Effect of pulsed light on postharvest disease control-related metabolomic variation in melon (Cucumis melo) artificially inoculated with Fusarium pallidoroseum

Combined analysis of metabolome and transcriptome of wheat kernels reveals constitutive defense mechanism against maize weevils

Sitophilus zeamais (maize weevil) is one of the most destructive pests that seriously affects the quantity and quality of wheat (Triticum aestivum L.). However, little is known about the constitutive defense mechanism of wheat kernels against maize weevils. In this study, we obtained a highly resistant variety RIL-116 and a highly susceptible variety after two years of screening. The morphological observations and germination rates of wheat kernels after feeding ad libitum showed that the degree of infection in RIL-116 was far less than that in RIL-72. The combined analysis of metabolome and transcriptome of RIL-116 and RIL-72 wheat kernels revealed differentially accumulated metabolites were mainly enriched in flavonoids biosynthesis-related pathway, followed by glyoxylate and dicarboxylate metabolism, and benzoxazinoid biosynthesis. Several flavonoids metabolites were significantly up-accumulated in resistant variety RIL-116. In addition, the expression of structural genes and transcription factors (TFs) related to flavonoids biosynthesis were up-regulated to varying degrees in RIL-116 than RIL-72. Taken together, these results indicated that the biosynthesis and accumulation of flavonoids contributes the most to wheat kernels defense against maize weevils. This study not only provides insights into the constitutive defense mechanism of wheat kernels against maize weevils, but may also play an important role in the breeding of resistant varieties.

A Comparative Assessment on the Recovery of Pectin and Phenolic Fractions from Aqueous and DES Extracts Obtained from Melon Peels

This work evaluates the purification of melon peel extracts obtained by two eco-friendly methods: autohydrolysis and sodium acetate/urea/water extraction (1:3:1.6), an alkaline deep eutectic solvent (DES). For that, sequential ethanol precipitation and resin adsorption/desorption stages were proposed for the separate recovery of the pectic and phenolic fractions. In order to screen the optimal purification conditions, in a first step, the effect of ethanol concentrations (from 70 to 85%) on the precipitation of pectic oligosaccharides was assayed. Subsequently, the influence of the selected resin (Amberlite XAD4, XAD16HP and XAD7HP), liquid/resin ratios, and desorption sequences (varying ethanol concentrations and pH) on the phenolic compounds was also studied. The highest pectin yields were achieved with 85% ethanol: 16.11 and 18.05 g pectin/100 g water-insoluble solids (WIS) for autohydrolysis and DES extracts, respectively. All pectins presented a galacturonic acid content of about 45%, while autohydrolysis pectin presented a higher amount of neutral sugar side chains. The presence of low methoxyl GalA and both linear and branched OGalA with DP from 2 to 20 was also confirmed by FTIR and HPAEC-PAD analysis, respectively. Concerning the phenolic fraction, the resin adsorption and desorption steps at the selected conditions (XAD4 resin, liquid/resin ratio of 2 mL/g, eluted with 50% ethanol thrice) resulted in 79.55 and 4.08 mg GAE/g non-volatile content (NVC) for autohydrolysis and DES extracts, respectively, with improved antioxidant capacity. Moreover, some phenolic acids (protocatechuic and ferulic acids) and flavonoids (orientin, vitexin and naringenin) were quantified in the extracts by HPLC–PDA-MS/MS.

Postharvest Ultraviolet Radiation in Fruit and Vegetables: Applications and Factors Modulating Its Efficacy on Bioactive Compounds and Microbial Growth

Ultraviolet (UV) radiation has been considered a deleterious agent that living organisms must avoid. However, many of the acclimation changes elicited by UV induce a wide range of positive effects in plant physiology through the elicitation of secondary antioxidant metabolites and natural defenses. Therefore, this fact has changed the original UV conception as a germicide and potentially damaging agent, leading to the concept that it is worthy of application in harvested commodities to take advantage of its beneficial responses. Four decades have already passed since postharvest UV radiation applications began to be studied. During this time, UV treatments have been successfully evaluated for different purposes, including the selection of raw materials, the control of postharvest diseases and human pathogens, the elicitation of nutraceutical compounds, the modulation of ripening and senescence, and the induction of cross-stress tolerance. Besides the microbicide use of UV radiation, the effect that has received most attention is the elicitation of bioactive compounds as a defense mechanism. UV treatments have been shown to induce the accumulation of phytochemicals, including ascorbic acid, carotenoids, glucosinolates, and, more frequently, phenolic compounds. The nature and extent of this elicitation have been reported to depend on several factors, including the product type, maturity, cultivar, UV spectral region, dose, intensity, and radiation exposure pattern. Even though in recent years we have greatly increased our understanding of UV technology, some major issues still need to be addressed. These include defining the operational conditions to maximize UV radiation efficacy, reducing treatment times, and ensuring even radiation exposure, especially under realistic processing conditions. This will make UV treatments move beyond their status as an emerging technology and boost their adoption by industry.