Ethylene Evolution Research Articles

A battery-powered air sampler to monitor the evolution of ethylene during reefer container transport of fruit

A battery-powered air sampler to monitor the evolution of ethylene during reefer container transport of fruit

Exploring the influence of a single-nucleotide mutation in EIN4 on tomato fruit firmness diversity through fruit pericarp microstructure.

Tomato (Solanum lycopersicum) stands as one of the most valuable vegetable crops globally, and fruit firmness significantly impacts storage and transportation. To identify genes governing tomato firmness, we scrutinized the firmness of 266 accessions from core collections. Our study pinpointed an ethylene receptor gene, SlEIN4, located on chromosome 4 through a genome-wide association study (GWAS) of fruit firmness in the 266 tomato core accessions. A single-nucleotide polymorphism (SNP) (A → G) of SlEIN4 distinguished lower (AA) and higher (GG) fruit firmness genotypes. Through experiments, we observed that overexpression of SlEIN4AA significantly delayed tomato fruit ripening and dramatically reduced fruit firmness at the red ripe stage compared with the control. Conversely, gene editing of SlEIN4AA with CRISPR/Cas9 notably accelerated fruit ripening and significantly increased fruit firmness at the red ripe stage compared with the control. Further investigations revealed that fruit firmness is associated with alterations in the microstructure of the fruit pericarp. Additionally, SlEIN4AA positively regulates pectinase activity. The transient transformation assay verified that the SNP (A → G) on SlEIN4 caused different genetic effects, as overexpression of SlEIN4GG increased fruit firmness. Moreover, SlEIN4 exerts a negative regulatory role in tomato ripening by impacting ethylene evolution through the abundant expression of ethylene pathway regulatory genes. This study presents the first evidence of the role of ethylene receptor genes in regulating fruit firmness. These significant findings will facilitate the effective utilization of firmness and ripening traits in tomato improvement, offering promising opportunities for enhancing tomato storage and transportation capabilities.

The Biophysical Properties of the Fruit Cuticles of Six Pear Cultivars during Postharvest Ripening

Pears are abundant in bioactive compounds, which exert favorable effects on human health. The biophysical attributes of fruit cuticles are pivotal in determining fruit quality, storability, and susceptibility to mold growth. This study aimed to elucidate the biophysical properties of six pear cultivars, ‘Conference’, ‘Celina’, ‘Abate Fetel’, ‘Packham’s Triumph’, ‘Sweet Sensation’, and ‘Williams’. Two maturity stages, unripe and fully ripened, were investigated. Furthermore, the efficacy of trimethyl-chitosan-coated pear surfaces in preventing Penicillium expansum (P. expansum) growth was assessed. Basic maturity indices (CIE color, ethylene evolution, firmness, soluble solids), cuticle contact angle, roughness, and zeta potential were analyzed. Surface roughness was measured using an optical profilometer, hydrophobicity was measured via profilometry, and zeta potential was quantified using an electrokinetic analyzer. The ‘Celina’ cultivar exhibited the highest roughness, whereas ‘Williams’ had the lowest roughness. All the cultivars’ cuticles demonstrated hydrophilic characteristics, with contact angles ranging between 65° and 90°. For pH values exceeding 3.5, all pear surfaces exhibited a negative zeta potential. P. expansum growth was the slowest on the ‘Packham’s Triumph’ and ‘Conference’ cultivars. Treatment with trimethyl chitosan effectively inhibited P. expansum growth in the initial hours of incubation. In conclusion, diverse pear cultivars manifest distinct biophysical surface properties and varying susceptibility to P. expansum growth. The growth of P. expansum correlates positively with roughness, contact angle, and zeta potential. These differences can significantly impact shelf life potential and the overall postharvest quality of pears.

Structuring Cu Membrane Electrode for Maximizing Ethylene Yield from CO2 Electroreduction.

Electrocatalytic ethylene (C2H4) evolution from CO2 reduction is an intriguing route to mitigate both the energy and environmental crises; however, to acquire industrially relevant high productivity and selectivity at low energy cost remains to be challenging. Membrane assembly electrode has shown great prospect and tailoring its architecture for maximizing C2H4 yield at minimum voltage with long-term stability becomes critical. Here a freestanding Cu membrane cathode is designed and constructed by electrochemically depositing mesoporous Cu film on Cu foam to simultaneously manage CO2, electron, water, and product transport, which shows an extraordinary C2H4 Faradaic efficiency of 85.6% with a full cell power conversion efficiency of 33% at a current density of 368mAcm-2, heading the techno-economic viability for electrocatalytic C2H4 production.

Impact of selenium fertilisation of ‘Red Jonaprince’ apple trees on selenium nutrition and fruit quality and storability

Selenium (Se) malnutrition in humans is caused by low soil Se availability, leading to an insufficient content of this nutrient in food. In this study, we examined the effect of Se fertilisation on the absorption and distribution of Se in apple (Malus domestica Borkh.) trees, as well as fruit quality and storability. The experiment was carried out on mature ‘Red Jonaprince’ apple trees grown in medium-textured soil. Fertilisation of Se (as sodium selenate) was applied as: (i) summer sprays, 4 times in a season at a rate of 50 g Se ha−1, (ii) a fall spray, 2 weeks before harvest at a rate of 200 g Se ha−1, (iii) soil application at a rate of 500 g Se ha−1, and (iv) fertigation at a rate of 100 g Se ha−1. Trees that were not fertilised with Se served as controls. The results revealed that the fall Se spray caused leaf burns and defoliation, but it did not affect tree vigour and fruit yield. The highest leaf Se concentration was found on Se-sprayed trees in the fall. Most Se in fruit was recorded on Se-sprayed trees in the fall and on Se-fertigated trees; fruit Se amounts from these combinations covered about 30 % of the recommended daily intake. None of the Se treatments affected fruit appearance (mean weight, skin russeting, and colour), flesh firmness, and acidity at harvest. Apart from the fall Se spray, the other treatments decreased the soluble solid concentration (SSC), starch index values, ethylene evolution, and increased Streif index values in apples at harvest. After storage, Se-enriched apples were firmer, contained more organic acids, and produced less ethylene than the control fruit. We conclude that Se fertigation or a fall Se spray can be recommended in apple orchards, at least for late season and winter varieties, to biofortify fruit with Se and delay their ripening process.

Evaluation and characterization of TILLING-based putative mutant populations of papaya cv. Arka Prabhath

Manifestation of virus resistance, shelf-life with dwarf stature are important pre-requisites for successful cultivation of papaya in India as it facilitates improved production, productivity and reduced post-harvest loss. One of the methods to create variability is to use mutagens in selected cultivar of papaya. Accordingly, the TILLING-based mutant populations of papaya cv. Arka Prabhath were generated through irradiation of gamma rays ranging from 50 to 500 Gy dosage. In this experiment, the putative mutant populations were evaluated and characterized based on morphological, fruit quality and physiological parameters. Desirable traits such as early flowering, reduced plant height and bearing height, papaya ring spot virus tolerant plants and fruits with extended shelf life were observed in the mutant population. Early flowering and reduced plant height with wide variation was found at 50 Gy wherein the first flowering was on 57 days with 43 cm of plant height in contrast to 80 days in control plants with 79 cm of plant height. Reduced bearing height (40 cm) was observed in 100 Gy with a mean bearing height of 70.65 cm in comparison to control plants (72.97 cm), range being 55 to 115 cm. Further, based on morphological traits twenty-one lines were selected for physiological and fruit quality trait evaluation. Reduction in physiological loss in weight, ethylene evolution rate and respiration rate were observed in the mutant lines treated with 150 Gy dosage. The results advocate the efficacy of gamma induced mutation for developing dwarf cultivar with improved quality and shelf-life of fruits.

Overexpression of OsACL5 triggers environmentally-dependent leaf rolling and reduces grain size in rice.

Major polyamines include putrescine, spermidine, spermine and thermospermine, which play vital roles in growth and adaptation against environmental changes in plants. Thermospermine (T-Spm) is synthetised by ACL5. The function of ACL5 in rice is still unknown. In this study, we used a reverse genetic strategy to investigate the biological function of OsACL5. We generated several knockout mutants by pYLCRISPR/Cas9 system and overexpressing (OE) lines of OsACL5. Interestingly, the OE plants exhibited environmentally-dependent leaf rolling, smaller grains, lighter 1000-grain weight and reduction in yield per plot. The area of metaxylem vessels of roots and leaves of OE plants were significantly smaller than those of WT, which possibly caused reduction in leaf water potential, resulting in leaf rolling with rise in the environmental temperature and light intensity and decrease in humidity. Additionally, the T-Spm contents were markedly increased by over ninefold whereas the ethylene evolution was reduced in OE plants, suggesting that T-Spm signalling pathway interacts with ethylene pathway to regulate multiple agronomic characters. Moreover, the osacl5 exhibited an increase in grain length, 1000-grain weight, and yield per plot. OsACL5 may affect grain size via mediating the expression of OsDEP1, OsGS3 and OsGW2. Furthermore, haplotypes analysis indicated that OsACL5 plays a conserved function on regulating T-Spm levels during the domestication of rice. Our data demonstrated that identification of OsACL5 provides a theoretical basis for understanding the physiological mechanism of T-Spm which may play roles in triggering environmentally dependent leaf rolling; OsACL5 will be an important gene resource for molecular breeding for higher yield.

Treatment of 'cripps pink' apples with nitric oxide in a controlled atmosphere ultra-low oxygen: Impacts on overall fruit quality and anaerobic compounds

The objective of this work was to evaluate the impact of nitric oxide application (in different doses 0, 1, 2, 5 e 10 μL L−1 of NO) on fruit quality and formation of anaerobic metabolism products of 'Cripps Pink' apples stored in a controlled atmosphere ultra-low oxygen (CA - ULO). Fruit were harvested at two maturity stages (less and more mature) and stored in CA - ULO (0.8 kPa of O2, <0.5 kPa of CO2, at temperature of 1.5 ± 0.2 °C, and 94 ± 2% RH) for four and eight months, followed by seven days of shelf life. Fruit in CA - ULO were treated weekly with 0, 1, 2, 5, or 10 μL L−1 of NO. In general, linear and quadratic models adjusted to quantitative levels of NO showed reduced respiration and ethylene evolution rates with the increase of NO concentrations. Also, the increase of NO concentration consistently reduced the activities of β-GAL and PG, preserved flesh firmness, and reduced the production of anaerobic metabolites (acetaldehyde and ethanol) and the incidence of decay in the fruit. These effects of NO concentrations on each quality attribute were dependent on maturity stage and storage duration (period in CA - ULO and/or subsequent shelf life). However, the results show that weekly application of 5–7 μL L−1 of NO during storage in CA - ULO maintained the quality of 'Cripps Pink' apples.

Aminoethoxyvinylglycine Reduces Preharvest Fruit Drop and Fruit Ethylene Evolution in ‘Red Delicious’ Apple but Affects Fruit Size and Quality Inconsistently

Aminoethoxyvinylglycine (AVG) is widely used in commercial apple (Malus ×domestica Borkh.) production to reduce preharvest fruit drop (PFD) and delay ripening for harvest management. Recently, the maximum allowable concentration of AVG was doubled (up to 264 mg⋅L−1). Reports of the relationship between the AVG concentration and fruit growth, size, and quality have been contradictory. We evaluated the relationship between the AVG concentration and PFD, fruit size, fruit quality, and expression of ethylene signaling-related and cell wall modification-related genes. Experiments were conducted in 2019 and 2020 using mature ‘Red Delicious’ in western North Carolina. The AVG treatments [0 and 132 (AVG-1x) and 264 mg⋅L−1 (AVG-2x)] were applied 3 weeks before the expected harvest. The AVG treatments reduced fruit drop and internal ethylene concentration relative to the control in both years. There was no difference in drop between AVG-1x and AVG-2x applications. Only in 2020 did AVG treatments delay fruit softening and starch hydrolysis and reduce soluble solids concentration. There were no effects on red fruit color development. Fruit size was unaffected by AVG in 2019, but it was reduced in 2020 with the AVG-2x application. AVG reduced ethylene synthesis and altered signaling, evidenced by decreased relative expression of genes related to ethylene signaling (ARGOS1, ARGOS2). AVG applications also reduced the expression of EXPA8;1, suggesting that reduced cell wall disassembly was associated with a reduction in fruit softening. These results indicate that preharvest applications of 132 mg⋅L−1 AVG effectively reduced PFD via altering ethylene evolution and signaling. Use of a higher AVG concentration was of limited benefit.

Ethylene sensitivity underscores the yield advantage of high-grain numbers in cylinder-shaped rice panicles

Panicle-wise grain-filling of individual spikelets is location-specific in rice; apical spikelets dominate over their basal counterparts. This pattern of grain filling changes with panicle architecture among cultivars, but the underlying mechanisms are not understood. The newly introduced rice cultivars with cylinder-shaped panicles, although suited for high yield, exhibit several instances of poor filling. In this study shoot apical meristem gene expressions in the ontogeny stage and their influence on spikelet survival at the post-anthesis stage were elucidated by screening two types of rice Recombinant Inbreed Lines (RIL) having similar spikelet density in the cylinder-shaped panicles, such as SR-157 (low-sterile) and SR-159 (high-sterile) and their parents NPT-V12 (low-sterile) and SPS-1–6–1 (high-sterile). Between cultivars, SR-157 versus SR-159, and spikelets located apically versus basally, grain filling was more vulnerable in the latter than the former owing to a more remarkable evolution of ethylene at anthesis. Combined genome analyses revealed that branching genes like DEP2, SPL-14, PTR, and FZP over-expressed in high-sterile compared to low-sterile cultivars during the ontogeny stage. But this over-expression had no matching improvement in grain-setting in the post-anthesis stage. Grain starch synthesis was higher, and expression of ethylene receptors and signal transducer genes was lower in the low- compared to high-sterile cultivars. Thus, the quantum of grain set in the post-anthesis stage determining actual panicle yield was not dependent on the expression of genetic factors in the pre-anthesis stage defining potential grain yield. It was concluded that the default expression of ethylene synthesis and transducer genes at anthesis cause spikelet degeneration and deride the yield advantage of a high spikelet number in some cylinder-shaped rice panicles. The genomic studies controlling ethylene evolution and action in rice panicles must be an inalienable part of any constructive contribution to the yield potential.

Ethylene, ACC, and the Plant Growth-Promoting Enzyme ACC Deaminase.

Here, a brief summary of the biosynthesis of 1-aminocyclopropane-1-carboxylate (ACC) and ethylene in plants, as well as overviews of how ACC and ethylene act as signaling molecules in plants, is presented. Next, how the bacterial enzyme ACC deaminase cleaves plant-produced ACC and thereby decreases or prevents the ethylene or ACC modulation of plant gene expression is considered. A detailed model of ACC deaminase functioning, including the role of indoleacetic acid (IAA), is presented. Given that ACC is a signaling molecule under some circumstances, this suggests that ACC, which appears to have evolved prior to ethylene, may have been a major signaling molecule in primitive plants prior to the evolution of ethylene and ethylene signaling. Due to their involvement in stimulating ethylene production, the role of D-amino acids in plants is then considered. The enzyme D-cysteine desulfhydrase, which is structurally very similar to ACC deaminase, is briefly discussed and the possibility that ACC deaminase arose as a variant of D-cysteine desulfhydrase is suggested.

Extending shelf life of Ney Poovan banana through active packaging for export market

The present study focuses on the impact of active packaging technology on the Ney Poovan banana variety, aiming to extend its shelf life for export purpose. The experiment comprised four treatments: an ethylene absorber, a moisture absorber, a control group, and packaging in vacuum-sealed polythene bags. These banana samples were subsequently stored at two different temperatures, namely room temperature (RT) and 13.5°C. The results obtained from the experiment indicated that the fruits packed with an ethylene absorber exhibited an extended shelf life of 72 days when stored at 13.5°C. The fruits remained fresh for 20 days when stored at RT. These ethylene-treated fruits also displayed the highest pulp-to-peel ratio (PPR) of 7.34 when held at 13.5°C, while the highest acid content (0.673%) was registered at RT. On the other hand, the control group fruits stored at RT tended to show the highest TSS content (29oBrix). The fruits stored at RT, irrespective of the treatments exhibited the highest content of TSS (21.11oBrix). The physiological loss in weight increased gradually during storage in both temperatures but was low in fruits packed with moisture absorbers. Though the ethylene evolution rate increased towards extended storage in both temperatures, the concentration was less in fruits packed with ethylene absorber.

Expression patterns of volatile compounds during ‘FL 47′ tomato ripening and their response to exogenous methyl salicylate (MeSA) fumigation

Aroma, a complex mixture of volatiles, is essential for tomato flavor; however, the expression patterns of most volatile compounds and their response to exogenous methyl salicylate (MeSA) treatment are still unclarified. In this study, in association with the alteration in ethylene evolution and its biosynthetic genes (SlACO1 and SlACS2/4), 31 volatiles fluctuated or accumulated during ‘FL 47′ tomato ripening with a burst at pink or red stage, resulting in the alteration in aroma quality. Meanwhile, the alternation of 29 volatiles, lycopene and β-carotenoid content as well as SlPSY1 and SlCCD1A/B mRNAs demonstrated a strong correlation with ethylene evolution. Further study validated the role of ethylene in apocarotenoid volatile biosynthesis. The formation of 24 volatiles were greatly suppressed in MeSA-treated fruit at red stage along with lower ethylene. In addition, the reduction of apocarotenoid volatiles was associated with downregulated SlPSY1 and SlCCD1A/B mRNAs and carotenoid accumulation when compared with control. In combination with the alternation of ethylene evolution and apocarotenoid volatile formation in SlACS2-overexpressing fruit after MeSA treatment, our results implied that ethylene played a critical role in MeSA-induced reduction of apocarotenoid volatiles via its influence on carotenoid biosynthesis and SlCCD1A/B expression. Although the formation of over 60% of the tomato volatiles was altered by MeSA fumigation, no difference in total volatile abundance or aroma quality could be detected between samples. On the other hand, the taste quality was substantiality altered by MeSA treatment in association with the reduction of TSS and TSS/TA ratio as well as TA increment. Taken together, our results illustrated that MeSA application for fruit quality control was at the expense of flavor alternation.

Prolonged low temperature exposure de-sensitises ABA-induced stomatal closure in soybean, involving an ethylene-dependent process.

Chilling can decrease stomatal sensitivity to abscisic acid (ABA) in some legumes, although hormonal mechanisms involved are unclear. After evaluating leaf gas exchange of 16 European soybean genotypes at 14°C, 6 genotypes representing the range of response were selected. Further experiments combined low (L, 14°C) and high (H, 24°C) temperature exposure from sowing until the unifoliate leaf was visible and L or H temperature until full leaf expansion, to impose four temperature treatments: LL, LH, HL, and HH. Prolonged chilling (LL) substantially decreased leaf water content but increased leaf ethylene evolution and foliar concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, indole-3-acetic acid, ABA and jasmonic acid. Across genotypes, photosynthesis linearly increased with stomatal conductance (Gs), with photosynthesis of HH plants threefold higher than LL plants at the same Gs. In all treatments except LL, Gs declined with foliar ABA accumulation. Foliar ABA sprays substantially decreased Gs of HH plants, but did not significantly affect LL plants. Thus low temperature compromised stomatal sensitivity to endogenous and exogenous ABA. Applying the ethylene antagonist 1 methyl-cyclopropene partially reverted excessive stomatal opening of LL plants. Thus, chilling-induced ethylene accumulation may mediate stomatal insensitivity to ABA, offering chemical opportunities for improving seedling survival in cold environments.

New Online Monitoring Approaches to Describe and Understand the Kinetics of Acetaldehyde Concentration during Wine Alcoholic Fermentation: Access to Production Balances

The compound acetaldehyde has complex synthesis kinetics since it accumulates during the growth phase and is consumed by yeast during the stationary phase, as well as evaporating (low boiling point) throughout the process. One recurrent question about this molecule is: can temperature both increase and decrease the consumption of the molecule by yeast or does it only promote its evaporation? Therefore, the main objective of this study was to describe and analyze the evolution of acetaldehyde and shed light on the effect of temperature, the main parameter that impacts fermentation kinetics and the dynamics of acetaldehyde synthesis. Thanks to new online monitoring approaches, anisothermal temperature management and associated mathematical methods, complete acetaldehyde production balances during fermentation made it possible to dissociate biological consumption from physical evaporation. From a biological point of view, the high fermentation temperatures led to important production of acetaldehyde at the end of the growth phase but also allowed better consumption of the molecule by yeast. Physical evaporation was more important at high temperatures, reinforcing the final decrease in acetaldehyde concentration. Thanks to the use of production balances, it was possible to determine that the decrease in acetaldehyde concentration during the stationary phase was mainly due to yeast consumption, which was explained by the metabolic links found between acetaldehyde and markers of metabolism, such as organic acids.

Nitric Oxide and Proline Modulate Redox Homeostasis and Photosynthetic Metabolism in Wheat Plants under High Temperature Stress Acclimation

The effects of exogenously-sourced NO (nitric oxide, as 100 µM SNP) and proline (50 mM) in the protection of the photosynthetic performance of wheat (Triticum aestivum L.) plants against heat stress were investigated. The study focused on the mechanisms of proline accumulation, activity, gene expression of antioxidant enzymes, and NO generation. Plants were exposed to a temperature of 40 °C for 6 h per day over 15 days, then allowed to recover at 28 °C. Heat-stressed plants showed increased oxidative stress, with higher levels of H2O2 and TBARS (thiobarbituric acid reactive substances) and increased proline accumulation, ACS activity, ethylene evolution, and NO generation, which in turn leads to increased accumulation of antioxidant enzymes and reduced photosynthetic attributes. In the tested wheat cultivar, the exogenous application of SNP and proline under heat stress improved the photosynthesis and reduced oxidative stress by enhancing the enzymatic antioxidant defense system. Potentially, the promoter AOX (alternative oxidase) played a role in maintaining redox homeostasis by lowering H2O2 and TBARS levels. The genes for GR antioxidant and photosystem II core protein encoding psbA and psbB were highly up-regulated in nitric oxide and proline treated heat-stressed plants, indicating that ethylene positively impacted photosynthesis under high temperature stress. Moreover, nitric oxide supplementation under high temperature stress optimized ethylene levels to regulate the assimilation and metabolism of proline and the antioxidant system, lowering the adverse effects. The study showed that nitric oxide and proline increased high temperature stress tolerance in wheat by increasing the osmolytes accumulation and the antioxidant system, resulting in enhanced photosynthesis.

Multiwavelength Speciation in Pyrolysis of n-Pentane and Experimental Determination of the Rate Coefficient of nC5H12 = nC3H7 + C2H5 in a Shock Tube.

We report the application of a multiwavelength speciation strategy to the study of n-pentane (nC5H12) pyrolysis behind reflected shock waves in a shock tube. Experiments were conducted with 2% nC5H12/0.8%CO2/Ar (by mole) between 1150 and 1520 K in the pressure range of 1-2 atm. Utilization of laser absorption spectroscopy at eight wavelengths allowed time-resolved measurements of n-pentane, ethylene, methane, heavy alkenes, and temperature. The measured time histories were compared against the predictions of four recently developed chemical kinetic models for heavy hydrocarbons. It was found that none of the models reconciled the measured species time histories simultaneously. Sensitivity analysis was conducted to identify key reactions influencing the evolution of ethylene and other major pyrolysis products. The analysis revealed that the unimolecular decomposition of n-pentane into n-propyl and ethyl radicals has a dominating influence over the evolution of ethylene in the temperature range of 1150-1450 K. The rate coefficient of this reaction was then adjusted to match the measured ethylene time histories for each experiment. The rate coefficients thus determined, were fit against temperature using an Arrhenius expression given by k1(T) = 3.5 × 1014 exp(-67.2 kcal/RT) s-1. The average overall 2σ uncertainty of the measured rate coefficient was found to be ±35%, resulting primarily from uncertainties in the rate coefficients of secondary reactions. The measured rate coefficient, when used with the models, leads to a significant improvement in the prediction of species time histories. Further improvements in the model are possible if the rate coefficients of relevant reactions pertaining to small hydrocarbon chemistry are determined with an improved accuracy, and less uncertainty. To the best knowledge of the authors, this is the first experimental determination of the rate coefficient of C5H12 → nC3H7 + C2H5.

Quantification of Ethylene Production in Leaf and Bud Tissue of the Subtropical Tree Crop Litchi (Litchi chinensis Sonn.) Using Gas Chromatography and Flame Ionization Detection.

Ethylene is an important plant hormone that is involved in the regulation of numerous processes in plant development. It also acts as a signaling molecule in response to biotic and abiotic stress conditions. Most studies have investigated ethylene evolution of harvested fruit or small herbaceous plants under controlled conditions, but only a few explored ethylene release in other plant tissues, such as leaves and buds, particularly those of subtropical crops. However, in light of increasing environmental challenges in agriculture (such as temperature extremes, droughts, floods, and high solar radiation), studies on these challenges and on potential chemical treatments for mitigating their effects on plant physiology have become more and more important. Thus, adequate techniques for the sampling and analysis of tree crops are needed to ensure accurate ethylene quantification. As part of a study on ethephon as a mitigating agent to improve litchi flowering under warm winter conditions, a protocol was developed for ethylene quantification in leaf and bud tissue of litchi following ethephon application, taking into account that these plant organs release lower ethylene concentrations than fruit. At sampling, leaves and buds were placed in glass vials of appropriate sizes for the respective plant tissue volumes and allowed to equilibrate for 10 min to release possible wound ethylene before incubating the samples for 3 h at ambient temperature. Thereafter, ethylene samples were aspirated from the vials and analyzed using a gas chromatograph with flame ionization detection, the TG-BOND Q+ column for separation of ethylene, and helium as the carrier gas. Quantification was achieved based on a standard curve derived from an external standard gas calibration with certified ethylene gas. This protocol will also be appropriate for other tree crops with similar plant materials as study foci. It will enable researchers to accurately determine ethylene production in various studies investigating the role of ethylene in general plant physiology or stress-induced plant responses following a range of treatment conditions.

Attenuating sugar spot and retaining quality of banana fruits by combined use of hot water and calcium lactate during storage.

Combined use of hot water (HW) treatment and calcium lactate (CL) is a promising postharvest approach to preserve the food value and prolong the shelf life of fruits. The present experiment aims to determine the physiological loss in weight, firmness, respiration rate, ethylene and biochemical attributes of banana fruits treated with hot water (50 °C for 7 min) and aqueous CL dipping (1, 2, and 3% for 2 min). Treated fruits were stored under ambient conditions (22-25°C temperature and 60-65% of relative humidity) for up to 9 days. The study showed that combined use of HW and CL (3%) maintained higher hue angle, peel firmness (4.4 N), reduced decay loss (10.63%), respiration and ethylene evolution rate of stored fruits. Also, CL treatments (3%) with HW proved the best which reduced 6-fold sugar spot and 1.5-fold decay loss over untreated fruits. At the end of storage sensory parameters such as mouthfeel, peel colour and overall acceptability (score 6.9) were recorded higher in HW and CL 3% treated fruits. The findings indicated that pre-storage combined use of HW and CL has a great potential to preserve quality, delay ripening, and reduce sugar spots, and postharvest decay loss in banana fruit without any adverse effect on consumer appeal.

Maturity indices of specific mango varieties produced at medium altitude agro-ecological zone in Kenya

The high postharvest losses (40 – 50%) reported in the mango value chain are partly attributed to lack of reliable maturity indices. Harvest maturity is dictated by the intended use and the target market for the fruits. The aim of this study was to establish maturity indices of three commercial mango varieties namely ‘Van dyke,’ ‘Kent’ and ‘Tommy Atkins’ in Embu County of Kenya. At least eighteen mango trees (six per variety) were randomly tagged at 50% flowering in each of the three selected small-scale farms in Embu County. Number of days from flowering to different maturity stages were recorded (computational method). For each variety and maturity stage, five fruits were randomly sampled from the pool and analysed for physical (size, density, firmness, colour), physiological (ethylene evolution and respiration rate) and biochemical (obrix/Total Soluble Solids (TSS), total titratable acidity (TTA) and their ratio) indices of maturity. The results showed that although size increased as the fruits developed, it was not a reliable index of maturity since some small-sized fruits attained advanced maturity earlier than others that were large-sized. The weight of the fruits fluctuated as the fruits developed and similar trend was observed on the specific gravity. Flesh firmness decreased gradually with maturity from a mean firmness of 40.54 N to 6.84 N. Tommy Atkins exhibited the lowest firmness levels at stage 4. Kent variety had the lowest ethylene at all stages while Tommy Atkins variety had the highest respiration rate of 21.40 ml/kg/hr at stage 1, which increased gradually to 32.10 ml/kg/hr at stage 4. The highest TSS: TTA values were reported in Kent variety. The results revealed significant differences in maturity indices of the three mango varieties despite similar physical indices. This study confirms the unreliability of physical maturity indices such as size and shape in establishing the right harvest stage of mango fruits. Computational, physiological and biochemical maturity indices should be incorporated in determination of accurate harvest maturity for mango. Key words: Ethylene, Harvest maturity, ‘Kent’, Maturity indices, Respiration, ‘Tommy Atkins’, ‘Van dyke’