The relationship between the flower color and flavonoid composition of petals was investigated in 10 cultivars of Impatiens walleriana. Thirteen known anthocyanins, and a new anthocyanin (peonidin 3-O-[6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(acetyl)-glucoside]) were identified from the flowers of Impatiens walleriana along with two known flavonol glycosides. Regarding the flower color from orange-red to purple, decreases in the hue values (b*/a*) of these cyanic petal colors were generally responsible for the acylation of anthocyanin with p-coumaric acid, decreasing total anthocyanins, and also methoxylation of the B-ring in anthocyanins.
A yellow flavonoid pigment was isolated from Saintpaulia ‘Tomorrow’s Snowy Night’ with pale yellow pigmentation at the petal base. The pigment, chalcononaringenin 2´,4´-diglucoside, was identified using chemical and spectroscopic methods. The amount of this pigment in somaclonal mutants from ‘Tomorrow’s Snowy Night’ whose petals looked yellow visually was eight-times higher than that in the mother plant, confirming that the accumulated yellow pigment in Saintpaulia petals was chalcononaringenin 2´,4´-diglucoside. Moreover, this yellow pigment also accumulated in the stamen filaments, and it was detected in the stamen filaments but not in the petals of the pink cultivar ‘Thamires’. This suggests that the yellow pigment generally accumulates in the stamen filaments of Saintpaulia and that most cultivars have the capability to biosynthesize this yellow pigment regardless of their flower colors. These results may be useful to reveal the genetic mechanism for chalcononaringenin 2´,4´-diglucoside biosynthesis.
Although many early-flowering cherry cultivars may have originated from Prunus campanulata, the origins of some of these cultivars are still unknown. Moreover, although P. campanulata is also found in southern Japan, China, and Taiwan, the genetic relationship between the regional populations of P. campanulata has yet to be elucidated. In this study, we conducted Amplified Fragment Length Polymorphism analysis to reveal the origins of early-flowering cherry cultivars from the viewpoint of both the species and regional population level. We selected 14 early-flowering cherry cultivars and three species, P. campanulata, P. lannesiana var. speciosa, and P. jamasakura, as the parental candidates of the cultivars. For P. campanulata, we collected samples from Japan, Taiwan, and China. Principal coordinate analysis and STRUCTURE analysis showed that many cultivars originated from P. campanulata. In addition, P. campanulata found in Japan, China, and Taiwan were genetically different from each other, thereby indicating the origins of the early-flowering cultivars from each region. In China and Taiwan, some P. campanulata were composed of a genetic cluster characteristic to Japan, suggesting the possibility of artificial genetic migration and/or introgression. Of the 14 early-flowering cherry cultivars analyzed, five were hybrids between P. campanulata and P. lannesiana var. speciosa and four were hybrids between P. campanulata and P. jamasakura. Three cultivars were suggested to be intraspecific variations of the original species. Furthermore, the samples of the two cultivars were composed of two and three genetic origins, respectively. To conserve the genetic diversities, early-flowering cherry cultivars and P. campanulata should be managed at the three regional levels.
A simple tensiometer is a device for measuring the degree of dryness of soil above pF 2.8, thereby lowering the water level within it. We studied the method to estimate water stress in citrus trees using the simple tensiometer. The results showed that the water level reduction per day using the simple tensiometer provided an indication of water stress in citrus trees. Citrus trees were under no stress, whereas the water potential of soil was above pF 2.8 when the water level of the simple tensiometer began to decrease. Citrus trees were under appropriate water stress associated with an increase in Brix of the fruit if the water level of the simple tensiometer was decreased to about 5 cm a day, at which the leaf water potential (LWP) should be -0.8 MPa or more. If the water level decreased to above 9 cm a day, with LWP being below -1.5 MPa, irrigation was required for citrus trees under high water stress. Brix of the fruit was higher as the integrated value of the water level reduction until harvest time became larger. The simple tensiometer is a useful device for estimating water stress in citrus trees.
Manuring with controlled-release fertilizer was studied to reduce the fertilizer application rate in ‘Miyagawa wase’ unshu over a period of five years. Reduction in the frequency from twice to once at each fertilization, a 20% reduction in the quantity of nitrogen ingredients, and 40–50% reduction in the quantity of phosphoric acid and potassium ingredients had no influence on the tree growth, yield, or fruit quality in wase unshu throughout the experimental period. The results suggest that controlled-release fertilizers can improve the fertilizer efficiency and reduce the labor required reguired for fertilization management in the cultivation of ‘Miyagawa wase’ unshu.
In this study, the effects of a tree joint training system for peach on tree growth, fruit production, and labor-saving cultivation management were compared with those of a straight line training system. Additionally, differences due to the height of two (1.55 and 1.85 m) of the main branches in the tree joint training system (tree joints I and II, respectively) were compared. There were no differences in the characteristics of fruit between the experimental plots, and the highest cumulative yield occurred in the first 4 years after planting in tree joint I. The number of working hours to prune tree joint I was the lowest, and the increase in the workers’ heart rate on harvesting was lower with tree joints I and II compared with the straight line training system. In conclusion, 1.55 m was a suitable height for the main branch in the tree joint training system based on these results. In comparison with the straight line training system, a mature orchard was achieved earlier with the tree joint training system, and cultivation management was more labor-saving.
Colony collapse disorder of the honey bee has been a serious problem throughout the world and farmers often face the insufficient supply of colonies. The shortages of bees have increased the cost to farmers renting them and resulted in a significant decrease in agricultural production. As an alternative pollinator to the honey bee for greenhouse crops, we investigated the practical utility of Phaenicia sericata Meig. (green brow fly), which is propagated artificially for medical maggot therapy. The efficiency of pollination was evaluated by applying a certain number of fly pupae to flowering strawberries, tomatoes, eggplants, and melons. For tomatoes, eggplants and melons, no significant increase of fruit set or in the number of seeds was noted in open pollinated fruit compared to flowers bagged with fine nets to prevent the visiting of flies or other insects. On the contrary, flies frequently visited strawberry flowers just after emergence from pupae and the rate of mis-shapen fruits decreased significantly compared to the fruits developing from flowers before emergence. Pollination efficiency was insufficient in some cultivars, when 400 pupae were applied in a 90-m2 plastic house. However, the efficiency was comparable to the honey bee when 1,000 pupae were applied in the plastic house.
We evaluated the early tree growth, early yield, and fruit quality of Japanese persimmon ‘Taishu’ grown on a joint V-shaped trellis (JV-trellis). On planting of the JV-trellis, the head of a nursery-tree was grafted to the trunk of an adjacent nursery-tree at 60 cm in height, and then lateral branches were trained in an upright position at 60º above the ground level, with which early expansion of the canopy area could be obtained with the JV-trellis. After planting, the early yield of the JV-trellis was 19.5 t・ha−1 in the 3rd year and 35.7 t・ha−1 in the 5th year. The cumulative yield of the 3rd to 5th years was 77.1 t・ha−1 with the JV-trellis, reaching up to 2.4-times compared to that of the free-standing training system. The skin color of the JV-trellis seemed to be more favorable than that of the free-standing training system, possibly due to increased light interception by the JV-trellis. The JV-trellis is considered to be suitable for the cultivation of Japanese persimmon ‘Taishu’ because of earlier fruit production and a higher yield and quality of fruit than with the free-standing training system.
To clarify cultivar variations of blueberry fruit cracking susceptibility, influences of the weight, morphology, and water absorption on fruit cracking were investigated. Fruit cracking rates ranged from 0 to 56.7%. A positive correlation between fruit cracking rates and fruit weights was found in moderate crack-susceptible cultivars. Highly crack-susceptible cultivars, ‘Duplin’, ‘Star’, and ‘Tifblue’, had relatively large calyxes and often cracked from fruit apexes. In contrast, low crack-susceptible cultivars, ‘Duke’, ‘Hannah’s Choice’, ‘New Hanover’, and ‘Sampson’, had relatively small fruit shape indexes and cracked from the sides and pedicel ends of fruit except for ‘Sampson’, in which no cracks occurred. These results indicate that cultivar variations in cracking susceptibility are affected by morphological factors through stress distribution. Concerning 23 cultivars, however, there were no correlations among fruit cracking rates and weights, morphology, and water absorption. Therefore, these factors may not independently determine fruit cracking susceptibility. Regarding ‘Star’ and ‘Tifblue’ harvested on the same day, the calyx basin diameter, pedicel scar diameter, and fruit cracking rate increased with the fruit weight. In these highly crack-susceptible cultivars, crack-susceptibility may increase as the result of the changing fruit morphology and the increasing amount of water absorption associated with increasing fruit size. However, no partial correlations were detected when the controlling variable was the fruit weight.
Seasonal changes in the water-soluble Ca concentration in the distal half of fruit tissue and the blossom-end rot (BER) incidence in relation to the fruit growth rate were examined in the medium-sized fruit tomato cultivar ‘Cindy Sweet’, which is less susceptible to BER than large-sized fruit tomato cultivars. The rate of BER incidence was higher in the plants fed low Ca solutions, 1/4Ca and 1/8Ca, compared to those fed Enshi standard solution in both spring and autumn cropping. It was significantly higher in plants grown in spring than in autumn. The water-soluble Ca concentration in the distal half of fruit tissue was negatively correlated with the BER incidence and was significantly lower in spring than in autumn. A marked increase in the incidence of BER was observed as the water-soluble Ca concentration in the distal half of fruit tissue decreased below 0.2 μmol・g−1FW. This value was similar to our previous findings on the large-sized fruit tomato cultivar ‘House Momotaro’. The fruit growth rate was 3-fold higher in the fruits from plants grown in spring, with its higher temperature and solar radiation, than in autumn. There was a significant negative correlation between the rate of fruit growth and water-soluble Ca in the tissue of the distal half of fruit. These results suggested that the vigorous fruit growth can lead to BER disorder by potentially causing the dilution of water-soluble Ca in fruit tissue and increased Ca demands for rapid fruit enlargement.
The effects of postharvest short-term irradiation with near infrared (NIR, 850 nm at 100 mmol・m−2・s−1 for 5 min) on weight loss, stomata apertures, and appearance quality were investigated in three leaf vegetables. Leaf lettuce, spinach, and spinach mustard (Komatsuna) at commercial maturity were exposed to NIR for 5 min once before storage or every day, packaged in perforated or non-perforated polyethylene bags, and then stored at 10°C under dark conditions. In all three leaf vegetables under both storage conditions, packaged in perforated and non-perforated polyethylene bags, weight loss rates and stomata aperture after 3 days of storage were reduced in NIR-exposed crops, compared with non-treated controls, resulting in a better appearance quality. The beneficial effects were more distinct in everyday treated than in single treated crops. When leaf vegetables packaged in perforated polyethylene bags were treated with NIR and stored at 10°C under dark or light conditions, weight loss rates were reduced and the appearance quality was better under both conditions, compared with non-treated controls. The beneficial effects were more marked in everyday treated than in single treated crops. The greatest benefits were observed in spinach. These results suggest that postharvest short-term NIR radiation has a promising potential as an additional quality control technique during the storage and transportation of leaf vegetables.
The phytopathogen Ralstonia solanacearum undergoes spontaneous phenotypic conversion (PC) from a wild-type pathogenic form to a non-pathogenic form in plants, soil, and broth culture, and after prolonged culture on agar plates. Using a bud piece and the plant grown from the bud piece, we investigated the suppression of bacterial wilt disease by the PC mutant 8266PC in potatoes that cannot be grafted. In plants inoculated with 108 cfu·mL−1 of 8266PC, the effective suppression of bacterial wilt disease was observed. This suppression effect was reduced at high temperatures and a high pathogenic bacterial density. However, we observed a high incidence of biological control (66.7%) even under severe conditions (30°C/27°C and 106 cfu·g−1). Bud pieces inoculated with less than 104 cfu·mL−1 of 8266PC emerged and grew like those grown in sterile distilled water. Consequently, we inoculated bud pieces with 104 cfu·mL−1 of 8266PC, but no suppression effect on bacterial wilt was observed.
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