Fruit Soluble Solids Research Articles

Postharvest Quality of ‘Carabao’ Mango as Affected by Spun-Bound Bagging Materials

A safe option to address some production problems such as insect damage, diseases, and blemishes in mango is fruit bagging. ‘Carabao’ mango fruit at 55 days after flower induction (DAFI) were bagged with three bagging materials: old newspaper (control), spun-bound high density polyethylene (SHDPE, DuPont™ Tyvek® Homewrap, 0.15 mm thick) and non-woven spunbound polypropylene (NSPP, 0.03mm thick). Bagged mango fruit were harvested at 118 DAFI. At harvest, NSPP bagging material resulted in better quality of fruit compared to newspaper and SHDPE. Advanced color change was observed both in newspaper and SHDPE at 4 and 8 days after harvest (DAH). Compared to newspaper and SHDPE, slower color change was observed in fruit bagged with NSPP up to 8 DAH. The degree of anthracnose infection did not differ among bagging materials. Higher degree of stem end rot (SER) infection was noted in newspaper at table ripe stage (TRS). Onset of SER was delayed by about a day in NSPP and SHDPE. At 8 DAH, lowest weight loss was observed in mango bagged with newspaper. Slightly longer shelf life of about a day (0.72 d) was noted in NSPP-bagged fruit. Shelf life was reduced in newspaper which may be attributed to fruit reaching TRS faster by a day and earlier onset of SER. Total soluble solids in fruit bagged with SHDPE was lower upon harvest and during storage at 8 days while firmness did not vary among bagging materials. NSPP showed potential as bagging material that can maintain better quality of ‘Carabao’ mango fruit.

Yield and Fruit Quality Traits of Dragon Fruit Cultivars Grown in Puerto Rico

Dragon fruit (Hylocereus sp. and Selenicereus sp.), also referred to as pitahaya or pitaya, is a member of the Cactaceae family and native to the tropical forest regions of southern Mexico, Central America, and northern South America. Its fruit is becoming increasingly popular as consumers seek healthy and more diverse food products. The crop adapts to different ecological conditions ranging from very dry regions to wet ones receiving more than 3500 mm of rainfall per year. U.S. commercial production of dragon fruit occurs mainly in Florida, southern California, and Hawaii. As growers learn more about this crop and how productive it can be, the acreage planted is likely to increase. Twelve dragon fruit cultivars grown on an Oxisol soil were evaluated for 5 years under intensive management at Isabela, PR. There were significant differences in number and weight of fruit per hectare among years. Cultivars exhibited an increase in fruit number and yield from 2010 to 2013 and then leveled off or declined. There were significant differences among cultivars for number of fruit and yield per hectare. Cultivars N97-17 and N97-15 produced significantly more fruit averaging 74,908 fruit/ha. Significantly higher fruit yield was obtained by cultivars N97-17, N97-20, N97-22, and NOI-13 averaging 17,002 kg·ha−1. Cultivar Cosmic Charlie had the lowest fruit yield, averaging only 25.1 kg·ha−1. Individual fruit weight was significantly higher in cultivars N97-20 and NOI-13 with fruit weight averaging 346.3 g. Cultivars NOI-16, N97-18, and Cosmic Charlie had significantly higher fruit soluble solids than others, averaging 17.4%. Some of the cultivars used in this study have shown horticultural potential and may serve as new planting material for growers.

Growing medium soluble carbon and nitrogen influence xylem sap and soluble solid contents in greenhouse cucumber fruits

Compelling evidence recently demonstrated that plants can take up nitrogen (N) as organic molecules. Yet, very little research addressed this issue in the context of organic horticulture, where N is provided as organic residues. Organic N and carbon (C) transported from roots to shoots could contribute significantly to the plant C and N accumulation. We posited that the type (organic or mineral) and amount of N fertilization affect the soluble organic N and C content of the growing medium, in turn influencing xylem sap N and C and fruit soluble solids content (SSC). To test this hypothesis, we collected growing medium, xylem sap, and fruit samples in a greenhouse cucumber crop grown in a peat-based growing medium and fertilized with organic (blood and feather meals) or mineral (ammonium nitrate) N fertilizers. The organic N source reduced growing medium concentrations of soluble mineral and organic N relative to the mineral source through microbial immobilization. Xylem sap C and N were positively linked to the soluble C and N contents of the growing medium, contributing to higher fruit SSC. A causal model is proposed, in which 62.6% of the variance observed in fruit SSC is explained by variation in mineral soluble N and soluble organic C in the growing medium and dissolved organic C and amino acids in xylem sap. Our results provide in situ indications that organic molecules in the growing medium are taken up by cucumber plants and contribute to fruit soluble solids in a context relevant to greenhouse horticulture.

Interactive effects of boron stress and mycorrhizal (AMF) treatments on tomato growth, yield, leaf chlorophyll and boron accumulation, and fruit characteristics

ABSTRACT High levels of boron (B) in soils cause toxicity in tomatoes, but inoculation of arbuscular mycorrhizal fungi (AMF) into plants can reduce it. This study aimed to evaluate the effects of AMF inoculation on morphological parameters (shoot height, plant fresh and dry weights), yield, leaf chlorophyll and boron content, and fruit characteristics (weight, water and soluble solid contents, firmness, color) of tomato plants grown in boron stress (0.06, 0.5, 1.0, 2.0, 4.0, and 8.0 mM). Increased boron concentrations reduced all parameters except leaf boron content, fruit soluble solids and firmness. However, the highest values of the morphological parameters, fruit soluble solid contents and red color values (control, 0.5 and 1.0 mM B), fruit yield (<8.0 mM B), leaf chlorophyll content (≤2.0 mM B), fruit weight (control, 0.5 and 2.0 mM B), fruit firmness (control and 1.0 mM B) were obtained from mycorrhizal plants. No significant differences were found between the fruit water content and color values (brightness and yellow) of non-mycorrhizal and mycorrhizal plants in all boron stress levels. The leaf boron concentration in inoculated with mycorrhizal fungi had lower than non-inoculated ones. These results suggest that mycorrhizal-inoculation may limit excessive boron uptake and alternatively be used in boron contaminated soils.

A Special Summer Pruning Method Significantly Increases Fruit Weight, Ascorbic Acid, and Dry Matter of Kiwifruit (‘Jinyan’, Actinidia eriantha × A. chinensis)

Jinyan (Actinidia eriantha × A. chinensis) is one of the gold-fleshed kiwifruit cultivars currently being promoted in south China. However, its fruit dry matter is usually less than 16%, which seriously affects fruit quality including taste and flavor. This causes a financial loss to growers: not only are the prices paid for the fruit low because of their bad reputation for quality, but some orchards have been removed. Improvement of fruit quality is essential. In this study, a method is described for squeezing and twisting flowering shoots before flowering and removing the distal vegetative parts of flowering shoots after fruit set. The effects on fruit quality were determined. The dry matter of fruit was increased by 6.6%. Fruit size also increased as did the chlorophyll a content and the chlorophyll:carotenoid ratio. The significantly increased fruit dry matter, resulting in significant increases in fruit soluble solids concentrations (P &lt; 0.01), thereby possibly improving fruit taste. Fruit weight, fruit length, and carotenoid and ascorbic acid concentrations were significantly enhanced in comparison with controls (P &lt; 0.01), increasing by 20%, 7%, 12%, and 19%, respectively. However, there was no significant difference in soluble sugar concentrations, titratable acid concentrations, and the reduced chlorophyll b concentrations. This research provides a practical method to increase fruit dry matter, and hence a way to allow fruit quality to reach commercial requirements for cultivars such as Jinyan, which under previous management systems had significant shortcomings in fruit flavor and taste.

Crecimiento, rendimiento y calidad de fresa por efecto del régimen nutrimental

El objetivo de la investigación fue determinar el régimen nutrimental que favorece el crecimiento, rendimiento y calidad física y bioquímica de fresa producida en hidroponía bajo cubierta plástica. En 2017 se realizó un experimento en el campo experimental de la Facultad de Ciencias Agropecuarias de la Universidad Autónoma del Estado de Morelos, en el que se evaluaron 27 regímenes nutrimentales conformados por la combinación de variaciones de la concentración de NO-3 en la fase vegetativa (10, 12 y 14 meq L-1), H2PO4- en la fase reproductiva (0.75, 1 y 1.25 meq L-1) y K+ en la fase de fructificación (5, 7 y 9 meq L-1). Los tratamientos se distribuyeron en un diseño experimental bloques completamente al azar con cuatro repeticiones por tratamiento. La unidad experimental fue un contenedor de polietileno negro (15.14 L), con tezontle rojo como sustrato y una planta de fresa. Los resultados indicaron que las plantas de fresa producidas en hidroponía con régimen nutrimental manifestaron respuesta significativamente diferente en el contenido relativo de clorofila, área foliar, biomasa seca de hojas, diámetro de flor, longitud y diámetro ecuatorial del fruto, peso promedio del fruto, rendimiento por planta y concentración de sólidos solubles totales en fruto, en función de las concentraciones de NO3-:H2PO4-:K+, en las fases vegetativa, reproductiva y de fructificación, respectivamente. El régimen nutrimental de 10 meq L-1 de NO3- en la fase vegetativa, 1 meq L-1 de H2PO4- en la reproductiva y 7 meq L-1 de K+ en fructificación, es el recomendable para producir fresa en hidroponía porque incrementó de forma significativa el diámetro del fruto y el rendimiento por planta.

ХИМИЧЕСКИЙ СОСТАВ ПЛОДОВ ВИШНИ СЕЛЕКЦИИ ТАТАРСКОГО НИИ СЕЛЬСКОГО ХОЗЯЙСТВА

The research was carried out with the aim of comparative assessment of varieties and selected forms of sour cherries by the chemical composition of fruits to identify the best genotypes with their subsequent use in breeding, as well as industrial, farm and collective gardening. The experiments were carried out in 2016–2019 in triplicate. The garden was laid out in 2004-2005 and is located in the southwestern part of the Republic of Tatarstan. The material for the study was 20 varieties and selected hybrids of sour cherries of different ripening periods of the breeding of Tatar Research Institute of Agriculture. On average, over the years of research in fruits of different varieties, the content of soluble solids varied within 16.69 ... 26.49%, sugars - 3.72 ... 6.35%, organic acids - 0.96 ... 2.64%, vitamin C - 11.70 ... 15.90 mg per 100 g. The variability of the content of soluble solids and vitamin C was average (V = 15.1 ... 19.3 and 10.3 ... 14.3%, respectively). The amount of sugars, organic acids and the sugar acid index changed more significantly - V = 20.9… 25.2, 22.0… 25.8 and 29.0… 37.7%, respectively. The genotype had a greater influence on the variability of the content of soluble dry substances, sugars and organic acids in sour cherry fruits (30.2 ... 65.9%) than the conditions of the year (3.0 ... 24.7%) and the interaction of these factors (11.4 ... 29.2%). A positive relationship was noted between the content of soluble solids in fruits and the sugar-acid index (r = 0.85), the content of sugars (r = 0.76), acids (r = 0.50), the sum of positive summer temperatures (r = 0.69 ); an insignificant negative relationship with vitamin C (r = -0.45) and summer precipitation (r = -0.60). Sources of a high content of soluble solids in fruits (21.84 ... 26.49%) in the breeding can be Shelangovskaya, Pamyat Sakharova, Sevastyanovskaya varieties, selected forms - Chereshnevaya No. 1, 1-11-31, 80-8, 1-10 -30 and 37-8; high content of vitamin C (15.16 ... 15.90%) - varieties Shelangovskaya, Low-growing and selective form Chereshnevaya No. 1. In industrial, farm, collective gardening it is recommended to use varieties Shelangovskaya, Pamyat Sakharova, Sevastyanovskaya.

Translocation of photoassimilates in melon vines and fruits under salinity using 13C isotope

Both yield and quality of Cantaloupe melon in semi-arid regions are threatened by high levels of salinity in irrigation waters. Our study aimed to characterize the translocation of photoassimilates in melon plants cultivated under salinity condition, using carbon 13 (13CO2) isotopic enrichment. Plants of the melon hybrid ‘Zielo’ were cultivated and drip-irrigated with waters of electrical conductivity (ECw) of 0.5 and 3.5 dS m−1. Leaves were evaluated for concentrations of Na, Cl, and sucrose and their CO2 assimilation rate. Fruits were evaluated for their weight, yield, sucrose, and soluble solids. Salinity stress affected both assimilation and accumulation of sugars, decreased fruit number and size. The natural (before enrichment) and enriched 13C in leaves from three stem regions and fruits were evaluated in the two final weeks of the crop cycle. The isotopic enrichment was applied to leaves of the basal and apical regions of the primary stem and apical leaves of the secondary stem. Although Na and Cl accumulated in all leaves, accumulation was the highest in basal leaves, causing a significant reduction of net assimilation of CO2 in these leaves. Although salinity significantly reduced fruit numbers and weight, it did not affect fruit soluble solids. Under saline conditions, leaves had a greater isotopic preference for the fixation of 13C than 12C. Two weeks before fruit harvest, regardless of salinity, fruits were the preferential sinks for carbon originated from leaves from the basal and apical parts of the stem. During fruit harvest week, basal and apical leaves of plants irrigated with water of ECw =0.5 dS m−1 had little or no 13C contribution to the fruit, whereas leaves (mainly basal) of plants irrigated with ECw =3.5 dS m−1 continued to send photoassimilates to the fruit. Thus, saline stress reduced fruit size and number significantly and delayed carbon translocation to fruits, delaying fruit maturation. Results suggest that under saline stress, eliminating fertigation two weeks before fruit harvest to reduce fertilizer costs may not be beneficial to melon producers. However, fertigation can be stopped in the last week before harvest when using low-salinity water. Further studies are needed to determine if extending the crop cycle under salinity may compensate for delayed fruit maturation and increase fruit sugars.

A Comparative Study of PLSR and SVM-R with Various Preprocessing Techniques for the Quantitative Determination of Soluble Solids Content of Hardy Kiwi Fruit by a Portable Vis/NIR Spectrometer.

Linear partial least square and non-linear support vector machine regression analysis with various preprocessing techniques and their combinations were used to determine the soluble solids content of hardy kiwi fruits by a handheld, portable near-infrared spectroscopy. Fruits of four species, namely Autumn sense (A), Chungsan (C), Daesung (D), and Green ball (Gb) were collected from five different areas of Gwangyang (G), Muju (M), Suwon (S), Wonju (Q), and Yeongwol (Y) in South Korea. The dataset for calibration and prediction was prepared based on each area, species, and in combination. Half of the dataset of each area, species, and combined dataset was used as calibrated data and the rest was used for model validation. The best prediction correlation coefficient ranges between 0.67 and 0.75, 0.61 and 0.77, and 0.68 for the area, species, combined dataset, respectively using partial least square regression (PLSR) method with different preprocessing techniques. On the other hand, the best correlation coefficient of predictions using the support vector machine regression (SVM-R) algorithm was 0.68 and 0.80, 0.62 and 0.79, and 0.74 for the area, species, and combined dataset, respectively. In most cases, the SVM-R algorithm produced better results with Autoscale preprocessing except G area and species Gb, whereas the PLS algorithm shows a significant difference in calibration and prediction models for different preprocessing techniques. Therefore, the SVM-R method was superior to the PLSR method in predicting soluble solids content of hardy kiwi fruits and non-linear models may be a better alternative to monitor soluble solids content of fruits. The finding of this research can be used as a reference for the prediction of hardy kiwi fruits soluble solids content as well as harvesting time with better prediction models.

Efficient management of the application of paclobutrazol for the production and quality of 'Tommy Atkins' mango

The application of paclobutrazol (PBZ) by irrigation system to induce the flowering of mango may be an economically and environmentally more efficient practice. The objective of this work is to determine the most efficient dose of PBZ to be applied by irrigation system to manage the production and quality of fruits of the mango cultivar ‘Tommy Atkins’ in the middle region of the São Francisco Valley. The experimental design was randomized blocks with five paclobutrazol doses applied by irrigation system (0.5, 1.0, 1.5, 2.0 and 2.5 g a.i.-1, linear canopy) and an additional treatment (control) with the application of a dose using the conventional form (2.0 g a.i.-1 linear canopy applied manually by haul), and four replications. The variables analyzed were number of panicles, panicle length, number of fruits per plant, average fruit weight, production per plant, economic viability, and qualitative characteristics of fruits. The application of paclobutrazol by irrigation system is more efficient than the conventional application, in which the dose 1.4 g a.i.-1 linear canopy provided a greater number of fruits and a greater production per plant. The highest content of total soluble solids in fruits was obtained at the dose 1.3 g a.i.-1 linear canopy, and acidity decreased as the applied dose of PBZ increased. Regarding the economic analysis, the results show that the application of PBZ by irrigation system increases the revenue by R$ 5,328.00 per hectare in comparison with the conventional application.

Iodine biofortification of field-grown strawberries – Approaches and their limitations

The potential of iodine biofortification in strawberry fruits by means of soil and foliar fertilization was investigated in three field experiments and a preliminary phytotoxicity test in the greenhouse. In the main experiment iodine was applied by one-time potassium iodate soil drenches two weeks after planting or, alternatively, by using potassium iodide foliar sprays from the beginning of flowering. Beside the iodine accumulation in fruits, effects on crop yield and quality were determined. The soil fertilization resulted in a relatively low iodine accumulation in strawberry fruits, probably because the concentration of phytoavailable iodine in the soil rapidly decreased after its application. A markedly higher iodine content in fruits was achieved when it was aerially applied, either by a single treatment shortly before harvest or by repeated sprays during the flowering period. Yield, firmness and total acidity concentration of strawberry fruits were not significantly affected by any of the tested iodine applications. However, as a result of repeated foliar sprays the concentration of soluble solids in fruits was slightly diminished. Attemps to substantially increase the iodine content in fruits of strawberry plants cultivated in the second and third year failed, even following frequent sprays. In conclusion the results of this study suggest that only a relatively small proportion of exogenously applied iodine enters the fruits of field-grown strawberries due to its strong retention in soil and low phloem mobility in plants.

Cultivar Selection and Placement of Shadecloth on Midwest High Tunnels Affects Colored Bell Pepper Yield, Fruit Quality, and Plant Growth

Growing colored bell peppers in high tunnels enhances fruit quality and accelerates ripening. While there are benefits to high tunnel pepper production, increased heat inside the structures can lead to plant stress, blossom drop, sunscald, and reduced marketable yields. The objective of this study was to test shadecloth treatments placed on high tunnels to mitigate heat stress and improve colored bell pepper yield and fruit quality, while also identifying cultivars that perform well within Midwest high tunnel systems. Research was conducted at the Iowa State University Horticulture Research Station (Ames, IA) from 11 May to 11 Oct. in 2017 and 3 May to 9 Oct. in 2018. Six single-poly passively ventilated Quonset high tunnels were used for the experiment. The shade treatments (no shadecloth, 30% light-reducing shadecloth, and 50% light-reducing shadecloth) were applied in June of each season. Within each shade treatment, there were three randomized complete blocks of the seven colored bell pepper cultivars (Archimedes, Delirio, Flavorburst, Red Knight, Sirius, Summer Sweet, and Tequila). Data were collected on yield, fruit quality, and plant growth characteristics. Environmental parameters were monitored throughout the growing season. Both the 30% and 50% shadecloth treatments reduced monthly average and maximum air temperatures within high tunnels, with the largest differences occurring in the months of July and August. The use of a shadecloth reduced the incidence of sunscald by 59% between no shade and 50% shadecloth treatments. While there was no difference between 30% and 50% shade treatments, the use of 50% shadecloth caused a decrease in both marketable number (32%) and weight (29%) of pepper fruit compared with the control. ‘Tequila’, ‘Delirio’, and ‘Flavorburst’ had more marketable fruit per plant. Shade treatments did not affect fruit soluble solids content (SSC), pH, or total titratable acidity (TTA). Shade treatments had no effect on Soil Plant Analysis Development (SPAD) readings, shoot biomass, the number of leaves per plant or the total leaf area per plant; however, plant height increased by an average 14.5 cm for plants under shadecloth treatments. Average leaf size was 11.2 cm2 larger on plants grown under the 50% shadecloth, compared with the control. Several cultivar differences existed for each fruit quality and plant growth parameter. While differences in fruit quality and plant growth parameters were limited among shade treatments, decreasing marketable yield is concerning. Our research suggests that Midwest growers should not exceed 30% light-reducing shadecloth on their high tunnels for colored bell pepper production.

Response of kiwifruit yield and fruit quality to chloride‐containing fertilizers

AbstractA 3‐yr field experiment was conducted to determine the effects of chloride‐containing fertilizer application on the yield and fruit quality of kiwifruit and the distribution of chloride ions (Cl–) in plants and soil. Five chlorine treatments were applied in a 10‐yr‐old kiwifruit (Actinidia deliciosa ‘Hayward’) orchard: (1) CO(NH2)2 + Ca(H2PO4)2 + K2SO4 (control, 0 kg Cl ha−1); (2) CO(NH2)2 + Ca(H2PO4)2 + 1/2KCl + 1/2K2SO4 (170 kg Cl ha−1); (3) CO(NH2)2 + Ca(H2PO4)2 + KCl (340 kg Cl ha−1); (4) 1/2CO(NH2)2 + 1/2NH4Cl + Ca(H2PO4)2 + KCl (910 kg Cl ha−1); and (5) NH4Cl + Ca(H2PO4)2 + KCl (1480 kg Cl ha−1). In terms of the 3‐yr average (2015–2017), a higher yield of kiwifruit was obtained under chlorine treatments at levels of 170 and 340 kg Cl ha−1, which increased by 18 and 12.5% compared with the control. Despite no significant differences in fruit soluble solids, titratable acid, and soluble sugar contents, all chlorine treatments, especially 910 and 1480 kg Cl ha−1, resulted in less vitamin C content after 3 yr of application compared with the control. Increasing chlorine application increased Cl– concentrations in both the plants and soil; however, maximum concentrations did not exceed the safe concentrations (&lt;20 g kg−1 and &lt; 400 mg kg−1, respectively). In conclusion, applying a restricted amount of chloride‐containing fertilizers (170–340 kg Cl ha−1) could increase kiwifruit yield under the experimental conditions, with no harm to plant leaves or soil.

Bell Pepper (Capsicum annum L.) under Colored Shade Nets: Fruit Yield, Postharvest Transpiration, Color, and Chemical Composition

Colored shade nets may affect plant growth and fruit yield of horticultural crops. The understanding of how colored shade nets influence plants, however, is far from complete. The objective of this study was to determine the effects of colored shade nets on bell pepper fruit yield, postharvest transpiration, color, chemical composition, and antioxidant capacity. The experiment was conducted in Tifton, GA, during the spring of 2015 and 2016. The experimental design was a randomized complete block with four replications and five colored shade net treatments (black, red, silver, and white nets, and an unshaded control). The nets were placed on the top of wooden rectangular structures (15 m wide × 6 m long × 5 m high), leaving the sides of the structures uncovered. Results showed that in both 2015 and 2016, marketable and total fruit number, yield, and individual fruit weight were reduced under the unshaded treatment. There were inconsistent differences in marketable and total fruit number, yield, and individual fruit weight among colored shade nets. Postharvest fruit transpiration and skin permeance were also reduced in unshaded conditions, and no differences were found among colored shade nets. Fruit color L* and b* values were highest, and a* value was lowest in unshaded conditions. Fruit soluble solids, total phenols, flavonoids, and antioxidant capacity [Cupric Reducing Antioxidant Capacity (CUPRAC) and Trolox Equivalent Antioxidant Capacity (TEAC)] responded differently among colored shade nets in the 2 years. Total phenols, flavonoids, and TEAC, however, were among the highest in unshaded conditions. In conclusion, results of the present study support previous findings that shade nets increase fruit yield and quality in bell pepper compared with fruit produced in unshaded conditions. Nevertheless, there were no consistent differences in fruit total and marketable yield and postharvest fruit transpiration and chemical composition of fruit produced under colored shade nets.

Impacts of Vaccinium arboreum Rootstocks on Vegetative Growth and Yield in Two Southern Highbush Blueberry Cultivars

Vaccinium arboreum Marsh is a small tree adapted to low-organic matter soils and is one of the few ericaceous species that tolerates soil pH greater than 6.0. It has a deep root system and is more drought tolerant than cultivated blueberry. The use of V. arboreum as a rootstock for commercial blueberry production has been studied previously in young blueberry plantings. The objective of the current study was to expand on earlier work and evaluate growth, productivity, and tolerance to bacterial leaf scorch (Xylella fastidiosa) in established plantings of own-rooted vs. grafted southern highbush blueberry (SHB). Two field plantings of grafted and own-rooted ‘Meadowlark’ and ‘Farthing’ SHB were established in May 2011: one at the University of Florida–Institute of Food and Agricultural Sciences (UF-IFAS) Plant Science Research and Education Unit in Citra, FL, and the other at a commercial blueberry farm in Archer, FL. At both sites, four rootstock–scion combinations were grown in either pine bark-amended or nonamended soil. Canopy volume was greater in grafted compared with own-rooted ‘Meadowlark’ at both locations throughout the 4 years of the study (2015–18), whereas canopy volume in ‘Farthing’ was not consistently different. For both cultivars and both locations, canopy volume was greater on amended compared with nonamended soil. Although canopy growth was not consistently increased in the grafted compared with own-rooted plants, yield was greater in grafted plants of both cultivars at both locations. Cumulative yield over the 4 years was similar between grafted plants grown on both amended and nonamended soil, and was significantly greater than yield of own-rooted plants on nonamended soil, suggesting the use of this rootstock may decrease the requirement for pine bark amendment. In general, grafted plants produced larger berries, with no negative impacts on fruit soluble solids, titratable acidity, or firmness. ‘Meadowlark’—an SHB cultivar that exhibits high sensitivity to bacterial leaf scorch—displayed decreased development of bacterial leaf scorch symptoms when grafted onto V. arboreum compared with own-rooted plants. These results indicate the potential benefits of grafting SHB onto V. arboreum rootstock, particularly under marginal soil conditions. However, a complete economic analysis that also takes into account any differences in longevity between the two systems must be done to determine whether the benefits of using grafting are feasible financially for the grower.

Paclobutrazol in the flowering management affects the quality of Malpighia emarginata fruits

ABSTRACT Floral management using the growth regulator paclobutrazol may be an alternative for promoting the uniformity of flowering and fruiting in West Indian cherry (Malpighia emarginata D.C.) plants. However, the effects of its use on fruit quality are still unknown. This study aimed to evaluate the effect of paclobutrazol doses on the fruit quality of M. emarginata. The experimental design was randomized blocks, in a 2 x 5 factorial arrangement, with three replications and three plants per plot, with the studied factors consisting of two M. emarginata cultivars ('Junko' and 'Flor Branca') and five paclobutrazol doses (0, 0.4, 0.8, 1.2 and 1.6 g a.i. m-1 of canopy diameter). The following variables were evaluated: fruit mass, fruit transverse and longitudinal diameters, pH, soluble solids content, titratable acidity, soluble solids/titratable acidity ratio and vitamin C content. The use of paclobutrazol, to some extent, promoted the increase of fruit mass, longitudinal diameter and soluble solids contents. The 'Junko' cultivar presented a higher vitamin C content than that for 'Flor Branca', and the maximum vitamin C contents were obtained with the paclobutrazol doses of 0.64 and 0.81 g a.i. m-1, respectively for the 'Junko' and 'Flor Branca' cultivars. None of the studied factors promoted differences for pH and fruit acidity.

Nutrient Status and Root Density of Huanglongbing-Affected Trees: Consequences of Irrigation Water Bicarbonate and Soil pH Mitigation with Acidification

The Candidatus Liberibacter asiaticus bacterium, associated with Huanglongbing (HLB) disease of citrus trees, moves downward in the phloem and infects the roots soon after transmission by the Asian Citrus Psyllid (Diaphorina citri) vector into shoots. Before canopy symptoms appear, 30–50% of the roots are damaged. Without aggressive management to reduce abiotic and biotic stress, root loss increases to 70–80%. An extensive survey of HLB-affected groves in central and south-central Florida indicated that a greater decline in fibrous root health as well as a greater expression of HLB symptoms is observed where irrigation water is high in bicarbonates (&gt;100 mg L−1) and soil pH is &gt;6.5. Over three seasons of survey, acidification of irrigation water in the central and south-central citrus growing regions of Florida reduced the decline in root density associated with HLB. Irrigation water treatment with sulfuric acid and soil amendment with elemental sulfur for 36 months to establish a soil pH range from 4.0 to 7.0 increased root growth, soil nutrient availability, and the uptake of Ca, Mg, Mn, and Zn in response to a gradual reduction in soil pH in young and mature Valencia orange groves on Swingle citrumelo rootstock. The reduction in soil pH increased yield and soluble solids in fruit and so would improve citrus production.

Effects of three irrigation systems on ‘Piel de sapo’ melon yield and quality under salinity conditions

The melon crop is moderately sensitive to soil salinity and, as a consequence, its yield decreases under saline conditions. Nevertheless, the exposure to moderate salinity also influences the melon quality by improving it, which offers compensation to the farmer. As a consequence, in moderately salt-affected lands, like the traditional irrigation area of the ‘Vega Baja del Segura’ (Alicante, Spain), melons are being grown. In this area the modernization of the secular irrigation system through the replacement of flood by drip systems, is currently being fostered. This fact, however, is generating some controversy, due to the known salt leaching effect that flood irrigation followed by drainage makes in the soil. In this study, the effects of three irrigation systems, namely, drip (DI), subsurface drip (SDI) and flood (FI), on soil salinity and thus, on the yield and quality of the melon, were compared. According to the results, the FI system kept the soil salt levels during the growth period at 4.1 ± 0.3 dS/m, that is, significantly lower than the 4.7 ± 0.2 dS/m attained with the DI and SDI systems. Nevertheless, the DI and, overall, SDI, provided higher and more homogenous soil moisture completely counteracting the effect of salinity as revealed by the soil water potential calculations. As a result, the SDI gave 27 ± 5 Mg/ha of total yield in comparison to 23 ± 2 Mg/ha (DI) and 20 ± 6 Mg/ha (FI). Besides, the SDI system reduced the number of damaged melons, thus additionally contributing to the significant higher marketable yield of the SDI (25 ± 4 Mg/ha) in comparison to the DI (20 ± 1 Mg/ha) and the FI (19 ± 7 Mg/ha). On the contrary, in the SDI treatment the fruit soluble solids content, tritatable acidity and pulp firmness decreased a bit, however, in the sensory evaluation no differences among irrigation treatments were observed.

II. Horticultural performance of ‘Honeycrisp’ grown on a genetically diverse set of rootstocks under Western New York climatic conditions

A field experiment with 31 rootstocks representing a genetically diverse group of rootstocks featuring ‘Honeycrisp’ as the scion was planted in 2010 at Geneva, NY USA. Rootstocks included three from the Malling series (UK), nine from the Budagovsky series (Russia), 16 from the Cornell Geneva series (USA) and three from the Pillnitz series (Germany). Over the first 8 years (2010–2017) we measured final tree size (trunk cross-sectional area: TCA) and cumulative yield. In the last 4 years we measured fruit soluble solids, bitter pit incidence, biennial bearing, and leaf zonal chlorosis. Tree size varied dramatically with the largest trees on B.70-20-20 and smallest trees on B.71-7-22. Setting the most vigorous rootstock at 100% we categorized rootstocks into 5 size categories: sub-dwarfing class (10–25%), dwarfing class (25–35%), semi-dwarfing class (35–50%), semi-vigorous category (50–70%) and vigorous class (70–100%). Cumulative yield varied 8 fold between the highest yielding rootstock (CG.3001) and the lowest yielding rootstock (B.71-7-22). We calculated theoretical yield per ha by multiplying cumulative yield per tree by a theoretical optimal tree density (trees/ha) based on tree size (TCA). The dwarfing rootstocks G.814, G.41TC, G.11 and B.10 had the highest yields per hectare while the most vigorous rootstocks B.70.20.20 and B.71-7-22 were the least productive. Theoretical cumulative yields varied from a high of 400 t/ha to a low of 50 t/ha, an 8-fold difference. Rootstock also influenced the incidence of bitter pit with the lowest levels of bitter pit with the rootstocks B.10, CG.2034, B.71-7-22, G.41N, CG.4003, G.202N, G.214, and Supporter 3. Considering bitter pit, yield, and optimum tree density, the theoretical yield of bitter pit free fruit varied from a high of 340 t/ha to a low of 35 t/ha, almost a 10-fold difference. The dwarfing rootstocks B.10, G.11, G.41TC, G.214 and G.814 had the highest yields per hectare of bitter pit free fruit. Rootstocks B.9 and M.26 had significantly lower cumulative bitter pit free yield/ha. These data indicate that rootstock not only has a large influence on mature tree cumulative yield but also bitter pit incidence which combine to create a large economic impact of rootstock choice on the long-term economic result of an orchard. This leads to the need for “designer rootstocks” which combine the rootstock characteristics needed to maximize the economic potential of each scion cultivar.

Low Temperature Storage Stimulates Fruit Softening and Sugar Accumulation Without Ethylene and Aroma Volatile Production in Kiwifruit.

Fruit ripening in response to propylene (an ethylene analog), 1-methylcyclopropene (1-MCP, an ethylene action inhibitor), and low temperature (5°C) treatments was characterized in “Kosui” kiwifruit (Actinidia rufa × A. chinensis). Propylene treatment induced ethylene production, with increased expression levels of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 1 (AcACS1) and ACC oxidase 2 (AcACO2), and rapid fruit softening together with increased expression levels of polygalacturonase (AcPG) and expansin 1 (AcEXP1) within 5 days (d). Fruit soluble solids concentration (SSC) and contents of sucrose, glucose, and fructose together with the expression levels of β-amylase 1 (Acβ-AMY1), Acβ-AMY2, and invertase (AcINV3-1) increased rapidly after 5 d exposure to propylene. Furthermore, propylene exposure for 5 d was sufficient to induce the production of key aroma volatile compounds, ethyl- and methyl butanoate, accompanied with increased expression levels of alcohol acyl transferase (AcAAT). Application of 1-MCP at the start of the experiment, followed by continuous exposure to propylene, significantly delayed fruit softening, changes in SSC and sugars, and strongly suppressed the production of ethylene, aroma volatiles, and expression of associated genes. During storage, fruit softening, SSC and sugar increase, and increased expression of genes associated with cell wall modification and carbohydrate metabolism were registered without detectable ethylene production; however, these changes occurred faster at 5°C compared to 22°C. Interestingly, ethyl and methyl butanoate as well as AcAAT expression were undetectable in kiwifruit during storage, while they were rescued by post-storage propylene exposure, indicating that the production of aroma volatile compounds is strongly ethylene-dependent. Transcript levels of a NAC-related transcription factor (TF), AcNAC3, increased in response to both propylene and low temperature treatments, while AcNAC5 was exclusively up-regulated by propylene. By contrast, transcript levels of a MADS-box TF, AcMADS2, exclusively increased in response to low temperature. The above findings indicate that kiwifruit ripening is inducible by either ethylene or low temperature signals. However, fruit ripened by low temperature were deficient in ethylene-dependent aroma volatiles, suggesting that ethylene signaling is non-functional during low temperature-modulated ripening in kiwifruit. These data provide further evidence that ethylene-dependent and low temperature-modulated ripening in kiwifruit involve different regulatory mechanisms.