Search

Bamboo shoots are highly nutritious but possess poor shelf life after harvest due to rapid decline of tenderness mostly result from lignification processes. Present investigation was performed to evaluate the potential of gamma radiation as a postharvest technology to preserve bamboo shoots. The effects of 0.5 kGy gamma radiation on quality and lignification of bamboo shoots during storage at 2 °C were investigated. The results showed that gamma radiation reduced the decay rate of bamboo shoots by 71% at the end of storage. It also significantly retarded ethylene production through controlling the activities of ACC synthase (ACS) and ACC oxidase (ACO), which may contribute to inhibition of lignin synthesis. Meanwhile, gamma radiation decreased the activities of phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD), which are associated with lignin accumulation, thus reduced lignin content by 12.5% than that of the control after twenty-eight days of storage. These results demonstrated the potential of the gamma radiation as a promising postharvest technique to maintain the quality and inhibit the lignification of bamboo shoots. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ethylene was measured in two apple progeny using a standard GC and a novel PTR-ToF-MS method. [•] The two genes involved in the ethylene pathway, Md-ACS1 and Md-ACO1, were positioned on a genetic map on linkage groups 15 and 10, respectively. [•] Two QTLs were identified for ethylene production in apple, co-mapping with the genetic positions of these two genes. [•] The functional allele of Md-ACS1 regulates ethylene production under a dosage effect. [•] In apple, other elements besides Md-ACS1 and Md-ACO1 contribute to final ethylene production. [ABSTRACT FROM AUTHOR]

Highlights: [•] ACCO antisense melon yielded reduced ethylene production and low ACCO expression. [•] Transgenic melon lines showed varied response to exogenously applied ethylene. [•] Ethylene unresponsive melon showed up-regulation of cytokinin associated genes. [•] Transgenic melon unresponsive to exogenous ethylene had elevated cytokinin content. [Copyright &y& Elsevier]

Abstract: Ripening in apple is mediated though the hormone ethylene in a dose-dependent manner. From work in model plants, it is known that the ethylene receptors are negative modulators of the ethylene signal, and therefore likely to play an important part in apple fruit ripening. Our mining of the recently completed whole apple genome identified a total of nine receptor genes, including three new sequences. Phylogenetic comparisons with other fruit species identified each of the homeologous pairs. Using ACC OXIDASE 1-suppressed apple fruit induced with ethylene, eight genes were expressed in fruit, while the ninth gene remains a predicted gene model with no current supporting evidence for expression. Five genes were upregulated by ethylene within 12h of treatment. This study demonstrates the potential for the whole genome sequence to be used as a resource for determining large multi-gene families important for postharvest responses in apple. [Copyright &y& Elsevier]

Abstract: Changes in ethylene biosynthesis, respiration and firmness were studied during on-tree ripening, controlled atmosphere (CA) storage and shelf-life of ‘Jonagold’ apples. Particular attention was paid to the influence of harvest time on subsequent ripening during CA storage and shelf-life and on the effect of treatment with the ethylene inhibitor 1-MCP. The influence of harvest time was most prominent on firmness, with late harvested apples being significantly softer throughout the whole postharvest life. Respiration rate was mainly influenced by the surrounding temperature and air conditions and to a lesser extent by the harvest time. Ethylene production rate depended on harvest time straight after harvest and during storage but this effect disappeared upon movement from storage to shelf-life. When apples were treated with 1-MCP, ethylene biosynthesis was almost completely suppressed throughout the whole postharvest life, with exception of the late harvested apples which regained some ethylene forming capacity after two weeks of shelf-life. A detailed overview of ethylene biosynthesis including the often neglected metabolite S-adenosyl-l-methionine (SAM) was generated. The changes in SAM concentration could not directly be linked to the changes in ethylene production rate as such and SAM was not a limiting factor in apple ethylene biosynthesis during ripening. In vitro 1-aminocyclopropane-1-carboxylate synthase (ACS) and oxidase (ACO) activities were differently affected by CA storage conditions with ACS being the most dominant controlling factor in the biosynthesis of ethylene. [Copyright &y& Elsevier]

Abstract: To better understand physiological response to cold stress and physiological changes triggered by 1-MCP treatment in relation to softening recovery, ‘Conference’ pears were harvested in three orchards, at three maturities and treated with 0.3μLL−1 1-MCP for 24h. Changes in 1-aminocyclopropane carboxylic acid (ACC) and malonyl-ACC (MACC) levels, ACC synthase (ACS) and ACC oxidase (ACO) activity were followed during cold storage and 2 weeks of further ripening at 20°C. Cold storage induced significant changes in ACC metabolism which depended on the maturity of the fruit at harvest and to a lesser extent on the orchard location. In control fruit, ripening behaviour upon removal from cold storage directly relied on the amount of ACC accumulated during cold storage as well as on harvest maturity-dependent increases in ACO and the capacity to convert ACC to MACC. Similar to control fruit, the increase of ACC levels during cold storage determined the further softening behaviour of 1-MCP treated fruit. However, in 1-MCP treated fruit, malonylation had a more limited role and the capacity of the fruit to recover softening was directly related to the inhibition of ACO and mainly to the residual ACS activity which was maintained after 1-MCP treatment during cold storage. [Copyright &y& Elsevier]

Abstract: The ripening characteristics and physiology of two guava cultivars, ‘Jen-Ju Bar’ (‘JJB’) and ‘Li-Tzy Bar’ (‘LTB’), were investigated and compared because of their divergent storability. During storage at 20°C, mature-green ‘LTB’ fruit exhibited ripening behavior typical for a climacteric fruit, including increases in respiration and ethylene production (3.75mmolCO2 kg−1 h−1 and 1.37×103 nmolC2H4 kg−1 h−1 at peak levels, respectively), yellow color development, flesh softening, and volatile production. By contrast, ‘JJB’ is considered a nonclimacteric fruit because it features low and stable rates of respiration (0.61–0.73mmolCO2 kg−1 h−1) and ethylene production (less than 4nmolC2H4 kg−1 h−1) while retaining its pale-green color and firmness throughout a 20d observation period. Furthermore, the nonclimacteric nature of ‘JJB’ fruit was revealed through its responses to various levels of applied ethylene, as its respiration rate increased in a concentration-dependent manner. This respiration enhancement occurred only when exogenous ethylene was present and could be evoked repeatedly in the same ‘JJB’ fruit. The ripening characteristics of ‘JJB’ do not result from a defect in ethylene signaling, but instead result from a lack of autocatalytic ethylene synthesis, as propylene ventilation stimulated normal fruit ripening and an upsurge of respiration without a massive endogenous ethylene release. However, a cutting treatment of ‘JJB’ was able to induce stress-responsive ethylene production expected from system 1 ethylene biosynthesis. The finding that 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC synthase (ACS) activity were significantly lower in ‘JJB’ than in ‘LTB’ fruit after harvest, together with the finding that treatment with ACC (rather than S-adenosyl-l-methionine) led to both fully ripened ‘JJB’ fruit and endogenous ethylene production, strongly suggest that insufficient ACC synthesis, i.e., the reaction catalyzed by ACS, prevents system 2 ethylene biosynthesis in ‘JJB’ guava fruit. [Copyright &y& Elsevier]

Abstract: A feature of ‘Honeycrisp’ apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] is that they maintain flesh firmness over extended storage. The objective of this study was to elucidate molecular mechanisms that are responsible for slow softening of ‘Honeycrisp’ as compared with a rapidly softening cultivar, ‘McIntosh’. Fruit from both cultivars were picked during the normal harvest period and stored at 20°C for 10d. Internal ethylene concentrations (IECs) in ‘Honeycrisp’ fruit were lower than in ‘McIntosh’, but at climacteric levels of ethylene ‘Honeycrisp’ fruit maintained their firmness over this period, while ‘McIntosh’ softened rapidly. Concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) were higher in ‘Honeycrisp’ than in ‘McIntosh’ apples. qRT-PCR analysis was carried out for genes involved in ethylene biosynthesis, perception and signaling [ACC synthase (MdACS); ACC oxidase (MdACO); ethylene receptors (MdETR and MdERS); constitutive triple response (MdCTR); ethylene response factor (MdERF)], as well as those involved in cell wall metabolism [polygalacturonase (MdPG); xyloglucan endotransglucosylase (MdXTH); expansin (MdEXP); β-galactosidase (Md β-GS); arabinofuranosidase (MdAFase); pectate lyase (MdPL)]. At comparable IECs, the expression of genes involved in ethylene synthesis, ethylene perception and signal transduction was generally much higher in ‘Honeycrisp’ than in ‘McIntosh’ fruit. However, the expression of MdAFase and MdEXP3 was generally lower in ‘Honeycrisp’ than in ‘McIntosh’, while that of MdPG and MdPL was extremely low in ‘Honeycrisp’. Expression of MdPG1 was very low, even though IECs were at climacteric levels. Absence of fruit softening in ‘Honeycrisp’ is probably associated with restricted cell wall enzyme activity. The lower maximum IECs found in ‘Honeycrisp’ compared with ‘McIntosh’ do not appear to be related to expression of genes involved in ethylene biosynthesis. [Copyright &y& Elsevier]