Sweetness is one of the most important drivers of consumer preference in apples (Malus × domestica Borkh.). The increase in sugar during the ripening period of fruit is mainly brought about by the ...hydrolysis of starch accumulated before the ripening period. However, sugars are also continuously translocated into the fruit during the ripening period, as seen in watercored fruits. The objective of this study was to estimate the contribution of translocated sugars that accumulated in the apoplast to the increase in soluble solids content (SSC) of fruit during ripening. The amount of apoplastic solution (AS) tended to be high in the fruit of trees on vigorous rootstocks, such as ‘JM2’ and ‘Marubakaido’. On the other hand, fruit with more AS had lower SSC. Therefore, although AS increased during ripening, the contribution of AS to the increase in SSC was small. After fruit matured and during storage, dehydration increased the SSC of the fruit. On the other hand, the SSC decreased simultaneously due to a reduction in organic acids and any soluble solids, which was expressed as a decrease in titratable acidity (TA). Under standard refrigerated conditions, the increase in SSC due to dehydration and the decrease in SSC due to respiration were likely to be quantitatively comparable. The contribution of translocated sugars to the increase in SSC during ripening was small, suggesting that managing trees and fruit to increase starch accumulation before fruit ripening is crucial for the production of fruits with high sugar content.
•Year-dependent variation in SSC could be explained by solar radiation after late August.•Tree-dependent variation in SSC could be explained mainly by crop load.•The solar radiation determined the ...amount of starch accumulated in fruit.•Production of high SSC fruit required lighter crop load than to prevent biennial bearing.
Sweetness is one of the most important drivers of consumer preference in apples (Malus x domestica Borkh.). Despite the market demand for apples with high sugar content, cultural and agronomic practices applied in the field for producing apples with high soluble solids content (SSC) has not been established. We tried to clarify what factors regulate the SSC of fruit by creating a regression model that predicts SSC with factors related to meteorology and crop load management as variables. The highest correlation with SSC was obtained from six-year meteorological data using a four-week average solar radiation value starting August 28. When the SSC was estimated by a regression model using the average solar radiation (SR), the number of fruits per cm2 trunk cross-sectional area (CL), and the number of fruits per tree (NF), the estimated and measured values were close to each other, indicating that year- and tree-dependent variation in the SSC of fruit can be explained mainly by the SR and the CL or NF, respectively. The four weeks starting August 28 coincided with the time when starch was most accumulated in fruit, and a high correlation was found between the starch content in this period and the SSC at harvest. It could be said that it is necessary to restrict the number of fruits per tree by the period—90 days after full bloom—to produce fruit with high SSC in ‘Fuji’. A target number of fruit per tree for maximizing the cumulative yield of fruit with an SSC of 14 oBrix or more was estimated to be less than that for maximizing the cumulative yield without biennial bearing.
As juvenile stage management suitable for the V-shaped orchard system of the columnar type apple Morioka No. 74, we investigated the effect of the number of scaffold branches on growth and the effect ...of gibberellin paste application. The number of scaffold branches was 2, 4, and 6. Gibberellin paste application was not applied to some of the trees with 4 scaffold branches. The application of gibberellin paste in the first and second years of planting promoted shoot elongation, and the amount of elongation in the 4 scaffold branch system was twice as much as that in the non-applied shoots. At the end of the second year of planting, more shoots reached the target length (300 cm) in the 2 scaffold branch system, however, more flower buds were formed in the 6 scaffold branch system. The number of flower buds was higher when the total growth of shoots in the first year of planting was greater, indicating that the application of gibberellin paste contributed to the increase in the number of flower buds. In the 6 scaffold branch system, completion of the tree form was delayed by one year compared with that of the 2 scaffold branch system, but the control of tree vigor is expected by producing fruits. These results suggest that the 6 scaffold branch system with gibberellin paste application is suitable for the V-shaped orchard system of Morioka No. 74/JM2.
Apple MdMADS13 has a transcription factor with MADS domain. Moreover, it is expressed specifically at petals and carpels. The product forms a dimer with MdPISTILLATA (MdPI) protein as a class B gene ...for floral organ formation. Reportedly, in parthenocarpic cultivars of apple (Spencer Seedless, Wellington Bloomless, Wickson and Noblow) the MdPI function is lost by genome insertion of retrotransposon, which cultivars show a homeotic mutation of floral organs, petals to sepals and stamens to carpels. Apple fruit is pome from receptacle tissue, and MdSEPALLATA (MdMADS8/9) and AGAMOUS homologues MdMADS15/22 involved in the fruit development, the transgenic apple suppressed these gene showed poor fruit development and abnormal flower formation. This article describes that the MdMADS13 retained expression after blossom and small fruits of parthenocarpic cultivars. Yeast two-hybrid experiment showed specific binding between MdPI and MdMADS13 proteins. Furthermore, transgenic Arabidopsis with 35S::MdMADS13 have malformed stamens and carpels. These results suggest strongly that MdMADS13 is related to flower organ formation as a class B gene with MdPI.
In common apple cultivars with white flesh and red skin, it is known that fruit overload lowers fruit quality, and that skin anthocyanin concentrations are reduced by bagging treatment and warmer ...climatic conditions. In this study, the effects of these factors on anthocyanin accumulation in the flesh of red-fleshed apples were investigated using ‘Geneva’ and ‘Pink Pearl’ apple cultivars. Excess fruiting resulted in decreased anthocyanin concentration in the flesh and the titration acidity of the fruit in both cultivars. Fruit bagging treatments using double-layer paper bags revealed that anthocyanin was synthesized to a certain extent in the flesh under dark conditions in both cultivars. The treatment significantly reduced anthocyanin accumulation in the flesh of bagged ‘Geneva’ apples compared with unbagged fruit, but no inhibitory effect was clear in ‘Pink Pearl’ apples. In both cultivars, the anthocyanin concentration in the flesh of unbagged apples grown in sunlight was higher than that in unbagged apples grown in shade, whereas there was no difference between positions for bagged fruit. In apples grown in either sunlight or shade, no significant difference was found between anthocyanin concentrations in the sun-exposed side and shaded side of fruits. These results indicate that sunlight irradiation partially promoted anthocyanin accumulation in the flesh of unbagged ‘Geneva’ and ‘Pink Pearl’ apples and accelerated its accumulation on both the sun-exposed and the shaded side. A comparison of the fruit quality of ‘Pink Pearl’ apples grown in different climatic regions showed that apples harvested at Suzaka, a warmer region, were lower in firmness, starch index, and titration acidity and higher in soluble solids concentration compared with those from Morioka, a cooler region. The anthocyanin concentration in the flesh of ‘Pink Pearl’ apples from the trees grown at Morioka was more than ten-fold higher than that in apples from the trees grown at Suzaka. Our results suggest that an appropriate fruit load, growth in sunlight, and growth under cooler climatic conditions, may redden the flesh of red-fleshed apples, as is the case for common apples.
The columnar apple ‘McIntosh Wijcik’, which is a mutation of ‘McIntosh’ shoots, has short internodes, thick stems, upright growth, poor lateral branches, and increased spur density. These columnar ...traits are controlled by a single dominant gene known as
Co
. We previously identified a putative dioxygenase gene (designated as 91071) as a promising
Co
candidate (expressed in the shoot apices of ‘McIntosh Wijcik’). However, tissue expression and function of the 91071 gene in noncolumnar apples is still not clear. In this study, we used reverse transcription polymerase chain reaction to demonstrate that the 91071 gene is mainly expressed in the roots of noncolumnar apples, whereas it is also expressed in shoot apices and leaves of columnar apples. In situ hybridization revealed that the 91071 gene is expressed at the primordium of lateral roots and root tips of both noncolumnar and columnar apple trees and in the shoot meristem and leaf primordium in the columnar apple ‘McIntosh Wijcik’. Grafting experiments of noncolumnar scion onto columnar rootstocks revealed that the columnar growth phenotype is not transmissible from rootstock to scion. These results indicated that ectopic expression of the 91071 gene in aerial parts causes columnar growth, whereas the expression of the 91071 gene in roots does not produce columnar growth. Furthermore, transgenic apples overexpressing the 91071 gene showed larger median adventitious root length and higher median number of lateral roots than control apples. Our result suggests that the 91071 gene may be related to root development.
•We develop a model to predict the change of the rate of flower-bud formation (RF) according to the crop load.•The model can estimate parameters by which the probability of biennial bearing can be ...compared between cultivars.•The model can predict the fluctuation of the RF depending on the thinning management.
Regular cropping is important for improving fruit quality and profitability of the apple (Malus x domestica Borkh.) orchards. To identify a thinning target that makes the rate of flower-bud formation constant every year, we investigated the relationship between crop load (CL) and the rate of flower-bud formation (RF) and developed a model to predict the change of the RF according to the CL. Because a Gompertz curve fitted well to the relationship between the RF of following year and the current year in both biennial and annual bearing cultivars, we developed a prediction model based on an equation of the Gompertz curve. The prediction model can clarify varietal differences in the ease of getting flower buds. When trees are 10 years old, the RF of the following year in ‘Morinokagayaki’ would be 0.9 or more, even though the CL is adjusted to 8 fruits per cm2 trunk cross-sectional area (TCA). On the other hand, trees of ‘Fuji’ and columnar selections are predicted to display a biennial bearing cycle under the same CL. When the CL is adjusted to 2 fruits per flower cluster at 30 days after bloom every year, the yield of ‘Morinokagayaki’ is predicted to be maintained at around 200 fruits per tree after 7 years. In the case of ‘Fuji’ and columnar selection, it would be necessary to restrict the CL to around 0.5 fruits per cluster every year to obtain a stable yield. The model can estimate the parameters by which the probability of biennial bearing can be compared between cultivars and predict the fluctuation of the RF depending on the thinning management. Therefore, the model would be very useful for growers to strategize for crop load management.
The apple (
Malus
×
domestica
Borkh.) is one of the commercially important fruit crops in the worldwide. The apple has a relatively long juvenile period (up to 4 years) and a long reproductive ...period between the flower initiation and the mature fruit (14–16 months), which prevent the fruit breeding. Therefore, the understanding of the flowering system is important to improve breeding efficiency in the apple. In this study, to examine the temporal and spatial expression patterns of the floral genes,
MdTFL1
,
MdAP1
(
MdMASD5
)
,
AFL2
, and
MdFT
, we conducted in situ hybridization analysis in the apple shoot apex. In vegetative phase,
MdTFL1
was expressed on the rib meristem zone. When vegetative meristem began converting into inflorescence meristem, the expression level of
MdTFL1
was drastically decreased. At the early stage of inflorescence meristem, the expression levels of
AFL2
,
MdFT
, and
MdAP1
were up-regulated in the leaf primordia and the upper region of cell layers on the shoot apex. In late stage, the expression levels of
AFL2
and
MdAP1
were up-regulated in the young floral primordia. At a more advanced stage, high expression of
MdAP1
was observed in the inflorescence primordium through the inner layer of sepal primordia and the outer layer of receptacle primordia and floral axis. Our results suggest that
AFL2
,
MdFT
, and
MdAP1
affect to convert from the vegetative meristem into the inflorescence meristem after the decline of
MdTFL1
expression. After that,
AFL2
and
MdAP1
promote the formation of the floral primordia and floral organs.
•Subchronic and mild social defeat increased body weight and food and water intakes in mice.•Defeated mice showed social aversion and a trend of anxiety-like behaviors.•Defeated mice showed low ...levels of albumin and blood urea nitrogen just after stress.•Defeated mice kept much more water in their body than non-stressed control mice.•Our defeated mice might be a good model for stress-induced overhydration and over-eating.
Development and characterization of animal models of depression are essential for fully understanding the pathogenesis of depression in humans. We made and analyzed a mouse model exhibiting social deficit and hyperphagia-like behavior using a subchronic and mild social defeat stress (sCSDS) paradigm. The body weight, food and water intake of mice were monitored during a test period, and their behaviors and serum components were analyzed at two stages: immediately after the sCSDS period and 1 month after the sCSDS. The body weight and food intake of defeated mice were significantly higher than control mice at the sCSDS period, and these differences were sustained until 1 month after the sCSDS, whereas the water intake of defeated mice was significantly higher than control mice for the period of sCSDS only. Behavioral analyses revealed that the defeated mice exhibit significant social aversion to unfamiliar mice in a social interaction test and a trend of anxiety-like behavior in an elevated-plus maze test. Possibly due to polydipsia-like symptoms, defeated mice had significantly lower levels of albumin and blood urea nitrogen than control mice immediately after the sCSDS period but not at 1 month after sCSDS. The present study revealed that our sCSDS mice keep much more water in their body than control mice. This study reports the first step toward an understanding of the mechanisms of stress-induced overhydration, over-eating and resultant weight gain.
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