The color of an apple is an important index of its appearance quality, which affects the fruit’s marketability and value. The green variety “Granny Smith” remains green when ripe, and the pigment in ...the peel is mainly chlorophyll. The chlorophyll in the peel of the yellow variety “Golden Delicious” degrades as the fruit ripens. To explore the different mechanisms of chlorophyll degradation in the “Golden Delicious” and “Granny Smith” varieties, transcriptomic analysis was performed on the mature peels of both cultivars. High-quality sequences totaling 48,206,940 and 48,796,646 raw bases, as well as 9632 differentially expressed genes (DEGs), were identified. A total of 1206 DEGs were classified in 118 KEGG metabolic pathways. Additionally, 3258 transcription factors from 428 gene families were predicted, and DEGs associated with chlorophyll degradation, including MdSGR2, MdNYC1 and MdHCAR, were identified. Subsequently, the MdSGR2 gene was isolated from the mature peel of “Granny Smith” apples. Subsequent subcellular localization analysis confirmed that MdSGR2 specifically targets chloroplasts. The transient overexpression of MdSGR2 was found to negatively regulate chlorophyll degradation, leading to the inhibition or deceleration of chlorophyll breakdown, thereby maintaining green coloration in the leaves and peel. Conversely, silencing MdSGR2 positively regulated chlorophyll degradation, resulting in chlorosis in the leaves and peel. These findings offer valuable insights into the regulatory mechanism governing apple fruit coloration and lays a solid foundation for further investigation in this field.
The fruit processing industries are experiencing surge due to the increasing demand of food products as a result of burgeoning human population. Apple and apple products are one of the major fruit ...and fruit products consumed all over the world. Apple processing industries generate huge quantities of solid and liquid sludge wastes. The solid residues consist of a mixture of skin, pulp and seeds derived from the production of concentrated apple juice, jam, and sweets and are collectively known as ‘apple pomace’. Being highly biodegradable, the disposal of these wastes represents a serious environmental problem and presents many challenges. Often only 20% is retrieved as animal feed and the rest 80% goes to landfill, is incinerated or is sent to composting sites which results in release of greenhouse gases. However, advancement in technology has led to the alternative options of utilization of apple pomace. It can be used as a promising raw material for direct extraction of bioactive compounds and bioproduction of high value-added products, such as enzymes, organic acids, biofuels, among other products. This article reviews the work done for value-addition of this precious biomass which can help in setting up integrated process in the existing apple industries itself or separate small scale industries.
Multiple recalls and outbreaks involving Listeria monocytogenes-contaminated apples have been linked to the post-harvest packing environment where this pathogen can persist in biofilms. Therefore, ...this study assessed L. monocytogenes survival on apples as affected by harvest year, apple cultivar, storage atmosphere, and growth conditions. Unwaxed Gala, Granny Smith, and Honeycrisp apples were dip-inoculated in an 8-strain L. monocytogenes cocktail of planktonic- or biofilm-grown cells (~6.5 log CFU/mL), dried, and then examined for numbers of L. monocytogenes during air or controlled atmosphere (CA) (1.5% Osub.2, 1.5% COsub.2) storage at 2 °C. After 90 days, air or CA storage yielded similar L. monocytogenes survival (p > 0.05), regardless of harvest year. Populations gradually decreased with L. monocytogenes quantifiable in most samples after 7 months. Apple cultivar significantly impacted L. monocytogenes survival (p < 0.05) during both harvest years with greater reductions (p < 0.05) seen on Gala compared to Granny Smith and Honeycrisp. Biofilm-derived cells survived longer (p < 0.05) on L. monocytogenes-inoculated Gala and Honeycrisp apples compared to cells grown planktonically. These findings should aid in the development of improved L. monocytogenes intervention strategies for apple growers and packers.
•New primers specific for ASGV and ASPV were designed based on conserved sequence region identified in updated virus genome sequences.•Newly designed primers for an internal amplification control, ...EF-1α, were used to improve the accuracy of PCR reactions.•The multiplex RT-PCR could simultaneously detect both viruses and viroids in field-collected apple samples for practical disease diagnosis.
Apple chlorotic leaf spot virus (ACLSV), Apple stem grooving virus (ASGV), and Apple stem pitting virus (ASPV) are three latent viruses frequently occurring in apple trees worldwide. In field orchards, these viruses are frequently found in a mixed infection with viroids in the genus Apscarviroid, including Apple scar skin viroid, and Apple dimple fruit viroid. Together these viruses and viroids could cause serious damage to apple fruit production worldwide. Rapid and efficient detection methods are pivotal to identify and select the virus-free propagation material for healthy apple orchard management. In this study a multiplex Reverse Transcription-PCR (RT-PCR) was developed and optimized for simultaneous detection and differentiation of the three latent viruses and apscarviroids. With newly designed specific primers for ACLSV, ASGV, APSV, and EF-1α (as an internal control), and a pair of degenerate primers for apscarviroids, optimized parameters for multiplex RT-PCR were determined. The resulting PCR products from each target virus and viroid could be easily identified because their product sizes differ by at least a 100bp. The multiplex RT-PCR method is expected to detect different variants of the viruses as the test results showed that a variety of isolates from different regions in China gave positive results. To the best of our knowledge, this multiplex RT-PCR assay is the first to simultaneously detect multiple viruses and viroids infecting apple trees in a single reaction tube. This assay, therefore, offers a useful tool for routine certification and quarantine programs.
Nitrate is one of the main sources of nitrogen for plant growth. Nitrate transporters (NRTs) participate in nitrate uptake and transport, and they are involved in abiotic stress tolerance. Previous ...studies have shown that NRT1.1 has a dual role in nitrate uptake and utilization; however, little is known about the function of MdNRT1.1 in regulating apple growth and nitrate uptake. In this study, apple MdNRT1.1, a homolog of Arabidopsis NRT1.1, was cloned and functionally identified. Nitrate treatment induced an increased transcript level of MdNRT1.1, and overexpression of MdNRT1.1 promoted root development and nitrogen utilization. Ectopic expression of MdNRT1.1 in Arabidopsis repressed tolerance to drought, salt, and ABA stresses. Overall, this study identified a nitrate transporter, MdNRT1.1, in apples and revealed how MdNRT1.1 regulates nitrate utilization and abiotic stress tolerance.
Apple canker, caused by Neonectria ditissima (Tul. and C. Tul.) Samuels and Rossman, is a major disease of apples (Malus domestica) worldwide. N. ditissima infects through natural and artificial ...wounds. Infected wood develops canker lesions which girdle branches and main stems causing reduced yield and tree death. N. ditissima is difficult to control; removal of inoculum (cankers) is expensive and therefore seldom practiced, whilst effective chemical products are being banned and no biocontrol products have been found to be effective against N. ditissima. This study used cues from a previous apple endophyte community analysis to isolate and test fungal endophytes belonging to the genus Epicoccum as potential endophytic biocontrol agents. Epicoccum nigrum B14-1, isolated from healthy apple trees, antagonised N. ditissima in vitro and reduced the incidence of N. ditissima infections of leaf scars by 46.6% and pruning wounds by 5.3% in field conditions at leaf fall. Autumn application of B14-1 conidia increased E. nigrum abundance in apple tissues at 10-20 days post-inoculation by ca. 1.5×, but this returned to control levels after one year. E. nigrum B14-1 did not cause detrimental effects on apple foliage, buds, fruit, or growth and could therefore present a new biocontrol agent to manage N. ditissima in commercial apple production.
Superficial scald of pear fruit is a physiological disorder that easily occurs during cold storage and seriously affects pear eating quality and commodity value. It is important to study the ...mechanism of superficial scald disorder. Our previous study reported that the incidence of superficial scald of calcium chloride (CaClsub.2)-treated pear fruit during storage was significantly lower than that of untreated fruit. In this study, we found that the accumulation of lignin in CaClsub.2-treated fruit was significantly lower than that of untreated fruit. The expression of the Pb4CL2 gene in the lignin synthesis pathway was downregulated in the CaClsub.2-treated fruit. The lignification level of the fruit overexpressing Pb4CL2 was significantly higher than that of the empty vector fruit. Therefore, we speculate that downregulation of Pb4CL2 after CaClsub.2 treatment plays an important role in CaClsub.2 inhibiting superficial scald disorder by affecting lignin accumulation in pear fruit.
Apple pomace (AP) was processed into a freeze-dried powder to add into stirred-type yogurt to create 1, 2, and 3% (w/w) AP-fortified yogurt. Both texture analysis and rheological testing were used to ...evaluate the effect of AP on the structure and texture of yogurt during cold storage. The results indicated that apple pomace altered the structure of stirred yogurt, making it firmer and more cohesive, increased its viscosity and significantly reduced whey release during cold storage. Stronger influence on the parameters was observed at higher AP concentrations. Apple pomace added to a diluted yogurt system has the potential to stabilise the acid drink and reduce the sedimentation of protein aggregates. Addition of AP to already fermented milk gel allowed a higher concentration of AP (up to 6% w/w) to be incorporated, which made the stirred yogurt and yogurt drinks a vehicle for delivering a higher level of dietary fibre and phytochemicals (as compared to AP added to milk prior to fermentation). This study demonstrated that apple pomace has a potential as a natural stabiliser as well as a dietary fibre source in stirred type yogurts and yogurt drinks.
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•Apple pomace (3%) reduced the syneresis of stirred yogurt by half that of the control.•AP addition (2–3%) resulted in a firmer, more viscous and cohesive stirred yogurt.•AP contributed total phenolics and dietary fibre to stirred yogurt.•AP (4–6%) could stabilise yogurt drinks with low MSNF (<5%).
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