Low Crop Load Research Articles

Ripening Trends of Vitis vinifera L. cv Sugrasixteen (SABLE SEEDLESS®) Table Grapes at Different Crop Loads and Bunch Sizes

Crop load and bunch size manipulation are two prominent viticultural practices used in the production of Vitis vinifera L. cv. Sugrasixteen table grapes. However, their respective effects on berry ripening are unknown and were investigated in this study. A split-plot vineyard block design with three different crop loads (low, medium, and high) as the main treatments and two bunch size treatments (small and large) as the subplot factors were used. Weekly berry samples from veraison to harvest from each treatment were analysed for mass, total soluble solids (TSS), titratable acidity (TA), and pH. Data mining established the ripening trends and explored the possibility of estimating optimal harvest dates using EC50 values. Results showed that berries of large bunches had higher average mass than small bunches during ripening. Increased crop loads resulted in berries with lower mass, TSS and TSS: TA ratio, and delayed berry ripening. Conversely, berries from the low crop load increased in mass and accumulated TSS faster during ripening than higher crop loads, reaching EC50 two to four days earlier with accumulation starting to slow down at higher values. EC50 could be used to estimate harvest dates for low to medium crop loads, but not for high crop loads. This study provides the first in-depth analysis of SABLE SEEDLESS® ripening trends concerning crop load and bunch size management. The results have implications for the grape’s overall eating quality. The statistical prediction of optimal harvest dates for lower crop loads could have practical benefits for the industry.

Rootstock and Crop Load Effects on ‘Honeycrisp’ Photosynthetic Performance and Carbohydrate Accumulation

Rootstock selection and crop load adjustment are key practices in apple orchard management; nevertheless, the effects of rootstocks and crop load levels on important physiological processes of the scions, such as photosynthetic performance and carbohydrate accumulation, are still unclear. To investigate the impact of different rootstocks and crop load levels on scion photosynthesis and carbohydrate buildup, in 2020, ‘Honeycrisp’ trees grafted on rootstocks ‘G.41’, ‘G.935’, and ‘M.9-T337’ were thinned to low and high crop load levels, and photosynthetic performance and carbohydrate accumulation in leaves and fruit were evaluated. Leaves from ‘G.935’ showed the highest net photosynthesis and electron use efficiency of photosynthesis and the lowest activity for non-net carboxylative processes, all together indicative of enhanced photosynthetic performance. High crop load determined an increase in gas exchange, suggesting a positive feedback of high fruit competition on carbon assimilation. While rootstock ‘M.9-T337’ showed a higher accumulation of starch in leaves, no pattern regarding the composition of leaf-soluble sugars among rootstocks could be identified. Conversely, by the end of the harvest season, leaves from low-cropping trees had higher fructose, glucose, and sorbitol than those from high-cropping trees, but differences in starch content were not significant. Fructose and sorbitol concentrations were affected by rootstock and crop load, respectively. Overall, this study showed that high cropping enhanced photosynthesis in ‘Honeycrisp’ apple and determined lower accumulation of some soluble carbohydrates (fructose, glucose, sorbitol) in leaves. This study also provided insights into how rootstocks affect photosynthetic performance of ‘Honeycrisp’, highlighting ‘G.935’ as the rootstock conferring the highest photosynthetic capacity under the present experimental conditions.

Unraveling the occasional occurrence of berry astringency in table grape cv. Scarlet Royal: a physiological and transcriptomic analysis.

Scarlet Royal, a mid-season ripening table grape, is one of the popular red grape varieties in California. However, its berries develop an undesirable astringent taste under certain conditions. Among the various factors contributing to the degradation of berry attributes, the levels and compositions of polyphenols play a fundamental role in defining berry quality and sensory characteristics. To comprehend the underlying mechanism of astringency development, Scarlet Royal berries with non-astringent attributes at the V7 vineyard were compared to astringent ones at the V9 vineyard. Biochemical analysis revealed that the divergence in berry astringency stemmed from alterations in its polyphenol composition, particularly tannins, during the late ripening stage at the V9 vineyard. Furthermore, transcriptomic profiling of berries positively associated nineteen flavonoid/proanthocyanidins (PAs) structural genes with the accumulation of PAs in V9 berries. The identification of these genes holds significance for table grape genetic improvement programs. At a practical level, the correlation between the taste panel and tannin content revealed a threshold level of tannins causing an astringent taste at approximately 400 mg/L. Additionally, berry astringency at the V9 vineyard was linked to a lower number of clusters and yield during the two study seasons, 2016 and 2017. Furthermore, petiole nutrient analysis at bloom showed differences in nutrient levels between the two vineyards, including higher levels of nitrogen and potassium in V9 vines compared to V7. It's worth noting that V9 berries at harvest displayed a lower level of total soluble solids and higher titratable acidity compared to V7 berries. In conclusion, our results indicate that the accumulation of tannins in berries during the ripening process results in a reduction in their red color intensity but significantly increases the astringency taste, thereby degrading the berry quality attributes. This study also highlights the association of high nitrogen nutrient levels and a lower crop load with berry astringency in table grapes, paving the way for further research in this area.

Suitable crop loading: An effective method to improve "Shine Muscat" grape quality.

Berry thinning was applied to control crop load of "Shine Muscat" grape variety. Primary and secondary metabolites released during berries development were monitored, and the correlation between physicochemical parameters and core aroma compounds was analyzed. Results revealed a significant increase in single-berry weight and sugar-acid ratio of berries under low crop load conditions. Furthermore, phenolic content and antioxidant activity under low crop load were significantly higher than those of the other groups. Grapes with low crop loads also exhibited better aroma characteristics and higher sensory scores than those of the other groups, chiefly due to significantly increased terpene and C13-norisoprenoid contents and substantially decreased C6 compound and aldehyde contents. Moreover, correlation analysis revealed total soluble solid accumulation was positively correlated to terpene accumulation, while hexanal, 2-hexanal, (E)-2-hexanal, and (E)-2-octenal were positively correlated with titratable acidity content. Thus, better grape quality could be achieved by precisely controlling berry crop load.

Irrigation and Crop Load Management Lessen Rain-Induced Cherry Cracking.

The combined effects of deficit irrigation and crop load level on sweet cherry (Prunus avium L.) physiological and agronomic response were evaluated during the 2019 season in a commercial orchard located in southeastern Spain. Two irrigation treatments were imposed: (i) control treatment (CTL) irrigated above crop water requirements at 110% of crop evapotranspiration (ETC) and (ii) a deficit irrigation treatment (DI) irrigated at 70% ETC. Within each irrigation treatment, crop load was adjusted to three levels: 100% (natural crop load-high), 66% (medium crop load), and 33% (low crop load). The water relations results were more affected by the irrigation strategies applied than by the crop load management. The deficit irrigation strategy applied reduced soil water availability for DI trees, which led to a continuous decrease in their gas exchange and stem water potential. At harvest, the fruit water potential and osmotic potential of cherries from the DI treatment resulted in significantly lower values than those measured in cherries from CTL trees. On the other hand, both the irrigation strategies imposed and the crop load management used impacted fruit quality. Trees with the lowest level of crop load had fruits of greater size, regardless of the irrigation treatment assayed, and in the DI treatment, cherries from the trees with the lowest crop load were darker and more acidic than those from the trees with the highest crop load. Our results emphasize the different effects that rainfall before harvest has on mature cherries. Thus, cracked cherries at harvest represented 27.1% of the total yield of CTL trees while they were 8.3% of the total yield in DI trees. Cherries from CTL trees also showed a greater cracking index than those from DI trees. Moreover, a linear relationship between crop load and fruit cracked at harvest was observed, particularly for the CTL treatment; thus, the lower the crop load, the greater the proportion of cracked cherries.

Crop Load and Thinning Methods Impact Yield, Nutrient Content, Fruit Quality, and Physiological Disorders in ‘Scilate’ Apples

Most apple cultivars produce too many flowers to enable consistent yields of high-quality fruit, thus, crop load management (thinning) is an integral part of orchard management in modern apple cultivation. Crop load is managed by thinning excess flowers and/or fruit from a tree, however ideal targets vary between cultivars. In this two-year study, the effect of thinning methods at different levels of crop load on fruit quality and production, post-harvest storability and physiological disorders, and fruit and leaf nutrient content in ‘Scilate’ apples were investigated in southern Tasmania, Australia. Two thinning methods, artificial bud extinction (ABE) and hand thinning (HT), were compared at three levels of crop load: 3, 6, or 12 fruit cm−2 limb cross-sectional area (LCSA), described as low, medium, and high, respectively. During the second season, all the ABE and HT treatments received additional chemical thinning (CT). The results demonstrated that ABE consistently outperformed HT in terms of improved fruit set, return bloom, and fruit weight. The fruit quality parameters, such as flesh firmness, total soluble solids, dry matter content, malic acid content, and fruit shape, were also improved under the ABE regime, with these positive effects being the clearest in the second season. In general, high-quality fruits were obtained from the low and medium crop loads, while the fruit quality was poor for the high crop load trees, but the low crop load fruit had a slightly higher incidence of internal flesh browning (predominantly radial) and fruit softening after regular atmosphere storage. The crop load also impacted on the fruit and leaf mineral nutrient content, where fruit N, Ca, Mn, and Zn, and leaf N, Fe, Zn, and Cu content increased while fruit and leaf K declined with a higher crop load. High crop load, irrespective of the thinning regime, and HT with a medium crop load, induced severe biennial bearing, whereas, the fruit yield was relatively consistent with ABE, even with a medium crop load. We conclude that ABE with a medium crop load (around six fruit cm−2 LCSA) is an effective method of managing crop load and optimizing the fruit quality in ‘Scilate’ apples.

Metabolic Pathways for Observed Impacts of Crop Load on Floral Induction in Apple.

The triggers of biennial bearing are thought to coincide with embryonic development in apple and occurs within the first 70 days after full bloom (DAFB). Strong evidence suggests hormonal signals are perceived by vegetative apple spur buds to induce flowering. The hormonal response is typically referred to as the floral induction (FI) phase in bud meristem development. To determine the metabolic pathways activated in FI, young trees of the biennial bearing cultivar ‘Nicoter’ and the less susceptible cultivar ‘Rosy Glow’ were forced into an alternate cropping cycle over five years and an inverse relationship of crop load and return bloom was established. Buds were collected over a four-week duration within 70 DAFB from trees that had maintained a four-year biennial bearing cycle. Metabolomics profiling was undertaken to determine the differentially expressed pathways and key signalling molecules associated with biennial bearing. Marked metabolic differences were observed in trees with high and low crop load treatments. Significant effects were detected in members of the phenylpropanoid pathway comprising hydroxycinnamates, salicylates, salicylic acid biosynthetic pathway intermediates and flavanols. This study identifies plant hormones associated with FI in apples using functional metabolomics analysis.

Response of olive (Olea europaea L.) trees to foliar spray of nano chelated and chemical potassium fertilizers

Global challenges resulting from increased population and increased use of water and soil resources encourage researchers to focus on new compounds, such as nano-fertilizers. Hence, the present study aims to find out and compare the impact of foliar spray of two potassium (K) sources with the different formula, i.e. nano-chelated potassium and potassium nitrate, on olive oil yield and content over two successive years (2017–2018). During the bud-swelling stage, before blooming, the pit hardening stage, and shortly after the harvest of table olive, the fertilizers are used at the concentration of 1.84 (K1) and 2.45 (K2) g potassium nitrate, 3 (nano-K1) and 4 (nano-K2) g potassium nano-chelated, corresponding to 0.81 g (K1 and nano-K1) and 1.08 g (K2 and nano-K2) pure potassium per liter. The results show that fruit yield and characteristics are affected by k2 foliar application. High oil percentage is achieved by k1, which results in a low crop load and the highest leaf carbohydrate content in August. Traits, such as total phenol compound and antioxidant capacity of oil, are strongly enhanced under nano-K1 fertilizer, but quality characteristics of olive oil are relatively affected. Furthermore, nano-K1 treatment can positively affect fatty acid composition through the improvement of leaf mineral content rather than controlling tree. According to the results, fruit yield and traits are better under potassium nitrate (K2) treatment, and the quality of olive oil is more stable after nano-chelate potassium (nano-K1) foliar application.

Control of Curculio caryae (Coleoptera: Curculionidae) with Reduced Rates of a Microbial Biopesticide

Control of Curculio caryae (Coleoptera: Curculionidae) with Reduced Rates of a Microbial Biopesticide

Branch Numbers and Crop Load Combination Effects on Production and Fruit Quality of Flat Peach Cultivars (Prunus persica (L.) Batsch) Trained as Catalonian Vase.

Thinning and pruning are expensive cultural practices in peach cultivation, but essential to obtain adequate production. This study evaluated the effects of combining two pruning (four and six scaffold branches) and three thinning (low, medium, and high crop load) levels on yield and fruit quality of four different flat peach cultivars, trained as Catalonian vase in 2017–2018 in Italy. Productive (average fruit weight, plant total production, and fruit circumference), qualitative (fruit firmness and overcolor, Soluble Solids Content, and Titratable Acidity), and nutritional (Total Antioxidant Capacity, and Total Phenol Content) parameters were evaluated. For productive parameters, a high crop load level led to a decrease in fruit weight and circumference, while a high crop load resulted in higher plant yield. Regarding the qualitative parameters, fruit SSC significantly increased with the diminution of the crop load level in both years of study, while TA was not influenced by crop load and number of branches. Both the total antioxidant capacity and the polyphenol content decreased with an increase in branches number. The findings derived from this study will help growers to select the most suitable combination among genotypes and plant management, to obtain the desired productive or qualitative goals.

Exogenous application of salicylic acid to control coffee rust

The exogenous application of salicylic acid can induce plant resistance against pathogens. However, little is known about the potential uses of this bioregulator for controlling coffee diseases. In this study, we assessed the effect of applying salicylic acid (SA – 150 mg L-1) on the management of coffee rust (Hemileia vastatrix) in a 7-year-old coffee plantation with low crop load (651.6 kg ha-1 in 2017). For comparison, plants were sprayed with protectant fungicide (copper hydroxide – CH) and standard fungicides (SF) used by local farmers (boscalid, pyraclostrobin + epoxiconazole, and copper hydroxide). Non-treated plants were included as a negative control. Five monthly applications were performed from November 2016 to March 2017. Rust incidence and severity, defoliation, and growth of plagiotropic branches were evaluated monthly. The activity of catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and total proteins was assessed one day after the first, third, and fifth product applications. Compared to untreated plants, SA reduced the severity and incidence of rust from 36.3 to 54.7%, while CH and SF reduced disease from 31.8 to 54.6% and from 83.8 to 88%, respectively. SA reduced defoliation by 54.1%. SA increased the concentration of CAT, APX, and SOD after the first application. However, this effect was not observed after subsequent applications. Foliar application of SA reduces the severity and incidence of coffee rust and defoliation in plants with a low crop load.

Leaf Photosynthesis and Carbon Metabolism Adapt to Crop Load in ‘Gala’ Apple Trees

It is widely accepted that a tight coordination between carbon (C) utilization in the sink and C assimilation and metabolism in the source exists in higher plants. However, much of our current understanding is based on research from herbaceous plants, where the source and sink interaction is less sophisticated compared to woody perennials with a significant sink presence. Apple (Malus x domestica Borkh.) is a good representative of the latter category, and its production and transport of sorbitol, in addition to sucrose, adds complexity to C regulation. In this study, four-year-old “Gala”/”M.26” apple trees were subjected to crop load levels at 2.5, 7.5, and 15 fruits/cm2 trunk cross-sectional area. Low crop load trees exhibited reduced leaf C assimilation and extra accumulation of non-structural carbohydrates (NSC). This was primarily a result of reduced activity of Rubisco and increased activities of key enzymes that synthesize starch, sucrose, and sorbitol. Among the NSC, leaf starch was found to be most sensitive to crop load and could function as a leading indicator for source–sink balance in apple. However, even the high crop load trees still retained a significant amount of NSC in leaves at dawn, demonstrating that apple is fundamentally different from herbaceous plants in the way it balances leaf carbon inventories at dawn with carbon export at night for sink growth.

Organic fertilization and crop load in yield and quality of organic nectarines in Italy

Abstract Organic fertilization in orchards aims at increasing soil fertility, at impacting plant productivity and environmental sustainability. This study aimed at verifying the effects of organic fertilization and fruit load on two nectarine cultivars with high and low fruit loads. The experiment was carried out in an orchard under organic management in Fratta Terme, Po valley, in northeastern Italy. Nectarine cultivars Big Top and Carene, implemented in 2017 and grafted onto GF677, were used. Three levels of compost (0, 20 and 40 t dw ha-1) were combined with two fruit loads (low and high) to set up a factorial experimental design with two factors and four randomized replicates. Compost was incorporated at 20 cm depth. The following parameters were evaluated: nitrate- and ammonium- N concentrations in soil at 20 - 40 cm depth, macro and micronutrients in leaves, tree yield, number of fruits, fruit mass and diameter, soluble solids and pulp firmness. The supply of compost enhanced nitrate-N release in soil. In both cultivars, macro- and micronutrient concentrations in leaves were not affected by organic fertilization or fruit load, except for iron, which increased as a consequence of the compost supply. Low crop load induced higher fruit size in both varieties, a fact that was observed after pit hardening. However, the organic fertilization rate did not influence tree yield, fruit mass and soluble solids.

Stem water potential-based regulated deficit irrigation scheduling for olive table trees

Regulated deficit irrigation (RDI) involves water stress management in different phenological periods throughout the season. Research in olive trees (oil production) suggested RDI during pit hardening based in pre-dawn and midday stem water potential (SWP) thresholds. However, the previous thresholds may not be extrapolated to table olive because fruit size, a very important feature in the table olive yield quality, is very sensitive to water stress. RDI in table olive deserve further research to determine the optimal water potential thresholds and the duration of the RDI periods for the specificity of the crop (low crop load to promote high fruit size). The aim of this work was to study different RDI schedules during pit hardening, considering different levels and durations of water stress. The experiment was performed in the 2015, 2016 and 2017 seasons, in a commercial mature table olive orchard (cv. Manzanilla) in Dos Hermanas (Seville, Spain). Control treatments were based on midday SWP measurement in order to optimize the water status with values around −1.4 MPa. Two RDI treatments were applied during pit hardening, dated (according to the changes in longitudinal fruit growth) from mid-June to the last week of August) to maintain water potential values around −2 MPa (RDI-1) and −3.5 MPa (RDI-3). Another RDI treatment (RDI-2) received irrigation to maintain values around −3.5 MPa but the recovery was performed at early July in order to obtain different durations of water stress. Irrigation strategies were evaluated with water relations measurements (soil moisture, gas exchange), fruit and shoot growth and quality and quantity yield indicators. Yield was not significantly affected in any of the RDI treatments with an ANOVA analysis. However, fruit drop estimated as the percentage of fruit lost only in the period of water deficit was related with water stress parameters (SWP and stress integral, IS). In addition, the relationship between fruits size and these latter parameters were significant and change according to yield level. Irrigation treatments did not affect next season yield because shoot growth and number of inflorescence at the beginning of each season were not different. RDI effect changed according to yield level, mainly in relation with fruit size. Data suggest that yield levels up to 12 t ha−1 were possible to manage RDI without affecting fruit size or reducing commercial quality.

Evaluation of Canopy Division and Cane Pruning to Retrofit Spur-Pruned, Vertical Shoot-Positioned Petit Manseng

Summary Goals: Single canopy training with vertical shoot positioning is the predominant training and shoot positioning system in Vitis vinifera vineyards. We questioned if a single canopy with vertical shoot positioning was the most productive system on which to cultivate the modest-yielding cultivar Petit Manseng. We retrofitted low, bilateral cordon-trained, spur-pruned Petit Manseng vines trained to a single canopy by dividing the canopy and implementing bilateral or quadrilateral cane pruning (QCP). Our goals were to evaluate the effects of three different pruning techniques in combination with two training techniques on canopy architecture, crop yield, and primary fruit composition over two years. Key findings: Spur pruning increased pruning weight by 0.1 kg/m row compared to QCP. Divided, vertical shoot positioning increased pruning weight by 0.1 kg/m row compared to single canopy, vertical shoot positioning. A 101% greater leaf exposure layer and 56% greater leaf layer number were observed in midcanopies of single canopy, vertical shoot-positioned plots relative to divided, vertical shoot-positioned plots. QCP increased crop yield by 44% (2017) and 34% (2018) when compared to the average of bilateral cane pruning and spur pruning. QCP combined with divided, vertical shoot positioning increased crop yield by 79% when compared to spur pruning combined with single canopy, vertical shoot positioning in 2018. QCP produced an average crop load of 12.4, 126% greater than that produced by spur pruning over two seasons; while divided, vertical shoot positioning produced an average crop load of 7.2, 33% lower than that produced by single canopy, vertical shoot positioning. Impact and significance: Spur pruning produced a lower crop load than QCP. The relatively high crop load in QCP indicated overcropping. That unbalanced source:sink relationship was alleviated through the use of canopy division, which decreased canopy self-shading and increased crop yield when compared to single canopy, vertical shoot-positioned training in the second of two years. “Athena” is a novel training system that combines a divided, vertical shoot-positioned canopy with QCP to improve exposed canopy leaf area and crop production, respectively. While similar to a Lyre system, which generally employs cordon training and spur pruning, Athena employs cane pruning and is a retrofit option in vineyards trained to single canopies. The Athena system does require further testing over an extended time period, in various growing conditions and in several cultivars, and it is already being tested by southeastern U.S. growers.

Alternate bearing in pistachio (Pistacia vera L.): a review

In this review, the main internal and environmental hypotheses regarding alternate bearing and abscission of inflorescence buds and also, the methods to mitigate this physiological phenomenon have been investigated. Alternate bearing is annually fluctuating heavy (‘on’) and light (‘off’) crops, which occurs in most fruit trees. There are multiple visible causes, decreased shoot growth and flower buds or imperfect flowers, but all occur in association with a heavy crop, suggesting a carbohydrate resource limitation to shoot growth, or flower initiation, induction or differentiation. Pistachios bear on 1-year-old shoots from axillary buds produced the previous year. The visible mechanism is bud abscission on current season’s growth during ‘on’ years and bud retention in low crop load (‘off’) years. Though bud abscission is visible, the underlying cause is unknown. This review classifies the multiple hypotheses as internal, genetic, carbohydrate resources and hormones or environmental, abiotic and biotic stresses. Our examination of potential hypotheses and recent research suggests alternate bearing in pistachio is a result of the carbohydrate resource limitation generated by the heavy ‘on’ year crop maturation. However, the specific signal producing bud abscission is unknown. Alternate bearing in pistachio can be mitigated by a vigorous rootstock, particularly if combined with proper pruning. We hypothesize the vigorous rootstock may produce a better carbohydrate resource status through a larger tree with more leaf surface area. The pruning does not address the bud abscission but alters the ratio of non-bearing to bearing shoots, resulting in a lower alternate bearing index. Furthermore, we conclude alternate bearing in pistachio, while a within shoot phenomenon, can be triggered by severe environmental events that damage a current crop.

The flush development of evergreen recurrent flushing perennials: an experimental overview with insights into the flowering of olive

Recurrent flushing perennials are those that grow by episodic waves of shoot extension under conditions continuously favourable for growth. Here we review the habit for evergreen perennials. The commencement of a new flush appears to depend on the stimulation of buds by plant growth regulators. The determination of a new flush as vegetative or floral most likely occurs during early shoot development. Cool temperatures are usually florally inductive, but other factors such as periods of water stress before flush commencement, and low crop loads may also enhance induction. There is little evidence for the control of the final size of vegetative shoots, and even less for the size of floral shoots. The time between successive flushes is cyclic and temperature dependent. New work with olive is presented and shows that pruning increases the proportions of vegetative shoots to develop from comparable nodes of pruned and non-pruned branches. It also shows that immature vegetative flushes on olive branches in winter inhibit flowering to some extent, a result previously shown for other evergreen recurrent flushing trees.

Preliminary Study on Effect of Early Defoliation on Dry Matter Accumulation and Storage of Reserves on ‘Abbé Fétel’ Pear Trees

Annual accumulation of starch is affected by carbon reserves stored in the organs during the growing season and is controlled mainly by sink strength gradients within the tree. However, unfavorable environmental conditions (e.g., hail events) or application of management practices (e.g., defoliation to enhance overcolor in bicolor apple) could influence the allocation of storage carbohydrates. This preliminary research was conducted to determine the effects of early defoliation on the dry matter, starch, and soluble carbohydrate dynamics in woody organs, roots, and mixed buds classified by age and two levels of crop-load for one growing season in ‘Abbé Fétel’ pear trees (Oct. 2012 to mid-Jan. 2013 in the northern hemisphere). Regardless of the organs evaluated (woody organs, roots, and mixed buds), an increase of soluble carbohydrate concentration was observed in these organs in the period between after harvest (October) and January (dormancy period). Among all organs, woody short-old spurs showed the highest increase (+93.5%) in soluble sugars. With respect to starch, woody organs showed a clear trend of decreasing in concentration between October and January. In this case, short-old spurs showed the smallest decline in starch concentrations, only 6.5%, whereas in other tree organs starch decreased by 34.5%. After harvest (October), leaves showed substantially higher starch and soluble sugar concentrations in trees with lower crop-loads. These results confirm that in the period between October and January, dynamic interconversions between starch and soluble carbohydrates occur at varying magnitudes among organs in pear trees.

The impact of foliar application of boron nano-chelated fertilizer and boric acid on fruit yield, oil content, and quality attributes in olive (Olea europaea L.)

A wide range of Boron-containing compounds is available in the world market, with different formulations and efficiencies. Among these compounds, nano-chelated products are becoming popular, although there is only limited information on their efficiency. Thus, this study considers the effects of boron nano-chelated fertilizer and boric acid foliar sprays on fruit and oil yield in olive cv. ‘Zard’. Their quality attributes were studied during the growing seasons of 2017 and 2018. Fertilizers were used at the concentration of 105 (B1) and 158.8 (B2) mg boric acid, 200 (nano-B1) and 300 (nano-B2) mg nano-chelated boron, corresponding to 180 mg (B1 and nano-B1) and 270 mg (B2 and nano-B2) pure boron per liter. Spraying with water was considered as the control (B0). Fruit characteristics were affected mainly by nano treatments and fruit yield efficiency increased by the use of nano-B2. In spite of the heavy fruit weight and yield, the nano-B2 caused a lower amount of oil accumulation in fruits. A high oil percentage was achieved by the treatment of boron (B2) which resulted in a low crop load. Traits such as oil yield, free fatty acids, antioxidant activity and total phenol content were improved by the application of nano-B2 fertilizer. Fatty acid composition was affected by B1 foliar application. Generally, the data obtained from this study showed that nano-B2 could provide beneficial effects on the growth, fruit and oil yield rather than on oil percentage. The main fatty acid composition was influenced more by boric acid treatments.

Relationships among the rootstock and morphogenetic behaviour of apple tree in aspect for fruit quality

The relationships among rootstock and some physiological (yield, fruit quality) and physical (endogenous hormones, leaf mineral composition) indices and their effect on fruit quality were evaluated. The commercial important apple cultivar ‘Ligol’ was grafted on semi-dwarf rootstock M.26, dwarf rootstock M.9, and super-dwarf rootstock P 22. Crop load was adjusted to 60, 105 and 150 inflorescences tree‑1. Crop load and the rootstock influenced apple yield, fruit weight, most of fruit quality and maturity parameters as well as nutrient status of ‘Ligol’ apple tree. Higher crop load guaranteed higher yields, but smaller fruits. Better fruit colour and faster maturation was achieved at low crop load. P 22 rootstock had negative effect on fruit weight, but the apples on this rootstock were more firm and ripen faster. The concentration of tested hormones and total leaf nutrients were significantly higher in apple trees grafted on M.9 rootstock, but mineral status did not depend on the crop load. Generally, reduced apple tree vigor resulted in significant increase of N, K, and Fe. Observed hormonal changes showed that IAA and ABA can be control factors of ripening as sharp increase of both hormones accumulation occurred and followed with relevant fruit quality indices – significant increase of IAA concentration in trees grafted on M.9 rootstock lead to slower ripening; significant increase of ABA concentration and the fastest ripening was found in ‘Ligol’ apple trees with the lowest crop load.