Decreased Fruit Yield Research Articles

Light‐limited photosynthesis under energy‐saving film decreases eggplant yield

AbstractGlasshouse films with adjustable light transmittance and energy‐efficient designs have the potential to reduce (up to 80%) the high energy cost for greenhouse horticulture operations. Whether these films compromise the quantity and quality of light transmission for photosynthesis and crop yield remains unclear. A “Smart Glass” film ULR‐80 (SG) was applied to a high‐tech greenhouse horticulture facility, and two experimental trials were conducted by growing eggplant (Solanum melongena) using commercial vertical cultivation and management practices. SG blocked 85% of ultraviolet (UV), 58% of far‐red, and 26% of red light, leading to an overall reduction of 19% in photosynthetically active radiation (PAR, 380–699 nm) and a 25% reduction in total season fruit yield. There was a 53% (season mean) reduction in net short‐wave radiation (radiometer range, 385–2,105 nm upward; 295–2,685 nm downward) that generated a net reduction of 8% in heat load and reduced water and nutrient consumption by 18%, leading to improved energy and resource use efficiency. Eggplant adjusted to the altered SG light environment via decreased maximum light‐saturated photosynthetic rates (Amax) and lower xanthophyll de‐epoxidation state. The shift in light characteristics under SG led to reduced photosynthesis, which may have reduced source (leaf) to sink (fruit) carbon distribution, increased fruit abortion and decreased fruit yield, but did not affect nutritional quality. We conclude that SG increases energy and resource use efficiency, without affecting fruit quality, but the reduction in photosynthesis and eggplant yield is high. The solution is to re‐engineer the SG to increase penetration of UV and PAR, while maintaining blockage of glasshouse heat gain.

The influence of compact sowing on tomato yield and economic efficiency of its cultivation

Purpose. To identify the possibility of tomato cultivation in compact sowing and obtaining additional yield of compacting plants in the Northern Steppe of Ukraine. Methods. The studies were carried out in 2016–2018 at the Dnipropetrovsk Experimental Station of Institute of Vegetable and Melon Growing of NAAS. Field trials were laid out as both transplanting and direct seeding crop at row spacing of 1.4 m with drip irrigation system. Tomato was the main crop; grey shallot for use as green onions and sweet corn for use in milk-wax ripeness were the compacting (companion) plants. The total yield of the main crop and the compacting plants with calculating the efficiency of cultivation in compact sowing was measured after the crops were harvested according to the experimental technique in vegetable and melon growing. Results. Tomato compact sowing influenced on plant growth and development, as well as was reflected in yield components. The average tomato fruit weight with shallot compacting was almost the same as in the control with no compacting (59.2 vs. 59.7 g in transplanting crop and 56.2 vs. 56.8 g in direct seeding crop) while with sweet corn compacting it was lower by 7.1 and 10.2 %. The yield of tomato in the control variant was 42.2 t/ha in transplanting crop and 37.7 t/ha in direct seeding crop; when shallot compacting, it was reduced by 1.6 and 1.7 t/ha and was within the standard error. A more noticeable decrease in fruit yield (by 2.7 and 3.1 t/ha or 6.4 and 8.2 %) as compared to the control was revealed with sweet corn compacting. Additionally, it was produced 9.3 and 8.9 t/ha of grey shallot, 2.6 and 2.5 t/ha of sweet corn. The more total yield (49.8 t/ha) was obtained with shallot compacting in transplanting crop that exceeds the control by 7.6 t/ha (18 %). The total yield of tomato and sweet corn was within the control variant (42.1 and 37.1 t/ha). The profit and profitability depended on productivity of the main crop and the compacting plants. The total profit through various variants of compact tomato sowing was 87,000–146,600 UAH/ha that exceeded the control by 4,600–48,600 UAH/ha. The profitability level increased by 6.5 and 21.0 % with shallot compacting and by 12.7 and 6.5 % with sweet corn compacting. The most total profit (146,600 and 124,500 UAH/ha) and profitability level (186.3 and 199.5 %) were obtained when compact tomato sowing with shallot as compared to sowing with no compacting. Conclusions. Resulted from the research, elements of the technology for growing tomato with compact sowings in the conditions of the Northern Steppe of Ukraine have been developed which provide an increase in the yield of vegetable products per unit area due to compacting plants.

Precision cane meristem management can influence productivity and fruit quality of floricane red raspberry cultivars

In Bosnia and Herzegovina, the hedgerow system is the main raspberry growing system, which has no clearly-defined standards regarding plant density and fruit-bearing potential per meter of hedgerow. This study evaluates the effect of precision cane meristem management in growing major floricane red raspberry cultivars in Bosnia and Herzegovina. During 2015 and 2016, in Willamette, Meeker, and Tulameen, grown under the hedgerow system, mixed buds were selected on fruiting laterals with the fruitbearing potential of 80, 100, and 120 well-developed and well-positioned mixed buds per meter of hedgerow. High stable yields were recorded under the medium load of 100 buds per meter of hedgerow. Yield ranged from 22.6 t/ha to 24.9 t/ha in Meeker and from 17.7 t/ha to 24.5 t/ha in Tulameen. The yield variation over the experimental years was somewhat higher in Willamette (10.4-21.8 t/ha). Fruit size was largest under the 100-bud load per meter of hedgerow. The biochemical characteristics of the fruit, expressed through vitamin C, phenol, flavonoid, and anthocyanin contents, and the antioxidant capacity, indicated differences among cultivars and the effect of the experimental year. The load of 100 mixed buds well-positioned on canes per meter of hedgerow was the optimum load of fruit-bearing potential. The reduction in bud numbers per meter of hedgerow led to a significant decrease in fruit yield, with no changes in fruit quality. Conversely, the increase in the number of buds per meter of hedgerow resulted in a decline in fruit quality, while not adversely affecting fruit yield.

How Soil Ecological Intensification by Means of Cover Crops Affects Nitrogen Use Efficiency in Pepper Cultivation

Ecological intensification, based on agricultural practices that promote ecosystem services, has been recently proposed to match crop yield and environmental concerns. Two-year experiments were conducted in a Mediterranean environment. The treatments were: (i) four intensification levels (common vetch (CV), ryegrass (RG), bare soil without Nitrogen (N) fertilization (Control-N0) and with 100 kg ha−1 of N fertilization (Control-N100) applied during pepper cultivation), and(ii) two soil tillage [soil tillage at 15 cm and 30 cm of soil depth (ST-15 and ST-30, respectively)]. The field experiment was disposed in a randomized block design with three replications. Cover crop, soil samples, and pepper samples were collected for analysis. Soil available nitrogen increased after soil tillage, especially in CV, which showed the highest fruit yield. The reduced soil N availability in RG decreased fruit yield and N uptake. The agro-physiological efficiency of pepper was similar in common vetch and Control-N100, while it was low in ryegrass. However, the adoption of RG increased the soil organic matter more than both control treatments, which, in turn, caused a depletion of soil organic matter. Moreover, reduced tillage practices for green manuring that both cover crops arepreferable to reduce external inputs in terms of fuel saving and farming operations.

Coriander (Coriandrum sativum L.) response to different levels of agronomic factors in Poland

Crop yields are determined by complex interactions between various agronomic factors. Knowledge of crop responses to various levels of agronomic inputs and their interactions is essential for developing high-yielding production technologies. Field experiments with the sk−p fractional factorial design are highly useful for selecting the optimal production technology for crops whose agronomic requirements have been insufficiently researched under specific agroecological conditions.A field experiment with the sk−2 fractional factorial design and resolution IV, with five factors (k = 5) at three levels (s = 3), was performed at the Agricultural Experiment Station in Bałcyny (north-eastern Poland) in 2006–2008. Experiments with the 35−2 fractional factorial design offer a rapid and relatively cheap method for determining the influence of various agronomic factors and their interactions on crop yields. The results of multifactorial experiments conducted under the same weather and soil conditions facilitate the choice of the optimal production technology and the determination of the optimal intensity of the main agronomic treatments.This study analyzed the responses of coriander to the key yield-forming factors (seeding date, rates of phosphorus, potassium, magnesium, sulfur, and micronutrient fertilization) and yield-protection factors (weed control and fungal disease management). In the agroecological conditions of north-eastern Poland, weed control had a significant influence on the yield of coriander fruits. The highest fruit yield was obtained in the treatment where herbicide (1500 g ha−1 metobromuron) was applied to the soil after sowing. Mechanical weed control (single inter-row treatment in the two leaves unfolded stage) reduced fruit yields by nearly 20%, whereas the absence of weed control decreased fruit yields by 62%. The treatments where various weed control methods were applied differed in the number of coriander plants m−2. Chemical weed control increased stem length, the number of primary branches, the number of inflorescences (umbels), and fruit mass. The responses of coriander plants to delayed sowing were determined by precipitation levels during the growing season. In seasons with abundant precipitation (398–425 mm), delayed sowing decreased fruit yield by around 15–19%. In years with low precipitation (193–319 mm), a 14-day delay in sowing was well tolerated by coriander plants. Mineral fertilization (P, K, S, Mg, and micronutrients) had no significant effect on the growth, development or yield of coriander. Coriander plants also demonstrated a weak (non-significant) response to chemical disease control.

Prevalence of Viruses in Commercial Wine Grape Vineyards in Georgia

Virus diseases are major constraints to Vitis vinifera wine grape production worldwide. Grapevine leafroll-associated virus 3 (GLRaV-3) was first confirmed in Georgia in 2008. The negative impacts of GLRaV-3, such as decreased fruit yield and quality, were confirmed from samples taken in 2009 and 2010. In light of these findings, studies were initiated to determine the prevalence and types of grapevine viruses present in vineyards in Georgia. Five vineyard blocks were visited during August and September of 2011 and 2012. Leaf samples were collected from a total of 50 grapevines showing symptoms of and suspected as being infected by grapevine leafroll disease (GLD). Samples from individual grapevines were extracted and tested separately for 20 grapevine viruses listed in standard virus indexing programs. Reverse transcription polymerase chain reaction (RT-PCR) or PCR, depending on the nature of the virus genome, was used to detect these viruses with species-specific primers. The results showed the presence of GLRaV-1, -2, -3, and -4 (strains 4, 5, and 6), grapevine virus B, grapevine rupestris stem pitting-associated virus, and grapevine red blotch virus. Many vineyards had multiple viruses detected from individual grapevines showing typical GLD or GLD-like symptoms.

INVESTIGATING EFFECTS OF OVER-IRRIGATION AND DEFICIT IRRIGATION ON YIELD AND FRUIT QUALITY IN PINK LADYTM ‘ROSY GLOW’ APPLE

Fruit production has to be adapted to climate change that is often associated with heat and water deficit episodes. To develop efficient strategies on how to manage commercial orchards under deficit water supply, we need to know the effects of water-stress on crop production. However, when the water supply is abundant apple growers often think that over-irrigation gives higher marketable fruit yield than potential evapotranspiration-based or sensor-based (e.g. tensiometer, dendrometer) irrigation. We therefore aimed to evaluate the effects of three water regimes, namely well-watered (100% of crop evapotranspiration – ETc, WW), 25% of ETc water deficit over the season (water-stressed, WS), and twofold of WW (200% of ETc, 2xWW), on midday stem water potential (SWP), crop yield and fruit quality of Pink LadyTM ‘Rosy Glow’ apples. As expected, SWP was lower in WS than in the others, but both WS and 2xWW decreased fruit yield, although 2xWW tended to increase yield in the >70% color class and ensured quite a constant amount of yield at each picking time. Soluble solid content (SSC) in fruit was higher in WS. As a whole, our results suggest that over-irrigation that is sometimes recommended to keep a safety margin should be considered with caution. Rather, a mild water-stress, between WS and WW in our experiment, may represent a good compromise for a good quality yield.

Effects of Insect Herbivory on Bilberry Production and Removal of Berries by Frugivores.

The evolutionary purpose of a fleshy fruit is to attract seed dispersers and get the seeds dispersed by frugivorous animals. For this reason, fruits should be highly rewarding to these mutualists. However, insect herbivory can alter plant reproductive success e.g. by decreasing fruit yield or affecting the attractiveness of the fruits to mutualistic seed dispersers. Under natural conditions, we tested the effects of experimental larval-defoliation on berry ripening and consumption of a non-cultivated dwarf shrub, the bilberry (Vaccinium myrtillus L.), which produces animal-dispersed berries with high sugar and anthocyanin concentration. Bilberry ramets with high fruit yield were most likely to have their berries foraged, indicating that frugivores made foraging choices based on the abundance of berries. Moreover, the probability for berries being foraged was the lowest for non-defoliated ramets that grew adjacent to larval-defoliated ramets, even though larval-defoliation did not affect the biochemical composition (total concentrations of anthocyanins, sugars and organic acids) or the probability of ripening of berries. We hypothesise that the lower probability for berries being foraged in these ramets may be a consequence of rhizome- or volatile-mediated communication between ramets, resulting in a priming effect of the herbivore defence and lower attractiveness of the non-defoliated ramets.

The effects of CaCl2 on fruit yield, quality and nutrient contents of tomato under NaCl stress conditions

In this study, the effects of CaCl2 on fruit yield, quality Ca/Na and K/Na ratios and Na content of tomato leaves under NaCl stress conditions were determined. The doses of 0, 6.8 and 16.8 mM CaCl2 were combined with the doses of 0, 44.4, 70.4 mM NaCl in complete nutrient solution. General, NaCl and CaCl2 decreased fruit yield, NaCl decreased stem amount, whereas it increased at 6.8 mM CaCl2. CaCl2 decreased fruit yield without NaCl, but it increased fruit yield significantly at 44.4 mM dose and caused tolerance to NaCl. The 6.8 mM dose of CaCl2 increased stem amount without NaCl. However, CaCl2 did not cause tolerance at high doses of NaCl in terms of growth. CaCl2 decreased brix of fruit, while NaCl increased it. CaCl2 increased brix without NaCl, but decreased it at 44.4 and 70.4 mM NaCl. CaCl2 and NaCl decreased fruit juice pH significantly. Besides, CaCl2 decreased fruit juice pH at 0 and 44.4 mM of NaCl. The number of fruits which were found to have blossom-end rot (NFBER) did not change without NaCl with the influence of CaCl2. However, CaCl2 applied at high doses of NaCl decreased the NFBER and provided tolerance to NaCl. Increasing dose of NaCl increased significantly the Na content in leaves, but the addition CaCl2 decreased significantly the Na content in leaves. Increasing the dose of CaCl2 applications at 0 and 44.4 mM NaCl levels increased the Ca/Na ratio in tomato leaves. But, the effect of CaCl2 on Ca/Na ratio of leaves was statistically insignificant. The addition of NaCl into the solution nutrient decreased the Ca/Na and K/Na ratios in tomato leaves. The effect of CaCl2 on the K/Na ratio of leaves was not found significant.

Physiological response of Okra cv. Kano to foliar application of putrescine and humic acid under water deficit stress

To investigate effects of putrescine (Put) and humic acid (HA) on fruit yield and physiological attributes of okra (Abelmoschus esculentus L. 'Kano') under water deficit stress, a field experiment was conducted in split plot based on a randomized complete block design with three replications. Plants were exposed to three different irrigation regimes (33%, 66% and 100% ETc) and were treated with foliar application of Put (0, 0.5, 1 and 1.5 mM) and HA (0, 150 and 300 mg l-1). The results showed that deficit irrigation significantly decreased fruit yield, relative water content (RWC), vitamin C and water use efficiency (WUE), whereas proline content and catalase and peroxidase activities were increased. Foliar application of HA and Put significantly increased fruit yield, RWC, vitamin C and proline contents, catalase and peroxidase activities and WUE. The results suggested that HA at 300 mg l-1 and Put at 1.5 mM can improve growth, yield and quality of okra fruits.

Potassium silicate alleviates deleterious effects of salinity on two strawberry cultivars grown under soilless pot culture

We aimed to understand the impact of two potassium silicate (K2O3Si) levels (1000 and 1500ppm) on vegetative growth, physiological parameters and fruit yield of two strawberry cultivars under saline (50mM NaCl) and non-saline conditions during 2014 and 2015. Supplementary Si counteracted the negative effects of salinity on dry matter, leaf area, and root length and volume. Leaf relative water content and chlorophylls content were also improved by application of K2O3Si under salinity. NaCl imposed oxidative damages to cell manifested as decreased membrane stability index (MSI) as well as increased malondialdehyde (MDA) and H2O2 content. Higher MSI as well as lower MDA and H2O2 in Si-supplied plants representing a systemic palliative effect of Si to salinity induced cellular injuries. Salinity led to an increase of proline and soluble carbohydrates suggesting a physiological osmotic strategy to increase salt tolerance. Reduction of proline content further supports the beneficial roles of Si in alleviation of the adverse effects of salt stress. Significant increase in activity of peroxidase (POD) and superoxide dismutase (SOD) enzymes was only observed during 2015 under saline conditions. The induction of antioxidant enzymes coincided with a decrease in concentration of MDA and H2O2. Salinity decreased fruit yield in both cultivars with a drastic reduction in Paros. K2O3Si nutrition could recover yield loss with almost a 50% increase in fruit weight per plant. Overall, our results suggest that drenching potassium silicate in the nutrient solution of strawberry plants could be considered as a routine strategy to maintain strawberry growth and yield under salinity.

Growth and Yield of Tomato Influenced by Condition of Culture, Mulch, and Planting Date

ABSTRACTBelow optimal temperatures can restrict growth of autumn planted tomato (Solanum lycopersicum L.), resulting in delayed fruiting and decreased fruit yield under field conditions. Technology for growing tomato under protected structures needs to be standardized. This study was conducted to determine effects of culture condition, planting date, and application of mulch on plant growth and fruit yield of tomato. To determine whether time of establishment affected results, plants were established in the first and third weeks of October and the first week of November of 2010 and 2011 in a polyhouse or open field using the mulch treatments black polyethylene, clear polyethylene, paddy straw, or no mulch. Root zone and air temperatures and net radiation were measured. Treatments affected plant height, fruit number, fruit weight, early yield, marketable yield, and total yield. Except for early yield, results were consistent between years. Black polyethylene mulch increased fruit number under the polyhouse and in the open field. Fruit weight was improved by mulch treatments only in the open field. Highest early, marketable, and total yields were from planting in the polyhouse in the third week of October using black polyethylene mulch, and this is attributed to increased root zone temperature, air temperature, and net radiation. Use of polyhouse and black plastic mulch combined with appropriate planting time improves early and total yields of tomato in areas where the production is constrained by suboptimal temperature conditions.

Nitrogen and Straw Applications Increase Population Size ofBacillusandPseudomonasspp. in Greenhouse Soil

Root zone N management can reduce N fertilizer input and avoid nitrate pollution in greenhouse tomato production; however, little information is available on how reduced N affects soil microbes, especially dominant bacteria populations in long-term continuous greenhouse systems. This study investigated the effects of different combinations of N and straw on the population size of soil total bacteria and two dominant bacteria (Pseudomonas spp. and Bacillus spp.), and microbial community structure in a 6-year greenhouse tomato trial. The treatments were basal fertilizer (10 t ha -1 chicken manure; control), conventional high N treatment (600 kg N ha -1 ), conventional high N treatment with wheat straw, reduced N treatment (300 kg N ha -1 less than conventional), and reduced N treatment with wheat straw. Six years of reduced mineral N fertilization did not lead to a decrease in fruit yield. Both mineral N fertilizer and straw increased the numbers of soil bacteria (Bacillus spp. and Pseudomonas spp.) compared with the control, but the numbers were not affected by the amount of mineral N fertilizer (high vs reduced). Different denaturing gradient gel electrophoresis patterns were evidence that soil bacterial communities were changed by N treatments and straw application, but little difference in bacterial diversity was detected between high N and reduced N treatments. These results indicated that a reduction in N fertilizer input was possible in greenhouse tomato production and was beneficial in sustainable agriculture.

Floor Management Systems in an Organic Apple Orchard Affect Fruit Quality and Storage Life

In an organic apple orchard, standard mechanical cultivation was compared with four different orchard floor management systems (OFMS): acetic acid (V), living mulch (L), a sandwich system during the growing season (SSS), and a sandwich system during the whole year (SSW). The effects of these OFMS on weed management, soil conditions, tree growth, tree yield, fruit quality, and fruit storage potential in a cool climate were evaluated. Acetic acid treatment showed good weed suppression without any amendatory effect on soil conditions, fruit quality, or tree performance. The L and SSS systems increased soil respiration, decreased tree vigor, and improved fruit quality, but had no sufficient influence on weed competition and thus decreased fruit yield. Only SSW gave better weed control, higher soil respiration, and acceptable tree growth with no yield reduction. Fruit from this system also showed better quality at harvest than fruit from other OFMS and maintained this good quality during storage. A 6-week weed-free period from late May to mid-July gave the highest apple yield in two OFMS (SSW and V).

Cross-talk between environmental stresses and plant metabolism during reproductive organ abscission.

In plants, flowering is a crucial process for reproductive success and continuity of the species through time. Fruit production requires the perfect development of reproductive structures. Abscission, a natural process, can occur to facilitate shedding of no longer needed, infected, or damaged organs. If stress occurs during flower development, abscission can intervene at flower level, leading to reduced yield. Flower abscission is a highly regulated developmental process simultaneously influenced and activated in response to exogenous (changing environmental conditions, interactions with microorganisms) and endogenous (physiological modifications) stimuli. During climate change, plant communities will be more susceptible to environmental stresses, leading to increased flower and fruit abscission, and consequently a decrease in fruit yield. Understanding the impacts of stress on the reproductive phase is therefore critical for managing future agricultural productivity. Here, current knowledge on flower/fruit abscission is summarized by focusing specifically on effects of environmental stresses leading to this process in woody plants. Many of these stresses impair hormonal balance and/or carbohydrate metabolism, but the exact mechanisms are far from completely known. Hormones are the abscission effectors and the auxin/ethylene balance is of particular importance. The carbohydrate pathway is the result of complex regulatory processes involving the balance between photosynthesis and mobilization of reserves. Hormones and carbohydrates together participate in complex signal transduction systems, especially in response to stress. The available data are discussed in relation to reproductive organ development and the process of abscission.

Effects of controlled-release fertilizer on leaf area index and fruit yield in high-density soilless tomato culture using low node-order pinching.

To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method.

Abscisic acid-mediated leaf phenolic compounds, plant growth and yield is strawberry under different salt stress regimes

The present research was conducted to evaluate the interaction effects of exogenous abscisic acid (ABA) and salt stress on phenolic compounds, growth and yield of two short day strawberry cvs "Queen Elisa" and "Kurdistan". Plants were subjected to control, gradual salt stress (up to 20 mmol L-1 over 5 weeks) and salinity shock (20 mmol L-1). ABA treatments included: 0 (control), 5, 10, 20 and 40 µmol L-1. The experiment was carried out based on a complete randomized design in factorial experiment. The highest level of ferulic acid was observed by applying 40 µmol L-1 ABA in "Queen Elisa" under salt stress shock but effective increase in caffeic acid and p-coumaric acid was shown at gradual salt stress for both cultivars at the same ABA level. Maximum level of ABA led to the highest gentisic acid and gallic acid at gradual salt stress in "Kurdistan". Methyl gallate and flavonoid content showed a striking increase at the same conditions in "Queen Elisa". The interaction effect of salt stress regimes and ABA resulted in an increase in ellagic acid content for both cultivars. The interaction effect of ABA and salt shock caused higher reduction in root and shoot fresh dry weights and decrease in fruit yield in "Kurdistan". The results of this experiment accounts for the important role of exogenous ABA in the activation of antioxidant defense mechanism, growth and yield maintenance under gradual salt stress in strawberry.

Is the productive performance of olive trees under localized irrigation affected by leaving some roots in drying soil?

Localized irrigation, which wets a part of the root zone only, is widely used in olive orchards. The effect of partial wetting of the root zone on plant performance is unknown. The aim of this work was to compare fruit and oil yields in olive trees under localized irrigation (LI treatment) to those from trees with the whole root zone under non-limiting soil water conditions (Pond treatment). The LI trees received enough water to replace the crop water needs. The study was made for three consecutive years in mature ‘Manzanilla de Sevilla’ olive trees growing under field conditions. Main variables were also measured in young trees of the same cultivar growing in 50L pots. Samples from rain-fed trees were also analysed. The LI trees showed similar water status than the Pond trees, but reduced stomatal conductance. As expected, the effect of the irrigation treatments on net photosynthesis was less evident. We observed a decrease in fruit yield in the LI trees, as compared to the Pond trees, likely because of the reduced gas exchange. No differences between the LI and Pond treatments were found for fruit weight, pulp:stone ratio, volume and the longitudinal and equatorial diameters. The LI treatment did not cause detrimental effect either on total oil content or virgin olive oil yield. The phenols content was greater in the LI treatment, but the (E)-hex-2-enal, one of the major volatile compounds and most related to the positive attributes of olive oil, was lower. No significant differences with the Pond treatment were found, however, in the sensory description of the oil flavours.

Effects of elevated CO2 and temperature on yield and fruit quality of strawberry (Fragaria × ananassa Duch.) at two levels of nitrogen application.

We investigated if elevated CO2 could alleviate the negative effect of high temperature on fruit yield of strawberry (Fragaria × ananassa Duch. cv. Toyonoka) at different levels of nitrogen and also tested the combined effects of CO2, temperature and nitrogen on fruit quality of plants cultivated in controlled growth chambers. Results show that elevated CO2 and high temperature caused a further 12% and 35% decrease in fruit yield at low and high nitrogen, respectively. The fewer inflorescences and smaller umbel size during flower induction caused the reduction of fruit yield at elevated CO2 and high temperature. Interestingly, nitrogen application has no beneficial effect on fruit yield, and this may be because of decreased sucrose export to the shoot apical meristem at floral transition. Moreover, elevated CO2 increased the levels of dry matter-content, fructose, glucose, total sugar and sweetness index per dry matter, but decreased fruit nitrogen content, total antioxidant capacity and all antioxidant compounds per dry matter in strawberry fruit. The reduction of fruit nitrogen content and antioxidant activity was mainly caused by the dilution effect of accumulated non-structural carbohydrates sourced from the increased net photosynthetic rate at elevated CO2. Thus, the quality of strawberry fruit would increase because of the increased sweetness and the similar amount of fruit nitrogen content, antioxidant activity per fresh matter at elevated CO2. Overall, we found that elevated CO2 improved the production of strawberry (including yield and quality) at low temperature, but decreased it at high temperature. The dramatic fluctuation in strawberry yield between low and high temperature at elevated CO2 implies that more attention should be paid to the process of flower induction under climate change, especially in fruits that require winter chilling for reproductive growth.

INFLUENCE OF GRAFTED WATERMELON PLANT DENSITY ON YIELD AND QUALITY IN SOIL INFESTED WITH MELON NECROTIC SPOT VIRUS

Abstract The decrease in fruit yield and quality caused by soil diseases is one of the major problems of watermelon production. Soil disinfection with methyl bromide (MB) has been used to prevent fungus attacks; however, its use is being restricted because this substance damages the ozone layer. Field experiments were carried out in open field in soils infested with Olpidium bornovanus and Melon necrotic spot virus (MNSV) in Colima, Mexico, where watermelons had only been grown previously using soil fumigation with MB. Yield and quality of the watermelon cultivar ‘Triploid Tri-X 313’ grafted on two rootstocks of Cucurbita maxima × Cucurbita moschata (‘RS841’ and ‘Shintosa Camelforce’) were evaluated during 2007-2008. Each experiment had five treatments, two of them with non-grafted plants at a density of 3472 plants/ha, with and without MB fumigation. The remaining three treatments had grafted plants in non-fumigated soil with plant densities of 2778, 2083, and 1736 plants/ha. The use of watermelon grafted on ‘RS841’ and ‘Shintosa Camelforce’ rootstocks significantly increased the average fruit weight and the total yield of watermelon. Grafting may be considered as an alternative to MB fumigation. With the use of grafted watermelon plants, planting density may be reduced by 50%, obtaining higher yields than those obtained from non-grafted plants grown in fumigated soil. Fruits harvested from grafted plants had higher firmness than those harvested from non-grafted plants, without affecting the content of soluble solids. INTRODUCTION