vaccinium, a wild species native to Japan, and 8 rabbiteye blueberry (V. virgatum Aiton) cultivars (2 n = 6 x = 72) of the section Cyanococcus using reciprocal crossing. Fertile seeds were obtained from 5 of 8 cross combinations, of which V. uliginosum was used as a seed parent, whereas no fertile seed was obtained when V. uliginosum was used as a pollen parent. This result showed that unilateral cross incompatibility would exist in the crosses between V. uliginosum and V. virgatum. Consequently, 13 seedlings were obtained from the crosses and 12 seedlings were from the cross between V. uliginosum and T100. These 12 seedlings (KT strain) were used for evaluating their hybridity, ploidy level, nuclear DNA content, morphological characteristics, and fruit quality. RAPD analysis showed that 10 of the 12 seedlings of the KT strain were intersectional hybrids between Vaccinium and Cyanococcus. The hybrids were also confirmed to be hexaploids by flow cytometory; however, the nuclear DNA contents among their hybrids were different. Some of them grew vigorously on their own root in south-west Japan, and 8 hybrids bore flowers. While 2 of the 8 hybrids did not produce fertile pollen, all 8 hybrids set fruits in an open field without artificial pollination. Each fruit had a peduncle with a pair of bractlet leaves on its middle part which often attached to the peduncle of V. uliginosum. The fruit quality was different among their hybrids, sugar and organic acid contents in fruit of KT-9 and 15 were almost equal to those of T100, and anthocyanin and polyphenol contents and antioxidant activity in fruit of KT-4, 9 and 15 were almost equal or above those of V. uliginosum. In the future, these hybrids may be useful as breeding material to establish some new cultivars with high quality and functionality adaptable to south-western Japan.
In order to determine the drip irrigation zone adequate to control drought stress, we investigated the influence of drought stress under different ratios of the irrigation zone on citrus trees. The results showed that there was a clear correlation between the irrigation zone and drought stress of trees. It was indicated that, in the case of young trees, a greater than 50% irrigation zone out of the root zone was required in order to protect them from overdryness. In the case of adult trees, over 19.5% was necessary for 13-year-old ‘Shiranui’, and over 14.2% for 21-year-old ‘Haraguchi-wase’. Drip tubes should be placed within 100 cm from trunks where fine roots are densely distributed. An appropriate irrigation time was estimated to be 20 minutes in granite soil, 20–60 minutes in basalt soil, and 60 minutes in andesite and volcanic ash soils. In addition, it was indicated that the dripper interval should be more than 20 cm in granite soil and more than 30 cm in the three other kinds of soil to reduce water wastage.
Influences of the light condition on the aroma, bitter, and functional components of processed Japanese apricot liqueur (ume liqueur) were investigated in Japanese apricot (Prunus mume Siebold et Zucc.) ‘Nanko’. In fruit located in the shaded part of the canopy covered with cheesecloth, cutting out 90% of the sunlight, the timing of fruit drop at full ripeness was 6 days later than in the non-treated part of the canopy. There were no differences in the temperature of the inner side of the canopy and maturity index of fully ripened fruit between shaded and non-treated parts. Ume liqueur made from fruit located in the shaded part of the canopy tended to have less aroma components, such as γ-decalactone, δ-decalactone, ethyl butyrate, and butyl acetate, and have more ethyl benzoate, exhibiting immature flavors, than that made from fruit in the non-treated part of the canopy. Ume liqueur made from fruit located in the shaded part of the canopy also had less functional components, such as citric acid, malic acid, sorbitol, and phenolics, as well as less free radical scavenging activity than that made from fruit from the non-treated part of the canopy. These results show that poor sunlight had an adverse effect on the quality of ume liqueur by decreasing aroma and functional components, and increasing immature flavors. Hence, Japanese apricot fruit should be grown under rich sunlight to produce high-quality ume liqueur.
We investigated the supply of small-flowered, spray-type chrysanthemums to meet the peak demand from July to September (beginning of July, beginning of August, middle of September), using cuttings obtained from the same mother stock, and with night-interruption treatment (NI). Peak demand supply was investigated using 9 varieties that flower from June to July under a natural day length. In ‘Seikomaki’, ‘Subaru’, ‘Haruka’, and ‘Seichigusa’, early budding was completely prevented and flowering was adjusted arbitrarily, using NI. Therefore, we consider that the peak demand can be met using these four varieties. The flowering time under natural day length conditions and the delay of budding induced by NI were investigated in thirty-three June-to-August flowering varieties after planting on 28 April, 2011. Plants flowered between July 4 and July 19 under natural day length conditions and NI delayed budding for more than twenty days in ‘Seiun’, ‘Seikomaki,’, ‘Subaru’, ‘Haruka’, and ‘Seichigusa’, which are suitable to meet the peak demand using NI. This shows that the five varieties had a flowering time and delay of budding induced by NI in common. Therefore, we propose that it is possible to select chrysanthemum varieties suitable to meet the peak demand on the basis of these flowering parameters.
The relationship between the critical day length and the most effective night-break (NB) time on the depression of flower bud initiation in chrysanthemum was investigated using five cultivars of summer-autumn (SA) flowering types: ‘Floral Yuka’, ‘Iwanohakusen’, ‘Southern Grape’, ‘Southern Chelsea’, and ‘Southern Pegasus’, and five of autumn (A) flowering types: ‘Jinba’, ‘Sanyo Ougon’, ‘Yukihime’, ‘Hakusui’, and ‘Shuhouno-chikara’, in Japan. The critical day length (night length) of the SA flowering types was found to be 15 (9)–16 (8) h during the August flowering and cropping period. The duration from dusk to NBmax, which is the most effective NB time, was 6.5–8.5 h when one hour of NB was included. On the other hand, the critical day length (night length) of the A cultivars was 13 (11) h during the December flowering and cropping period. The duration from dusk to NBmax was 9.0–10.5 h when 40 min of NB was included. Similarly, the SA cultivars with a short critical dark length had a shorter dusk-NBmax period compared to the A cultivars with a similar critical dark length and dusk-NBmax period. The results suggest that the dusk-NBmax duration is associated with the critical night length. The present study demonstrates that the critical day length (night length) is closely associated with the dusk-NBmax duration, thereby suggesting that estimation of the most effective night-break time for each cultivar is possible if the critical day length is ascertained.
The application of an acoustic vibration method for the discrimination of fruit with freezing or granulation of juice sacs (GJS) in Citrus was studied. The elasticity index (EI) of fruit with freezing in blood orange ‘Moro’ was significantly lower than in that without freezing. There was no relationship between the degree of freezing and EI. The specific gravity of fruit significantly decreased as the degree of freezing increased. A relatively strong positive correlation was found between the specific gravity and EI. The discrimination rate of fruit with freezing was approximately 70% when estimated using EI 80 × 105 as a threshold; however, it was approximately 78% when estimated using the specific gravity of 0.88 as a threshold. The EI of fruit with the initial stage of GJS in Hassaku was significantly higher than without GJS. The specific gravity of fruit significantly decreased as the GJS increased. No significant differences were detected among the degree of freezing in blood orange in the total soluble solids content (TSS), but the citric acid in the fruit with a higher degree of freezing was lower than in that without freezing. TSS in Hassaku fruit without GJS was slightly higher than in that with a higher GJS; however, there was no significant difference in citric acid among the degrees of GJS. The results of this study showed that the discrimination of fruit with freezing or GJS in Citrus is possible using a nondestructive acoustic vibration method.
Garlic bulbs are stored at about −2°C for year-round shipping. After storage, the bulbs start to develop roots and sprouts, which lowers their commercial value. The conventional hot air treatment to inhibit the growth of roots and sprouts after the storage, which aims to keep the temperature inside bulbs at 48°C for 6 h, sometimes causes heat injury. Here, we searched for a more favorable condition of hot air treatment for practical use. Bulbs that had been stored at −2°C from August for various periods were then treated at 40–50°C for 4–48 h in 26 temperature-duration combinations, and then kept at 15°C for 4 weeks. In the bulbs stored until October, 5 temperature-duration combinations inhibited root growth, and 3 combinations inhibited sprout growth. On the other hand, in those stored until April, all combinations inhibited root growth, and 15 combinations inhibited sprout growth. An increase in the duration of treatment intensified the inhibitory effect in many cases, but a higher treatment temperature often did not. Treatment at 40–44°C given in December inhibited root growth more intensely than that at 46–48°C. The effectiveness of hot air treatment at 48°C for 8 h (an equivalent to the conventional treatment) and that at 41°C for 12–48 h given to the bulbs removed from the storage periodically from September to June was compared. Treatment at 41°C for 12–48 h inhibited root growth more effectively than that at 48°C for most of these 10 months. Treatments at 41°C for 48 h and at 48°C were sometimes injurious, while treatment at 41°C for 12–24 h caused no injury. These results indicate that hot air treatment at 41°C is markedly effective and safe, and is more practical than conventional treatment.
A new sweet cherry cultivar, ‘Juno Heart’, was selected from the cross of ‘Benisyuhou’ × ‘Summit’ at Kennan Fruit Tree Section, Apple Research Institute, Aomori Prefectural Industrial Technology Research Center. The crossing was conducted in 1998, and it was selected from 35 seedlings in 2004. In Aomori, it matures in early July (about 57 days after full bloom), about 5 days after ‘Satonishiki’. The fruit size is large, being about 11 g. The shape is short cordate. The skin color is a yellow back ground color with dark red. The flesh is firm. The fruit is sweet (19°Brix) and shows low acidity (0.53％ titrtable acidity). The stone size is large. However, because the stone is semifree, it is easy to remove. The S genotype is S1S6. It is pollinated by ‘Satonishiki’, ‘Benisyuhou’, ‘Nanyo’, and ‘Summit’, but it is incompatible with ‘Benisayaka’ and ‘Hokkoh’. It can be planted as a compatible pollinizer for ‘Satonishiki’. ‘Juno Heart’ is expected to provide gift or tourist farm attractions because of its attractive appearance and sweet taste.