Search

In this study, changes in gene transcription during adventitious root formation in hardwood cuttings of Marubakaido apple rootstock were examined by RNA-seq analysis. In line with above, 11 genes related to root development were identified as candidate genes for modulator of adventitious root formation. Among them, the induction of ABC transporter G family member-, NO VEIN-, and Auxin transporter-like protein 2-like genes, which are known to be associated with cellular auxin distribution and maintenance of root meristem niche, before the appearance of the first visible adventitious root formation in Marubakaido was revealed by quantitative RT-PCR. In addition, we conducted comprehensive co-expression network and MAPMAN analysis, and found a relationship between adventitious root formation and phytohormones such as cytokinin and abscisic acid (ABA). Finally, we also found the genes encoding receptor of plant peptide hormone, such as Barely any meristem 3-like gene (a receptor of plant peptide hormone CLAVATA45) and phloem intercalated with xylem-like gene (a receptor of the plant peptide hormone known as tracheary element differentiation inhibitory factor or TDIF), assuming the association of plant peptide hormone with adventitious root formation in Marubakaido apple rootstock. CLAVATA and TDIF are known as plant peptide hormones related to root stem cell and vascular differentiation, respectively. Therefore, we conclude that the process of adventitious root formation such as the maintenance of stem cell and vascular differentiation in Marubakaido apple rootstock was controlled by complex plant hormone signalling, including auxin, cytokinin, ABA, and plant peptide hormone.

“M.9” rootstock is considered as one of the most useful apple (MalusxdomesticaBorkh.) rootstocks; it produces dwarfing trees efficiently. As “M.9” rootstock shows a poor, brittle, and shallow roots system, we grafted “M.9” rootstocks onto “Marubakaidou” (M. prunifoliaBorkh. var. ringo Asami Mo 84-A). We then propagated them by mound layering to establish a high-density root system. It was found that covering the roots with rice seed coat (RSC), RSC + smoked rice seed coat (SRSC), and vermiculite during mound layering was effective for the initiation of rooting. Utilizing RSC and SRSC seemed especially effective for producing “M.9” roots efficiently.

Lopsided apple fruits were found in an orchard consisting of a single commercial cultivar Fuji and pollinizers of crab-apples under conditions of natural pollination. Speculating that it was caused by inadequate partial pollination, we devised an appropriate model. We artificially pollinated one out of five pistils of apple gynoecium, and then investigated the correlations among inadequate partial pollination, seed number, distribution, and fruit shape. It was speculated that a decrease in seed number and an increase in the rate of lopsidedness were caused by inadequate partial pollination. A deviation in seed distribution was also a factor in the occurrence of lopsided fruits. Since many of the main pollinator Osmia cornifrons visited a flower repeatedly at an orchard consisting of a single cultivar and pollinizers, we analyzed the effect of repeated pollination on increasing and improving seed number in fruits and fruit shape, respectively, using artificial pollination of a pollinizer and cultivars with various S -genotypes. Repeated pollination at 24-h intervals did not contribute to fertilization, but those at 4-h intervals contributed significantly as pollen parents of seeds in fruits. The ability of pistil fertilization was maintained until four days after flowering regardless of pollination, but once fertilization occurred, this pistil was not considered to contribute to seed production 24 h after initial pollination. Those results suggested that pollinizers in full bloom be shifted more than a day seemed unnecessary at an orchard with single commercial cultivar, and repeated artificial pollination must be done within one day.

We have used a red-fleshed apple cultivar, Malus ×domestica Pink Pearl, and its progeny, ‘JPP 35’, as paternal parents for producing new red-fleshed cultivars suitable for fresh use or processing such as pie fillings, dried apple, apple juice, or cider. In this process, we found that the S3-RNase allele of ‘Pink Pearl’ was linked to its red flesh trait. It was suggested that this trait might be controlled by a new gene apart from the MYB10 (MdMYB10) gene. Using ‘JPP 35’ (S-RNase allele genotype; S3S7) produced by ‘Jonathan’ (S7S9) × ‘Pink Pearl’ (S3Sx) as a paternal parent, we developed a system for producing red-fleshed progenies suitable for fresh use. That is, 96% and 86% of progenies from ‘Shinano Sweet’ (S1S7) × ‘JPP35’ (S3S7) and ‘Orin’ (S2S7) × ‘JPP35’ (S3S7) containing the S3-RNase allele, respectively, showed the red flesh trait. Similarly, red-fleshed progenies suitable for apple pie or natural red juice could be produced by ‘Jonathan’ (S7S9) × ‘JPP35’ (S3S7).

We investigated the foraging behavior ofOsmia cornifronsRadoszkowski, which is a useful pollinator in apple orchards consisting of only one kind of commercial cultivars such as “Fuji”, and of different types of pollinizers, such as the red petal type, “Maypole” or “Makamik”. It was confirmed that, in terms of the number of foraging flowers per day, visiting flowers during low temperatures, strong wind, and reduced sunshine in an apple orchard,O. cornifronswere superior to honeybees. We indicated thatO. cornifronsseemed to use both petals and anthers as foraging indicator, and that not only female, but also males contributed to apple pollination and fertilization by the pollen grains attached to them from visiting flowers, including those at the balloon stage. It was confirmed thatO. cornifronsacts as a useful pollinator in an apple orchard consisting of one kind of cultivar with pollinizers planted not more than 10 m from commercial cultivars.

An apple orchard consisting of a single commercial cultivar and of pollinizers such as Crab apples under the condition of natural pollination needs pollinators for stable fruit production. We investigated the foraging behavior of pollinators, especially Osmia cornifrons Radoszkowski, in order to evaluate their use instead of honeybees. O. cornifrons showed strong flower constancy for 4–8 min during one pollen–nectar foraging trip, as observed in honeybees. However, the bees seemed to forage for different types of flowers, e.g. from a red to a white petal color, during their 16–22 pollen–nectar foraging trips based on the S-RNase allele and simple sequence repeat (SSR) analyses of pollen loaves made during those trips. After one pollen–nectar foraging trip, the bees brushed their abdomen with their hind legs at a nester tube, but ca. 10% of pollen was not brushed from their bodies. The remaining pollen on the body retained the ability for the fertilization of apple for 12 days, suggesting that the pollen on the pollinator's body from a pollinizer could be used for the fertilization of a commercial cultivar visited on their next foraging trip. O. cornifrons seems to be a useful pollinator in apple orchards consisting of a single cultivar, such as, ‘Fuji’, and of pollinizers of different types, such as the red petal color type, ‘Maypole’ or ‘Makamik’. Moreover, most pollen loaves investigated contained S28-RNase allele, which was specific for pollen of ‘Starking Delicious’ planted at a great distance (55.2 m) from the nestiny shelter, suggesting that O. cornifrons is a useful pollinator for ‘Delicious’, which is difficult for honeybees to use as a pollinator for its sideworking behavior.

An apple orchard consisting of a single cultivar under the condition of natural pollination must have suitable pollinizers such as Crab apples to ensure stable fruit production. We selected ‘Maypole’ and ‘Dolgo’ as pollinizers for the cultivar ‘Fuji’, and investigated the rate of fruit and seeds in ‘Fuji’ fruits produced by pollen of the pollinizers. We developed a method for tracing pollen flow based on the leaf color of progeny and S-RNase allele of ‘Maypole’, and on Simple Sequence Repeat (SSR) analyses of ‘Maypole’ and ‘Dolgo’. These were powerful tools for determining the distance insects (mainly Osmia cornifrons) carry pollen from the pollinizers to ‘Fuji’. Although the fruit set of ‘Fuji’ apples was not reduced with increasing distance between ‘Fuji’ apple trees and pollinizers (probably due to pollen flow from other commercial cultivars planted outside the area), the rate of ‘Fuji’ apple fruit produced by the pollen of the pollinizers decreased with increasing distance. The rate of fruit produced by the pollinizers was 84% and 77% when ‘Fuji’ was 2.5 m from ‘Maypole’ and ‘Dolgo’, respectively, and 71% and 64% when ‘Fuji’ was 5 m from ‘Maypole’ and ‘Dolgo’, respectively, but was reduced to 47% and 39% when ‘Fuji’ was 10 m from ‘Maypole’ and ‘Dolgo’, respectively. However, the spacing could cause reduced fruit size, and require extra fruit thinning for producing large fruits. It could also cause reduction of the yield for increasing the planting area of pollinizers. We recommend that pollinizers should be planted not more than 10 m from ‘Fuji’.

Recently there has been a marked increase in wind power generation. From a power system point of view, because a wind turbine is an intermittent generator with large output fluctuation, any increase in the number of wind turbines gives rise to concerns about the adverse effects of wind turbines on power quality. The smoothing effects of wind turbine output fluctuation are of great importance in assessing the impacts of a large number of wind turbines. With regard to impacts on power system frequency (generation‐demand balance), smoothing effects on a power system-wide scale need to be examined in greater detail, because impacts of wind turbines on power system frequency are dominated by the total power output of wind turbines interconnected to the system. This article examines smoothing effects of wind power output on a power system-wide scale. First a summary of wind measurements, in which observations were made at 16 sites, is presented. Next, correlation coefficients of wind power output of distant wind turbines are analysed; considerable differences are observed in the correlation coefficients from day to day. Then a new indicator for assessing the smoothing effects—average coherence—is introduced to resolve difficulties of conventional indicators such as coherence. Average coherence is evaluated for the measured data; the results show that smoothing effects among wind farms distributed over some hundreds of kilometres may not be so significant for periods of more than about 100 min. Copyright © 2004 John Wiley & Sons, Ltd.

Recently there has been a marked increase in wind power generation. From a power system point of view, because a wind turbine is an intermittent generator with large output fluctuation, any increase in the number of wind turbines gives rise to concerns about the adverse effects of wind turbines on power quality. The smoothing effects of wind turbine output fluctuation are of great importance in assessing the impacts of a large number of wind turbines. This article examines smoothing effects at a wind farm. First it presents a summary of wind measurements taken at two locations with six masts over a period of 1 year on both flat and complex terrain. Then the spatial coherence of wind speed is analysed, paying special attention to its dependence on the distance between observation points, wind direction, wind velocity and fluctuation frequency. Approximation equations for coherence of frequency and distance are obtained by applying Davenport's expression to the observed data. Second, coherence between turbine output at a wind farm is investigated; the results indicate that coherence for wind speed and turbine output shows a considerable resemblance. The article also examines smoothing effects at a wind farm using power spectral density through a theoretical approach. The study proves that smoothing effects can be approximated with a lowpass filter and that the effects at a wind farm should not be taken into account for periods of more than 10 min in case of assessing them on the safe side. Copyright © 2004 John Wiley & Sons, Ltd.

The mechanism of flower thinning by calcium formate was investigated in the Japanese pear cv. Kosui (Pyrus pyrifolia Nakai). Calcium formate thinned 30-40% flowers when a 1% solution was applied to the pistils just before or 24 hours after pollination, whereas 1% calcium acetate and calcium lactate were ineffective. Both adhesion of pollen grains to stigmatic surface and tube elongation in the style were reduced by calcium formate application. Calcium formate at 0.05% or higher concentrations was a much stronger inhibitor on pollen germination in vitro compared to calcium acetate or calcium lactate. When the inhibitory effect of formic acid, acetic acid, and lactic acid in vitro on pollen germination was compared, formic acid was the strongest inhibitor, suggesting that the compound induces floral abscission by preventing fertilization through the action of formate. At harvest, there was little or no difference in size and sugar content between the treated and control fruits. Thus, calcium formate may be a promising chemical thinner for Japanese pear flowers by reducing the cost of hand thinning.