Browsing by Author "Dardick, Christopher"

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    Effect of Washing, Waxing and Low-Temperature Storage on the Postharvest Microbiome of Apple
    Abdelfattah, Ahmed; Whitehead, Susan R.; Macarisin, Dumitru; Liu, Jia; Burchard, Erik; Freilich, Shiri; Dardick, Christopher; Droby, Samir; Wisniewski, Michael (MDPI, 2020-06-23)
    There is growing recognition of the role that the microbiome plays in the health and physiology of many plant species. However, considerably less research has been conducted on the postharvest microbiome of produce and the impact that postharvest processing may have on its composition. Here, amplicon sequencing was used to study the effect of washing, waxing, and low-temperature storage at 2 °C for six months on the bacterial and fungal communities of apple calyx-end, stem-end, and peel tissues. The results of the present work reveal that tissue-type is the main factor defining fungal and bacterial diversity and community composition on apple fruit. Both postharvest treatments and low temperature storage had a strong impact on the fungal and bacterial diversity and community composition of these tissue types. Distinct spatial and temporal changes in the composition and diversity of the microbiota were observed in response to various postharvest management practices. The greatest impact was attributed to sanitation practices with major differences among unwashed, washed and washed-waxed apples. The magnitude of the differences, however, was tissue-specific, with the greatest impact occurring on peel tissues. Temporally, the largest shift occurred during the first two months of low-temperature storage, although fungi were more affected by storage time than bacteria. In general, fungi and bacteria were impacted equally by sanitation practices, especially the epiphytic microflora of peel tissues. This research provides a foundation for understanding the impact of postharvest management practices on the microbiome of apple and its potential subsequent effects on postharvest disease management and food safety.
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    Fox Hunting in Wild Apples: Searching for Novel Genes in Malus Sieversii
    Wisniewski, Michael; Artlip, Timothy; Liu, Jia; Ma, Jing; Burchard, Erik; Norelli, John; Dardick, Christopher (MDPI, 2020-12-14)
    Malus sieversii is considered the progenitor of modern apple (Malus pumila) cultivars and to represent a valuable source of genetic diversity. Despite the importance of M. sieversii as a source of disease resistance, stress tolerance, and novel fruit traits, little is known about gene function and diversity in M. sieversii. Notably, a publicly annotated genome sequence for this species is not available. In the current study, the FOX (Full-length cDNA OvereXpressing) gene hunting system was used to construct a library of transgenic lines of Arabidopsis in which each transgenic line overexpresses a full-length gene obtained from a cDNA library of the PI619283 accession of M. sieversii. The cDNA library was constructed from mRNA obtained from bark tissues collected in late fall–early winter, a time at which many abiotic stress-adaptative genes are expressed. Over 4000 apple FOX Arabidopsis lines have been established from the pool of transgenic seeds and cDNA inserts corresponding to various Gene Ontology (GO) categories have been identified. A total of 160 inserts appear to be novel, with no or limited homology to M. pumila, Arabidopsis, or poplar. Over 1300 lines have also been screened for freezing resistance. The constructed library of transgenic lines provides a valuable genetic resource for exploring gene function and diversity in Malus sieversii. Notably, no such library of t-DNA lines currently exists for any Malus species.
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    Global analysis of the apple fruit microbiome: are all apples the same?
    Abdelfattah, Ahmed; Freilich, Shiri; Bartuv, Rotem; Zhimo, V. Yeka; Kumar, Ajay; Biasi, Antonio; Salim, Shoshana; Feygenberg, Oleg; Burchard, Erik; Dardick, Christopher; Liu, Jia; Khan, Awais; Ellouze, Walid; Ali, Shawkat; Spadaro, Davide; Torres, Rosario; Teixido, Neus; Ozkaya, Okan; Buehlmann, Andreas; Vero, Silvana; Mondino, Pedro; Berg, Gabriele; Wisniewski, Michael; Droby, Samir (2021-03-18)
    We present the first worldwide study on the apple (Malus x domestica) fruit microbiome that examines questions regarding the composition and the assembly of microbial communities on and in apple fruit. Results revealed that the composition and structure of the fungal and bacterial communities associated with apple fruit vary and are highly dependent on geographical location. The study also confirmed that the spatial variation in the fungal and bacterial composition of different fruit tissues exists at a global level. Fungal diversity varied significantly in fruit harvested in different geographical locations and suggests a potential link between location and the type and rate of postharvest diseases that develop in each country. The global core microbiome of apple fruit was represented by several beneficial microbial taxa and accounted for a large fraction of the fruit microbial community. The study provides foundational information about the apple fruit microbiome that can be utilized for the development of novel approaches for the management of fruit quality and safety, as well as for reducing losses due to the establishment and proliferation of postharvest pathogens. It also lays the groundwork for studying the complex microbial interactions that occur on apple fruit surfaces.