In this paper, I reviewed research studies and records of the occurrence of physiological disorders such as ‘Yuzuhada’ disorder, water core, and cork spot like disorder in Japanese pear (Pyrus pyrifolia (Burm. f.) Nakai) fruit. The incidence of these flesh disorders varied not only with the climate of the growing season and soil condition but also according to the tree age and cultivation techniques, such as pruning and fertilization. The histological and biochemical characteristics of the disorders differ from each other as follows: ‘Yuzuhada’ disorder refers to an increase in the thickness of the cell wall; the water core is the degradation focus of cell wall polysaccharides, and cork spot like disorder involves the suberization of cells in pear flesh. The common cause of these three disorders was considered to be competition for water between the fruit and leaves. This paper also discusses future trends in research on physiological disorders affecting Japanese pear fruit.
The flower trait of a long-lasting corolla with a temporal color change, called “misome-sho”, is found in several evergreen azalea cultivars of Japan. For the purpose of applying the “misome-sho” trait for breeding, we investigated the floral morphology and inheritance pattern using these cultivars and their crossed progenies. All five “misome-sho” cultivars have smaller corolla and smaller epidermal cells on the abaxial surface of the corolla compared with wild type flowers. Also “misome-sho” cultivars have a number of stomata and trichomes on the abaxial surface of the corolla. This may lead to sepaloid features occurring at the corolla. All F1 progenies between wild type flowers and “misome-sho” cultivars showed wild type flowers. On the other hand, all F1 progenies between “misome-sho” cultivars showed “misome-sho” trait flowers. Wild type flowers and “misome-sho” trait flowers were segregated at a 3 : 1 ratio in the crossed progenies between F1 hybrids of wild type flowers and “misome-sho” cultivars. These results indicate that the “misome-sho” trait is controlled by a single recessive gene and a similar morphological mutation is caused by a common gene mutation in “misome-sho” cultivars. To increase the size of the small corolla of “misome-sho” cultivars, the effectiveness of using large-flower cultivars as cross parents was indicated in a breeding program.
Symptoms of grapevine anthracnose after spray inoculation were evaluated by imaging analysis to develop a method for anthracnose resistance evaluation. The results suggested that the lesion area could be stably evaluated with a few replicates, whereas many replicates are necessary for lesion number evaluation. Therefore, a visual rating scale on the basis of the lesion size, equivalent to the lesion area, was established for high throughput and reliable evaluation. Then, 575 seedlings in total from different hybridizations were evaluated by visual rating for three years in a greenhouse, and then they were evaluated in a fungicide-free orchard. The visual evaluation was significantly correlated with the successive evaluation in the fungicide-free orchard with Spearman’s rank correlation coefficient of 0.66 to 0.68. Seedlings evaluated as highly resistant or susceptible were observed as resistant or susceptible in the fungicide-free orchard, respectively. However, the evaluation of individuals rated as slightly resistant by the seedling visual rating highly fluctuated in the fungicide free orchard, suggesting that it is difficult to evaluate low-level resistance by visual rating. Hence, highly resistant or susceptible seedlings should be selected or discarded based on visual rating, whereas seedlings rated as partially resistant should be evaluated in detail with more replicates.
A new Chinese chive (Allium ramosum L.) cultivar, ‘Yume Midori’, was obtained from a cross combination, ‘Koshu Nira’ × ‘Thunder Green Belt’, and it was developed for the first time by seedling selection of crossbreds using pollen parent-specific RAPD (Random Amplified Polymorphic DNA) markers. This new cultivar is estimated to have a sufficiently low crossing rate and exhibit excellent quality, such as high-yielding, broad leaf width, and long leaf sheath. Also, it is possible to improve the efficiency of shipping preparation. In addition, it is suitable for wintering to be harvested from winter to spring because of its shallow dormancy and high low-temperature elongation property, so even with summer harvesting from summer to autumn, the same yield and quality can be obtained compared with other varieties, making it suitable for annual production.
‘Natsumi seedless’ is a new citrus cultivar that produces fewer seeds than the original cultivar, ‘Natsumi.’ ‘Natsumi seedless’ was produced by soft-X irradiation of the scions of ‘Natsumi.’ After top-grafting those scions, a strain was selected on the basis of few seeds per fruit. The average number of seeds in ‘Natsumi’ was 8.9 per fruit, and the rate of its seedless fruit was 0 percent. On the other hand, the number of seeds in the new cultivar was 0.2 seeds per fruit, which was extremely few, and the rate of its seedless fruit was high at 86.7%. With the exception of the number of seeds, the characteristics of fruit and trees of the new cultivar were similar to those of ‘Natsumi’. The possibility of female sterility in ‘Natsumi seedless’ was shown by cross-pollination between Natsudaidai, as a pollen parent, and two cultivars, ‘Natsumi’ and the new cultivar, as a seed parent, revealing that only the new cultivar had seedless fruit and its rate was high. In addition, male sterility in the new cultivar was indicated by two findings: First, the pollen fertility of the new cultivar was 1.9%, being noticeably lower than that of Natsudaidai or ‘Natsumi’. Second, cross-pollination between the new cultivar (pollen parent) and Natsudaidai (seed parent) resulted in it not bearing fruit, while it bore fruit when the pollen parent was ‘Natsumi’. From these results, the new cultivar, ‘Natsumi seedless’, may have both female and male sterilities.
The Asiatic hybrid lily cultivar Kitakirari can produce multiple flower stalks from the same bulb, and the bulb’s size and bud number affect the cut flower quality of ‘Kitakirari’. For example, it is desirable to have three buds per 12–14-cm bulb, but there are no bulb production techniques that control the bud number. This study examined the relationship between the bulb size and division in the first year of bulb production, the effects of the first-year bulb size and number of daughter bulbs on second-year growth rates, and the division style. In the first year, 46.7% of large bulbs (greater than 7-mm width) bolted. Non-bolted plants produced very few daughter bulbs, but all of the bolted plants formed two or three daughter bulbs from the mother bulb. In the second year, the first-year bulb size did not affect the number of daughter bulbs produced. The greater the number of daughter bulbs produced by first-year bulbs, the greater the number of daughter bulbs produced by second-year bulbs. However, the weight per daughter bulb was lower. These bulbs could not be used for cut flower production. The growth characteristics of first-year bulbs derived from non-bolted plants were examined. One or two daughter bulbs arose from the axillary bud of the last-produced scale or the scale before it, respectively. The average number of daughter bulbs that had formed by early May was 3.2.
To utilize the irrigation function of the Farm-Oriented Enhanced Aquatic System (FOEAS) in an upland field converted from a paddy field, we examined the effect of sub-irrigation at different growth stages of onion and different levels of precipitation on growth and yield of pot-cultured autumn-sown summer-harvest onion. Onion seedlings were transplanted into a large pot of andosol or gray lowland soil under rain shelter. The level of feed-water in a connected tank was automatically maintained at –30 cm from the soil surface. Plants were irrigated in each cultivation period (Early, Middle, Late, and Total periods) except for right before harvest under low-level precipitation (25% of monthly average amount of precipitation). By comparing with plants without sub-irrigation supplied with 25% of the monthly average amount of precipitation, soil water suction in sub-irrigated plots with 25% of the monthly average amount of precipitation remained low, and plant shoots grew larger. In both soils, the Total period treatment led to the largest bulb weights and diameters, and the second best was the Late plot. The increased effect of sub-irrigation on the growth in andosol was more marked than that in gray lowland soil. In the year with higher reference evapotranspiration, plants with sub-irrigation with 50 and 100% precipitation during the Total period except for right before harvest had larger bulb weights compared with those receiving 50 and 100% precipitation without sub-irrigation. In the year with a more than 10-mm higher monthly reference evapotranspiration than the average year, sub-irrigation was more effective with respect to the bulb weight and diameter. The results indicate that sub-irrigation according to the growth stage of plants and rainfall may prevent drought and increase the yield of onion.
We investigated the effects of the fertilization scheme and planting distance on the incidence of cavitation and the pithiness of thickening roots of ‘Sakurajima daikon’ (Raphanus sativus L.). Two cultivars: the open-pollinated ‘Native cultivar (Sakurajima)’ used in the Sakurajima region and the F1 cultivar ‘Kagoshima No5’, were used in this study. The prevalence of cavitation was increased in both cultivars when preplanting fertilizer was mainly applied to them with a reduced amount of additional fertilizer, compared with the scheme in which preplanting fertilizer was decreased and additional fertilizer was increased. Cavitation was also increased with sparse planting compared with dense planting. A positive correlation was noted between the occurrence rate of cavitation and the nitrogen levels in soil at the time of thinning excess seedlings, suggesting that a high dose of nitrogen in an early growth stage could cause the cavitation of ‘Sakurajima daikon’. As for the pithiness of thickening roots, this symptom was more frequently observed when additional fertilizer was increased, compared with the scheme in which additional fertilizer decreased and preplanting fertilizer increased. However, the problem regarding pithiness may be avoided if the F1 cultivar ‘Kagoshima No. 5’ is chosen instead of the ‘Native cultivar (Sakurajima)’ for cultivation, because the progression of pithiness in the former is much slower than in the latter.
Bamboo is known to interfere with mountain maintenance because of its rapid growth and expansion. The applicability of bamboo chips, which is one of various organic mediums, as a strawberry high bench culture medium were investigated. A strawberry cultivar, ‘Tochiotome’, was cultured in pots filled with bamboo chips mixed with peat moss (bamboo chips : peat moss = 4 : 1, v/v). The vegetative growth, fruit yield, and physical characteristics of strawberries in the culture medium were measured, and compared with those of strawberries cultured in pots with coir (standard medium). The yield with bamboo chips was lower than that with coir. The low proportion of the liquid phase of bamboo chips was considered to cause a low yield. The amount and frequency of watering should be doubled or peat moss is required to increase the yield. Continuous use of the medium containing bamboo changed the proportion of the liquid phase, which was higher than that initially, leading to the same yield as the standard medium.
The effect of irradiation with far-red (FR) light at the end of the day (EOD) on the yield and traits of 4 varieties of Japanese mustard spinach (Brassica rapa var. perviridis) and 3 cultivars of pak-choi (B. rapa var. chinensis) were investigated. When the ‘Maruba-komatsuna’ of Japanese mustard spinach was exposed to FR light under high irradiation (96.0 mW・m–2) by EOD treatment, all investigated traits tended to increase more than in plants without treatment. On the other hand, for other varieties, ‘Hakkei’, ‘Nanasa’, and ‘Nanane’ receiving low irradiation (34.3 or 13.4 mW・m–2) were compared with those receiving strong irradiation (96.0 or 56.7 mW・m–2). Depending on cultivars, they are different reactions under low or high irradiation for Japanese mustard spinach. Also, in ‘Okinawa-Chingensai’ of pak-choi, stem elongation on receiving EOD-FR treatment was promoted by more than 2 times in comparison with no treatment, but this was not observed with ‘Mini-chingensai’ or ‘Choyo’. The results showed that EOD-FR treatment promoted the effect of stem elongation in some cultivars, but it had no effect on pak-choi.
For effective CO2 enrichment in protected horticulture, it is necessary to understand the distribution of the CO2 concentration in a greenhouse. In this study, we used sodium hydroxide (NaOH) aqueous solution, whose pH decreases when it absorbs CO2 to estimate the CO2 concentration in a greenhouse. When plastic boxes with containing NaOH solutions were placed in various CO2 concentration environments, there was a positive correlation between the CO2 concentration and reduction the pH. Further, the pH was affected by the surface area and temperature of the aqueous solution, NaOH concentration, and CO2 absorbing treatment time. We considered that using a hard plastic box with 50 mL of 0.004 mol・L–1 NaOH solution was suitable for measuring the pH in the greenhouse. We examined the associations among the CO2 concentration, solution temperature, and pH in different environments using a growth chamber, and we formulated relational expressions. About 100 plastic boxes with 50 mL of 0.004 mol・L–1 NaOH solution were placed for 3 hours in a greenhouse with a CO2 enrichment tube that was set for medium planted strawberry plants. pH changes differed depending on the location. The estimated CO2 concentration was higher in the greenhouse than outside, and varied depending on the distance from the CO2 enrichment tube and height from the ground in the greenhouse. The estimated CO2 concentrations were about 100 ppm higher than the measured CO2 concentrations, possibly affected by light and wind. We propose that using NaOH solution is a simple and effective method to estimate the distribution of the CO2 concentration in a greenhouse.
In this study, the effects of the scion cultivar and rootstock on reproductive growth were investigated with ‘Setoka’ and ‘Shiranuhi’ grafted on trifoliate orange (Poncirus trifoliata L. Raf.) or ‘Hiryu’ (Flying Dragon) for three or four years. In November, which is the period of floral induction in citrus, expression of one of the flowering-related genes, citrus FLOWERING LOCUS T (CiFT), was quantified in stems of trees with each combination of scion cultivar and rootstock. In the analysis without distinction of the combination, the mRNA level of CiFT was correlated with flower numbers in the following spring. In both ‘Setoka’ and ‘Shiranuhi’, the average CiFT mRNA level in each combination was markedly changed annually when the trees were grafted on ‘Hiryu’. Yields were about 3 kg・m–3 every year in all combinations of the scion cultivar and rootstock, and there were no significant differences in each combination among years. Two-way ANOVA of the alternate bearing index in each tree showed that the annual change in the CiFT mRNA level was significant in trees grafted on ‘Hiryu’. These results suggest that using ‘Hiryu’ as a rootstock makes flowering unstable in ‘Setoka’ and ‘Shiranuhi’, although this instability has no impact on their yield.
To clarify the relationship between the occurrence of a cork spot-like disorder and the maturation time of fruit in the Japanese pear (Pyrus pyrifolia) ‘Akizuki’, the effects of the flower position and flowering time on the occurrence of this disorder were investigated. The fruit from the sixth to eighth flowers in a flower cluster matured later and displayed more cork spots than those from the second to fifth flowers. Moreover, the fruits of ‘Akizuki’ and ‘Oushuu’ were treated with ethephon (2-chloroethylphosphonic acid). The ‘Akizuki’ fruit treated with ethephon around 100 days after full bloom matured earlier than the control fruit, and had only a few cork spots. The ‘Oushuu’ fruit treated with ethephon also had fewer cork spots, but displayed severer water-soaked disorder. These results suggest that making trees bear fruit from the second to fifth flower in a cluster and spraying ethephon on fruits after around 100 days after full bloom were effective for reducing the occurrence of cork spot-like disorder.
The objective of this study was to investigate the effect of the harvest date and 1-methylcyclopropene (1-MCP) treatment on the incidence of internal browning disorders in ‘Fuji’ apples stored in a snow cellar for six months. The fruits were harvested three times in Nagano. The average temperature and relative humidity in the snow cellar during storage were 0.9°C and ≧95%, respectively. The degree of shriveled skin and internal browning were investigated after six months storage and then at 20°C for seven days. Internal browning can be categorized into the following three parts: core browning, coreline browning, and flesh browning. Storage in the snow cellar inhibited the occurrence of shriveled skin because of the cellar’s low temperature and high humidity environment. Core browning, which is a major problem associated with snow cellar storage, was inhibited by 1-MCP, whereas flesh browning was increased in the late-harvest fruits. These results indicate that harvesting by an optimal date when flesh browning is less marked and treatment with 1-MCP are both necessary to obtain high-quality fruits after six months of storage in a snow cellar.
In response to an increasing demand for small-sized vegetables, which are not wasted even by small families, the present study was conducted to determine the position of small-sized, or mini, carrots among all types, and discuss the forms of the sales of mini carrots and price settings, with the aim of promoting their production and sales. A questionnaire survey was conducted at farm stands and event sites of university to examine consumers’ awareness of mini and other carrots. The results suggested that the respondents were attracted to the mini carrot because they: “do not need to be peeled for cooking”, “can be eaten raw as an ingredient of salad”, and “are sweet and juicy”, and that it may be developed into a product suitable for salad or to be eaten raw. Regarding the forms of the sales of mini carrots, many of the respondents preferred product packages including orange carrots and a smaller number of yellow ones. The optimal price of the product sample including six orange carrots and two yellow ones was estimated to be 142 to 150 yen according to the buy-response curve. Since the period of time required to cultivate the mini carrot is shorter than the periods required for standard types of carrots, including the one called “Gosun Carrot”, its yield is expected to increase. Therefore, it is a promising agricultural product to be grown in the suburbs of large cities.
We previously study, reported that a bacterial wilt disease of eggplant was suppressed by pre-inoculation with a non-pathogenic (phenotypic conversion: PC) mutant of Ralstonia solanacearum. In the present study, we examined the suppression of Verticillium wilt disease in eggplant using a PC mutant for which the biocontrol of other soil-borne diseases had already been achieved. We tested the suppression of Verticillium wilt by pre-inoculation with live bacteria, heat-killed bacteria, and a culture filtrate of the PC mutant, and found that the disease was suppressed when eggplant was inoculated with live bacteria. Biocontrol was increased by inoculation with a high concentration of the PC mutant. However, suppression decreased when the PC mutant-inoculated seedlings were transplanted into soil containing a high concentration (>106 conidia・g–1) of the pathogen. In cultivations at 20°C and 25°C after PC mutant inoculation, biocontrol was reduced compared with that at 30°C.