Search Results (12)

Calcium-dependent protein kinases (CDPKs) are unique serine/threonine kinases that play significant roles in response to environmental stresses in plants. In this study, we comprehensively characterized the CDPK gene family in the apple cultivar ‘Hanfu’ at the genome-wide level, and 38 MdCDPKs were identified. They were unevenly distributed across 14 chromosomes. Based on phylogenetic analysis, the MdCDPKs were classified into four subfamilies. Conserved domain analysis indicated that MdCDPKs contain the catalytic kinase domain and the Ca²⁺ binding domain. During Colletotrichum gloeosporioides infection, the expression level of MdCDPK24 was significantly upregulated. Subsequently, MdCDPK24 was fused to GFP to generate the MdCDPK24-GFP construct, and confocal microscopy imaging confirmed its cytoplasmic localization in Nicotiana benthamiana leaves. Using agrobacterium-mediated transformation, we generated the overexpression of MdCDPK24 transgenic calli. MdCDPK24-overexpressing calli demonstrated significantly reduced disease severity against C. gloeosporioides infection, indicating its positive role in apple bitter rot resistance. The analysis of the CDPK gene family in the apple cultivar ‘Hanfu’ provides a new insight into the identification of CDPK genes involved in biotic stress. MdCDPK24 represents a promising candidate for genetic manipulation to enhance apple bitter rot resistance. Full article

Colletotrichum fructicola is a member of the gloeosporioides complex and can act as a pathogen, causing anthracnose in various plants and as an endophyte residing in healthy plants. As a plant pathogen, C. fructicola has been frequently reported to cause anthracnose in chili fruit and tea plants, bitter rot in apples and pears, crown rot in strawberries, and Glomerella leaf spot in apples, which are the most common diseases associated with this pathogen. Over the years, C. fructicola has been reported to infect a wide range of plants in tropical, subtropical, and temperate regions, including various types of fruit crops, ornamental and medicinal plants, tree nuts, peanuts, and weeds. Several reports have also been made regarding endophytic C. fructicola recovered from different plant parts. Endophytic C. fructicola has the ability to switch to a pathogenic state, which may contribute to the infection of host and other susceptible plants. Due to the economic importance of C. fructicola infections, the present review highlighted C. fructicola as a plant pathogen and endophyte, providing a summary of its infections in various plants and endophytic ability to inhabit plant tissues. Several control measures for managing C. fructicola infections have also been provided. Full article

Glomerella leaf spot (GLS) and bitter rot (BR) are severe diseases of apple. Colletotrichum nymphaeae and Colletotrichum chrysophillum are the main species in Brazil. To control GLS and BR in Brazilian apple orchards, mancozeb and thiophanate-methyl fungicides are still used despite reported Colletotrichum resistance to these active ingredients. In addition, mancozeb has been banned from apple-importing countries and it has been a great challenge for apple producers to find products for its replacement that are eco-friendly. So, this study aimed to search for alternatives to control the diseases. We assessed the antifungal activity of eugenol, isoeugenol, thymol, carvacrol, and some of their ester derivatives. The best products to inhibit the pathogen in in vitro assays were thymol, thymol butyrate, and carvacrol, completely inhibiting mycelial growth at 125 mg L⁻¹ and conidial germination at 100 mg L⁻¹. In detached apple fruit, eugenol, eugenyl acetate, carvacryl acetate, and thymol butyrate, significantly reduced BR symptoms caused by Colletotrichum species with some variation between experiments and species, decreasing the risk of BR with the time compared to control. In detached leaves, all tested compounds significantly reduced the risk of development of GLS symptoms with disease control varying from 30 to 100%. The compounds tested are promising alternatives to replace fungicides to control bitter rot and Glomerella leaf spot on apple culture and should be tested for field conditions. Full article

Species of the genus Colletotrichum are among the most important plant pathogens globally, as they are capable of infecting many hosts—apple (Malus spp.) and other fruit and woody plant species—but also vegetable crops, cereals, legumes, and other annual and perennial herbaceous plants. The apple (Malus spp.) is attacked by various species from the genus Colletotrichum, whereby 27 different species from this genus have been described as the causative agents of apple bitter rot (ABR) and 15 as the cause of Glomerella leaf spot (GLS). These species generally belong to one of three species complexes: Colletotrichum acutatum, Colletotrichum gloeosporioides, and Colletotrichum boninense. The largest number of apple pathogens of the genus Colletotrichum belong to the species complex C. acutatum and C. gloeosporioides. However, further data on these species and the interactions between the species complexes of the genus Colletotrichum that cause these two apple diseases is needed for the development of effective control measures, thus ensuring successful and profitable apple cultivation. To contribute to this endeavor, a comprehensive review of the causative agents of ABR and GLS from the genus Colletotrichum is provided. In addition to presenting the species’ current names, distribution, economic significance, and the symptoms they cause in apple, their development cycle, epidemiology, and molecular detection strategies are described, with a particular emphasis on control measures. Full article

The bitter rot of apple is caused by Colletotrichum spp. and is a serious pre-harvest disease that can manifest in postharvest losses on harvested fruit. In this study, we obtained genome sequences from four different species, C. chrysophilum, C. noveboracense, C. nupharicola, and C. fioriniae, that infect apple and cause diseases on other fruits, vegetables, and flowers. Our genomic data were obtained from isolates/species that have not yet been sequenced and represent geographic-specific regions. Genome sequencing allowed for the construction of phylogenetic trees, which corroborated the overall concordance observed in prior MLST studies. Bioinformatic pipelines were used to discover CAZyme, effector, and secondary metabolic (SM) gene clusters in all nine Colletotrichum isolates. We found redundancy and a high level of similarity across species regarding CAZyme classes and predicted cytoplastic and apoplastic effectors. SM gene clusters displayed the most diversity in type and the most common cluster was one that encodes genes involved in the production of alternapyrone. Our study provides a solid platform to identify targets for functional studies that underpin pathogenicity, virulence, and/or quiescence that can be targeted for the development of new control strategies. With these new genomics resources, exploration via omics-based technologies using these isolates will help ascertain the biological underpinnings of their widespread success and observed geographic dominance in specific areas throughout the country. Full article

Bitter rot of apple is an economically important worldwide disease caused by different Colletotrichum species, depending on many factors such as climate, geography, other hosts, and crop management practices. Culture, morphology, and single-locus sequencing-based methods for identifying the Colletotrichum species are severely limited in effectiveness, while the multilocus sequence typing methods available for delineating species are costly, time-intensive, and require high expertise. We developed species-specific hydrolysis probe real-time PCR assays for the following nine Colletotrichum species causing bitter rot in the Mid-Atlantic U.S.A.: C. fructicola, C. chrysophilum, C. noveboracense, C. gloeosporioides s.s., C. henanense, C. siamense and C. theobromicola from the C. gloeosporioides species complex, and C. fioriniae and C. nymphaeae from the C. acutatum species complex. After searching 14 gene regions, we designed primers and probes in 5 of them for the nine target species. Four primer–probe set pairs were able to be duplexed. Sensitivity tests showed as little as 0.5 pg DNA were detectable. These real-time PCR assays will provide rapid and reliable identification of these key Colletotrichum species and will be critically important for studies aiming to elucidate their biology, epidemiology, and management on apples as the number one produced and consumed tree fruit in the U.S.A. Full article

The use of microbial biocontrol agents for control of postharvest disease has been the subject of intensive research over the past three decades resulting in commercialization of several biocontrol products. The objective of this research was to test endospore-forming bacteria collected from apple leaves for suppression of bitter rot and blue mold on apple. Bacteria were collected from abandoned, low-input, organic, and conventionally managed orchards in Pennsylvania and were screened for their ability to produce endospores, hydrolyze chitin, reduce pathogen growth in vitro, and suppress postharvest disease in vivo. Several isolates reduced bitter rot lesion size on ‘Rome Beauty’ from 40–89% compared to untreated controls. Bacillus megaterium isolates, A3-6 and Ae-1, resulted in the greatest suppression of bitter rot lesion size. One isolate, A3-2, suppressed blue mold lesion size. Scanning electron microscopy of inoculated apple wounds suggests parasitism as a mode of action explains the suppression of bitter rot lesion size by isolate A3-6. Of the top seventeen isolates exhibiting biocontrol potential, 70% were collected from abandoned or unmanaged locations. This research demonstrates abandoned apple orchards can be a source of new biocontrol agents for control of postharvest diseases of apple. Full article

Bitter rot and Glomerella leaf spot (GLS) of apples, caused by Colletotrichum species, are major diseases of apples around the world. A total of 98 isolates were obtained from apple fruits with bitter rot, and 53 isolates were obtained from leaves with leaf spot in the primary apple production regions in China. These isolates were characterized morphologically, and five gene regions (ITS, ACT, GAPDH, CHS-1 and TUB2) were sequenced for each isolate. A phylogenetic analysis, combined with a comparison of the morphological, cultural and pathogenic characters, sorted bitter rot isolates into six species: C. alienum, C. fructicola, C. gloeosporioides sensu stricto, C. nymphaeae, C. siamense and one new species, C. orientalis Dandan Fu & G.Y. Sun. Among these, C. siamense was the predominant pathogen associated with bitter rot. Isolates from leaf spot were identified as two species, C. aenigma and C. fructicola. This is the first report of C. orientalis as an apple bitter rot pathogen worldwide, and the results provide important insights into the diversity of Colletotrichum species in China. Full article

Watercore is a physiological disorder which often occurs on the pear fruit and the excessive accumulation of sorbitol in fruit intercellular space is considered to be an important cause of watercore. Our previous studies found that the metabolic disorder of sugars may lead to hypoxia stress and disturb respiration, resulting in aggravated fruit rot and the formation of bitter substances. However, the further changes of respiration and the fruit response mechanism are not well understood. A comprehensive transcriptome analysis of ‘Akibae’ pear watercore fruit was performed in this study. The transcriptome results revealed the hypoxia stress significantly induced the expression of several key enzymes in the TCA cycle and may lead to the accumulation of succinic acid in watercore fruit. The glycolytic pathway was also significantly enhanced in watercore fruit. Moreover, the γ-aminobutyric acid (GABA) synthesis related genes, glutamate decarboxylase (GAD) genes and polyamine oxidase (PAO) genes, which associated with the GABA shunt and the polyamine degradation pathway were significantly upregulated. In addition, the PpGAD1 transcript level increased significantly along with the increase of GAD activity and GABA content in the watercore fruit. Above all, these findings suggested that the hypoxic response was marked by a significant increase of the hypoxia-inducible metabolites succinic acid and GABA and that PpGAD1 may play a key role in response to watercore by controlling the GABA synthesis. Full article

Watercore is a physiological disorder that commonly occurs in sand pear cultivars. The typical symptom of watercore tissue is transparency, and it is often accompanied by browning, breakdown and a bitter taste during fruit ripening. To better understand the molecular mechanisms of watercore affecting fruit quality, this study performed transcriptome and metabolome analyses on watercore pulp from “Akibae” fruit 125 days after flowering. The present study found that the “Akibae” pear watercore pulp contained higher sorbitol and sucrose than healthy fruit. Moreover, the structure of the cell wall was destroyed, and the content of pectin, cellulose and hemicellulose was significantly decreased. In addition, the content of ethanol and acetaldehyde was significantly increased, and the content of polyphenol was significantly decreased. Watercore induced up-regulated expression levels of sorbitol synthesis-related (sorbitol-6-phosphate dehydrogenase, S6PDH) and sucrose synthesis-related genes (sucrose synthesis, SS), whereas it inhibited the expression of sorbitol decomposition-related genes (sorbitol dehydrogenase, SDH) and sorbitol transport genes (sorbitol transporter, SOT). Watercore also strongly induced increased expression levels of cell wall-degrading enzymes (polygalactosidase, PG; ellulase, CX; pectin methylesterase, PME), as well as ethanol synthesis-related (alcohol dehydrogenase, ADH), acetaldehyde synthesis-related (pyruvate decarboxylase, PDC) and polyphenol decomposition-related genes (polyphenol oxidase, PPO). Moreover, the genes that are involved in ethylene (1-aminocyclopropane- 1-carboxylate oxidase, ACO; 1-aminocyclopropane- 1-carboxylate synthase, ACS) and abscisic acid (short-chain alcohol dehydrogenase, SDR; aldehyde oxidase, AAO) synthesis were significantly up-regulated. In addition, the bitter tasting amino acids, alkaloids and polyphenols were significantly increased in watercore tissue. Above all, these findings suggested that the metabolic disorder of sorbitol and sucrose can lead to an increase in plant hormones (abscisic acid and ethylene) and anaerobic respiration, resulting in aggravated fruit rot and the formation of bitter substances. Full article

Fungal storage rots like blue mould, grey mould, bull’s eye rot, bitter rot and brown rot destroy large amounts of the harvested apple crop around the world. Application of fungicides is nowadays severely restricted in many countries and production systems, and these problems are therefore likely to increase. Considerable variation among apple cultivars in resistance/susceptibility has been reported, suggesting that efficient defence mechanisms can be selected for and used in plant breeding. These are, however, likely to vary between pathogens, since some fungi are mainly wound-mediated while others attack through lenticels or by infecting blossoms. Since mature fruits are considerably more susceptible than immature fruits, mechanisms involving fruit-ripening processes are likely to play an important role. Significant associations have been detected between the susceptibility to rots in harvested fruit and various fruit maturation-related traits like ripening time, fruit firmness at harvest and rate of fruit softening during storage, as well as fruit biochemical contents like acidity, sugars and polyphenols. Some sources of resistance to blue mould have been described, but more research is needed on the development of spore inoculation methods that produce reproducible data and can be used for large screenings, especially for lenticel-infecting fungi. Full article

Cashew apples are by-products in the production of cashew nuts, which are mostly left to rot in the fields. Cashew apple juice (CAJ), a highly nutritious beverage, can be produced from them. It is rich in sugars and ascorbic acid, but its high polyphenol content makes it bitter and astringent, and therefore difficult to commercialize. The kingdom of fungi contains more than 2000 yeast species, of which only a few species have been studied in relation to their potential to produce aroma compounds. The aim of this research was to develop a new low-alcoholic fermented beverage to valorize cashew apples. For this purpose, a screening was carried out employing non-conventional yeast species and some species of the genus Saccharomyces for comparison, followed by a more detailed study with four selected strains cultured at different conditions. The production of volatile aroma compounds as a function of the presence of oxygen, temperature, and yeast species was investigated. The results showed that the more diverse aroma profiles appeared at 25 °C under anaerobic cultivation conditions, where Saccharomyces cerevisiae WUR 102 and Hanseniaspora guilliermondii CBS 2567 excelled in the synthesis of certain aroma compounds, such as β-phenylethanol and its acetate ester (rose aroma). Further studies are needed to test consumer acceptance of these new products. Full article