Preclimacteric Stage Research Articles

Innovative Postharvest Management for Hass Avocado at the Preclimacteric Stage: A Combined Technology with GABA and 1-MCP.

Avocado (Persea americana Mill.) is a subtropical climacteric fruit with a limited shelf life due to its high sensitivity to low temperatures. Chilling injury (CI) produced by cold storage displays symptoms in avocado fruit such as irregular ripening, darkening of the mesocarp, hardening of vascular strands, lipid oxidation with "off flavors", and pitting and darkening of the skin, increasing weight loss. Accordingly, we studied the effect of γ-aminobutyric acid (GABA) and 1-methylcyclopropene (1-MCP) alone or in combination as postharvest treatments to maintain quality and to increase cold tolerance. Hass avocados were stored at 5 °C plus 5 days at room temperature. The results showed that the combined treatment improved fruit quality parameters as compared with control fruit and with those treated with only 1-MCP or GABA. The combined treatment delayed synergistically the postharvest ripening process. This delayed pattern was concomitant with a delayed ethylene pattern in GABA + 1-MCP or 1-MCP fruit batches. CI symptoms and electrolyte leakage were minimized in all GABA and 1-MCP fruit batches specifically in the combined treatment. For this reason, the synergistic effect of the combination of treatments may be recommended as an effective alternative strategy to prolong the postharvest quality of avocado during refrigerated storage.

Comparative study of expression patterns of aquaporin (AQP) genes in apple fruits with contrasting ripening behavior

This research compared expression patterns of aquaporin (AQP) genes in two apple cultivars that exhibit contrasting ripening behavior. Commercially-mature apple fruits of cultivars ‘Golden Delicious’ and ‘Red Fuji’ were chosen as materials. The results showed that compared with ‘Red Fuji’, ‘Golden Delicious’ generally had higher rate of respiration, ethylene production, weight loss, dry matter concentration (DMC), titratable acidity (TA), total soluble solids (TSS) and soluble sugar contents during ripening. At 35 d, cells in ‘Golden Delicious’ were loosely arranged with larger intercellular space, while in ‘Red Fuji’, cells were still densely packed. A total of 20 AQPs were detected in both cultivars. Expression of these identified genes was in a tissue- and cultivar-specific manner during ripening. Generally, expression of MdAQPs was differentially induced at climacteric stage in peel and flesh tissues of ‘Golden Delicious’. In contrast, expression of most MdAQPs was differentially up-regulated at preclimacteric stage in peel and flesh tissues of ‘Red Fuji’. These results will be useful for further study the relationships between MdAQPs and storability of different apple cultivars.

Response of different cultivars of apricots to gamma irradiation under different storage conditions

A study was carried out to evaluate the physicochemical and phytochemical characteristics of various apricot cultivars (CITH-1, CITH-2, and Tilton) as well as the effect of gamma irradiation on their quality and shelf life. After harvesting at the pre-climacteric stage from the Central Institute of Temperate Horticulture, J & K (UT), apricot cultivars were gamma-irradiated in the dosage range of 0.25–1.0 kGy at the Bhaba Atomic Research Centre (BARC), Srinagar, and then stored at ambient temperature (25 ± 2 °C, RH 70–80%) and refrigerated temperature (3 ± 1 °C, RH 80–85%). The apricots were evaluated for their physicochemical and phytochemical composition. According to the HPLC analysis, the total polyphenol content of the cultivars differed significantly (p < 0.05), with Tilton having the highest total phenolic acid concentration of 5.85 mg/kg FW, followed by CITH-1 (5.14 mg/kg FW) and CITH-2 (3.25 mg/kg FW). In terms of lower weight loss, inhibition of enzyme activity, colour values, and maintaining quality and extending storage stability, irradiation at 0.25 kGy and 0.5 kGy was found to be significantly (p < 0.05) more effective than 0.75 kGy and 1.0 kGy. At dose levels of 0.5 kGy and 0.75 kGy, gamma irradiation was found to be significantly (p < 0.05) efficient in maintaining the firmness and bio-yield point without affecting overall acceptability. However, the 1.0 kGy dosage was found to be ineffective in delaying the occurrence of fruit rot and prolonging shelf life in both ambient and refrigerated storage. Thus, low-dose gamma radiation in the range of 0.25 kGy–0.75 kGy can be used to improve the quality and shelf life of apricots while also enhancing their therapeutic constituents intact for up to 21 days at ambient storage and 42 days under refrigerated conditions.

Multifaceted roles of nitric oxide in tomato fruit ripening: NO-induced metabolic rewiring and consequences for fruit quality traits.

Nitric oxide (NO) has been implicated as part of the ripening regulatory network in fleshy fruits. However, very little is known about the simultaneous action of NO on the network of regulatory events and metabolic reactions behind ripening-related changes in fruit color, taste, aroma and nutritional value. Here, we performed an in-depth characterization of the concomitant changes in tomato (Solanum lycopersicum) fruit transcriptome and metabolome associated with the delayed-ripening phenotype caused by NO supplementation at the pre-climacteric stage. Approximately one-third of the fruit transcriptome was altered in response to NO, including a multilevel down-regulation of ripening regulatory genes, which in turn restricted the production and tissue sensitivity to ethylene. NO also repressed hydrogen peroxide-scavenging enzymes, intensifying nitro-oxidative stress and S-nitrosation and nitration events throughout ripening. Carotenoid, tocopherol, flavonoid and ascorbate biosynthesis were differentially affected by NO, resulting in overaccumulation of ascorbate (25%) and flavonoids (60%), and impaired lycopene production. In contrast, the biosynthesis of compounds related to tomato taste (sugars, organic acids, amino acids) and aroma (volatiles) was slightly affected by NO. Our findings indicate that NO triggers extensive transcriptional and metabolic rewiring at the early ripening stage, modifying tomato antioxidant composition with minimal impact on fruit taste and aroma.

Aloe vera gel coating aggravates superficial scald incidence in ‘Starking’ apples during low-temperature storage

The effects of aloe vera (Aloe vera (L.) Burm. f.) gel treatment on the incidence of superficial scald in ‘Starking’ apples (Malus domestica Borkh. Var. Starking) during cold storage were studied. Apples were harvested at the pre-climacteric stage and treated with aloe vera gel. The treatment increased malondialdehyde content and membrane lipid damage. Furthermore, it inhibited the release of ethylene at the early stage but increased it in the later stage. The expression level of ACC synthase 1 (MdACS1) also increased, and the antioxidant capacity in apples, particularly, catalase, peroxidase, and superoxide dismutase activities, all decreased, while concomitantly, the content of α-farnesene and its oxidation product, conjugated triene increased, thereby aggravating superficial scald incidence during storage at low temperature.

Evidence for pre-climacteric activation of AOX transcription during cold-induced conditioning to ripen in European pear (Pyrus communis L.).

European pears (Pyrus communis L.) require a range of cold-temperature exposure to induce ethylene biosynthesis and fruit ripening. Physiological and hormonal responses to cold temperature storage in pear have been well characterized, but the molecular underpinnings of these phenomena remain unclear. An established low-temperature conditioning model was used to induce ripening of 'D'Anjou' and 'Bartlett' pear cultivars and quantify the expression of key genes representing ripening-related metabolic pathways in comparison to non-conditioned fruit. Physiological indicators of pear ripening were recorded, and fruit peel tissue sampled in parallel, during the cold-conditioning and ripening time-course experiment to correlate gene expression to ontogeny. Two complementary approaches, Nonparametric Multi-Dimensional Scaling and efficiency-corrected 2-(ΔΔCt), were used to identify genes exhibiting the most variability in expression. Interestingly, the enhanced alternative oxidase (AOX) transcript abundance at the pre-climacteric stage in 'Bartlett' and 'D'Anjou' at the peak of the conditioning treatments suggests that AOX may play a key and a novel role in the achievement of ripening competency. There were indications that cold-sensing and signaling elements from ABA and auxin pathways modulate the S1-S2 ethylene transition in European pears, and that the S1-S2 ethylene biosynthesis transition is more pronounced in 'Bartlett' as compared to 'D'Anjou' pear. This information has implications in preventing post-harvest losses of this important crop.

UTILIZAÇÃO DE REVESTIMENTOS ALTERNATIVOS NA CONSERVAÇÃO PÓS-COLHEITA DE MAMÃO ‘SUNRISE SOLO’

A cultura do mamão apresenta expressiva participação na produção da fruticultura nacional. Porém, ainda apresenta alta taxa de perda pós-colheita. Em busca de fontes alternativas para a conservação de frutas, o presente trabalho tem por objetivo avaliar o efeito da aplicação de revestimentos alternativos de origem vegetal na conservação pós-colheita de frutos de mamão papaia cultivar Sunrise Solo. O experimento foi conduzido em delineamento inteiramente casualizado, em esquema fatorial 4 x 4 (quatro tratamentos x quatro períodos avaliados), com quatro repetições, onde cada repetição corresponde a um fruto de mamão, totalizando 64 frutos (64 parcelas). Os tratamentos foram distribuídos de forma aleatória: T1: Testemunha (sem uso de revestimento); T2: Óleo purificado de coco babaçu na concentração de 3%; T3: Fécula de mandioca na concentração de 5%; T4: Cera de carnaúba Aruá BR Tropical 18%. Foram selecionados frutos no estádio pré-climatérico. Estes foram imersos durante um minuto em seus respectivos tratamentos e acondicionados em recipientes descartáveis. Após, foram armazenados à temperatura média de 28,6 ºC ± 3 ºC e umidade relativa média de 54,5%. Foram avaliadas as variáveis: coloração da casca, perda de massa fresca, pH e sólidos solúveis totais. O uso de revestimentos alternativos em frutos de mamão retarda a mudança de coloração ao decorrer das avaliações em comparação ao tratamento sem aplicação (controle), destacando-se o tratamento com aplicação de fécula de mandioca (5%). Os frutos revestidos com cera de carnaúba (18%) apresentam os menores valores na perda de massa em todas as épocas de avaliações, diferindo significativamente dos demais tratamentos. Os tratamentos com cobertura não influenciam significativamente no valor do pH e nos sólidos solúveis totais dos frutos de mamão durante todas as épocas de avaliação.

Primary Metabolism in Avocado Fruit.

Avocado (Persea americana Mill) is rich in a variety of essential nutrients and phytochemicals; thus, consumption has drastically increased in the last 10 years. Avocado unlike other fruit is characterized by oil accumulation during growth and development and presents a unique carbohydrate pattern. There are few previous and current studies related to primary metabolism. The fruit is also quite unique since it contains large amounts of C7 sugars (mannoheptulose and perseitol) acting as transportable and storage sugars and as potential regulators of fruit ripening. These C7 sugars play a central role during fruit growth and development, but still confirmation is needed regarding the biosynthetic routes and the physiological function during growth and development of avocado fruit. Relatively recent transcriptome studies on avocado mesocarp during development and ripening have revealed that most of the oil is synthesized during early stages of development and that oil synthesis is halted when the fruit is harvested (pre-climacteric stage). Most of the oil is accumulated in the form of triacylglycerol (TAG) representing 60–70% in dry basis of the mesocarp tissue. During early stages of fruit development, high expression of transcripts related to fatty acid and TAG biosynthesis has been reported and downregulation of same genes in more advanced stages but without cessation of the process until harvest. The increased expression of fatty acid key genes and regulators such as PaWRI1, PaACP4-2, and PapPK-β-1 has also been reported to be consistent with the total fatty acid increase and fatty acid composition during avocado fruit development. During postharvest, there is minimal change in the fatty acid composition of the fruit. Almost inexistent information regarding the role of organic acid and amino acid metabolism during growth, development, and ripening of avocado is available. Cell wall metabolism understanding in avocado, even though crucial in terms of fruit quality, still presents severe gaps regarding the interactions between cell wall remodeling, fruit development, and postharvest modifications.

Avocado Fruit Pulp Transcriptomes in the after-Ripening Process

Avocado is an important tropical fruit whose after-ripening process is still poorly understood. The fatty acid, phenolics, flavonoids, and tannins were analyzed in ‘Lisa’ avocado (Persea americana Mill. ‘Lisa’) fruit pulp during after-ripening. The transcriptome was analyzed to screen for transcripts associated with the aforementioned after-ripening parameters. The results showed that there were no significant differences in the total fatty acid content among the preclimacteric, climacteric, and postclimacteric stages. Nevertheless, the concentrations of C18:3 (α-linolenic acid) were significantly higher in the climacteric and postclimacteric stages than the preclimacteric stage. RNAseq generated 235,082 transcripts and 151,545 unigenes. In addition, 4,324 DEGs were produced among the three stages. KEGG analysis of the DEGs suggested the pathways about “α-linolenic acid metabolism, unsaturated fatty acid biosynthesis”, “fatty acid degradation”, “linoleic acid metabolism and fatty acid biosynthesis”, “linoleic acid metabolism and fatty acid elongation”, and “fatty acid elongation” may all contribute to the C18:3 variations in ‘Lisa’ avocado fruit pulp. Several transcription factors, including the ethylene-related transcription factors, such as NAC, MYB, bHLH, and WRKY, were also identified in the DEGs database. This study generated transcript data and screened the transcription factors involved in the avocado after-ripening process. This information could be used to control after-ripening in avocado and maintain fruit quality during storage.

MaMADS2 repression in banana fruits modifies hormone synthesis and signalling pathways prior to climacteric stage

BackgroundWhile the role of ethylene in fruit ripening has been widely studied, the contributions of additional plant hormones are less clear. Here we examined the interactions between the transcription factor MaMADS2-box which plays a major role in banana fruit ripening and hormonal regulation. Specifically, we used MaMADS2 repressed lines in transcriptome and hormonal analyses throughout ripening and assessed hormone and gene expression perturbations as compared to wild-type (WT) control fruit.ResultsOur analyses revealed major differences in hormones levels and in expression of hormone synthesis and signaling genes mediated by MaMADS2 especially in preclimacteric pulp. Genes encoding ethylene biosynthesis enzymes had lower expression in the pulp of the repressed lines, consistent with reduced ethylene production. Generally, the expression of other hormone (auxin, gibberellins, abscisic acid, jasmonic acid and salicylic acid) response pathway genes were down regulated in the WT pulp prior to ripening, but remained high in MaMADS2 repressed lines. Hormone levels of abscisic acid were also higher, however, active gibberellin levels were lower and auxin levels were similar with MaMADS2 repression as compared to WT. Although abscisic level was higher in MaMADS2 repression, exogenous abscisic acid shortened the time to ethylene production and increased MaMADS2 mRNA accumulation in WT. Exogenous ethylene did not influence abscisic acid level. CRE - a cytokinin receptor, increased its expression during maturation in WT and was lower especially at prebreaker in the repressed line and zeatin level was lower at mature green of the repressed line in comparison to WT.ConclusionsIn addition to previously reported effects of MaMADS2 on ethylene, this transcription factor also influences other plant hormones, particularly at the pre-climacteric stage. The cytokinin pathway may play a previously unanticipated role via MaMADS2 in banana ripening. Finally, abscisic acid enhances MaMADS2 expression to promote ripening, but the transcription factor in turn auto inhibits ABA synthesis and signaling. Together, these results demonstrate a complex interaction of plant hormones and banana fruit ripening mediated by MaMADS2.

Oxylipin affects ethylene metabolism and ethylene receptor gene expression levels in peach fruit (Prunus persica L. Batsch)

ABSTRACTThe effects of two oxylipins – jasmonic acid (JA) and 9, 10-ketol-octadecadienoic acid (KODA) – on ethylene metabolism and ethylene receptor genes were examined in peach fruit (Prunus persica L.) harvested at 88 days after full bloom (DAFB), in the pre-climacteric stage, and at 102 DAFB, at the beginning of the climacteric stage. Immediate post-harvest applications of either n-propyl dihydrojasmonate (PDJ) (a JA analog) or KODA stimulated ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) concentrations in fruit that were harvested at 88 and 102 DAFB. KODA application significantly increased levels of ACC oxidase (PpACO1) expression at 5 and 8 days after treatment (DAT) in 88-DAFB-harvested fruit, and at 1 DAT in 102-DAFB-harvested fruit. Expression levels of ethylene response factors (PpERS1) were not influenced by either PDJ or KODA applications at 88 or 102 DAFB. In contrast, levels of ethylene-receptor-coding genes (PpETR1) expression in 88-DAFB KODA-treated fruit increased at 8 and 14 DAT. Expression levels of constitutive triple response (PpCTR1) in the untreated control fruit decreased with DAT in both 88- and 102-DAFB-harvested fruit.These results suggest that certain oxylipins may promote ethylene production in peach fruit, and that PpETR1 and PpCTR1 may be associated with the autocatalytic system of ethylene production.

CARBOHYDRATES, PHENOLIC COMPOUNDS AND ANTIOXIDANT ACTIVITY IN PULP AND PEEL OF 15 BANANA CULTIVARS

ABSTRACT The aim of this study was to quantify and compare the levels of carbohydrates and phenolic compounds and the antioxidant activity in the pulp and peel of 15 banana cultivars in two ripening stages. Four bunches per cultivar were harvested in the pre-climacteric stage, six fruits were used by sample unit. Fruits were analyzed in the pre-climacteric stage and after ripening. Total, reducing and non-reducing soluble sugars, starch, phenolic compounds and antioxidant activity were evaluated. Cultivar and ripening stage influenced all characteristics analyzed. Unripe pulp and peel had small percentage of sugar, but high percentage of starch, especially ‘Terrinha’ and ‘Marmelo’ cultivars. AAB and ABB cultivars presented the highest percentages of starch, when compared to AA and AAA cultivars. For the phenolic compounds, the highest content was observed in ripe peel, followed by ripe pulp and unripe peel and pulp, highlighting ‘Terrinha’ cultivar in all parts and stages evaluated. The antioxidant potential was higher in ripe peel, followed by unripe peel, ripe and unripe pulp. Fruits of Terrinha, Marmelo, Maçã, Ouro and Caru-Verde cultivars showed the highest carbohydrate contents, and phenolic compounds or antioxidant activity, justifying future actions in the expansion of planting and consumption of these fruits.

STUDY OF THE RELATION BETWEEN PEACH RIPENING AND PHENOLIC COMPOUNDS

Rising interest in beneficial health properties of fruit and achievement of the best organoleptic qualities in relation to ripening times, led to focus the attention on peach fruits. Phenolic composition in peach fruit changes during ripening process and influences the final quality. A collection field has been set-up, where different peach genotypes of interest (melting flesh=MF and not melting flesh=NMF) have been grown. After pit hardening, fruits growth and ripening have been monitored, the latter using a non-destructive portable instrument (DA-meter) providing an index linked with the chlorophyll degradation thus related to ripening degree. Classical destructive quality analysis was also carried out during the sampling. The general aim of this research has been to investigate about the possible relation between phenolic compounds and ripening stages in peach fruit. Differences in the amount of phenolic compounds in flesh and peel during the maturation process have been evaluated. Quantification of the most important phenolic compounds was obtained using a LC-MS/MS system. Results reported that the DA index (I(DA)) decreased reaching the ripening stage, in both peach genotypes (MF and NMF) and it also showed a relationship with ethylene production of fruits, demonstrating a good reliability of the instrument. Preliminary results showed that from ‘Oro A’s phenolic analysis in pre-climacteric stage, the amount of quercetin 3-rutinoside and cyanidin 3-glucoside in the peel resulted substantially higher than in the flesh. Among the main flavan-3-ols, catechin resulted in higher content compared to epicatechin, in agreement with previous works. Among hydroxycinnamic acids, chlorogenic acid resulted in higher amount than neo-chlorogenic as reported by other studies.

Postharvest Ripening and Quality of Guatemalan-West Indian Avocado Hybrids under Simulated Commercial Shipping Temperatures Following Treatment with Aqueous 1-Methylcyclopropene

Two Guatemalan-West Indian avocado (Persea americana) hybrids (‘Monroe’ and ‘Booth 8’) were treated with an aqueous formulation of 1-methylcyclopropene (1-MCP) to determine effects on ripening and quality during storage simulating commercial shipping temperatures. Fruit harvested at preclimacteric stage were immersed in aqueous 1-MCP at 75 μg·L−1 (1.39 mmol·m−3) or in deionized water for 1 minute, stored at 10 °C for 14 days, and then transferred to 20 °C until ripe. Respiration rate, ethylene production, softening, and change in epidermal hue* angle were delayed and/or suppressed in both cultivars exposed to 1-MCP, although effects were less pronounced with Booth 8. Hue* angles for 1-MCP-treated ‘Monroe’ fruit had the highest values (darkest green peel color) of all treatments at full-ripe stage (hue* angle = 117). For control and treated ‘Monroe’ fruit respiration peaked on days 15 and 21, while ethylene production from both treatments peaked on day 16. Respiration and ethylene production peaked on day 16 for both control and 1-MCP–treated ‘Booth 8’ fruit. Fruit treated with 1-MCP consistently showed diminished respiration and ethylene peaks. Days to full-ripe stage were unaffected by treatment. ‘Booth 8’ fruit from both treatments were considered ripe (15 N whole fruit firmness) after 17 days; however, only 8% of control fruit were marketable, whereas 58% of 1-MCP-treated fruit were marketable, based on subjective appearance ratings using the Jenkins–Wehner score. The development of peel blemishes during storage was the primary cause of unmarketable fruit. ‘Monroe’ control and 1-MCP–treated fruit were soft after about 22 days and were significantly more marketable (control 70% and 1-MCP 85%). Avocados treated with 1-MCP ripened over a longer period than control fruit but maintained a higher percentage of marketable fruit.

Ripening and sensory analysis of Guatemalan-West Indian hybrid avocado following ethylene pretreatment and/or exposure to gaseous or aqueous 1-methylcyclopropene

Previous reports showed that both gaseous and aqueous 1-methylcyclopropene (1-MCP) delay ripening of avocado (Persea americana Mill.), but there are no reports of the influence of 1-MCP on its sensory attributes. The objective of this study was to evaluate the effects of ethylene pretreatment and/or exposure to gaseous or aqueous 1-MCP on fruit ripening and sensory attributes of ‘Booth 7’ avocado, a Guatemalan-West Indian hybrid. Separate experiments were conducted during two seasons (2008 and 2009) with fruit harvested at preclimacteric stage in October (early season) and in November (late season). Fruit from Season 1 were exposed to ethylene (4.07μmolL−1) for 12h at 20°C, and stored for more 12h at 20°C in an ethylene-free (ethylene, <0.1μLL−1) room prior to treatment with either aqueous (1.39 or 2.77μmolL−1 a.i.) or gaseous (3.15 or 6.31nmolL−1 a.i.) 1-MCP. Ripening was monitored and firmness, respiration, ethylene production and weight loss were measured. Texture profile analysis and sensory analysis were performed on ripe fruit only (firmness, 10–15N). Fruit from Season 2 were not exposed to ethylene pretreatment but treated only with aqueous 1-MCP 24h after harvest. Fruit were assessed exclusively for sensory analysis when ripe (firmness, 10–15N). Treatment with either 1-MCP formulation effectively delayed ripening from 4 to 10d for early-season fruit, and from 4 to 6d for late-season fruit. Higher concentrations of 1-MCP of either formulation had the greatest effect on selected pulp textural parameters of early-season fruit; the gaseous formulation had greater effect on late-season fruit quality than the aqueous formulation. In general, sensory panelists ratings of overall liking were not affected by 1-MCP treatment. Both aqueous and gaseous 1-MCP formulations delayed ripening of the Guatemalan-West Indian ‘Booth 7’ avocado without significant loss in appearance or in sensory attributes and, therefore, could be considered for use as a postharvest treatment for this hybrid.

Effect of different levels of Sigatoka disease severity on banana pulp colour and early ripening

Bananas are usually harvested at a green preclimacteric stage prior to sale. The preclimacteric phase is called green life (GL), which is defined as the number of days between harvesting and initiation of the natural ripening process. Sigatoka disease (SD) has previously been shown to influence the postharvest behaviour of banana fruit. This work was set out to determine whether there is a relationship between the level of SD severity and the extent of the effects on banana quality as characterized by several pomological traits, especially pulp colour. In an experiment conducted with fruits harvested at a constant physiological age, our results showed that SD had a major effect on the percentage of fruit ripening in the field and on fruit weight, but not on fruit diameter. We showed too that pulp colour was greatly affected by SD; when severity increased, pulp colour parameters were modified – L* (lightness) decreased, a* (axis red to green) and b* (axis yellow to blue) increased, giving a more greyish pulp colour, with less green and more yellow and red. These results may enable the development of a method for controlling fruit quality, by measuring pulp colour in the field, in order to reduce post-harvest losses.

Necrotic leaf removal, a key component of integrated management ofMycospaerellaleaf spot diseases to improve the quality of banana: the case of Sigatoka disease

Introduction. Bananas are harvested at the green preclimacteric stage prior to sale. The time between harvest and the initiation of the natural ripening process is called green life. Black Leaf Streak Disease and Sigatoka Disease are the main foliar diseases affecting banana production. Sigatoka Disease (SD) is due to Mycosphaerella musicola , which frequently causes early ripening in commercial banana plantations, considered as an important source of damage. Our work aimed at determining the effectiveness of the removal of necrotic leaves, one month before harvest, on recovering banana quality arising from SD-infested plants. Materials and methods. Banana plants (totaling 80) at the flowering stage were selected in an experimental plot. These plants were divided into two groups of SD infestation levels: level 1 (Severity Index at flowering 25%). We divided each group into two treatments: a treatment with no necrotic leaf removal and a treatment with necrotic leaf removal. Fruits were harvested at the same physiological age, at 900 degree-days. Fruit quality was characterized by weight, diameter, % of ripe fruit in the field and fruit green life. Results. Our results showed that the removal of necrotic leaves causes a reduction in size parameters but leads to a strong reduction in SD effects on the fruit maturity, thereby preventing premature ripening. Banana plants whose necrotic leaves were removed produced fruit with a very long green life. Discussion. Removal of necrotic leaves allows thwarting the negative effect of SD on fruit physiology. This shows that the presence of necrosis during the last month of fruit growth is responsible for this fruit physiological modification characterized by early ripening. Conclusion. Removal of necrotic leaves one month before the date of harvest may be a technique that can limit production losses when the infestation level by SD is high. (Resume d'auteur)

Relation between the severity of Sigatoka disease and banana quality characterized by pomological traits and fruit green life

Banana fruit are typically harvested at a green preclimacteric stage prior to sale. The green life (GL), which is defined as the number of days between harvesting and initiation of the natural ripening process, is important for harvesting, shipping and marketing. Sigatoka disease (SD) has previously been shown to influence the postharvest quality of banana fruit. The present study was conducted to determine (1) whether there is a relationship between the level of SD severity and the banana quality as characterized by several pomological traits and fruit green life, and (2) whether there is a level of SD severity that is acceptable for fruit exporting. In an experiment conducted with fruit harvested at a constant physiological age, our results showed that the disease decreases fruit GL. Based on the relationship established between SD severity and GL, it is possible to define an acceptable disease level threshold corresponding to a specified GL. Additionally, we found that high SD infections caused a reduction in fruit weight but did not affect fruit size. Possible explanations are discussed.

Volatile profiles of ripening West Indian and Guatemalan-West Indian avocado cultivars as affected by aqueous 1-methylcyclopropene

Separate experiments were conducted with three major commercial avocado (Persea americana Mill.) cultivars grown in Florida: ‘Simmonds’ (early-season, West Indian race); ‘Booth 7’ (mid-season, Guatemalan-West Indian hybrid); and ‘Monroe’ (late-season, Guatemalan-West Indian hybrid). Fruit were harvested at preclimacteric stage and left untreated (Control) or treated 24h after harvest with aqueous 1-methylcyclopropene (1-MCP) at 1.39 (treatment M1) or 2.77μmolL−1 a.i. (treatment M2) (75 or 150μgL−1) for 1min at 20°C. Whole fruit ripening was monitored at 20°C/92%±3% R.H. and based on whole fruit firmness, respiration and ethylene evolution. Fruit volatiles were assessed at preclimacteric (24h after harvest), mid-ripe (half of initial fruit firmness) and ripe maturity stages, from 100g of chopped pulp using a purge and trap system. Untreated, firmer fruit ‘Monroe’ (268N at harvest) ripened within 12 d of harvest while softer fruit ‘Simmonds’ (118N) ripened within only 6 d. 1-MCP treatment extended ripening time from 33% (M1) to 83% (M2). All fruit softened normally, indicating the potential benefits of aqueous 1-MCP as a postharvest treatment for avocado when applied at these concentrations. Volatile profiles differed among the three cultivars with several compounds detected in only one cultivar, results that may contribute to a potential identification of the origin of the cultivar based on fruit volatile composition. The West Indian cultivar ‘Simmonds’ had much higher emission of hexanal (preclimacteric fruit) and cis-3-hexenal and cis-3-hexen-1-ol (ripe fruit) than the Guatemalan-West Indian hybrids ‘Booth 7’ and ‘Monroe’. On the other hand, these latter hybrids had much higher levels of alkanes than ‘Simmonds’. Treatment with 1-MCP increased emissions of alkanes during ripening of ‘Booth 7’ and ‘Monroe’. Total volatiles of avocado decreased during ripening mainly due to the significant reduction of sesquiterpenes, the main group of volatiles in all cultivars at harvest (‘Simmonds’, 53%; ‘Booth 7’, 78%; ‘Monroe’, 66%). β-Caryophyllene was the major compound at harvest, but decreased to less than 2% in ripe fruit, at which point most sesquiterpenes were not detected. Among the 10 sesquiterpenes commonly found in the avocado cultivars in this study, only α-Copaene had significantly higher emissions in mid-ripe fruit treated with the higher concentration of 1-MCP (2.77μmolL−1 a.i.), suggesting that ethylene participates in the regulation of this sesquiterpene.

Controle da antracnose na pós-colheita de bananas-'prata' com produtos alternativos aos agrotóxicos convencionais

Produtos alternativos aos agrotóxicos convencionais foram avaliados no controle da antracnose causada por Colletotrichum musae em pós-colheita de bananas 'Prata' [Musa spp. (AAB)]. Foram utilizados buquês com três frutos, com diâmetro médio de 32 mm a 36 mm, no estádio pré-climatérico, com coloração de casca totalmente verde. Os frutos foram pulverizados com uma suspensão de conídios de C. musae, na concentração de 2,5x10(5) conídios/mL e mantidos em câmara úmida a 25 ºC, por 24 horas. Após esse período, foram pulverizados com as caldas dos produtos alternativos extrato cítrico 'Biogermex', óleo de nim 'Organic Neem' e óleo de alho 'Probinatu', na concentração de 10,0 mL/L, óleo de pimenta-longa e óleo de cravo-da-índia na concentração de 5,0 mL/L e quitosana na concentração de 10,0 mg/mL, além do fungicida Tectoï SC (tiabendazol) na concentração de 0,65 mL/L. Água destilada foi utilizada como tratamento-testemunha. Os frutos tratados com quitosana, óleo de nim e óleo de alho tiveram a severidade da doença reduzida. O óleo de alho foi o produto mais eficiente, com redução também da incidência da doença. A qualidade dos frutos não foi depreciada por nenhum dos tratamentos alternativos nas concentrações utilizadas.