Fruit Growth Period Research Articles

Water deficit drip irrigation promotes citrus sugar accumulation during the late growth stages

Water deficit drip irrigation (WDDI) in citrus orchards was found has a positive effect on fruit quality, particularly enhancing the soluble sugar content during the late period of fruit growth. However, the underlying molecular mechanism remains unclear. In this study, four deficit irrigation levels of D-60%, D-45%, D-30%, and D-15% were set at fruit expansion stage (stage III) and maturation stage (stage IV), respectively, and a fully irrigated treatment was set as the control (CK). Combined analysis of metabolomics and transcriptomics was used to reveal the molecular mechanism of sugar accumulation changes under different water deficit (WD) treatments. The results showed that sugar metabolism was growth stage dependent: stage III is a key period of sucrose metabolism and synthesis, while for stage IV, the accumulation of glucose and fructose increased significantly. Importantly, III-D15% and IV-D30% treatments were identified as optimal strategies for enhancing sugar content of citrus fruits. WDDI during the late growth stages up-regulated the expression of sugar metabolism-related differential expression genes (DEGs), consequently increasing the content of sugar-related differential expression metabolites (DEMs), and ultimately enhancing sugar accumulation in citrus fruits. For III-D15% treatment, DEMs related to sugar metabolism were mainly enriched in ‘carbon metabolism’, with significant increases in Sucrose, ɑ-D-Glucose-6 P and ß-D-Fructose-6 P content observed. SPS showed significant up-regulation, wihle BGLU, GN, TPS11, TPPF and TPPJ were down-regulated. For IV-D30% treatment, most DEMs were significantly enriched in ‘Glycolysis/Gluconeogenesis’. Key DEMs (Sucrose, D-Glucose-6 P, ß-D-Fructose-6 P) and DEGs (SUS, SPS, BGLU, HXK) involved in the metabolism and synthesis of sucrose, fructose and glucose were significantly increased. This study sheds light on the molecular mechanisms of sugar accumulation in citrus fruit under appropriate WDDI, providing valuable guidance for high-quality fruit production.

Optimization of multi-dimensional indices for kiwifruit orchard soil moisture content estimation using UAV and ground multi-sensors

Accurately estimating of soil moisture content (SMC) is essential for effective irrigation water management and optimizing plant water productivity. Recent advancements in multi-sensor platforms and ensemble learning (EL) algorithms such as the use of UAV-based multispectral (MS) and thermal infrared (TIR) images, have enabled precise mapping of SMC at the field level. The purpose of this study is to optimize the multi-dimensional (n-D) index set and EL model to achieve accurate inversion mapping of SMC in the 0–60 cm root zone at a kiwifruit orchard during the fruit growth period (May-Sep 2022). The n-D index set was computed using kiwifruit canopy MS and TIR data from UAV along with in-field temperature data (air temperature [Ta], kiwifruit canopy temperature [Tc], soil temperature [Ts], and Ta-Tc, Ta-Ts, Tc-Ts). The primary findings of this study are as follows: (1) The Three-Dimensional Drought Index (TDDI), Temperature Vegetation Drought Index (TVDI), and Crop Water Stress Index (CWSI) demonstrated superior performance in capturing temporal variations of root zone SMC compared to Normalized Difference Vegetation Index (NDVI) and Enhance Vegetation Index (EVI). (2) The optimal Categorical Boosting (Catboost) model with two optimal TDDIs (TDDI22: (Tc-Ts)-EVI10,6,2-CWSI space and TDDI7: Tc-NDVI7,3-CWSI space), exhibited exceptional performance for SMC estimation, with determination coefficient (R2) and root-mean-square error (RMSE) of 0.966 ± 0.010 and 0.046 ± 0.003%, respectively. (3) The planted-by-planted mapping performed well in estimating root zone SMC at different growth stages and under different irrigation treatments, with a correlation coefficient (R) of 0.936 ± 0.074 (p < 0.001). This study demonstrated that the integration of multi-sensor indicators and EL models can improve the accuracy of SMC estimation due to its robust adaptability to various field conditions. Furthermore, the planted-grid-based SMC mapping framework can be considered as a valuable approach for monitoring dynamic SMC, facilitating informed irrigation decisions at the individual planting grid.

Yield and physical-chemical quality of table olives in different hedgerow canopy positions (cv. Manzanilla de Sevilla and Manzanilla Cacereña) as affected by irradiance

Unlike olive orchards intended for olive oil, the production of table olives in narrow hedgerows is very recent and the information available about this cropping system is yet very scarce. In this work, we studied for the first time in table olive hedgerows (3.75m x 1.35m, N-S oriented) of Manzanilla de Sevilla and Manzanilla Cacereña cultivars, the distribution within the canopy of yield components and physical-chemical fruit quality traits in response to the incident irradiance. Hedgerow canopies were divided into four positions on each side (East and West) according to height aboveground: 0.5–1.0m, 1.0–1.5m, 1.5–2.0m, 2.0–2.5m, and an additional top canopy position (> 2.5m) integrated for both sides. Total production, number of fruits and size distribution were recorded for each position and the following fruit traits were assessed: fresh weight, length, equatorial diameter, pulp-to-pit ratio, color index, bruising percentage, oil content, water content, total sugars and total phenols. Individual phenolic compounds were also quantified. The incident irradiance at each position was calculated over the fruit growth period using a model based on hedgerow parameters, resulting in a positive gradient from base to top canopy positions. For both cultivars, yield components and most quality traits were positively affected by incident irradiance as they followed a similar trend showing larger mean values with increasing canopy heights. Conversely, the total contents in sugar and phenols and individual phenolic compounds were not affected by the canopy positions. No remarkable differences between East and West sides of the hedgerow were observed.

Estimating stomatal conductance of citrus under water stress based on multispectral imagery and machine learning methods.

Canopy stomatal conductance (Sc) indicates the strength of photosynthesis and transpiration of plants. In addition, Sc is a physiological indicator that is widely employed to detect crop water stress. Unfortunately, existing methods for measuring canopy Sc are time-consuming, laborious, and poorly representative. To solve these problems, in this study, we combined multispectral vegetation index (VI) and texture features to predict the Sc values and used citrus trees in the fruit growth period as the research object. To achieve this, VI and texture feature data of the experimental area were obtained using a multispectral camera. The H (Hue), S (Saturation) and V (Value) segmentation algorithm and the determined threshold of VI were used to obtain the canopy area images, and the accuracy of the extraction results was evaluated. Subsequently, the gray level co-occurrence matrix (GLCM) was used to calculate the eight texture features of the image, and then the full subset filter was used to obtain the sensitive image texture features and VI. Support vector regression, random forest regression, and k-nearest neighbor regression (KNR) Sc prediction models were constructed, which were based on single and combined variables. The analysis revealed the following: 1) the accuracy of the HSV segmentation algorithm was the highest, achieving more than 80%. The accuracy of the VI threshold algorithm using excess green was approximately 80%, which achieved accurate segmentation. 2) The citrus tree photosynthetic parameters were all affected by different water supply treatments. The greater the degree of water stress, the lower the net photosynthetic rate (Pn), transpiration rate (Tr), and Sc of the leaves. 3) In the three Sc prediction models, The KNR model, which was constructed by combining image texture features and VI had the optimum prediction effect (training set: R2 = 0.91076, RMSE = 0.00070; validation set; R2 = 0.77937, RMSE = 0.00165). Compared with the KNR model, which was only based on VI or image texture features, the R2 of the validation set of the KNR model based on combined variables was improved respectively by 6.97% and 28.42%. This study provides a reference for large-scale remote sensing monitoring of citrus Sc by multispectral technology. Moreover, it can be used to monitor the dynamic changes of Sc and provide a new technique for gaining a better understanding of the growth status and water stress of citrus crops.

Increased Temperature Affects Tomato Fruit Physicochemical Traits at Harvest Depending on Fruit Developmental Stage and Genotype

In this study, we investigated how increasing temperature affects tomato fruit physicochemical traits and looked for genetic variability to help maintain fruit quality in the context of climate change. High temperature (HT: +3 °C) was applied at four fruit developmental stages, from anthesis and 15, 30 or 45 days after anthesis until ripening to three genotypes, a commercial cultivar (Money Maker, “MM”) and two genotypes likely more tolerant to HT (Campeche 40 “C40”, a landrace from a warm, humid region, and a hybrid Chapingo F1, “F1”, resulting from crossbreeding landraces tolerant to high temperature). Increasing average diurnal temperature (from 27.0 to 29.9) reduced fruit firmness and size and affected fruit composition according to genotype. Sugar and acid contents were highly impacted in MM and C40 fruits, especially when HT was applied during the rapid fruit growth period. The application of HT at different fruit developmental stages revealed that HT could enhance acid accumulation and degradation (rate and/or duration), resulting in different effects on fruit acidity between genotypes. The F1 genotype appeared to be more adapted to HT, producing larger fruits with higher sugar, lower acid and increased vitamin C and calcium content. These results provide interesting directions for breeding programs that want to maintain future tomato fruit yields and quality.

Magnesium Effects on Carbohydrate Characters in Leaves, Phloem Sap and Mesocarp in Wax Gourd (Benincasa hispida (Thunb.) Cogn.)

Magnesium (Mg) is critical for agricultural production and human health. The wax gourd yield was greatly affected by Mg fertilizer and it serves as an excellent crop to study Mg functioning in sink growth; however, as a Cucurbitaceae plant which is called a raffinose family oligosaccharides (RFOs)-transporting plant, its adaptive mechanism of photoassimilates transportation and distribution to Mg nutrients remains unknown. Herein, we used two Mg treatments (+Mg 90 kg ha−1; CK as control 0 kg ha−1) to observe the effects of Mg on the photoassimilates status in the leaves, phloem sap and fruit of wax gourd grown across the entire growth stage under a field condition. For the first time, we confirmed that stachyose and raffinose, which accounted for 54.9–78.0% of the total carbohydrates across the whole growth phase in the phloem sap, were the most predominant sugars used for the long-distance transport of wax gourds. They were strongly increased by Mg application which started from the seedling stage to the end of growing season. This response was earlier and more dramatic than the over-accumulation of sucrose in leaves regardless of positions. Hexoses (glucose plus fructose) were the main soluble sugars in the source leaves as well as in the mesocarp tissues, and their responses to Mg varied with temporal and spatial differences. The difference in the sugar status in the leaves between the upper, middle and lower positions is closely related to the concentration of Mg ions. Compared with Mg deficiency (CK), Mg application stimulated sugar accumulation in the leaves at the seedling and flowering stages by 10.6–24.5%. On the contrary, after fruit set, Mg supplementation significantly reduced the soluble sugar concentration in leaves by 33.5–67.9%. Mg treatment also spiked the fructose and glucose in fruit at the fruit expansion stage by 26.7% and 16.4%, respectively. Taken together, our results showed that Mg tailors the carbohydrate status in the source (leaves), flow (phloem sap) and sink (mesocarp tissues) in wax gourds, especially during the fruit growth period. The lower stachyose in the phloem at the beginning of fruit setting may be an early indication of a curtailed sink process in wax gourds grown in Mg deficient soil.

Digital Mapping of Root-Zone Soil Moisture Using UAV-Based Multispectral Data in a Kiwifruit Orchard of Northwest China

Accurate estimation of root-zone soil moisture (SM) is of great significance for accurate irrigation management. This study was purposed to identify planted-by-planted mapping of root-zone SM on three critical fruit growth periods based on UAV multispectral images using three machine learning (ML) algorithms in a kiwifruit orchard in Shaanxi, China. Several spectral variables were selected based on variable importance (VIP) rankings, including reflectance Ri at wavelengths 560, 668, 740, and 842 nm. Results indicated that the VIP method effectively reduced 42 vegetation indexes (VIs) to less than 7 with an evaluation accuracy of root-zone SM models. Compared with deep root-zone SM models (SM40 and SM60), shallow root-zone SM models (SM10, SM20, and SM30) have better performance (R2 from 0.65 to 0.82, RRMSE from 0.02 to 0.03, MAE from 0.20 to 0.54) in the three fruit growth stages. Among three ML algorithms, random forest models were recommended for simulating kiwi root-zone SM during the critical fruit growth period. Overall, the proposed planted-by-planted root-zone SM estimation approach can be considered a great tool to upgrade the toolbox of the growers in site-specific field management for the high spatiotemporal resolution of SM maps.

Responses of tomato fruit water balance and xylem hydraulic property of pedicel and calyx to water deficit and salinity stress

Moderate water scarcity and high soil salinization always limit fruit growth but largely promote fruit quality. Water is transported to the fruit via xylem and phloem and lost via transpiration, which is important for fruit growth and quality parameters. So far, few studies have quantified the relationship between fruit water balance and fruit growth and quality under water deficit and salinity stress (especially combined water deficit and salinity stress). In this study, tomato (Solanum lycopersicum) plants were grown under full irrigation (CK), water deficit (WD), salinity stress (SS), and combined water deficit and salinity stress (WS). We measured fruit size and quality parameters, investigated fruit water balance using a subtraction method, evaluated xylem hydraulic resistance of pedicel and calyx applying a hydraulic head, and assessed the xylem functionality by fruit rehydration and dye-tracing experiments. Results showed that WD, SS, and WS decreased plant water status and leaf gas exchange and fruit growth, but increased fruit total soluble solids. These effects were more pronounced in WS than both WD and SS. The inhibition of fruit growth by three treatments was caused by the jointly reduced xylem and phloem flow. Although xylem hydraulic resistance of pedicel and calyx at 35 d after anthesis was not significantly affected under WD and SS, it greatly increased by 112% under WS, which coincided with a significant reduction of daily growth rate and xylem flow computed on a per fruit basis by 83% and 87% under WS. These results also suggested that the xylem tissues were still functional regardless of the applied stress and fruit growth period. Phloem flow computed on a per fruit basis was decreased under all treatments, resulting in a reduction in fruit dry matter quantity, partly due to the decreased photosynthates. Phloem flow and fruit transpiration computed on a per fruit fresh weight basis were not affected due to the synergistic reduction of flow and fruit size by all treatments. This study provides a new understanding on the water relations of plant-fruit system under water deficit and salinity stress.

Flower Thinning Improves Fruit Quality and Oil Composition in Camellia oleifera Abel

Camellia oleifera is a woody oil tree with overlapping flower bud differentiation and fruit maturation. Therefore, mechanical harvesting of fruits leads to flower abscission. The present study investigated the effects of flower number per tree on fruit growth, yield, nutrient accumulation, and oil fatty acid composition in C. oleifera. Here, we set different flower numbers per tree by thinning flowers. Heavy flower thinning (T2 and T3) significantly reduced fruit yield and the proportion of palmitic, palmitoleic, linoleic, and linolenic acid in fatty acids compared with other treatments. However, heavy thinning favored an increase in fruit size and weight, seed and dry kernel rate of fresh fruit, soluble protein and oil accumulation in seeds, and the proportion of oleic acid and stearic acid in fatty acids, and it had no significant effect on oil yield per tree compared with light thinning (T1) and control (T0). T2 and T3 decreased soluble sugar content in the kernels at the later stage of fruit development (260–320 days after full bloom (DAFB)) in contrast to the rapid fruit growth period (200–230 DAFB). As the crop load decreased, fruit ABA content increased continuously during 260–320 DAFB, while fruit IAA content increased during 260–300 DAFB and then decreased during 310–320 DAFB. These data suggest that the abscission of a few flowers during mechanical harvesting will not affect fruit production efficiency in C. oleifera.

Phenotyping Olive Cultivars for Drought Tolerance Using Leaf Macro-Characteristics

This work investigates the relationships between leaf traits and olive response to water stress through two complementary field experiments in order to screen genotypes for drought tolerance. The first experiment consisted of the phenotyping of 32 olive varieties for 11 leaf morpho-physiological traits during a fruit set phase under well-watered conditions. In the second experiment, the yield and vegetative responses of five representative varieties to the withholding of irrigation during the whole fruit growth period were assessed to identify leaf traits that are associated with olive resilience plasticity and that could be used as drought tolerance markers. The results highlighted large phenotypic variability for leaf area (LA, 2.9–9.5 cm2), petiole elasticity (8.0–36.0°), water loss in detached leaves (WLDL, 3.6–11.6%), stomatal density (222.6–470.1 no mm−2), stomatal length (11.4–18.7 µm), trichome density (120.5–204.4 no mm−2), trichome width (103.6–183.4 µm), leaf contents in cuticular wax (CWC, 44.7–606.2 µg cm−2), and soluble sugars (SSC, 15.8–536.9 mg gdw−1). Among these leaf traits, WLDL displayed a significant correlation with the yield stability index (r = −0.973) and water use efficiency (r = −0.939), suggesting its use as relevant drought tolerance phenotypic marker. Likewise, LA, SSC, and CWC were singled out as second-level drought tolerance markers, being strongly correlated with stability of leaf size and leafing intensity in response to water stress. Cluster analysis highlighted 12 distinct levels of drought tolerance within the studied olive collection. Based on the four identified phenotypic markers, “Lechin de Sevilla” alongside “Picholine Marocaine” were found to be the most drought-tolerant varieties, while Frantoio was the most sensitive. This study provides the first, unprecedented, insights into the usefulness of leaf phenotyping in olive drought tolerance screening, with a focus on structural and functional leaf traits.

The water status of pear (Pyrus communis L.) under application of regulated deficit irrigation in high tropical latitudinal conditions

Irrigation management in fruit crops affects the water status of the plant, which directly affects production and quality in various growing cycles. The objective was to evaluate the impact of regulated deficit irrigation (RDI) on the water status of the pear tree cv. 'Triunfo de Viena', under high tropical latitudinal conditions. The applied irrigation treatments corresponded to water regimens with one control (T1), irrigated at 100% of ETC; 74% and 48% crop evapotranspiration (ETc) in the T2 treatment and 60% and 27% ETc in the T3 treatment during the period of rapid fruit growth, in 2014 and 2015, respectively. During the rest of the season, all treatments were watered equally to 100% of the ETc. This implied water savings in the deficit treatments T2 and T3 of 26.4% and 39.6% during 2014 and 51.7% and 72.8% in 2015, respectively. The leaf water potential at predawn (Ψpdl), mid-day stem water potential (Ψstem), the water potential of the fruit at predawn (Ψpdf), and water potential of the fruit at mid-day (Ψf) were clear indicators of the water status of the plant, however, between treatments were generally not different. Ψstem remained between −0.25 and −1.03, showing that RDI treatments evaluated did not cause water stress. The parameters obtained from the pressure-volume curve were similar between treatments because irrigation levels did not generate water stress, mainly due to rains and water reserves in the soil during the experiment. Therefore, osmotic adjustment was not made in any of the treatments. Maximum daily trunk shrinkage was a good indicator of hydric status and responded quickly to environmental conditions allowing its use in irrigation management and, adjusting to a crop under specific conditions. The results contributed to an understanding of the mechanisms of the water status of pears under RDI in high tropical latitudinal conditions.

Functional Traits of Male and Female Leaves of Hippophae tibetana on the Eastern Edge of the Tibetan Plateau and Their Altitudinal Variability.

To date, there have been few studies of the functional traits of the dioecious Hippophae tibetana Schlecht leaves, either male or female, in response to ecological factors such as altitude. Elucidating these relationships will establish an important scientific basis for vegetation restoration and reconstruction of the Tibetan Plateau ecosystem. The natural populations of H. tibetana, distributed across three field sites, at 2868 m, 3012 m and 3244 m, in Tianzhu, Gansu, were studied by field survey sampling and laboratory analysis. In particular, the adaptions of leaf functional traits to elevation in these dioecious plants were analyzed. The results show that: (1) there is no “midday depression” of photosynthetic activity in either male or female plants. Over a one-day period, the net photosynthetic rate (Pn) and transpiration rate (Tr) of H. tibetana female plants were higher than those of male plants (p < 0.05). This correlated to the period of vigorous fruit growth in the female plant. The measured Pn and Tr were maximal at the intermediate altitude (3012 m). The light compensation point (LCP) of the leaves of male and female plants were 57.6 and 43.2 μmol·m−2·s−1, respectively, and the light saturation points (LSP) of the leaves were 1857.6 and 1596.8 μmol·m−2·s−1. (2) Altitude had a significant effect on plant and leaf functional traits of male and female H. tibetana (p < 0.05), and no significant difference was noted between plants at the same altitude. The values for leaf area (LA), specific leaf weight (LMA), leaf phosphorus content per unit mass (Pmass) and leaf phosphorus content per unit area (Parea) were also maximal at the intermediate altitude. Leaf nitrogen content per unit area (Narea) and leaf nitrogen content per unit mass (Nmass) increased with altitude. This indicated that the functional traits of male and female plants and leaves of H. tibetana showed a strong “trade-off relationship” with altitude. (3) Pearson correlation analysis showed that there were significant correlations among functional traits of H. tibetana leaves. Redundancy analysis (RDA) showed that soil water content (SWC), altitude (Alt) and soil organic carbon (SOC) had significant effects on the functional traits of H. tibetana leaves (p < 0.05).

Japanese plums behavior under water stress: impact on yield and biochemical traits

This work investigates response to drought of nine local cultivars alongside two exotic varieties of Japanese plum (Prunus salicina L.) through their yield and fruit quality components. It was carried out at Sais plain, northern Morocco, over two consecutive years (2019–2020). Water stress was imposed by a deficit irrigation (DI) treatment of 50% ETc during the whole fruit growth period, compared to full irrigation of 100% ETc (CI). At their full ripening stage, the cultivars were assessed for their yield, fruit weight and fruit quality attributes, namely total soluble solids (TSS), pH, titratable acidity (TA), maturity index (MI), soluble sugars content (SSC), amino acids content (AAC), total phenolic compounds (TPC) and total antioxidant capacity (TAC). Results displayed significant decrease in yield and fruit weight since the first year of DI application. Owing to calculated stability indexes of the aforementioned traits along with water use efficiency, the local cultivar ‘Fortu-43’ was the most insensitive to drought, whereas ‘Timhdit’ and ‘Black-D35’ showed the lowest drought tolerability. The effects of water stress on fruit chemical and biochemical traits varied significantly among cultivars, exhibiting an overall significant improvement in fruit quality. Two-dimensional clustered heatmap analysis subdivided the cultivars into two distinct clusters, mainly discriminated based on stability indexes of SSC, MI, TPC and TAC. Among the latter, SSC stability index was probably the most significant drought tolerance marker for Japanese plum.

Impact of genetic and climatic parameters on split-pit incidence in peach and nectarine

Split-pit in peach (Prunus persica L. Batsch) is a physiological disorder occurring during fruit growth causing significant losses to growers, retailers and the canning industry worldwide. In the present study the split-pit susceptibility of 59 recently grown melting-peach and nectarine cultivars was investigated and occurrences were related with phenotypic traits such as ripening date, yield and fruit and stone traits, and climatic parameters such as growing degree hours and rainfall during different periods of fruit growth, in 4 growing seasons. Cultivars with lower propensity to split-pit was separated. The split-pit incidence was higher in nectarine compared with melting-peach, and also in yellow- compared with white-flesh cultivars. Early ripening was the most important parameter related with higher percentage of fruit with split-pit, followed by larger fruit and higher rainfall during 30d after blooming. The fruit and stone dimensions were not related with split-pits, neither was the sum of growing degree hours calculated during different periods after blooming. In conclusion, the present study provides information on the propensity to split-pit disorder of modern melting-peach and nectarine cultivars that may be important information for growers and breeders. A cultivation practice for reducing the split-pit incidence in sensitive cultivars is to aim for smaller fruit sizes, while the spring rainfall experienced could be used by growers as an indication for adjusting fruit load accordingly so that to diminish the expected damages.

Breeding of Persian walnut: Aiming to introduce late-leafing and early-harvesting varieties by targeted hybridization

Due to climate change, late-spring frost is considered as a main limiting factor for walnut production. The sustainable strategy to alleviate this challenge is to use late-leafing cultivars with desirable nut characteristics. In order to achieve late-leafing and early-harvesting cultivars, this breeding program including 3635 controlled crosses between ‘Persia’, ‘Caspian’, ‘Chandler’, ‘Pedro’ as female parents and ‘Franquette’, ‘Lara’ and superior genotype 35T as male parents was conducted during 2018–2019. The results showed that there is a significant difference between the cross combinations in terms of fruit set and pollen tube growth. So that, the highest final fruit set was observed in the cross ♀Chandler × ♂35T (67.90%). Also, the fruit growth period of different cross combinations varied between 134 and 157 days. The nut weight, kernel weight and kernel percentage of the obtained progenies ranged between 8.38–12.13 g, 4.19–8.24 g and 41.50–68.67%, respectively. The highest kernel percentage was observed in ♀Persia × ♂35T cross combination (68%). The hybrid seeds were planted in pots under greenhouse condition in the first year, and after initial growth, one-year-old seedlings were transferred to the nursery. Evaluation of the studied seedlings in 2020 showed that there was a significant variation (45 days) between seedlings in terms of leafing date. The early-and late-leafing genotypes were obtained when 35T and ‘Franquette’ used as male parents, respectively. Although, the studied seedlings have not yet reached the maturity phase for evaluating harvest date, but due to the great variation in leafing date, we hope to reach late-leafing and early-harvesting genotypes with desirable nut traits in the continuation of this breeding program.

Efecto del riego deficitario controlado (RDC) en el crecimiento vegetativo del peral variedad Triunfo de Viena (Pyrus communis L.)

One of the consequences of a water deficit in the vegetative growth is the modification of the plant vigor, which determines the extent and the rate of growth and lengthening in shoots, which, in this phase, is more important than fruit growth, which is very slow in terms of dry mass accumulation. The objective of this research was to determine the effect on the vegetative growth of the pear variety Triunfo de Viena (Pyrus communis L) of regulated deficit irrigation (RDI), which was compared with a control irrigated at 100% crop evapotranspiration (ETc). The irrigation treatments consisted of the application of watering regimes of 74 and 48% ETc in treatment T2 and 60 and 27% ETc in treatment T3 in 2014 and 2015, respectively, during the period of rapid fruit growth with the same watering regime used in T1 (control) applied during the rest of the season. The irrigation reduction used in T2 and T3 represented water savings of 26% and 40% in 2014 and 52% and 73% in 2015, respectively. In the deficit treatments, there were no significant differences with respect to the control for the length, or absolute and relative growth rates (AGR and RGR) of the shoots. The weight of the wood from the fructification pruning had a significant difference between T3 and the control.

Nitrendipine-Treatment Increases Cork Spot Disorder Incidence in Pear 'Akituki' (Pyrus pyrifolia Nakai.) by Altering Calcium Distribution Inside the Fruit.

‘Akituki’ (Pyrus pyrifolia Nakai.) is a very popular and profitable pear cultivar in China. However, its high susceptibility to cork spot disorder has limited its expansion of cultivated area. The mechanisms of cork spot disorder have been discussed extensively, focusing on Ca2+ deficiency, yet no consensus has been made. In this study, we applied nitrendipine (NI) as a Ca2+ uptake inhibitor to explore the role of calcium in cork spot disorder occurrence. Results showed that NI treatment on the fruit remarkably increased the incidence of cork spot disorder; alteration of mineral contents happened at the early developmental stage of the fruit, especially on the outer flesh and the peel of the fruit; and this gap was filled gradually along with the expansion of the fruit. Significant differences in the expression levels of Ca2+ transport-related genes were found in the inner flesh, outer flesh and peel during the fruit growth period. The observation of free Ca2+ localization indicated the intracellular imbalance of Ca2+ in the NI-treated fruit. In conclusion, NI treatment reduced the calcium content in the fruit at an early developmental stage, altered the related expression of genes and influenced the cellular Ca2+ balance in the fruit, which prompted the occurrence of cork spot disorder. Measures for the prevention and control of cork spot disorder should be taken at the early stage of the fruit development in the field.

Allocation of Photoassimilates in Bud and Fruit from Different Leaf Nodes of Camellia oleifera

The periods of flower bud differentiation and fruit growth for Camellia oleifera overlap greatly affect the allocation of photoassimilates to flower buds and fruit, resulting in obvious alternate bearing. To export the cause and mitigate alternate bearing of Camellia oleifera, the allocation of photoassimilates to buds and fruit supplied by leaves at different node positions was studied by the addition of labeled 13CO2 during the slow fruit growth stage. The fate of 13C photoassimilated carbon was followed during four periods: slow fruit growth (4 hours and 10 days after 13C labeling); rapid growth (63 days after 13C labeling); oil conversion (129 days after 13C labeling); and maturation (159 days after 13C labeling). Photosynthetic parameters and leaf areas of the leaves shared a common pattern (fifth &gt; third &gt; first), and the order of photosynthetic parameters of different fruit growth stages was as follows: oil conversion &gt; maturation &gt; rapid growth &gt; slow growth. The most intense competition between flower bud differentiation and fruit growth occurred during the oil conversion stage. Dry matter accumulation in different sinks occurred as follow: fruit &gt; flower bud &gt; leaf bud. Photoassimilates from the labeled first leaf were mainly translocated to the first flower bud, and the upper buds were always differentiated into flower buds. The photoassimilates from the labeled third leaf were distributed disproportionately to the third flower bud and fruit. They distributed more to the third flower bud, and the middle buds formed either flower or leaf buds. However, the photoassimilates from the labeled fifth leaf were primarily allocated to the fruit that bore on the first node of last year’s bearing shoot, and basal buds did not form flower buds. Based on our results, the basal leaves should be retained for a high yield in the current year, and the top leaves should be retained for a high yield in the following year. Our results have important implications for understanding the management of flower and fruit in C. oleifera. The thinning of fruit during the on-crop year can promote flower bud formation and increase the yield of C. oleifera crops in the following year. During the off-year, more fruit should be retained to maintain the fruit yield. The thinning of middle-upper buds could promote more photoassimilates allocate to the fruit.

Fruit Characteristics of Kiwifruit as Affected by Weather Conditions During the Period of Fruit Growth

Fruit Characteristics of Kiwifruit as Affected by Weather Conditions During the Period of Fruit Growth

Fruit Morphology Measurements of Jujube Cultivar ‘Lingwu Changzao’ (Ziziphus jujuba Mill. cv. Lingwuchangzao) during Fruit Development

‘Lingwu Changzao’ (Ziziphus jujuba Mill. cv. Lingwuchangzao), a cultivar of Ziziphus in the Rhamnaceae family, is a traditional jujube cultivar in Ningxia, China. For ‘Lingwu Changzao’, morphological traits are prominent in characterizing fruit yield, quality, and consumer acceptance. However, morphological measurements for ‘Lingwu Changzao’ cultivation are limited. Therefore, the objective of this study is to measure the growing patterns of selected morphological traits during ‘Lingwu Changzao’ fruit development. Eight morphological traits, including four fruit traits (fruit length, diameter, weight, and flesh (mesocarp) thickness), three stone traits (stone length, diameter, and weight), and fruit firmness (also known as fruit hardness), were measured over a 3-mo (months) period, covering a completed fruit development period. Results indicate that the growing patterns of fruit traits coincide with double ‘S’ growth curves, which mainly present the growth of ‘Lingwu Changzao’ fruit. Increases of stone traits terminated in the early fruit growth period, while fruit traits continuously increased till the end of the 3-mo period. That implies a high fruit-stone ratio, i.e., a desirable quality attribute for ‘Lingwu Changzao’ as fresh-eating fruits. The results presented in this study can serve as one part of the standard dataset for jujube fruit cultivation in China, and it can also support decisions in plant breeding and field managements for ‘Lingwu Changzao’.