We devised a method to evaluate anthracnose disease resistance that can generate highly accurate results on a small-scale basis in a relatively short period of time. Aseptically-sown strawberry seedlings were clonally multiplied on medium containing a cytokinin. After acclimation, resistance to anthracnose disease was evaluated by spray inoculation with Colletotrichum gloeosporioides (Glomerella cingulata) at a concentration of 1 × 104 spores・mL−1. This approach allows the evaluation of resistance within approximately 120 days after seeding, with accuracy equivalent to that of the existing method using runner plants. The new method requires no field for inoculation, and so assessment can be completed within a small-scale, closed space such as an acclimation case. Furthermore, susceptible individual seedlings may subsequently be used as materials for genetic analysis, as these plants can be preserved as uninfected clonal seedlings.
In order to evaluate the reliability of using bottle gourd (Lagenaria siceraria (Molina) Standl.) pollen to produce seedless watermelon, the fruit set rate and qualities of fruits obtained via parthenocarpy using the watermelon cultivar ‘Fujihikari TR’ were investigated. Pollen from several cultivars of bottle gourd was tested. To verify that pollen from another genus can be used universally to produce seedless fruit, the fruit set and fruit quality of several watermelon cultivars were measured in experiments using pollen from different bottle gourd cultivars. The timing of flowering and production of male bottle gourd flowers were investigated to identify the best combination for pollinating watermelon with bottle gourd pollen in the early spring season. Seedless watermelon could be produced from the pollen of several cultivars of bottle gourd. The watermelon fruit set rate after pollination with bottle gourd pollen was lower than that using watermelon pollen. The watermelon fruit set rate after pollination with L. siceraria var. hispida pollen was higher than that of L. sciceraria var. gourda pollen. There were no differences in the characteristics of seedless fruit produced by pollinating with different bottle gourd cultivars. Bottle gourd pollen could produce seedless fruit in several watermelon cultivars. Several common traits were evident in seedless watermelon fruit. Seedless fruit tended to be oblong, have hollow hearts, and have a higher °Brix compared with normal fruit. Seedless fruit had only empty seeds, and the number of empty brown seeds differed among watermelon cultivars. There were varietal differences in the male flower traits of bottle gourds. Seedless watermelon production can be facilitated by carefully evaluating the timing of anthesis in male bottle gourd flowers.
To develop a yellow-flowered ivy-leaved geranium, reciprocal crosses between Pelargonium peltatum and P. quinquelobatum, a species that produces pale yellow-green flowers, were performed. Seeds were obtained when P. peltatum was used as the pollen donor (3.3 seeds per fruit). The flower color of F1 plants varied from cream to extremely pale purple. Regarding cream flowers, the yellowish tone was paler on the adaxial surface of the petals compared with that on the abaxial surface. Ovule culture was performed for the cross P. × hortorum × P. peltatum, which aimed to expand the purple color palette of the flower. A total of 337 shoots were regenerated from 175 ovules, and 12 plants flowered after acclimatization. In many of these plants, the purple pigmentation of the petals was equal to that of P. peltatum. The highest malvidin content was 91%. Seven F1 plants showed high pollen fertility. These F1 plants are suitable for use as breeding material to produce promising new yellow- and purple-flowered ivy-leaved cultivars.
In order to contribute to the development of a summer-cropping type of Japanese bunching onion (Allium fistulosum L.) suitable for early-harvesting (July) in colder regions, we investigated the effects of the seeding time (Sept. 1, Sept. 16, Oct. 1, Oct. 15, and Nov. 4), cell tray size (128- and 200-cell trays), and number of seedlings (one and two seedlings) per cell on the growth habits and yield performance of seedlings grown in an unheated plastic house. Seedlings of two cultivars were used in this experiment: ‘Hanemidori-ipponbuto’ (a late-bolting cultivar) and ‘Natsuougi-power’ (a heat-tolerant cultivar). For both cultivars, seedling development from early seedings was superior to that from later seedings (after Oct. 1), and development was also more favorable in seedlings grown in 128- than in 200-cell trays, and also when one seedling was seeded per cell compared to two seedlings per cell. The results of multivariate regression analysis indicated that the seeding time was the most influential factor for promoting seedling growth, whereas cutting the leaf blade, which inhibits seedling growth, was the second most influential factor. Therefore, leaf-pruning treatment could induce the slow growth of seedlings, even for those seeded earlier in the season. A practical evaluation with regard to early-harvesting was carried out using the following critera: the first priority, no flower bud differentiation on transplanting in the absence of leaf-pruning treatment; and the second priority, a leaf sheath diameter of more than 6 mm. As a result, five practical combinations of seeding time, cell tray size, and number of seedlings per cell were selected for ‘Hanemidori-ipponbuto’ [seeding on Oct. 1 in a 128-cell tray with two seedlings per cell (Oct. 1–128-cell tray–two seedlings), Oct. 1–200-cell tray–one seedling, Oct. 15–128-cell tray–one seedling, Oct. 15–128-cell tray–two seedlings, Oct. 15–200-cell tray–one seedling], whereas three combinations were selected for ‘Natsuougi-power’ (Oct. 15–128-cell tray–one seedling, Oct. 15–128-cell tray–two seedlings, Oct. 15–200-cell tray–one seedling). Except for one combination (Oct. 15–128-cell tray–one seedling of ‘Hanemidori-ipponbuto’), all seedlings showed a yield greater than 300 kg・a−1, which was our target yield.
To improve the fruit set of sweet cherries, we investigated the effects of an acclimation method of pollen storage on the fruit bearing rate and pollen activity. Pollen stored at a low temperature, −30°C, led to a 14.0% germination rate immediately after being transferred from the freezer. When acclimated for 2 hours at relative humidity 90%, the germination rate rose significantly to 42.4%. By increasing the acclimation period to 4 hours, the germination rate did not change significantly at 45.9%. Under dry conditions of relative humidity 30% and an acclimation period within 4 hours, there was no significant difference in the pollen germination rate. Examination of the effect of the acclimation temperature on the pollen germination rate under relative humidity 90% for 2 hours showed little difference in the germination rates (43.0% at 4°C, 45.4% at 20°C). However, when pollen was acclimated for 12 hours at 25°C, the germination rate was significantly reduced to 7.9%. Artificial pollination using stored pollen that had been acclimated with the conventional method led to a fruit bearing rate of 2.5%. The fruit bearing rate was 17.2% with artificial pollination when stored pollen was acclimated for 2 hours at a high humidity (90%RH). Further more, the fruit bearing rate on artificial pollination with pollen acclimated under high humidity conditions was higher than when using pollen acclimated under dry conditions or using conventional methods.
The use of long-shaft scissors allows laborers to harvest spears in a standing posture for maintaining mother stem cultivation of asparagus. Typically, it is time-consuming and fatiguing work for laborers to find and harvest spears that emerge near the mother stems, because asparagus spears are often hidden by lateral branches of mother stems. We studied the training of asparagus branches to improve the visibility of young spears that emerge from ridges; training allows a continuous standing posture during harvest with long-shaft scissors. Firstly, the effects of branch training using strings or nets on the yield and quality of asparagus spears were investigated. We found that the yield and quality were similar, irrespective of branch training methods. Secondly, the effect of branch training on harvest work efficiency and bending of the upper body of laborers who used long-shaft scissors was evaluated. No difference was found in harvest work efficiency among the branch training methods. It was, however, observed that the bending angle of the upper bodies was decreased in laborers in their 50s or 60s when branch training with strings or nets was applied as compared to the control. Visibility of the spears was improved by training with strings or nets for laborers in their 30s, 50s, and 60s. Additionally, we compared the working efficiency of training branches with strings and nets, and found that training with strings permits reduction of the working time (21% of the work time on training with nets).
Effects of preservatives containing Artemisia capillaris Thunb. Extract (ACE), SK-253 and SK-202, applied on a packing-house line on reducing rind injury, fruit rot, and fruit quality were investigated in medium-late-maturing citrus ‘Kiyomi’ (Citrus unshiu Marc. × C. sinensis Osb.) fruit stored in a corrugated cardboard box for practical use. The ‘Kiyomi’ fruit gently wiped with a cloth impregnated with SK-253 showed significantly reduced weight loss than the control, but fruit treated with SK-202 did not. The spotted area per fruit tended to be smaller in order of SK-253, SK-202, and control. The incidence of rind injury with SK-202 treatment on the packing-house line was 2.3% in corrugated cardboard boxes randomly collected from different lots, whereas that of untreated fruit was 11.8%. Fruit rot with SK-202 treatment was also lower than in untreated fruit. The rate of good-quality fruit with SK-202 treatment on the packing-house line was approximately 10% higher than in untreated fruit. Furthermore, SK-253 treatment on the packing-house line led to reductions in ethylene evolution and the respiratory rate of fruit along with a lower incidence of rind injury compared with untreated fruit manually sorted by hand. It is suggested that ACE treatment on the packing-house line is effective to reduce damage caused by mechanical shock on passing along the line.
Green soybeans are usually harvested during the early growth stage when the bean components are rapidly changing; therefore evaluating the optimal harvesting time is a prerequisite for obtaining the best quality crops. In order to accurately evaluate the stage of the harvested pod, the flowering date of pods was recorded and then quality attributes were assessed for two early maturing green soybean cultivars, ‘Hukura’ and ‘Yuagari-musume’ over a wide range of different developmental stages. At stages before 30 days after flowering (DAF), both cultivars had small pods (<8 mm) with small beans which were not acceptable to consumers. After 40 DAF, the green soybean pods/beans started to desiccate and markedly turn yellow in ‘Hukura’ and to some extent in ‘Yuagari-musume’. The sucrose content increased gradually to a peak at 35 DAF. Glutamine acid and alanine levels were relatively high during 25–35 DAF. Green soybeans were harvested as a whole plant and the flowering period (from the earliest to latest anthesis in each plant) ran for around 10 days in both cultivars. Taken together, green soybeans during 30–40 DAF were acceptable to consumers. The pod thickness and color of individual samples in the same stage were less variable and closely related to DAF and quality attributes. The pod thickness and color index would be useful determinants to evaluate the growth stage and identify immature or over-mature beans before and after harvest.
Zeolite, a designated food additive, is known to absorb radioactive cesium via its cation exchange ability. In this study, we investigated the effects of zeolite treatment on the removal of radioactive cesium from flesh of the pickled plum during the production process, and found that the concentration of radioactive cesium in the flesh was reduced by the addition of zeolite. Taking the concentration of radioactive cesium in the pickled plum in the absence of zeolite as 100%, that in the presence of 10% zeolite was 55%, and that in the presence of 20% zeolite was 54%. On the other hand, the concentration of radioactive cesium was 74% when 10% granulated zeolite was added. Furthermore, when processed with brine, the radioactive cesium concentration was reduced to 31% by adding 10% zeolite.
Evaluation of the flesh texture and improvement of the storability of ‘Soshu’ persimmon were studied with acoustic resonance measurement. A significant positive correlation was found between the sensory score on palatability and the elasticity index measured by the resonant frequency. When the sensory score on palatability (ranging from −2: very poor to +2: very good) was 0 or higher, the elasticity index was about 22 × 106 cm2・Hz2 or higher, with the fruit immediately after harvest receiving the highest score. 1-Methylecyclopropene (1-MCP) treatment did not affect the maintenance of flesh firmness evaluated by the resonant frequency. However, the rate of softened fruit with collapsed or water-soaked tissue was kept low by 1-MCP treatment, improving the shelf-life. On the other hand, using a moisture-proof corrugated fiberboard box was found to have the effect of retaining flesh firmness. When the sensory score on palatability was 0 or higher for the fruit in the moisture-proof corrugated fiberboard box, it corresponded to the period immediately after harvest to around 10 days after, or about 4 days longer than for the fruit in the conventional corrugated fiberboard box. The weight loss of moisture-proof corrugated fiberboard box fruit was lower than that in the conventional corrugated fiberboard box, which was presumably because water loss from the fruit was suppressed.
The antifungal effect of blue LED (light emitting diode: maximum emission wavelength 465 nm, 80 µmol・m−2・s−1) irradiation on the blue mold, Penicillium italicum, in satsuma mandarin (Citrus unshiu Marc.) fruits after harvesting was investigated. Blue LED irradiation for 6 days after inoculation with Penicillium italicum significantly reduced symptom development in the fruits compared to that observed with dark treatment. The sporulation and mycelium area were markedly reduced by blue LED irradiation. On the other hand, blue LED irradiation for 6 days before inoculation reduced symptom development when the inoculum dose was low. Blue LED irradiation did not affect the fruit quality, except for the citric acid concentration and moisture loss. These results indicate that blue light irradiation could directly inhibit fungal growth in satsuma mandarin fruits and induce an antifungal response against the blue mold.
A new strawberry cultivar, ‘Kaorino’, has several attractive traits such as resistance to anthracnose, one of the most serious diseases of strawberry, extremely early flowering, and a high sugar content. This cultivar was bred for forcing culture at Mie Prefecture Agricultural Research Institute and registered as a new variety in 2010. ‘Kaorino’ breeding was started in 1990 by diallel crosses between ‘Nyoho’, ‘Aiberry’, ‘Toyonoka’, and ‘Hokowase’. We continued to select and cross the lines for 9 generations by adding ‘Akihime’, ‘Akasyanomituko’, ‘Tochiotome’, and ‘Sanchi-go’ as parents, and many strawberry lines with anthracnose resistance were developed. ‘Kaorino’ was a cultivar selected from a hybrid line between line ‘0028401’ and line ‘0023001’ in 2003. ‘Kaorino’ shows high-level anthracnose resistance equal to ‘Hokowase’ and ‘Sanchi-go’. Flower initiation is earlier than in ‘Akihime’, which is a representative early ripening cultivar under natural conditions in Japan, harvesting can be started in late November, and the yield until March is higher than in ‘Akihime’ and ‘Sanchi-go’ under forcing culture. The eating quality is superior: the fruit has a special, refined aroma, contains highly soluble solids, and shows low acidity. The conic fruit is large, with an orange-red skin color and white flesh and core. The cultivar distribution has been promoted by a project comprising administration, research, extension, and grower groups in Mie Pprefecture. A license system was established for growers both inside and outside of Mie Prefecture to promote ‘Kaorino’ cultivation. Cultivation guidance for ‘Kaorino’ has been disseminated, resulting in an increase in ‘Kaorino’ growers both inside and outside of Mie Prefecture.