Postharvest Period Research Articles

English

Loss of mass, shatter and decay are undesirable for fresh grapes, as they decrease the cluster quality during post-harvest conservation. The objective of this study was to assess the effect of abscisic acid (S-ABA) application on ‘Rubi’ grapes’ loss of mass, shatter, decay incidence and conservation periods. ‘Rubi’ grapes’ clusters used in the experiment were gotten from a commercial vineyard located in the town of São Miguel Arcanjo, SP, Brazil (23° 31’ S, 47° 35’ W and 660 m above sea level). The experimental design was completely randomized with subdivided plots and six replicates; the plots represented the concentration levels of S-ABA and the subplots represented the assessment days, starting on the day of harvest, extending up to 18 days after harvest. The concentrations of the isomer (S)-cis-abscisic acid (S-ABA) used were: Control (0 mg L-1); 400 mg L-1 of S-ABA at the beginning of maturation (BM); 400 mg L-1 in the BM + 200 mg L-1 at 25 days after the first application (25 DAFA); and 400 mg L-1 in the BM + 400 mg L-1 at 25 DAFA. The clusters were placed in expanded polystyrene trays and stored at room temperature (25.0 ± 5°C and 50 to 85% relative humidity (RH)). The loss of mass, berry shatter and decay incidence were assessed over the post-harvest conservation periods. The S-ABA influenced the evaluated characteristics. One application of S-ABA reduced shatter and decay incidence, while two applications (400 mg L-1 in the BM + 400 mg L-1 at 25 DAFA) reduced the loss of mass.   Key words: Post-harvest conservation, grapes, abscisic acid, shatter, decay incidence, cluster quality.

Effects of preharvest applications of natural antimicrobial products on tomato fruit decay and quality during long-term storage

The effects of preharvest sprays of Thyme essential oil, Propolis and Chitosan on postharvest quality and decay of a “long-storage” tomato, called “Vesuviano”, stored at room temperature for 120days, were investigated. Postharvest fruit quality [number of swollen-healthy fruits (SF), withered-healthy fruits (WF) and rotten fruits (RF)], organoleptic-related indexes (dry matter, soluble sugars, organic acids, volatiles) and health-related compounds (total carotenoids and phenols) were investigated at 40, 80 and 120days post-harvesting (T40, T80, T120). Propolis and Chitosan were able to reduce rotten fruits starting from T80, while the effect of Thyme was evident as early as T40. Furthermore Chitosan delayed fruit senescence (as expressed by SF/WF ratio) during the long-storage period. All treatments did not affect the overall postharvest quality, nevertheless some compounds (such as total soluble sugar for Chitosan and Thyme; total carotenoids and flavonols for Chitosan; total organic acids, 2-(E)-hexenal, 2-isobutylthiazole and terpenes for Propolis), were better retained than the control during postharvesting period. Among the three natural fungicides, Chitosan was most effective in reducing fruit senescence, maintaining a good quality of the fruits over a long-term.

Responses of Vitis vinifera L. cv. Sultanina to Water Deficits During Various Pre- and Post-Harvest Phases Under Semi-Arid Conditions

Performance of Sultanina grapevines irrigated at 60% plant-available water depletion (Tl) were compared to situations where water deficits were induced at budbreak (T2), before flowering (T3), after flowering (T4), at pea size (TS) and during ripening (T6). The field trial was performed on a fine sandy soil at Upington in the Lower Orange River region in South Africa. Treatments Tl to T6 were irrigated at 60% plant-available water (PAW) depletion during the post-harvest period and winter. A further four treatments were irrigated at 60% PAW depletion from budbreak until irrigation was terminated three weeks (T7), seven weeks (TS), eleven weeks (T9) and fifteen weeks (TlO) after harvest, respectively. The periods of water stress induced during the various pre-harvest phenological phases were too short to have a significant effect on vegetative growth. Water deficits during the early season (T2, T3 and T4) tended to affect yield more negatively than deficits applied between pea size and harvest (TS and T6). Yield reduction was associated with tendencies toward reduced bunch differentiation, berry shed and smaller berries. Berry size was significantly reduced by water deficits induced after flowering (T4). Water deficits had no significant effect on juice sugar content or on total titratable acids. No choice-grade sun-dried raisins could be produced when grapevines were subjected to water deficits during ripening (T6). In comparison to continued irrigation at 60% PAW depletion and water deficits induced up to pea size, significant browning of dipped raisins produced from TS and T6 grapevines occurred during some seasons. In combination with low relative humidity, water deficits between pruning and budbreak (T7 to TlO) reduced yields significantly compared to continued irrigation at 60% PAW depletion throughout the post-harvest period. Low relative humidity and dry soil also induced delayed budbreak and stimulated excessive shoot growth after harvest to such an extent that cane mass was significantly higher compared to irrigation at 60% PAW depletion. Neither water deficits nor significant shoot regrowth during the post-harvest period had any effect on cane starch content at pruning.

Response of Colombar Grapevines to Irrigation as Regards Quality Aspects and Growth

Plant response in terms of root, shoot and trunk growth as well as berry growth and composition, was determined in an irrigation trial with Colom bar comprising four soil moisture regimes, moisture stress during five phenological stages and four irrigation systems. All measurements were taken over a period of time to show parameter changes during variousstages within a season. A dry 25% soil moisture regime as well as trickle irrigation improved the sugar/acid ratio by lowering the malate and total titratable acid (TT A) concentrations and by increasing the total soluble solids (TSS) compared to soil moisture regimes of 50%, 70% and 90% which showed no significant differences with regard to either juice composition or berry size. Both the 25% moisture regime and water stress during flowering and phase I of berry growth were detrimental to berry size and yielded high tartrate concentrations at veraison. Tricklers and micro-jets at a 90% soil moisture regime yielded similar curves for cumulative berry growth. Root growth studied in situ reached maxima at flowering and in the post harvest period. The 25% soil moisture regime suppressed formation of new roots. Trunk circumference measured annually was a reliable indicator of vine water stress. Daily measurements of trunk radius with the aid of dendographs showed a maximum growth rate in November as well as an une.xpected negative rate from veraison until harvesting. A programme for regulated irrigation according to the growth patterns of the various plant parts is set forth. Suppression of undesirable shoot growth without a deleterious effect on berry growth, and acquisition of a more favourable grape composition seems possible.

Seasonal Uptake of Nutrients by Chenin Blanc in Sand Culture: II. Phosphorus, Potassium, Calcium and Magnesium

The seasonal uptake of phosphorus, potassium, calcium and magnesium as well as their distribution in the vine were determined for Chenin blanc/99R vines grown in sand culture under South African climatic conditions. Phosphorus absorption showed two distinct peaks-the first ranging from after bud burst until veraison, and the second, less prominent, from about five weeks after harvest into the leaf fall period. Potassium was absorbed from about three weeks after bud burst until four to five weeks after harvest. No potassium was absorbed during leaf fall. Active absorption of calcium started after bud burst and continued until veraison. A second, less pronounced absorption period occurred during the six weeks before leaf fall. Similarly, absorption of magnesium started after bud burst and continued until veraison, after which the absorption rate decreased and ceased with the onset of leaf fall. A significant amount of the phosphorus and potassium absorbed during the post harvest period was retained in the permanent parts of the vine. However, most of the post harvest calcium and magnesium gains were lost through leaf fall. Most of the calcium retained by the permanent parts of the vine, was stored in the bark. There was an apparent translocation of potassium from the leaves to the permanent structure of the vine during leaf fall. This was not noticeable for any of the other three nutrients.

Timing of Nitrogen Fertilisation and the Effect of Poultry Manure on the Performance of Grapevines on Sandy Soil. IL Leaf Analysis, Juice Analysis and Wine Quality

The effects of timing of nitrogen fertilisation and of different sources (organic vs inorganic) on leaf analysis, juice analysis and wine quality for grapevines on a sandy soil with low organic material were investigated over a period of nine years. Two Vitis vinifera L. cultivars, viz. Bukettraube (white) and Heroldrebe (red), both grafted onto Ramsey, were used. The control (No) received no N, while three treatments each received SO kg N/ha in inorganic form. The N was applied either as three equal installments, split between budbreak, fruitset and post-harvest (N1), or as a single application at budbreak (Ni), or as a single post-harvest application (N3). A fifth treatment (N4) received SO kg N/ha at budbreak in the form of poultry manure. Total Nin leaf blades and petioles, sampled at fruitset, tended to be highest for Ni and lowest for N0, but differences were relatively small. The N03-N in petioles showed larger differences, with the value for No generally being significantly lower than that of inorganically fertilised treatments. A single application of N at budbreak (Ni), delayed maturity for both cultivars, while this was also the case for split applications (N1) for the more vigorous cultivar (Bukettraube). Total Nin juice was lowest for No and N4 and higher for N1, Ni and N3, for both cultivars. In the case of Bukettraube, assimilable N was lowest for No, while the other treatments did not differ. For Heroldrebe, with a lower sugar content, assimilable N was lowest for No, Nz and N4 and higher for N1 and N3. Arginine was the predominant amino acid, constituting 61 % and 40% of total amino-N for Bukettraube and Heroldrebe, respectively. Wine quality (Bukettraube only) was always lowest for No and higher for Ni, Ni and N3. During most seasons quality did not differ between the latter three treatments. However, with Nz being more prone to fungal diseases, wine quality was reduced for this treatment when climatic conditions favoured Botrytis cinerea infection. Wine from the organic treatment (N4) scored marginally higher than N1, Nz and N3. Under the conditions of this trial, split applications of N (budbreak, fruitset, post-harvest) or a single application during the post-harvest period, or application of organic N ensured highest wine quality. Reaction to N may be different for less vigorous rootstocks.

Timing of Nitrogen Fertilisation and the Effect of Poultry Manure on the Performance of Grapevines on Sandy Soil. I. Soil Analysis, Grape Yield and Vegetative Growth

A field trial with two Vitis vinifera L. cultivars, viz. Bukettraube (white) and Heroldrebe (red), grafted onto Ramsey, was carried out over a nine-year period on a sandy, duplex soil. The control (No) received no N, while three other treatments each received 50 kg N/ha in inorganic form. The N was applied either as three equal installments, split between budbreak, fruitset and post-harvest (N1), or as a single application at budbreak (N2), or as a single postharvest application (N3). A fifth treatment (N4) received 50 kg N/ha at budbreak in the form of poultry manure. A winter cover crop (rye) was sown after harvest, chemically controlled before budbreak with a herbicide and left as an organic mulch on the soil surface. This cover crop management system maintained the soil's organic material (SOM) at the original level for all inorganic treatments, while N4 increased SOM. On average, Bukettraube yielded 11.4 t/ha, in comparison to only 6.0 t/ha for Heroldrebe. Yields of the four fertilised treatments (Ni, N2, N3 and N4) were comparable for each individual cultivar. Relative to N0, fertilisation increased yields by 24% and 48% for Bukettraube and Heroldrebe, respectively. In comparison to the control, all four fertilisation treatments increased shoot mass, with Nz being significantly higher than Ni, NJ and N4. The fact that Nz stimulated shoot growth, without a concomitant increase in yield, indicated that a single application of N at bud break can cause excessive growth, even on low-potential soil. In the case of Bukettraube, grapes from the Nz treatment showed the highest incidence of bunch rot during some seasons. Under the cultivation practices followed in this trial, split applications of N (budbreak, fruitset, post-harvest) or a single application during the post-harvest period was compatible with the most desirable pattern of vine growth and fruit development. Application of poultry manure was not associated with any specific advantages or disadvantages. Soil analysis showed that the control vines were fairly well supplied with mineral N at budbreak, but under-supplied at the time of fruitset.

Seasonal Uptake of Nutrients by Chenin blanc in Sand Culture: I. Nitrogen

The seasonal uptake and the distribution of nitrogen were determined for Chenin blanc/99R, grown in sand culture under South African conditions. Whole vines were sampled 14 times in the course of one year. Two distinct absorption peaks were found-the first starting after bud burst and lasting up to veraison, while the second extended from harvest into the leaf fall period. The amount of nitrogen absorbed during the second (post harvest) period amounted to 34% of the total for the season, and most of this was stored in the roots.The amount of nitrogen removed by the crop (1,39kg/ton of grapes) compared well with relevant literature, but the amount of nitrogen in leaves and canes associated with this, differed from results obtained in other countries.

Fruit quality and differentially expressed genes of winter-harvested pineapple in response to elevated temperature over a short postharvest period

The aim of this work was to investigate the influences of elevated postharvest temperature (EPT) for 1d and 2d on the physicochemical quality of pineapple fruit and the differentially expressed genes (DEGs) underlying this process by RNA-seq. The results suggested that EPT increased the L*, a*, b* of pineapple fruit skin. EPT decreased the L* and increased the a* and b* of pineapple pulp. EPT increased the total soluble solid (TSS), sucrose content and TSS/titratable acidity (TA) ratio and decreased the TA. EPT decreased the firmness of pineapple fruit. At 1d, EPT improved the production of aromatic alkenes. At 2d, EPT improved the production of aromatic esters and decreased the alkenes. A differential gene expression analysis suggested that a total of 6725 and 5845 DEGs were identified by comparing EPT and control at 1d and 2d, respectively. A number of DEGs were screened for their involvement in the EPT process effects on pineapple fruit, including those associated with coloration, sugar/acid metabolism, texture softening and aroma biosynthesis. A subset of these DEGs was validated by qPCR, which was consistent with the corresponding Reads Per Kilo bases per Million reads (RPKM values) from RNA-seq. The findings of this study contribute to our understanding of how EPT regulates the quality of pineapple fruit over different durations and the molecular mechanisms underlying this process.

Multi-pollutant emissions from the burning of major agricultural residues in China and the related health-economic effects

Abstract. Multi-pollutants in smoke particulate matter (SPM) were identified and quantified for the biomass burning of five major agricultural residues (wheat, rice, corn, cotton, and soybean straw) in China by an aerosol chamber system combined with various measurement techniques. The primary emission factors (EFs) for PM1. 0 and PM2. 5 are 3.04–12.64 and 3.25–15.16 g kg−1. Organic carbon (OC), elemental carbon (EC), water-soluble inorganics (WSIs), water-soluble organic acids (WSOAs), water-soluble amine salts (WSAs), trace mineral elements (THMs), polycyclic aromatic hydrocarbons (PAHs), and phenols in smoke PM1. 0/PM2. 5 are 1.34–6.04/1.54–7.42, 0.58–2.08/0.61–2.18, 0.51–3.52/0.52–3.81, 0.13–0.64/0.14–0.77, (4.39–85.72/4.51–104.79) × 10−3, (11.8-51.1/14.0-131.6) × 10−3, (1.1–4.0/1.8–8.3) × 10−3, and (7.7–23.5/9.7–41.5) × 10−3 g kg−1, respectively. Black carbon (BC) mainly exists in PM1. 0; heavy-metal-bearing particles favour residing in the range of smoke PM1. 0−2. 5, which is also confirmed by individual particle analysis. With respect to the five scenarios of burning activities, the average emissions and overall propagation of uncertainties at the 95 % confidence interval (CI) of SPM from agricultural open burning in China in 2012 were estimated to be 1005.7 (−24.6, 33.7 %), 901.4 (−24.4, 33.5 %), 432.4 (−24.2, 33.5 %), 134.2 (−24., 34.0 %), 249.8 (−25.4, 34.9 %), 25.1 (−33.3, 41.4 %), 5.8 (−30.1, 38.5 %), 8.7 (−26.6, 35.6 %), 0.5 (−26.0, 34.9 %), and 2.7 (−26.1, 35.1 %) Gg for PM2. 5, PM1. 0, OC, EC, WSI, WSOA, WSA, THM, PAHs, and phenols , respectively. The emissions were further spatio-temporally characterized using a geographic information system (GIS) in different regions in the summer and autumn post-harvest periods. It was found that less than 25 % of the total emissions were released during the summer harvest, which was mainly contributed by the North Plain and the centre of China, especially Henan, Shandong, and Anhui, which are the top three provinces regarding smoke particle emissions. Flux concentrations of primarily emitted smoke PM2. 5 that were calculated using the box-model method based on five versions of emission inventories all exceed the carcinogenic-risk permissible exposure limits (PEL). The health impacts and health-related economic losses from the smoke PM2. 5 short-term exposure were assessed. The results show that China suffered from 7836 cases (95,% CI: 3232, 12362) of premature mortality and 7 267 237 cases (95 % CI: 2 961 487, 1 130 784) of chronic bronchitis in 2012, which led to losses of USD 8822.4 million (95 % CI: 3574.4, 13 034.2) or 0.1 % of the total GDP. We suggest that the percentage of open-burnt crop straw in the post-harvest period should be cut down by over 97 % to ensure a reduction in carcinogenicity risk, especially in the North Plain and the northeast, where the emissions should decrease at least by 94 % to meet the PEL. With such emission control, over 92 % of the mortality and morbidity attributed to agricultural fire smoke PM2. 5 can be avoided in China.

Control of black rot caused by Alternaria alternata in yellow pitahaya (Selenicereus megalanthus) through hot water dips

Black rot by Alternaria alternata causes the majority of losses in yellow pitahaya (Selenicereus megalanthus) during postharvest period. Leading strategy for decay control is the use of synthetic fungicides, but constraints associated with the use of this kind of products have led to the search for alternative methods to reduce fungal infections. The efficacy of hot water dips at different temperatures and times (40 °C for 1 min; 40 °C for 2 min; 50 °C for 1 min and 50 °C for 2 min) for controlling black rot on yellow pitahaya was evaluated by measuring disease severity on fruit pre-inoculated with A. alternata. The results showed that both treatments, 50 °C for 2 min and the imazalil fungicide (0.4 g L−1), significantly reduced lesion diameter (63.1 and 70.5%, respectively) after 21 days at 12 °C compared with non-treated control fruit. Hot water dips at 50 °C for 2 min before cold storage maintained firmness, reduced weight loss, slowed the changes in fruit skin color, soluble solid content (SSC) and titratable acidity (TA) and did not affect sensory quality of yellow pitahaya. These results showed that dips in hot water may provide a postharvest alternative treatment to control or reduce black rot caused by A. alternata in yellow pitahaya.

Tree ripening and postharvest firmness loss of eleven commercial nectarine cultivars under Mediterranean conditions

On-tree and postharvest softening of 11 yellow flesh nectarine cultivars with different commercial harvest seasons (early, mid and late) were studied under Mediterranean conditions (Lleida, NE-Spain). Fruit were harvested weekly at five consecutive harvest dates (from H1 to H5) over three consecutive years (2009–2011). Diameter, percentage of skin overcolor (SC), flesh firmness (FF), IAD index (the difference in absorbance between 670 and 720nm), visible reflectance spectra, soluble solids content (SSC), titratable acidity (TA), ethylene synthesis, objective skin color and postharvest softening rate were measured. The decline in flesh firmness and the IAD were both significantly affected by cultivar and ripening season. Low acid (TA<6g of malic acid L−1) cultivars such as ‘Big Top’, ‘Nectareine’, ‘Honey Royale’, ‘Big Nectared’ and ‘Nectalady’, had a lower firmness decline than acid ones (TA≥6g of malic acid L−1), both on-tree and during postharvest, resulting in a better commercial and postharvest performance. A high and significant positive correlation was found between IAD and flesh firmness (r=0.72, P≤0.01). Early cultivars tended to lose flesh firmness and IAD faster than mid and late cultivars. The softening rate during the postharvest period was mainly dependent on ripening season. Early ripening nectarines soften faster than mid and late ones.

Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system

To investigate the effect of nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (3MP + TZ), on N2O emissions and yield from a typical vegetable rotation in sub-tropical Australia we monitored soil N2O fluxes continuously over an entire year using an automated greenhouse gas measurement system. The temporal variation of N2O fluxes showed only low emissions over the vegetable cropping phases, but significantly higher emissions were observed post-harvest accounting for 50–70% of the annual emissions. NIs reduced N2O emissions by 20–60% over the vegetable cropping phases; however, this mitigation was offset by elevated N2O emissions from the NIs treatments over the post-harvest fallow period. Annual N2O emissions from the conventional fertiliser, the DMPP treatment, and the 3MP + TZ treatment were 1.3, 1.1 and 1.6 (sem = 0.2) kg-N ha−1 year−1, respectively. This study highlights that the use of NIs in vegetable systems can lead to elevated N2O emissions by storing N in the soil profile that is available to soil microbes during the decomposition of the vegetable residues. Hence the use of NIs in vegetable systems has to be treated carefully and fertiliser rates need to be adjusted to avoid an oversupply of N during the post-harvest phase.

Influence of Irrigation Scheduling Using Thermometry on Peach Tree Water Status and Yield under Different Irrigation Systems

Remotely-sensed canopy temperature from infrared thermometer (IRT) sensors has long been shown to be effective for detecting plant water stress. A field study was conducted to investigate peach tree responses to deficit irrigation which was controlled using canopy to air temperature difference (ΔT) during the postharvest period at the USDA-ARS (U.S. Department of Agriculture, Agricultural Research Service) San Joaquin Valley Agricultural Sciences Center in Parlier, California, USA. The experimental site consisted of a 1.6 ha early maturing peach tree orchard. A total of 18 IRT sensors were used to control six irrigation treatments including furrow, micro-spray, and surface drip irrigation systems with and without postharvest deficit irrigation. During the postharvest period in the 2012–2013 and 2013–2014 growing seasons, ΔT threshold values at mid-day was tested to trigger irrigation in three irrigation systems. The results showed that mid-day stem water potentials (ψ) for well irrigated trees were maintained at a range of −0.5 to −1.2 MPa while ψ of deficit irrigated trees dropped to lower values. Soil water content in deficit surface drip irrigation treatment was higher compared to deficit furrow and micro-spray irrigation treatments in 2012. The number of fruits and fruit weight from peach trees under postharvest deficit irrigation treatment were less than those well-watered trees; however, no statistically significant (at the p &lt; 0.05 level) reduction in fruit size or quality was found for trees irrigated by surface drip and micro-spray irrigation systems by deficit irrigation. Beside doubles, we found an increased number of fruits with deep sutures and dimples which may be a long-term (seven-year postharvest regulated deficit irrigation) impact of deficit irrigation on this peach tree variety. Overall, deployment of IRT sensors provided real-time measurement of canopy water status and the information is valuable for making irrigation management decisions.

Effects of regulated deficit irrigation on physiology, yield and fruit quality in apricot trees under Mediterranean conditions

Scarce water resources mainly in arid and semi-arid areas have caused an increasing interest for applying irrigation protocols aiming to reduce water spends. The effects of regulated deficit irrigation (RDI) on the performance of apricot trees (Prunus armeniaca L. cv. “Búlida”) were assessed in Murcia (SE Spain), during three consecutive growing seasons (2008-2010). The hypothesis was that RDI would not restrict yield but increase fruit quality while saving water. Two irrigation treatments were established: i) control, irrigated to fully satisfy crop water requirements (100% ETc) and ii) RDI, that reduced the amount of applied water to: a) 40% of ETc at flowering and stage I of fruit growth; b) 60% of ETc during the stage II of fruit growth and c) 50% and 25% of ETc during the late postharvest period (from 60 days after harvest). Stem water potential, gas exchanges, trunk cross-sectional area (TCSA), fruit diameter, yield and fruit quality traits were determined. Vegetative growth was decreased by the use of RDI (12% less TCSA on average for the three years), whereas yield was unaffected. In addition, some qualitative characteristics of the fruits, such as the level of soluble solids, sweetness/acidity relation and fruit colour, were improved by the use of RDI. These results and average water savings of approximately 30%, lead us to conclude that RDI strategies are a possible solution for irrigation management in areas with water shortages, such as arid and semi-arid environments.

English

The aim of this work was to evaluate the uniformity of fruit maturity and the productivity of conilon coffee in function of different periods of water stress in the post-harvest period. The study was conducted in a field from August 2014 to July 2015 in an old coffee crop of conilon coffee, cultivar Vitoria 'Incaper 8142', cultivated at a spacing of 3.0 × 1.2 m, located at the Federal Institute of Espirito Santo Campus Santa Teresa, ES, Brazil. The experimental design was in randomized blocks, with 4 treatments and 10 repetitions. Each useful plot consisted of 12 plants. The treatments consisted of the application of different levels of water deficit, being: control (continuous irrigation with humidity close to the field capacity) (T1); water deficit of 20 (T2); 40 (T3); and 60 (T4) days after harvest. Productivity was determined by harvesting and weighing the grains of each useful plot. The maturation uniformity was evaluated by random harvesting of 100 fruits in each plot. The application of the treatment with 60 days of water deficit presented greater uniformity of fruit maturation and water saving when compared to the other treatments. The treatment with estimated water deficit of 33 days after harvest showed higher average grain yield (79.2 sc ha-1). Key words: Coffea canephora, irrigation management, grain quality, water, productivity.

Carbohydrate distribution during berry ripening of potted grapevines: Impact of water availability and leaf-to-fruit ratio

Insufficient leaf photoassimilation could allow mobilized carbohydrate reserves to contribute to berry sugar accumulation. However, the extent of this contribution during rapid and slow berry sugar accumulation is undefined. The potential effect of leaf-to-fruit ratio and water availability on carbohydrate reserve distribution in potted Tempranillo grapevines was examined during berry maturation. Within each leaf-to-fruit ratio treatment (full and 50% leaves), vines were grown under full or 50% reduced irrigation regimes. Dry biomass development, and the starch and soluble sugar concentrations were determined in the roots, trunks, stems and leaves. Berry sugar and anthocyanin accumulation were also assessed. Under full irrigation, no starch remobilization from roots was observed, regardless of the leaf-to-fruit ratio. Under reduced water supply, starch remobilization from roots was concurrent with rapid berry sugar accumulation, especially in grapevines with low leaf-to-fruit ratio. Soluble sugar accumulation coincided with starch depletion in the roots of grapevines under reduced water availability. When berry sugar accumulation slowed, an increase in carbohydrates was observed in the roots. Sustained water constraints during rapid berry sugar accumulation resulted in a forced reliance on stored carbohydrates to support berry sugar accumulation, but did not significantly alter the tempo of berry sugar and anthocyanin accumulation. A reduced leaf-to-fruit ratio intensified the reliance of fruit sugar accumulation on stored carbohydrates. Besides the importance of post-harvest carbohydrate reserve replenishment when root carbohydrate reserves are depleted during berry maturation, the reserves are also refilled during maturation when berry sugar accumulation slows. This study showed distinctly that root carbohydrate replenishment could already start a few weeks before harvest, and this replenishment could be important when the post-harvest carbon assimilation period is ineffective.

QUALITY OF ‘TAHITI’ ACID LIME FERTILIZED WITH NITROGEN AND POTASSIUM IN THE SEMIARID REGION OF MINAS GERAIS

ABSTRACT This study aimed to evaluate external characteristics and juice obtained from ‘Tahiti’ acid lime produced under nitrogen and potassium fertilization. This study had a completely randomized design with three replicates of four fruits of the two central plants, 4 x 5 factorial and four N doses (0, 25, 50 and 100 Kg ha-1 year- 1) and five K2O doses (0, 25, 50, 100 and 200 Kg ha-1 year- 1), totaling 20 treatments. In the postharvest period, external characteristics (size, color and skin thickness, firmness and fresh mass) and juice (content, percentage, soluble solids, technological index, pH, titratable acidity, ratio and ascorbic acid) of fruits were evaluated. Size, skin color, soluble solids content and pH of ‘Tahiti’ acid lime juice were not affected by N and K2O fertilization. Skin thickness, juice percentage and technological index increased with the N and K2O doses applied to the soil. Juice content and fruit firmness decreased with application of K2O doses. Titratable acidity and ascorbic acid content increased with K2O doses. The different nitrogen and potassium doses influenced more the juice quality than the external characteristics of ‘Tahiti’ acid lime in the postharvest period.

Development of the Capital Service Market in Agriculture: The Emergence of Tractor-Hire Services in Ghana

This article examines the role of the capital service market in increasing the use of mechanical technology in smallholder agriculture. Custom hiring services have been essential to the widespread use of agricultural machines in many countries where small farms predominate. In the past, some governments in Africa south of the Sahara (SSA) had attempted to supply agricultural mechanization services when there was no demand for such services. Recently, however, demand for mechanization in SSA has been on the rise. Tractor ownership has also increased considerably among medium- and large-scale farmers, who use the tractors on their own land and also hire them out to others. Using the example of Ghana, we examine the behavior of tractor owners and the role they are expected to play in the development of mechanization in SSA. We use survey data from eight districts in the transition and savannah agroecological zones of Ghana. The survey covered 1,843 farming households, including 408 tractor owners and was aimed at characterizing the transition from smallholder farming to medium- and large-scale commercial farming, including patterns of agricultural-machinery ownership and patterns of demand for agricultural mechanization. First, we analyze the relationships between tractor ownership, farm size, and tractor service provision using correlation analyses. Second, we estimate a tractor service cost function based on the hypothesis that hiring a tractor service is not a perfect substitute for owning one, especially for large-scale farmers. Our findings suggest that providing tractor services significantly increases the rate of tractor use, a precondition for economic use of tractors. Agricultural mechanization service providers are primarily medium- and large-scale farmers. These farmers buy tractors even if they cannot make full use of them on their own farms, and they provide tractor services to fellow farmers. Smallholders' use of these services is quite high. Increasing tractor use is essential to counter any risk that may be associated with owning a tractor. Traveling to a different rainfall zone to provide services or extending tractor use during the postharvest period (e.g., for shelling) can help to achieve this objective. While service provision and markets offer strong potential for the widespread adoption of mechanization, medium-scale farmers in particular will be important for spreading the use of tractors among farmers in SSA. The findings presented here support our belief that mechanization can develop where there is potential for a service market, even under smallholder agriculture.

SENSITIVITY TO ENVIRONMENTAL STRESS OF PRATA,JAPIRA AND VITÓRIA BANANA CULTIVARS PROVEN BY CHLOROPHYLL a FLUORESCENCE

ABSTRACT This study aimed to evaluate the physiological responses to environmental stress during pre- and post-harvest of the following banana cultivars: Prata (AAB), Japira (AAAB) and Vitoria (AAAB). Analyses were carried out on young plants at vegetative stage (daughter-plant) and adult plants at reproductive stage (motherplant). The experimental design was completely randomized. In the in vivo pre-harvest analysis were used seven replications, in a factorial scheme (3x2x2), three cultivars and two stages (vegetative and reproductive) and two collection periods (March and June). For the analysis of post-harvest quality were used five replications in a factorial design (3x2x5), corresponding to three cultivars, two development stages and five periods of post-harvest analysis, carried out every two days from stage 4 of fruit ripening. The chlorophyll a fluorescence emission kinetics showed low photochemical performance of the three cultivars in June, a period characterized by lower temperatures and water deficit. Prata was the cultivar with the lowest tolerance to abiotic physiological behavior changes, which also reflected in fruit quality, because there was a change in physical and physicochemical parameters. Japira and Vitoria cultivars showed similar physiological responses in the pre- and post-harvest periods, according to their phylogenetic proximity. The total performance index, i.e., the conservation of energy absorbed by PSII up to the reduction of the final PSI acceptors (PItotal) and the di-malonic aldehyde (MDA) content were significantly higher in Japira and Vitoria cultivars compared to Prata cultivar in the reproductive phase. There was no significant change in the potential quantum efficiency of PSII (FV / FM = jP0) among the three cultivars. It was concluded that Japira and Vitoria cultivars showed greater plasticity to tolerate or even adapt to abiotic variations keeping higher fruit yield. PItotal is the most sensitive parameter during the banana life cycle and important tool for distinguishing different cultivars yields.