Effective humidity control is essential to optimize strawberry production in greenhouses, where an excessive vapor-pressure deficit (VPD; kPa) can induce water stress. This study investigated water-stress responses in June-bearing strawberries (Fragaria & times; ananassa Duch.) using decision-tree analysis. Three cultivars-'Koiminori', 'Kaorino', and 'Sanukihime'-were grown without humidity control. Fruit-stalk diameter (FSD; mm) was measured at 1-min intervals, and relative changes in FSD (CFSD; mm.mm(-1)) and their rates (RCFSD; mm.mm(-1).min(-1)) were calculated. VPD and its rate of change (dVPD; kPa.min(-1)) were also recorded. Water-stress status was categorized into three classes: non-shrinkage, shrinkage with radial expansion, and shrinkage with further contraction. Decision-tree models (DTMs) were constructed using VPD and dVPD as explanatory variables. The models revealed cultivar-specific thresholds for strong water stress, defined by the condition "shrinkage with further contraction": for 'Koiminori', VPDt >= 1.29 kPa; for 'Kaorino', 1.70 <= VPDt < 2.09 kPa and the dVPD(t) >= 0.014 kPa & centerdot;min(-1); and for 'Sanukihime', VPDt >= 1.21 kPa and the dVPD(t) >= -0.012 kPa & centerdot;min(-1). In 'Sanukihime', dVPD was a key factor in determining whether the FSD contraction progressed, even under decreasing VPD conditions. The DTMs achieved moderate classification accuracy based on training data (e.g., 0.71 for 'Koiminori'). However, in 'Kaorino', the recall for the severe stress class ("shrinkage with further contraction") was notably lower due to frequent misclassification, indicating limited sensitivity to detect strong stress in this cultivar. Decision-tree analysis was employed to identify environmental thresholds for strawberry water stress. Incorporating dVPD into humidity control strategies may improve efficiency by preventing unnecessary humidification during recovery phases when plants transition from contraction to expansion. These findings support the development of advanced control systems tailored to cultivar-specific responses, contributing to improved yield and reduced physiological disorders in greenhouse strawberry cultivation.
Chili pepper (Capsicum annuum) is a member of the Solanaceae family. It is a widely consumed fruit crop that is used as a spice and a vegetable. Seedless fruits of chili pepper are favoured for their ease of consumption and suitability for processing. However, the absence of seeds can negatively affect fruit size. In this study, quantitative trait locus (QTL) analysis was performed in cross populations derived from a cross between a seedless mutant tane nashi-1 and a commercial large-fruited variety 'Tongari Power' to identify genetic loci affecting fruit size of seedless chili pepper. A major QTL on chromosome 7, designated as qFS7, was identified. It was found to be associated with the length, width, and weight of seedless fruit, explaining up to 35.5% of the phenotypic variation. Notably, a more than twofold increase in fruit weight was observed. QTL analysis using a seedy population also detected qFS7, indicating it affects the size of both seedless-fruit and seedy-fruit. Furthermore, evaluation of the QTL genotype in the progeny population confirmed its stable effect on fruit size. Histological analysis of ovary and mature fruit suggested that qFS7 enhanced ovary size by increasing the number of cell layers rather than cell size, leading to an enlarged fruit. Studying qFS7 will provide insights into the mechanisms of Capsicum fruit development and be useful for breeding seedless fruit cultivars with larger fruit size.
In closed-type plant production systems using LED lighting for tomato seedling cultivation, the physiological disorder known as intumescence has emerged as a significant issue, particularly in susceptible cultivars. The objective of this study was to investigate the effects of varying durations of red and blue LED light on the occurrence of intumescence and seedling growth in tomato. Using the intumescence-susceptible rootstock cultivar 'Arnold', we conducted a factorial experiment with red and blue light exposure durations set at 0, 4, 8, 12, 16, 20, and 24 hours, excluding the 0 & times; 0 combination, resulting in 48 treatment groups. Evaluations were conducted 15 days after sowing, including assessments of intumescence severity, shoot dry weight, and root ball formation rate. The results indicated the duration of red light irradiation exhibited a strong and significant positive effect on intumescence severity, whereas the effect of blue light irradiation duration was not significant. However, the interaction term between red and blue light showed a significantly negative coefficient, indicating that the promotive effect of red light on intumescence was partially mitigated when combined with blue light. Shoot dry weight and root ball formation rate, which indicate seedling growth, tended to increase with longer durations of red and blue light exposure. A second experiment involving 22 tomato cultivars under three red light durations (0, 8, and 12 hours) under continuous blue light exposure revealed that in intumescence-susceptible cultivars, symptoms were mitigated at 0, 8, and 12 hours of red light. In cultivars not prone to intumescence, growth performance was unaffected by transitioning from conventional lighting to blue light dominant conditions. These findings suggest that reducing the duration of red light to prevent intumescence, while using prolonged blue light exposure to maintain the daily light integral (DLI), may enable both healthy growth and suppression of physiological disorders in tomato seedlings.
Vigna spp. are fast-growing, affordable legumes that offer valuable nutrients; however, their optimal nutritional value across developmental stages remains underexplored. This study investigated the physicochemical properties, phytonutrient contents, and antioxidant activity of three Vigna spp.: mung bean (MB, V. radiata), black gram (BG, V. mungo), and adzuki bean (AB, V. angularis), at three developmental stages: seed, sprout, and microgreen. Fresh and dry weights, as well as plant length, were recorded. Comparative analyses were performed on seed, top (TOP), and middle (MID) parts to assess phytonutrient levels, antioxidant activity, and enzymatic antioxidants. The results revealed that AB microgreens exhibited the highest biomass and total phenolic content, while MB microgreens had the longest plant length, titratable acidity, ascorbic acid, and FRAP-based antioxidant activity. BG microgreens excelled in terms of total flavonoid content and catalase activity. Overall, microgreens demonstrated consistently higher phytonutrient and antioxidant capacity than sprouts and seeds, particularly within TOP. Conversely, seeds consistently exhibited higher protein and soluble solid contents than their sprout and microgreen counterparts. Distinct species- and part-specific variations were evident across developmental stages. This study highlights the importance of species selection and harvest timing in optimizing the nutraceutical value of legume-based sprouts and microgreens for functional food applications.
Understanding fruit growth and thermal requirements from anthesis to ripening can provide insights into the developmental process and productivity of whole plants. Fruit growth in sweet peppers (Capsicum annuum) can be estimated using sigmoid functions. The present study aimed to clarify the growth patterns of sweet pepper fruit using these functions. In a greenhouse, we hydroponically grew 10 sweet pepper cultivars that have a wide range of fruit dry matter content. Fruits at different growth stages were destructively sampled and measured for their length, width, dry and fresh weights, as well as dry matter content. Using the data, fruit growth curves in terms of length, width, water content, dry weight, and dry matter content were modeled using the Gompertz function. Results showed that fruit volume (i.e., fruit length and width), fruit water content, and fruit dry weight rapidly increased from 200-600, 400-800, and 600-1,200 degrees C & centerdot;d days after anthesis (DAA), respectively, in all the cultivar types. However, the increase in fruit dry weight from 600-1,200 degrees C & centerdot;d DAA differed among the cultivar types. Fruit dry matter content decreased to 0.04-0.05 g & centerdot;g-1 until about 600 degrees C & centerdot;d DAA regardless of the cultivar types, and thereafter it increased from 600-1,200 degrees C & centerdot;d DAA for the cultivars with high dry weight increase, but it barely increased for the cultivars with low dry weight increase. In conclusion, sweet pepper fruit initially began to expand in volume, followed by an increase in water content and dry weight. However, the increase in the fruit dry weight from 600-1,200 degrees C & centerdot;d DAA showed differences among the cultivar types, and this trait determined the cultivar-specific fruit dry matter content at harvest. The cultivar-specific dry matter increase affects the fruit load; therefore, it is probably related to the number of harvestable fruits (i.e., fresh yield) and plant exhaustion during production. The results of this study are expected to enable more precise growth prediction and plant management.
Garland chrysanthemums are conventionally ratooned and harvested by selective handpicking. Subsequently, the lateral shoots regrow, allowing for further harvests. We previously studied a new ratooning practice for garland chrysanthemums harvested by horizontal cutting, and reported the optimal plant height and cutting height. New shoot development is important for garland chrysanthemum ratooning. However, lateral shoot emergence characteristics of each node have not yet been studied. To address this issue, we investigated lateral shoot development in the garland chrysanthemum cultivar 'Stick-syungiku'. Each garland chrysanthemum was pinched twice, leaving different numbers of nodes. After each pinching, shoot emergence was evaluated at each nodal section. The emergence rate of new shoots in the entire plant was higher after the first pinching than after the second pinching. Lateral shoot emergence depended on node position. At the first lateral shoot emergence after the first pinching, the emergence rates from the first and second nodes of the main stem were higher than those from the upper nodes. At second lateral shoot development, the emergence rate of shoots from the first lateral shoot that developed from the first and second nodes of the main stem was higher than that of shoots from the first lateral shoot, which developed from the third to sixth nodes of the main stem. Among the first lateral shoots that developed from the third to sixth nodes of the main stem, the second lateral shoot emergence rates from the third and fourth nodes of the first lateral shoot were higher, and the rates from the first and second nodes were lower. These results indicate that lateral shoots originating in the first or second nodes of the main stem should be retained to promote regeneration. In addition, because regrowth from the lower node of the first lateral shoot developed from the upper nodes of the main stem may be weak, the upper node of the first lateral shoot should be retained.
Picking excess berries is essential to obtain high-quality bunches of table grapes. However, this process requires significant labor within a short period, so labor-saving techniques are needed. We observed that the number of flowers per inflorescence was significantly reduced when 250 mu L of 10%-15% trehalose was injected into the buds of 'Shine Muscat' using a microsyringe. Both the number of peduncles and the numbers of flowers on tip peduncles tended to decrease, showing that the synergistic effect of these two factors reduced the numbers of flowers in the inflorescences. However, a significant reduction in the number of flowers was observed only when trehalose was injected into buds with a vertical diameter of 10 to 15 mm, indicating that trehalose is effective only within a very limited time frame. To assess the degree of labor saving, we evaluated the time required for berry thinning by combining trehalose injection with two methods of cluster shaping: the conventional method and a labor-saving method. In the conventional method, we cut the peduncles with scissors and retained the main tip of the cluster at 4 cm, whereas in the labor-saving method, we cut the main axis of the rachis with scissors and used wing or lateral peduncle lengths of 4 cm. The average time required to pick berries from trehalose-treated grapes was significantly shorter (36.3 s) compared with untreated grapes. When scaled to 10 a (3,000 bunches), the combination of the conventional method and trehalose injection reduced the labor time required by approximately 40.3 h, while the labor-saving method combined with trehalose injection reduced labor time by approximately 100.3 h compared with conventional cultivation. The trehalose injection process required approximately five seconds per bud. Assuming injection of 6,000 buds on 3,000 shoots over 10 a, this would take an estimated 8.3 h. Thus, trehalose injection is an effective option even when accounting for the labor involved in the injection process. In addition, the trehalose injection did not have any adverse effects on the bunch quality. To develop a more effective method, further research is needed to elucidate the molecular mechanisms underlying the effect of trehalose on grape flower development.
Apple scab, caused by Venturia inaequalis, is a major disease in Malus & times; domestica. Although resistance genes such as Rvi6 have been introduced through breeding, the emergence of virulent pathogen races has raised concerns over the durability of single-gene resistance. Nonhost resistance (NHR), a broad-spectrum and durable form of immunity found in nonhost species, offers a promising alternative. This study assessed resistance to V. inaequalis in three Pyrus species and three intergeneric hybrids with M. & times; domestica. Following inoculation, macroscopic and microscopic evaluations revealed that susceptible Malus cultivars showed extensive lesion development and hyphal elongation. In contrast, no typical scab symptoms were observed in Pyrus, and hyphal growth was inhibited after initial conidial germination, indicating the presence of NHR in Pyrus species, including both European and Asian pears, against V. inaequalis. The intergeneric hybrids exhibited resistance phenotypes consistent with Pyrus-derived NHR. Our findings demonstrated that NHR can be inherited by Malus-Pyrus hybrids, suggesting that Pyrus could serve as a genetic source of novel, durable resistance for scab-resistant apple breeding.
