Exploring options for managing strategies for pea–barley intercropping using a modeling approach

Although quality of potato tubers is an important topic with regard to food and industrial processing, the consequences of future atmospheric carbon dioxide (CO₂) enrichment on related attributes are still unclear. Effects of elevated CO₂ concentrations on yield quality of potato (Solanum tuberosum L. cv. Bintje) were thus investigated in two full growing seasons under 380, 550 or 680 μmol mol^?1 CO₂ in open-top chambers (OTCs). When averaged over both years, tuber malformation was increased by 62.8% as CO₂ levels raised from 380 to 550 μmol mol^?1, resulting in a negative impact on tuber quality. In contrast, elevated CO₂ caused lower tuber greening and therefore enhanced tuber market value. Physical potato quality remained largely unchanged, except for the positive relationships between CO₂ and dry matter content, resulting in higher tuber quality for industrial processing. Significant relationships were also observed between CO₂ concentrations and several chemical quality parameters. The concentrations of glucose, fructose and total reducing carbohydrates were positively related to CO₂ levels, which decrease tuber quality due to the higher risk for browning and generation of acrylamide of fried products. The concentrations of protein, potassium, and as a trend of calcium, were negatively related to CO₂ enrichment, suggesting adverse impacts on tuber quality for human nutrition and aesthetic and sensory quality during processing. Significant negative relationships between CO₂ treatments and concentrations of leucine, phenylalanine and methionine, and as a trend for di-tyrosine, histidine and aspartic acid, were also indicated, which may decrease nutrition quality of potatoes because of the reduction in physiologically valuable amino acids. With regard to organic acids, CO₂-related alterations were restricted to lower concentrations of citric acid. This may reduce the processing quality of potato tuber, as there is a higher risk of discoloration, and at the same time improve quality aspects related to taste. In addition, the experiments indicated negative relationships between CO₂ concentrations and total glycoalkaloids and α-chaconine, which may have negative effects on the taste of potato at low concentration of glycoalkaloids of the present study. Concomitantly, the CO₂-induced decrease in glykoalkaloids may be regarded as an improvement of quality in terms of lower toxicological potential. CO₂ enrichment may thus cause substantial impacts, both positive and negative, on tuber quality of potato with regard to commercial value, industrial processing and consumer nutrition and health in the future. Currently, no clear evidence exists whether CO₂-induced beneficial changes will outweigh adverse effects on tuber quality.     

Trade-offs between water-use related traits,yield components and mineral nutrition of wheat under Free-Air CO2 Enrichment (FACE)

This study investigated trade-offs between parameters determining water use efficiency of wheat under elevated CO₂ in contrasting growing seasons and a semi-arid environment. We also evaluated whether previously reported negative relationships between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions. Two cultivars of wheat (Triticum aestivum L.), Scout and Yitpi, purportedly differing in water use efficiency related traits (e.g. transpiration efficiency) but with common genetic backgrounds were studied in a high yielding, high rainfall (2013), and in a low yielding, very dry growing season (2014) under Free-Air CO₂ Enrichment (FACE, CO₂ concentration of approximately 550 μmol mol⁻¹) and ambient (approximately 390 μmol mol⁻¹) CO₂. Gas exchange measurements were collected diurnally between stem elongation and anthesis. Aboveground biomass and nutrient content (sum of Ca, K, S, P, Cu, Fe, Zn, Mn and Mg) were determined at anthesis. Yield, yield components and harvest index were measured at physiological maturity. Cultivar Scout showed transiently greater transpiration efficiency (measured by gas exchange) over cultivar Yitpi under both ambient and elevated CO₂ conditions, mainly expressed in the high yielding but not in the low yielding season. Nutrient content was on average 13% greater for the lower transpiration efficiency cultivar Yitpi than the cultivar with higher transpiration efficiency (Scout) in the high yielding season across both CO₂ concentrations. Elevated CO₂ stimulated grain yield to a greater extent in the high yielding season than in the low yielding season where increased aboveground biomass earlier in the season did not translate into fertile tillers in cultivar Yitpi. Yield increased 27 and 33% in the high yielding and 0 and 19% in the low yielding season for cultivars Yitpi and Scout, respectively. Intraspecific variation in CO₂ responsiveness related mechanisms of grain yield were observed. These results suggest CO₂-driven trade-offs between traits governing water use efficiency are related to both growing season and intraspecific variations, and under very dry finishes, the trade-offs may even reverse. The negative relationship between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions.     

Vulnerability of lodging risk to elevated CO2 and increased soil temperature differs between rice cultivars

Anthropogenic increases in atmospheric carbon dioxide concentration [CO₂], and subsequent increases in surface temperatures, are likely to impact the growth and yield of cereal crops. One potential means for yield reduction is for climate parameters to increase the occurrence of lodging. Using an in situ free-air CO₂ enrichment (FACE) system, two morphologically distinct rice cultivars, KH (Koshihikari) and SY (Shan you 63), were grown at two [CO₂]s (ambient and ambient + 200 μmol mol⁻¹) and two soil temperatures (ambient and ambient ± 1.8 °C) over a two year period to assess and quantify lodging risk. Elevated [CO₂] per se had no effect on lodging resistance for either cultivar. However, elevated [CO₂] and higher soil temperature increased the lodging risk for SY, due to a relatively higher increase in plant biomass and height at the elevated, relative to the ambient [CO₂] condition. Elevated soil temperature per se also increased lodging risk for both cultivars and was associated with longer internodes in the lower portion of the tillers. These findings illustrate that lodging susceptibility in rice, an important cereal crop, can be increased by rising [CO₂] and soil temperature; however, variation observed here between rice cultivars suggests there may be sufficient intraspecific variability to begin choosing rice lines that minimize the potential risk of lodging.     

Effect of elevated carbon dioxide and temperature on phosphorus uptake in tropical flooded rice (Oryza sativa L.)

A field experiment was carried out to assess the impact of elevated carbon dioxide (CO₂) and temperature on phosphorous (P) nutrition in relation to organic acids exudation, soil microbial biomass P (MBP) and phosphatase activities in tropical flooded rice. Rice (cv. Naveen) was grown under chambered control (CC), elevated CO₂ (EC, 550 μmol mol⁻¹) and elevated CO₂ + elevated temperature (ECT, 550 μmol mol⁻¹ and 2 °C more than CC) in a tropical flooded soil under open top chambers (OTCs) along with unchambered control (UC) for three years. Root exudates were analyzed at different growth stages of rice followed by organic acids determination. Rhizospheric soil was used for analysis of soil phosphatase, MBP and available P. The total organic carbon (TOC) in root exudates was increased by 27.5% and 30.2% under EC and ECT, respectively over CC. Four different types of organic acids viz. acetic acid (AA), tartaric acid (TA), malic acid (MA) and citric acid (CA) were identified and quantified as dominant in root exudates, concentration of these was in the order of TA > MA > AA > CA. The TA, MA, AA and CA content were increased by 34.4, 31.1, 38.7 and 58.3% under ECT compared to that of UC over the period of 3 years. The P uptake in shoot, root and grain under elevated CO₂ increased significantly by 29, 28 and 22%, respectively than CC. Soil MBP, acid and alkaline phosphatase activity was significantly higher under elevated CO₂ by 35.1%, 27 and 36%, respectively, compared to the CC. Significant positive relationship exists among the organic acid exudation, MBP, phosphatase activities and P uptake by rice. The enhanced organic acid in root exudates coupled with higher soil phosphatase activities under elevated CO₂ resulted in increased rate of soil P solubilization leading to higher plant P uptake.     

Effect of free air carbon dioxide enrichment combined with two nitrogen levels on growth,yield and yield quality of sugar beet: Evidence for a sink limitation of beet growth under elevated CO2

The increase in atmospheric CO₂ concentration [CO₂] has been demonstrated to stimulate the growth of C₃ crops. However, little information exists about the effect of elevated [CO₂] on biomass production of sugar beet, and data from field experiments are lacking. In this study, sugar beet was grown within a crop rotation over two rotation cycles (2001, 2004) at present and elevated [CO₂] (375 μl l^?1 and 550 μl l^?1) in a free air CO₂ enrichment (FACE) system and at two levels of nitrogen supply [high (N2), and 50% of high (N1)], in Braunschweig, Germany. The objective of the present study was to determine the CO₂ effect on seasonal changes of leaf growth and on final biomass and sugar yield. Shading treatment was included to test whether sugar beet growth is sink limited under elevated [CO₂]. CO₂ elevation did not affect leaf number but increased individual leaf size in early summer resulting in a faster row closure under both N levels. In late summer CO₂ enrichment increased the fraction of senescent leaves under high but not low N supply, which contributed to a negative CO₂ effect on leaf area index and canopy chlorophyll content under high N at final harvest. Petioles contained up to 40% water-soluble carbohydrates, which were hardly affected by CO₂ but increased by N supply. More N increased biomass production by 21% and 12% in 2001 and 2004, respectively, while beet and sugar yield was not influenced. Concentration of α-amino N in the beet fresh weight was increased under low N and decreased under high N by CO₂ enrichment. The CO₂ response of total biomass, beet yield and white sugar yield was unaffected by N supply. Averaged over both N levels elevated [CO₂] increased total biomass by 7% and 12% in 2001 and 2004, respectively, and white sugar yield by 12% and 13%. The shading treatment in 2004 prevented the decrease in leaf area index under elevated [CO₂] and high N in September. Moreover, the CO₂ effect on total biomass (24%) and white sugar yield (28%) was doubled as compared to the unshaded conditions. It is concluded that the growth of the storage root of sugar beet is not source but sink limited under elevated [CO₂], which minimizes the potential CO₂ effect on photosynthesis and beet yield.     

Assessing the impact of increasing carbon dioxide and temperature on crop-weed interactions for tomato and a C3 and C4 weed species

Based on the carboxylation kinetics of the C₃ and C₄ photosynthetic pathway, it is anticipated that C₃ crops may be favored over C₄ weeds as atmospheric CO₂ increases. In the current study, tomato (Lycopersicon esculentum), a C₃ crop species, was grown at ambient (~400 μmol mol⁻¹) and enhanced carbon dioxide (~800 μmol mol⁻¹) with and without two common weeds, lambsquarters (Chenopodium album), a C₃ weed, and redroot pigweed (Amaranthus retroflexus), a C₄ weed, from seedling emergence until mutual shading of crop-weed leaves. Because growth temperature is also likely to change in concert with rising CO₂, the experiment was repeated at day/night temperatures of 21/12 and 26/18 °C. For both day/night temperatures, elevated CO₂ exacerbated weed competition from both the C₃ and C₄ weed species. A model based on relative leaf area following emergence was used to calculate potential crop losses from weeds. This analysis indicated that potential crop losses increased from 33 to 55% and from 32 to 61% at the 21/12 and 26/18 °C day/night temperatures, for ambient and elevated CO₂, respectively. For the current study, reductions in biomass and projected yield of tomato appeared independent of the photosynthetic pathway of the competing weed species. This may be due to inherent variation and overlap in the growth response of C₃ and C₄ species, whether weeds or crops, to increasing CO₂ concentration. Overall, these results suggest that as atmospheric CO₂ and/or temperature increases, other biological interactions, in addition to photosynthetic pathway, deserve additional consideration in predicting competitive outcomes between weeds and crops.     

Propensity for seed-mediated gene flow from potato crops and potential consequences for the coexistence of GM and non-GM potato systems

Potato is a critical crop to European growers, both economically and agronomically as a break crop in the standard cereal rotation. As studies investigating the agronomic performance and environmental impact of disease resistant, GM potatoes come to an end across several sites in Europe, past discussions on achieving the effective coexistence of GM and equivalent non-GM crops have too often focussed on the purported risk of excessive pollen-mediated gene flow. Dependent on the crop in question, the impact of seed loss pre- and/or post-harvest presents a greater challenge to securing efficient coexistence practises. To examine this issue for potato, a total of 51 fields that had been commercially cultivated with potatoes were surveyed in two separate cohorts for post-harvest tuber loss and/or volunteer emergence. Across 17 fields studied, the average post-harvest tuber loss was recorded at 141,758 ± 911 tubers ha⁻¹, with volunteer establishment in the following crop ranging from 400 ± 59 ha⁻¹ to 55,698 ± 47 ha⁻¹. In parallel, by surveying a separate cohort of 34 commercial fields an average of 30,789 ± 2658 volunteer ha⁻¹ was recorded in the subsequent cereal crop, with a repeat survey made after an additional year indicating an 87.2% reduction in this mean number of volunteers across the 34 fields (P < 0.001). Of the additional variables studied only location (P < 0.001), herbicide application (P = 0.037) and potato variety used (P = 0.045) significantly influenced volunteer proliferation. Volunteer fecundity was confirmed with upto 3 tubers produced per 1st generation volunteer, with tuber yield from the 2nd generation volunteers reduced significantly (P < 0.001). Assessments of the tuber lots from these 2nd generation volunteers confirmed their ability to sprout post-dormancy, therefore, indicating the potential for 3rd generation volunteers to emerge. Combined, the datasets confirm the potential for significant seed-mediated gene flow from commercial potato systems; indicating that the regulated 0.9% coexistence threshold would in all probability be compromised if GM potatoes were grown in rotations of 1:4 years or less, in the absence of a comprehensive tuber loss and/or volunteer management system.     

Soybean (Glycine max (L.) Merr.) growth and development response to CO2 enrichment under different temperature regimes

The carbon dioxide (CO₂) concentration of the global atmosphere has increased during the last decades. This increase is expected to impact the diurnal variation in temperature as well as the occurrence of extreme temperatures. This potentially could affect crop production through changes in growth and development that will ultimately impact yield. The objective of this study was to evaluate the effect of CO₂ and its interaction with temperature on growth and development of soybean (Glycine max (L.) Merr., cv. Stonewall). The experiment was conducted in controlled environment chambers at the Georgia Envirotron under three different temperatures and two CO₂ regimes. The day/night air temperatures were maintained at 20/15, 25/20 and 30/25 °C, while the CO₂ levels were maintained at 400 and 700 ppm, resulting in six different treatments. Plants were grown under a constant irradiance of 850 μmoles m⁻² s⁻¹ and a day length of 12 h; a non-limiting supply of water and mineral nutrients were provided. Five growth analyses were conducted at the critical development stages V4, R3, R5, R6 and R8. No differences in start of flowering were observed as a function of the CO₂ level, except for the temperature regime 25/20 °C, where flowering for the elevated CO₂ level occurred 2 days earlier than for the ambient CO₂ level. For aboveground biomass, an increase in the CO₂ level caused a more vigorous growth at lower temperatures. An increase in temperature also decreased seed weight, mainly due to a reduction in seed size. For all temperature combinations, final seed weight was higher for the elevated CO₂ level. This study showed that controlled environment chambers can be excellent facilities for conducting a detailed growth analysis to study the impact on the interactive effect of changes in temperature and CO₂ on soybean growth and final yield.     

Impact of high temperatures on the marketable tuber yield and related traits of potato

A rapid warming of 2.8–5.3 °C by the end of this century is expected in South Korea. Considering the current temperature during the spring potato growing season (emergence to harvest; ca. 18 °C), which is near the upper limit of the optimum temperature for potato yield, the anticipated warming will adversely affect potato production in South Korea. The present study assessed the impact of high temperature on the marketable tuber yield and related traits of cv. Superior (which makes up 71% of the annual potato production in South Korea) in four temperature-controlled plastic houses and an outdoor field (37.27°N, 126.99°E) during 2015–2016. The target temperatures of the four plastic houses were set to ambient (AT), AT+1.5 °C, AT+3.0 °C, and AT+5.0 °C. The marketable tuber yield was significantly reduced by 11% per 1 °C increase over a temperature range of 19.1–27.7 °C. The negative impact of high temperature was associated not only with the yield loss of total tubers, which was mostly explained by the slower tuber bulking rate, but also the reduced marketable tuber ratio under temperatures above 23 °C, which was mainly attributed to the reduced number of marketable tubers (r = 0.79***). Under moderate temperatures below 23 °C, the source limited the number of marketable tubers without reducing the marketable tuber ratio. In contrast, the number of marketable tubers was limited by the marketable tuber set at the early growth stage rather than the source under the higher temperatures, which resulted in the reduction in the marketable tuber ratio below 56%. These results suggest that the objectives of breeding and agronomic management for adapting to the rapid warming in South Korea should include maintaining the ability to form tubers at the early growth stage under high temperatures, as well as the photosynthetic capacity and sink strength of the tubers.     

Effects of ozone on sugar beet grown in open-top chambers

Sugar beet (Beta vulgaris cv. Patriot) plants were grown on field plots and in open-top chambers (OTCs) in two successive years. In the OTC treatments, plants were exposed to charcoal filtered air, unfiltered air or unfiltered air enriched with additional ozone (O₃). Ozone exposure continued for almost 5 months and the 8-h average concentration was raised from 34 to 39 nL L⁻¹ in the ambient air chambers to 62 nL L⁻¹ in the ozone enriched chambers. In both years, the AOT40 exposure index in the ozone enriched chambers exceeded 30 μL L⁻¹ h during the 5-month exposure period compared to 6.5 and 2.9 μL L⁻¹ h in ambient air in 2003 and 2004, respectively. Visible symptoms in the form of small white necrotic flecks appeared in both seasons in the ozone enriched chambers. When the data for both years were analysed statistically, a significant reduction of root yield of 6% and a slight reduction of sugar content were detected. These changes resulted in an overall reduced sugar yield ha⁻¹ of about 9%. Although the sensitivity of sugar beet to ozone is highly variety-dependent, in general this biennial crop appears less sensitive than annual crops such as wheat and potato. Ozone has limited effects on quality parameters in sugar beet, although an increase in α-amino-N content was observed, in agreement with the increased nitrogen content resulting from ozone exposure of wheat and potato.Enclosure within the OTCs increased aboveground biomass but decreased root yield (fresh biomass) and sugar content. These effects were most likely caused by a reduction of radiation by the chamber walls and annulus. The increased temperature in the chambers reduced yield quality by increasing mineral content.     

Phosphorus uptake and utilization efficiency in response to potato genotype and phosphorus availability

Increased phosphorus (P) use efficiency (PUE) of potato production systems through P uptake and P utilization efficiency (PUPE and PUTE, respectively) is one of the main challenges for potato breeding and crop management programs. The aim of this study was to assess PUE, PUPE, PUTE and related traits in different potato genotypes (Solanum tuberosum L.) in response to P availability. Three field experiments were carried out in southern Chile in Andisol soils. In each experiment treatments were the factorial combination of (i) 22 genotypes of potatoes and (ii) two P fertilization rates (0 and 130 kg P ha⁻¹, −P and +P, respectively). On average, biomass, P concentrations and P uptakes were reduced (P < 0.05) 32, 13 and 41% by −P, respectively. Conversely, −P increased PUTE (1.2-fold), PUPE (7-fold) and consequently PUE (8.3-fold). All traits were consistently affected (P < 0.01) by genotype (G), and the coefficient of variation (up to 47%) for each trait reflects the genotypic variability under both +P and −P. In all experiments, PUE and its main components were affected (P < 0.01) by P × G interaction. PUE was highly correlated with tuber yield, total biomass, P uptake and PUPE (P < 0.01; r = 0.74 − 0.99) but not to PUTE. In addition, PUPE was well correlated to yield and highly correlated with total P uptake (P < 0.01; r = 0.94–0.99). By contrast, PUTE was strongly negatively correlated (P < 0.01; r = −0.85 − 0.89) with P concentration in tubers. Genotypes from native (1 and 4), national cultivar (Puren-INIA, Yagana-INIA and Patagonia-INIA) and advanced line (R 89063 and RD 36–35) groups were among the best regarding PUE under −P. The PUPE was found to be more important than PUTE in determining PUE across a broad range of genotypes. Moreover, there is important genotypic variability in these traits with the potential to be used to improve PUE in potato crops through breeding and crop management programs.     

Yield,growth and grain nitrogen response to elevated CO2 in six lentil (Lens culinaris) cultivars grown under Free Air CO2 Enrichment (FACE) in a semi-arid environment

Atmospheric CO₂ concentrations ([CO₂]) are predicted to increase from current levels of about 400 ppm to reach 550 ppm by 2050. The direct benefits of elevated [CO₂] (e[CO₂]) to plant growth appear to be greater under low rainfall conditions, but there are few field (Free Air CO₂ Enrichment or FACE) experimental set-ups that directly address semi-arid conditions. The objectives of this study were to investigate the following research questions: 1) What are the effects of e[CO₂] on the growth and grain yield of lentil (Lens culinaris) grown under semi-arid conditions under FACE? 2) Does e[CO₂] decrease grain nitrogen in lentil? and 3) Is there genotypic variability in the response to e[CO₂] in lentil cultivars? Elevated [CO₂] increased yields by approximately 0.5 t ha⁻¹ (relative increase ranging from 18 to 138%) by increasing both biomass accumulation (by 32%) and the harvest index (by up to 60%). However, the relative response of grain yield to e[CO₂] was not consistently greater under dry conditions and might depend on water availability post-flowering. Grain nitrogen concentration was significantly reduced by e[CO₂] under the conditions of this experiment. No differences were found between the cultivars selected in the response to elevated [CO₂] for grain yield or any other parameters observed despite well expressed genotypic variability in many traits of interest. Biomass accumulation from flowering to maturity was considerably increased by elevated [CO₂] (a 50% increase) which suggests that the indeterminate growth habit of lentils provides vegetative sinks in addition to reproductive sinks during the grain-filling period.     

Changes in respiration of fresh-cut butterhead lettuce under controlled atmospheres using low and superatmospheric oxygen conditions with different carbon dioxide levels

The effect of different O₂ levels from 0 to 100 kPa in combination with 0, 10 and 20 kPa CO₂ on the respiration metabolism of greenhouse grown fresh-cut butter lettuce was studied. Controlled atmospheres of 20 or 75 kPa O₂ with 0 or 10 kPa CO₂ showed a constant respiration rate during the first 2–4 days at different temperatures (1, 5 and 9 °C). Therefore, constant respiration rates during a short period of 2–4 days could be considered as valid for a large part of the commercial life of, for instance, a modified atmosphere package development. The fresh-cut lettuce exposed to low O₂ levels (2–10 kPa) combined with moderate to high CO₂ levels (10 and 20 kPa) had a higher respiration rate than when 20–100 kPa O₂ were used. Moderate CO₂ levels (10 kPa) reduced the respiration rates of fresh-cut lettuce 20–40% at 9 °C. This effect was less noticed at lower temperatures. Gas composition with high CO₂ levels (20 kPa) probably caused a metabolic disorder increasing the respiration rate of fresh-cut butter lettuce. It was concluded that 80 kPa O₂ must be used in modified atmosphere packaging (MAP) to avoid fermentation of fresh-cut butter lettuce in combination with 10–20 kPa CO₂ for reducing their respiration rate.     

Respiration and quality responses of sweet cherry to different atmospheres during cold storage and shipping

Most sweet cherries produced in the US Pacific Northwest and shipped to distant markets are often in storage and transit for over 3 weeks. The objectives of this research were to study the effects of sweet cherry storage O₂ and CO₂ concentrations on the respiratory physiology and the efficacy of modified atmosphere packaging (MAP) on extending shelf life. Oxygen depletion and CO₂ formation by ‘Bing’ and ‘Sweetheart’ cherry fruit were measured. While respiration rate was inhibited linearly by reduced O₂ concentration from 21% to 3–4% at 20 °C, it was affected very little from 21% to ∼10% but declined logarithmically from ∼10% to ∼1% at 0 °C. Estimated fermentation induction points determined by a specific increased respiratory quotient were less than 1% and 3–4% O₂ for both cultivars at 0 and 20 °C, respectively. ‘Bing’ and ‘Sweetheart’ cherry fruits were packaged (∼8 kg/box) in 5 different commercial MAP box liners and a standard macro-perforated polyethylene box liner (as control) and stored at 0 °C for 6 weeks. MAP liners that equilibrated with atmospheres of 1.8–8.0% O₂ + 7.3–10.3% CO₂ reduced fruit respiration rate, maintained higher titratable acidity (TA) and flavor compared to control fruit after 4 and 6 weeks of cold storage. In contrast, MAP liners that equilibrated with atmospheres of 9.9–14.4% O₂ + 5.7–12.9% CO₂ had little effect on inhibiting respiration rate and TA loss and maintaining flavor during cold storage. All five MAP liners maintained higher fruit firmness (FF) compared to control fruit after 6 weeks of cold storage. In conclusion, storage atmospheres of 1.8–14.4% O₂ + 5.7–12.9% CO₂ generated by commercial MAP, maintained higher FF, but only the MAP with lower O₂ permeability (i.e., equilibrated at 1.8–8.0% O₂) maintained flavor of sweet cherries compared to the standard macro-perforated liners at 0 °C. MAP with appropriate gas permeability (i.e., equilibrated at 5–8% O₂ at 0 °C) may be suitable for commercial application to maintain flavor without damaging the fruit through fermentation, even if temperature fluctuations, common in commercial storage and shipping, do occur.     

Impact of atmospheric ozone-enrichment on quality-related attributes of tomato fruit

Tomato fruit (Lycopersicon esculentum L. cv. Carousel) were exposed to ozone concentrations ranging between 0.005 (controls) and 1.0 μmol mol⁻¹ at 13 °C and 95% RH. Quality-related attributes and organoleptic characteristics were examined during and following ozone treatment. Levels of soluble sugars (glucose, fructose) were maintained in ozone-treated fruit following transfer to ‘clean air’, and a transient increase in β-carotene, lutein and lycopene content was observed in ozone-treated fruit, though the effect was not sustained. Ozone-enrichment also maintained fruit firmness in comparison with fruit stored in ‘clean air’. Ozone-treatment did not affect fruit weight loss, antioxidant status, CO₂/H₂O exchange, ethylene production or organic acid, vitamin C (pulp and seed) and total phenolic content. Panel trials (employing choice tests, based on both appearance and sensory evaluation) revealed an overwhelming preference for fruit subject to low-level ozone-enrichment (0.15 μmol mol⁻¹), with the effect persisting following packaging.     

Physicochemical measurements in ‘Mondial Gala®’ apples stored at different atmospheres: Influence on consumer acceptability

Standard quality parameters, consumer acceptability, emission of volatile compounds and ethylene production of ‘Mondial Gala^®’ apples (Malus × domestica Borkh.) were determined in relation to storage atmosphere, storage period and shelf-life period. Fruit were harvested at the commercial date and stored in AIR (21 kPa O₂:0.03 kPa CO₂) or under three different controlled atmospheres (CAs): LO (2 kPa O₂:2 kPa CO₂), ULO1 (1 kPa O₂:1 kPa CO₂), or ULO2 (1 kPa O₂:2 kPa CO₂). Fruit samples were analysed after 12 and 26 weeks of storage plus 1 or 7 d at 20 °C.Apples stored in CA maintained better standard quality parameters than AIR-stored fruit. The volatile compounds that contributed most to the characteristic aroma of ‘Mondial Gala^®’ apples after storage were butyl, hexyl and 2-methylbutyl acetate, hexyl propanoate, ethyl butanoate, ethyl hexanoate, ethyl, butyl and hexyl 2-methylbutanoate. Data obtained from fruit analysis were subjected to principal component analysis (PCA). The apples most accepted by consumers showed the highest emission of ethyl 2-methylbutanoate, ethyl hexanoate, tert-butyl propanoate and ethyl acetate, in addition to the highest titratable acidity and firmness values.     

Controlled atmosphere storage of guava (Psidium guajava L.) fruit

The effects of controlled atmospheres (CA) on respiration, ethylene production, firmness, weight loss, quality, chilling injury, and decay incidence of three commercially important cultivars of guava fruit were studied during storage in atmospheres containing 2.5, 5, 8, and 10 kPa O₂ with 2.5, 5, and 10 kPa CO₂ (balance N₂) at 8 °C, a temperature normally inducing chilling injury. Mature light green fruit of cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’ and ‘Apple Colour’, were stored for 30 days either in CA or normal air, and transferred to ambient conditions (25–28 °C and 60–70% R.H.) for ripening. CA storage delayed and suppressed respiratory and ethylene peaks during ripening. A greater suppression of respiration and ethylene production was observed in fruit stored in low O₂ (≤5 kPa) atmospheres compared to those stored in CA containing 8 or 10 kPa O₂ levels. High CO₂ (>5 kPa) was not beneficial, causing a reduction in ascorbic acid levels. CA storage was effective in reducing weight loss, and maintaining firmness of fruit. The changes in soluble solids content (SSC), titratable acidity (TA), ascorbic acid, and total phenols were retarded by CA, the extent of which was dependent upon cultivar and atmosphere composition. Higher amounts of fermentative metabolites, ethanol and acetaldehyde, accumulated in fruit held in atmospheres containing 2.5 kPa O₂. Chilling injury and decay incidence were reduced during ripening of fruit stored in optimal atmospheres compared to air-stored fruit. In conclusion, guava cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’, and ‘Apple Colour’ may be stored for 30 days at low temperature (8 °C) supplemented with 5 kPa O₂ + 2.5 kPa CO₂, 5 kPa O₂ + 5 kPa CO₂, and 8 kPa O₂ + 5 kPa CO₂, respectively.     

Internal browning disorder and fruit quality in modified atmosphere packaged ‘Bartlett’ pears during storage and transit

Internal browning (IB) can be a serious problem with the use of modified atmosphere packaging (MAP) for ‘Bartlett’ pears (Pyrus communis L.) grown in the Pacific Northwest during storage and transit to distant markets. To investigate this disorder, ‘Bartlett’ pears harvested at commercial maturity were packed in a commercial MAP (MAPc), an experimental MAP (MAPe) and commercial perforated plastic bags (control) and stored in air at −1.1 °C. After 1 and 3 months of storage, samples of MAPc and control fruit were transferred to rooms at temperatures of 2, 4.5, 7.5, and 10 °C for 3 weeks to simulate transit temperatures and the time required to reach distant markets. MAPc maintained an average internal atmosphere of 12.3% O₂ + 5.6% CO₂ and significantly extended ‘Bartlett’ pear storage life with high eating quality and without IB and other disorders for up to 4 months at −1.1 °C. The internal gas atmosphere of MAPe equilibrated at 2.2% O₂ + 5.7% CO₂, which resulted in fruit with 25.5 and 62.3% IB after 3 and 4 months of storage, respectively. During simulated transit conditions of 2, 4.5, 7.5, and 10 °C, the CO₂ level in MAPc was maintained at 5.6–7.9%, while O₂ was reduced dramatically to 10.5, 5.0, 2.5, and 1.0%, respectively. IB developed at 7.5 and 10 °C but not at 2 and 4.5 °C, regardless of pre-transit storage duration (1 and 3 months) at −1.1 °C. The longer the storage duration and the higher transit temperature, the higher the incidence and severity of IB. The MAP-related IB disorder observed in this study included two types of symptoms: classic pithy brown core and wet brown flesh. The MAPc storage gas atmospheres maintained fruit firmness, color and higher eating quality after ripening, eliminated senescent scald and core breakdown, suppressed the loss of ascorbic acid (AsA) and titratable acidity, and slowed the accumulation of malondialdehyde (MDA) during storage at −1.1 °C for up to 4 months or 3 months + 3 weeks at simulated transit temperatures of 2 and 4.5 °C. In contrast, fruit held in MAP with low O₂ levels (1.0–2.5%) developed IB that appeared to be associated with a reduction in AsA, accumulated MDA and exhibited an increase in membrane leakage. MAP inhibited ripening at high CO₂ + high O₂ but lead to IB when the packaging material or elevated temperatures resulted in high CO₂ + low O₂ conditions. The incidence of IB closely correlated with lipid peroxidation and appeared to be related to fruit AsA concentration. The MAPc designed for pears appears to be suitable for ‘Bartlett’ fruit stored at −1.1 °C for up to 4 months or storage for 3 months and a transportation duration of up to 3 weeks at 0–4.5 °C during the early season and at 0–2 °C during the late packing season. These conditions yielded fruit of high eating quality and without IB or over-ripening upon arrival at distant markets.     

The relevance of N fertilization for the amount of total greenhouse gas emissions in sugar beet cultivation

The agricultural sector is highly affected by climate change and it is a source of greenhouse gases. Therefore it is in charge to reduce emissions. For a development of reduction strategies, origins of emissions have to be known. On the example of sugar beet, this study identifies the main sources and gives an overview of the variety of production systems. With data from farm surveys, calculations of greenhouse gas (GHG) emissions in sugar beet cultivation in Germany are presented. Emissions due to the production and use of fertilizers and pesticides, emissions due to tillage as well as field emissions were taken into account. All emissions related to the growing of catch crops during fall before the cultivation of sugar beet were also included. The emissions are related to the yield to express intensity.The median of total GHG emissions of sugar beet cultivation in Germany for the years 2010–2012 amounted to 2626 equivalents of CO₂ (CO₂eq) kg ha⁻¹ year⁻¹ when applying mineral plus organic fertilizer and to 1782 kg ha⁻¹ when only organic fertilizer was applied. The CO₂eq emissions resulting from N fertilization exclusively were 2.5 times higher than those caused by diesel and further production factors. The absence of emissions for the production of organic fertilizers led to 12% less total CO₂eq emissions compared to the use of mineral fertilizer only. But by applying organic fertilizer only, there were more emissions via the use of diesel due to larger volumes transported (126 l diesel ha⁻¹ vs. 116 l ha⁻¹ by applying mineral fertilizer exclusively).As there exists no official agreement about calculating CO₂eq emissions in crop production yet, the authors conclude that there is still need for further research and development with the aim to improve crop cultivation and crop rotations concerning GHG emissions and the therewith related intensity.     

Prestorage application of high carbon dioxide combined with controlled atmosphere storage as a dual approach to control Botrytis cinerea in organic ‘Flame Seedless’ and ‘Crimson Seedless’ table grapes

Pre-storage application of 40% CO₂ at 0 °C for 24 or 48 h and controlled atmosphere (12% O₂ + 12% CO₂) storage at 0 °C for up to eight weeks on decay control and quality of organic ‘Flame Seedless’ and ‘Crimson Seedless’ table grapes were studied as a postharvest disease control alternative. To simulate different potential field conditions, these organic treatments were applied to organic-grown grapes that were naturally infected (without inoculation), surface inoculated (berries inoculated by spraying with a conidia suspension), and nesting inoculated (clusters inoculated by placing in the middle an artificially infected berry) with the pathogen Botrytis cinerea, the cause of grape gray mold. Under these three conditions, a 40% CO₂ for 48 h pre-storage treatment followed by controlled atmosphere reduced the gray mold incidence from 22% to 0.6% and from 100% to 7.4% after four and seven weeks, respectively. High CO₂ pre-storage alone limited botrytis incidence in both naturally and artificially infected grapes, but was more effective when combined with CA. These treatments did not affect visual or sensory fruit quality. Exposure to high CO₂ for 24 or 48 h effectively inhibited mycelial growth of B. cinerea in PDA plates incubated at 22 °C for up to 72 h. Conidia germination in PDA plates was reduced ∼60% after 12 h incubation. In vitro studies demonstrated a fungistatic effect, but further studies on the mechanism of action could improve treatment performance. This novel high CO₂ initial fumigation followed by controlled atmosphere during storage or transportation could be a commercially feasible alternative for postharvest handling of organic and conventional table grapes. Our results encourage validating this combined physical treatment in other cultivars and under commercial conditions.