The identity,distribution, and impacts of non-native apple snails in the continental United States

Background  

Since the mid 1990s populations of non-native apple snails (Ampullariidae) have been discovered with increasing frequency in the continental United States. Given the dramatic effects that introduced apple snails have had on both natural habitats and agricultural areas in Southeast Asia, their introduction to the mainland U.S. is cause for concern. We combine phylogenetic analyses of mtDNA sequences with examination of introduced populations and museum collections to clarify the identities, introduced distributions, geographical origins, and introduction histories of apple snails.     

Assessment of allelic diversity in intron-containing Mal d 1 genes and their association to apple allergenicity

Background  

Mal d 1 is a major apple allergen causing food allergic symptoms of the oral allergy syndrome (OAS) in birch-pollen sensitised patients. The Mal d 1 gene family is known to have at least 7 intron-containing and 11 intronless members that have been mapped in clusters on three linkage groups. In this study, the allelic diversity of the seven intron-containing Mal d 1 genes was assessed among a set of apple cultivars by sequencing or indirectly through pedigree genotyping. Protein variant constitutions were subsequently compared with Skin Prick Test (SPT) responses to study the association of deduced protein variants with allergenicity in a set of 14 cultivars.     

On the origin and spread of the Scab disease of apple: out of central Asia

Background

Venturia inaequalis is an ascomycete fungus responsible for apple scab, a disease that has invaded almost all apple growing regions worldwide, with the corresponding adverse effects on apple production. Monitoring and predicting the effectiveness of intervention strategies require knowledge of the origin, introduction pathways, and population biology of pathogen populations. Analysis of the variation of genetic markers using the inferential framework of population genetics offers the potential to retrieve this information.

Methodology/Principal Findings

Here, we present a population genetic analysis of microsatellite variation in 1,273 strains of V. inaequalis representing 28 orchard samples from seven regions in five continents. Analysis of molecular variance revealed that most of the variation (88%) was distributed within localities, which is consistent with extensive historical migrations of the fungus among and within regions. Despite this shallow population structure, clustering analyses partitioned the data set into separate groups corresponding roughly to geography, indicating that each region hosts a distinct population of the fungus. Comparison of the levels of variability among populations, along with coalescent analyses of migration models and estimates of genetic distances, was consistent with a scenario in which the fungus emerged in Central Asia, where apple was domesticated, before its introduction into Europe and, more recently, into other continents with the expansion of apple growing. Across the novel range, levels of variability pointed to multiple introductions and all populations displayed signatures of significant post-introduction increases in population size. Most populations exhibited high genotypic diversity and random association of alleles across loci, indicating recombination both in native and introduced areas.

Conclusions/Significance

Venturia inaequalis is a model of invasive phytopathogenic fungus that has now reached the ultimate stage of the invasion process with a broad geographic distribution and well-established populations displaying high genetic variability, regular sexual reproduction, and demographic expansion.     

PR genes of apple: identification and expression in response to elicitors and inoculation with Erwinia amylovora

Background  

In the past decade, much work has been done to dissect the molecular basis of the defence signalling pathway in plants known as Systemic Acquired Resistance (SAR). Most of the work has been carried out in model species such as Arabidopsis, with little attention paid to woody plants. However within the range of species examined, components of the pathway seem to be highly conserved. In this study, we attempted to identify downstream components of the SAR pathway in apple to serve as markers for its activation.     

Molecular role of cytokinin in bud activation and outgrowth in apple branching based on transcriptomic analysis

Key message

Axillary bud activation and outgrowth were dependent on local cytokinin, and that bud activation preceded the activation of cell cycle and cell growth genes in apple branching.

Abstract

Cytokinin is often applied to apple trees to produce more shoot branches in apple seedlings. The molecular response of apple to the application of cytokinin, and the relationship between bud activation and cell cycle in apple branching, however, are poorly understood. In this study, RNA sequencing was used to characterize differential expression genes in axillary buds of 1-year grafted “Fuji” apple at 4 and 96 h after cytokinin application. And comparative gene expression analyses were performed in buds of decapitated shoots and buds of the treatment of biosynthetic inhibitor of cytokinin (Lovastatin) on decapitated shoots. Results indicated that decapitation and cytokinin increased ZR content in buds and internodes at 4–8 h, and induced bud elongation at 96 h after treatment, relative to buds in shoots receiving the Lovastatin treatment. RNA-seq analysis indicated that differential expression genes in auxin and cytokinin signal transduction were significantly enriched at 4 h, and DNA replication was enriched at 96 h. Cytokinin-responsive type-A response regulator, auxin polar transport, and axillary meristem-related genes were up-regulated at 4 h in the cytokinin and decapitation treatments, while qRT-PCR analysis showed that cell cycle and cell growth genes were up-regulated after 8 h. Collectively, the data indicated that bud activation and outgrowth might be dependent on local cytokinin synthesis in axillary buds or stems, and that bud activation preceded the activation of cell cycle genes during the outgrowth of ABs in apple shoots.

     

Aspirin eugenol ester regulates cecal contents metabolomic profile and microbiota in an animal model of hyperlipidemia

Background

Hyperlipidemia, with an increasing of prevalence, has become one of the common metabolic diseases in companion animal clinic. Aspirin eugenol ester (AEE) is a novel compound that exhibits efficacious anti-hyperlipidemia activities. However, its mechanisms are still not completely known. The objective of present study was to investigate the intervention effects of AEE on cecal contents metabonomics profile and microbiota in hyperlipidemia rats.

Results

Three groups of rats were fed with a control diet, or high fat diet (HFD) containing or not AEE. The results showed the beneficial effects of AEE in HFD-fed rats such as the reducing of aspartate aminotransferase (AST) and total cholesterol (TCH). Distinct changes in metabonomics profile of cecal contents were observed among control, model and AEE groups. HFD-induced alterations of eight metabolites in cecal contents mainly related with purine metabolism, linoleic acid metabolism, glycerophospholipid metabolism, sphingolipid metabolism and pyrimidine metabolism were reversed by AEE treatment. Principal coordinate analysis (PCoA) and cluster analysis of microbiota showed altered patterns with distinct differences in AEE group versus model group, indicating that AEE treatment improved the negative effects caused by HFD on cecal microbiota. In addition, the correction analysis revealed the possible link between the identified metabolites and cecal microbiota.

Conclusions

This study showed regulation effects of AEE on cecal contents metabonomics profile and microbiota, which could provide information to reveal the possible underlying mechanism of AEE on hyperlipidemia treatment.

     

MdSOS2L1 phosphorylates MdVHA-B1 to modulate malate accumulation in response to salinity in apple

Key message

Salt-induced phosphorylation of MdVHA-B1 protein was mediated by MdSOS2L1 protein kinase, and thereby increasing malate content in apple.

Abstract

Salinity is an important environmental factor that influences malate accumulation in apple. However, the molecular mechanism by which salinity regulates this process is poorly understood. In this work, we found that MdSOS2L1, a novel AtSOS2-LIKE protein kinase, interacts with V-ATPase subunit MdVHA-B1. Furthermore, MdSOS2L1 directly phosphorylates MdVHA-B1 at Ser³⁹⁶ site to modulate malate accumulation in response to salt stress. Meanwhile, a series of transgenic analyses in apple calli showed that the MdSOS2L1–MdVHAB1 pathway was involved in the regulation of malate accumulation. Finally, a viral vector-based transformation approach demonstrated that the MdSOS2L1–MdVHAB1 pathway also modulated malate accumulation in apple fruits with or without salt stress. Collectively, our findings provide a new insight into the mechanism by which MdSOS2L1 phosphorylates MdVHA-B1 to modulate malate accumulation in response to salinity in apple.

     

Dating and functional characterization of duplicated genes in the apple (<Emphasis Type="Italic">Malus domestica</Emphasis> Borkh.) by analyzing EST data

Background  

Gene duplication is central to genome evolution. In plants, genes can be duplicated through small-scale events and large-scale duplications often involving polyploidy. The apple belongs to the subtribe Pyrinae (Rosaceae), a diverse lineage that originated via allopolyploidization. Both small-scale duplications and polyploidy may have been important mechanisms shaping the genome of this species.     

Oligo-DNA custom macroarray for monitoring major pathogenic and non-pathogenic fungi and bacteria in the phyllosphere of apple trees

Background

To monitor the richness in microbial inhabitants in the phyllosphere of apple trees cultivated under various cultural and environmental conditions, we developed an oligo-DNA macroarray for major pathogenic and non-pathogenic fungi and bacteria inhabiting the phyllosphere of apple trees.

Methods and Findings

First, we isolated culturable fungi and bacteria from apple orchards by an agar-plate culture method, and detected 32 fungal and 34 bacterial species. Alternaria, Aureobasidium, Cladosporium, Rhodotorula, Cystofilobasidium, and Epicoccum genera were predominant among the fungi, and Bacillus, Pseudomonas, Sphingomonas, Methylobacterium, and Pantoea genera were predominant among the bacteria. Based on the data, we selected 29 major non-pathogenic and 12 phytopathogenic fungi and bacteria as the targets of macroarray. Forty-one species-specific 40-base pair long oligo-DNA sequences were selected from the nucleotide sequences of rDNA-internal transcribed spacer region for fungi and 16S rDNA for bacteria. The oligo-DNAs were fixed on nylon membrane and hybridized with digoxigenin-labeled cRNA probes prepared for each species. All arrays except those for Alternaria, Bacillus, and their related species, were specifically hybridized. The array was sensitive enough to detect 10³ CFU for Aureobasidium pullulans and Bacillus cereus. Nucleotide sequencing of 100 each of independent fungal rDNA-ITS and bacterial 16S-rDNA sequences from apple tree was in agreement with the macroarray data obtained using the same sample. Finally, we analyzed the richness in the microbial inhabitants in the samples collected from apple trees in four orchards. Major apple pathogens that cause scab, Alternaria blotch, and Marssonina blotch were detected along with several non-phytopathogenic fungal and bacterial inhabitants.

Conclusions

The macroarray technique presented here is a strong tool to monitor the major microbial species and the community structures in the phyllosphere of apple trees and identify key species antagonistic, supportive or co-operative to specific pathogens in the orchard managed under different environmental conditions.     

Biological control of invasive apple snails by two species of carp: Effects on non-target species matter

Molluscivorous fish, especially carp, have been adopted as bio-control agents of the invasive apple snail Pomacea canaliculata, but previous studies have focused on their effectiveness, with little attention paid to their undesirable effects on non-target plants and animals. We conducted an 8-week mesocosm study to compare the effectiveness of two indigenous fish, common carp (Cyprinus carpio) and black carp (Mylopharyngodon piceus), in removing P. canaliculata, and their potential side effects on macrophytes and non-target mollusks in a freshwater wetland. Three species of macrophytes and a community of mollusks in the wetland sediment were enclosed in 1 × 1 × 1 m enclosures either with apple snails (AS), with apple snails and common carp (AS + CC), with apple snails and black carp (AS + BC), or without apple snails and fish. Both species of carp were effective predators of P. canaliculata, removing most of the individuals in the enclosures except a few that were too big to fit into their mouth. By reducing apple snail population, black carp reduced grazing of apple snail on macrophytes. In contrast, although common carp controlled apple snail population, it did not reduce overall loss in plant biomass as the fish might also fed on macrophytes. Both species of carp preyed on non-target mollusks. Application of bio-control agents in invasive species management needs to consider their effects on both the pest and non-target plants and animals. Adoption of common and/or black carp to control apple snail populations thus depends on the weight given to their effectiveness and subtle different effects on non-target organisms by wetland management authority.     

Effect of storage conditions on virulence of Fusarium avenaceum and Alternaria alternata on apple fruits

To overcome difficulty in phytopathogenic fungi control during storage of apple fruits, the effect of different storage conditions on the occurrence and development of Fusarium avenaceum and Alternaria alternata infections on apple cultivar “Cripps Pink” was investigated during and after storage. Inhibitory effects of wild oregano essential oil on apple fruit rots caused by F. avenaceum and A. alternata were also tested as possible rot control measure. Artificially inoculated apple fruits were kept in cold storage with normal (NA) and controlled (CA) atmosphere for 95 days and at room temperature only. The obtained results indicated that different storage conditions significantly affect necrosis development on apple fruits caused by F. avenaceum and A. alternata after storage, as well as during shelf life.     

The beneficial effect of small toxic molecules on dormancy alleviation and germination of apple embryos is due to NO formation

Deep dormancy of apple (Malus domestica Borkh.) seeds is terminated by a 3-month-long cold stratification. It is expressed by rapid germination of seeds and undisturbed growth of seedlings. However, stimulation of germination of isolated apple embryos is also observed after applying inhibitors of cytochrome c oxidase: nitric oxide (NO) or hydrogen cyanide (HCN) during the first 3–6 h of imbibition of dormant embryos. The aim of this work was to compare the effect of yet another toxic gaseous molecule carbon monoxide (CO) with the effects of HCN and NO on germination of apple embryos and growth and development of young seedlings. We demonstrated that stimulation of germination after short-term pre-treatment with HCN, NO or CO was accompanied by enhanced NO emission from the embryo axes during their elongation. Moreover, similarly high NO production from non-dormant embryos, after cold stratification, was detected. Therefore, we propose that NO may act as signaling molecule in apple embryo dormancy break.     

The effects of temperature and drought on autumnal senescence and leaf shed in apple under warm,east mediterranean climate

Key message

Autumnal senescence of apple in a warm climate corresponds to accumulated degree-days beneath 22 °C. Summer drought delays senescence and enables replenishment of carbohydrate reserves. Recovery of the root system plays a key role.

Abstract

Autumnal senescence of apple (Malus domestica Borkh.), a deciduous, temperate climate species, is triggered by a rather abrupt temperature drop, down to the lower teens. Under the warmer, east Mediterranean climate of northern Israel, the temperature drop is gradual and much more moderate. Another characteristic of this climate is the complete lack of precipitation during summer. The aim of the present study was to elucidate the effects of summer drought on seasonal leaf senescence in a warm autumn. We hypothesized that summer drought delays senescence due to an increased demand for carbohydrates during autumn. The advent of autumnal senescence was followed for 3 years (2009–2011) on trees exposed to various levels of drought. Total canopy green area (effective leaf area, ELA) and hue angle were estimated periodically by means of image analysis, as a measure of leaf drop and autumnal color change. Photosynthesis, midday stem water potential, and roots’ non-structural carbohydrate contents were measured on several occasions. The time course of leaf drop followed the decline in air and soil temperatures. The rate of decline in ELA closely corresponded to accumulated degree-days beneath 22 °C in the soil, a much higher temperature threshold than previously reported for apple. Drought stress during the summer delayed leaf senescence even further, when compared with well-irrigated trees. Leaves maintained their photosynthetic functionality throughout autumn, until late December. The delayed senescence enabled replenishment of root carbohydrate reserves, which is critical for next year’s growth and fruiting. The eco-physiological significance of the findings is discussed.     

Stable expression and phenotypic impact of <Emphasis Type="Italic">attacin E</Emphasis>transgene in orchard grown apple trees over a 12 year period

Background  

Transgenic trees currently are being produced by Agrobacterium -mediated transformation and biolistics. The future use of transformed trees on a commercial basis depends upon thorough evaluation of the potential environmental and public health risk of the modified plants, transgene stability over a prolonged period of time and the effect of the gene on tree and fruit characteristics. We studied the stability of expression and the effect on resistance to the fire blight disease of the lytic protein gene, attacin E, in the apple cultivar 'Galaxy' grown in the field for 12 years.     

Biocontrol of Botrytis cinerea in apple fruit by Cryptococcus laurentii and indole-3-acetic acid

This study evaluated the effect of a yeast antagonist Cryptococcus laurentii and a plant regulator indole-3-acetic acid (IAA) on inhibition of Botrytis cinerea infection in harvested apple fruit. The results showed that the combined treatment with C. laurentii and IAA at 20 μg/ml was a more effective approach to reduce the gray mold rot in apple wounds than the C. laurentii alone. After 4 days of incubation, gray mold incidence in the combined treatment with C. laurentii and IAA was about 18%, which was a 50% reduction in incidence compared to the treatment with C. laurentii alone. Although IAA had no direct antifungal activity against B. cinerea infection when the time interval between IAA treatment and pathogen inoculation was within 2 h, application of IAA strongly reduced gray mold infection when IAA was applied 24 h prior to inoculation with B. cinerea in apple fruit wounds. Moreover, combination of IAA and C. laurentii stimulated the activities of superoxide dismutase, catalase and peroxidase with above 1.5-fold higher than that treatment with C. laurentii alone at 48 h. Therefore, combination of C. laurentii with IAA, which integrated the dual biological activity from the antagonistic yeast and plant regulator, might be developed to be a useful approach to control gray mold in harvested apple fruit.     

Modelling fruit-temperature dynamics within apple tree crowns using virtual plants

Background and Aims

Fruit temperature results from a complex system involving the climate, the tree architecture, the fruit location within the tree crown and the fruit thermal properties. Despite much theoretical and experimental evidence for large differences (up to 10 °C in sunny conditions) between fruit temperature and air temperature, fruit temperature is never used in horticultural studies. A way of modelling fruit-temperature dynamics from climate data is addressed in this work.

Methods

The model is based upon three-dimensional virtual representation of apple trees and links three-dimensional virtual trees with a physical-based fruit-temperature dynamical model. The overall model was assessed by comparing model outputs to field measures of fruit-temperature dynamics.

Key Results

The model was able to simulate both the temperature dynamics at fruit scale, i.e. fruit-temperature gradients and departure from air temperature, and at the tree scale, i.e. the within-tree-crown variability in fruit temperature (average root mean square error value over fruits was 1·43 °C).

Conclusions

This study shows that linking virtual plants with the modelling of the physical plant environment offers a relevant framework to address the modelling of fruit-temperature dynamics within a tree canopy. The proposed model offers opportunities for modelling effects of the within-crown architecture on fruit thermal responses in horticultural studies.     

Effect of apple intake on fecal microbiota and metabolites in humans

The effects of apple intake on the fecal flora, water content, pH, and metabolic activities in eight healthy volunteers and the utilization of apple pectin in vitro were investigated. Although several isolates of Bifidobacterium, Lactobacillus, Enterococcus, and the Bacteroides fragilis group utilized apple pectin, most isolates of Escherichia coli, Collinsela aerofaciense, Eubacterium limosum, and Clostridium perfringens could not. When fecal samples from healthy adults were incubated in liquid broth with apple pectin present or absent, the numbers of Bifidobacterium and Lactobacillus in the former were higher than those in the later. After the intake of apples (2 apples a day for 2 weeks) by eight healthy adult humans, the number of bifidobacteria in feces increased (p < 0.05 on day 7 and p < 0.01 on day 14 of the intake period), and the numbers of Lactobacillus and Streptococcus including Enterococcus tended to increase. However, lecithinase-positive clostridia, including C. perfringens, decreased (p < 0.05), and Enterobacteriaceae and Pseudomonas tended to decrease. Moreover, the concentrations of fecal acetic acid tended to increase on apple intake. The fecal ammonia concentration showed a tendency to reduce and fecal sulfide decreased (p < 0.05) on apple intake. These findings indicate that apple consumption is related to an improved intestinal environment, and apple pectin is one of the effective apple components improving the fecal environment.     

Arabinogalactan-protein secretion is associated with the acquisition of stigmatic receptivity in the apple flower

Background and Aims

Stigmatic receptivity plays a clear role in pollination dynamics; however, little is known about the factors that confer to a stigma the competence to be receptive for the germination of pollen grains. In this work, a developmental approach is used to evaluate the acquisition of stigmatic receptivity and its relationship with a possible change in arabinogalactan-proteins (AGPs).

Methods

Flowers of the domestic apple, Malus × domestica, were assessed for their capacity to support pollen germination at different developmental stages. Stigmas from these same stages were characterized morphologically and different AGP epitopes detected by immunocytochemistry.

Key Results

Acquisition of stigmatic receptivity and the secretion of classical AGPs from stigmatic cells occurred concurrently and following the same spatial distribution. While in unpollinated stigmas AGPs appeared unaltered, in cross-pollinated stigmas AGPs epitopes vanished as pollen tubes passed by.

Conclusions

The concurrent secretion of AGPs with the acquisition of stigmatic receptivity, together with the differential response in unpollinated and cross-pollinated pistils point out a role of AGPs in supporting pollen tube germination and strongly suggest that secretion of AGPs is associated with the acquisition of stigma receptivity.Key words: AGPs, arabinogalactan proteins, apple, Malus × domestica, pollen, pollen tube, stigma, stigmatic receptivity, flower receptivity     

Transpiration measurements on apple trees with an improved stem heat balance method

Since the late eighties a handy and user-friendly sap flow meter (Dynagage®) is on the market which can quantify 0205 the sap flow through intact plant stems, based on the stem heat balance method. The documentation about its accuracy and reliability, however, is still too limited to use it as a standard method in field experiments with apple trees. We therefore tested this commercial system on potted apple trees (Malus domestica L.; cv. Red Elstar and Jonagold; on rootstock M9 vf) with stem diameters of 1.8 to 4 cm. The measured sap flow was compared with mass loss measured by an automated balance, supposing the total mass loss of the trees was equal to the water loss by transpiration. The results revealed three major problems:

甘肃陇东旱塬不同树龄苹果园矿质氮的分布和积累特征

对甘肃陇东地区不同树龄苹果园土壤矿质氮的分布和积累特征进行了研究.结果表明：土壤铵态氮含量随着苹果树龄的增大呈上升趋势,2～3年生、5年生、10年生、15年生、20年生、22年生果园0～120 cm土层铵态氮含量分别为3.3、5.8、6.5、9.1、12.1和15.3 mg·kg^-1;不同树龄果园0～60 cm土层铵态氮含量大于60～120 cm土层.不同树龄果园硝态氮含量在0～40 cm土层相对较低,随土层深度增加,其含量迅速增加;随着种植年限增加,不同苹果园硝态氮累积量也呈显著增加趋势,22年生果园0～120 cm土层硝态氮累积量达到2602.5 kg·hm^-2.旱塬苹果园表现为土壤铵态氮呈浅层积累、而硝态氮呈深层积累的特征.