Title:

Title: More than just another fungal virulence factor: multiple roles for patulin in plant-fungusmicrobe interactions

Abstract:

Mycotoxin contamination is a leading cause of food spoilage around the world. Among one of the top mycotoxins of global concern is patulin, which is found in processed apple products (e.g. juice, sauce, and butter). Produced mainly by Penicillium and Aspergillus species, patulin is a lactone polyketide that has cytotoxic effects in humans, survives pasteurization, and is not destroyed following fermentation. While much has been discovered regarding the impact of patulin on human health, there are significant knowledge gaps for how it impacts the host and other fungi. Here, we have utilized purified patulin to determine if the toxin could mimic blue mold symptoms. Directly inoculating apple fruit with different amounts of patulin revealed a cultivar-independent susceptibility, as well as a dose response where blue mold symptoms and toxin concentration coincided. Patulin biosynthesis was recently discovered to be produced outside of the fungal cell, so understanding how it impacts other phytopathogenic fungi was investigated. Preliminary results show that conidial germination for postharvest pathogens Colletotrichum fiorinae and Alternaria alternata were inhibited. Additional studies will be performed to understand its impact on nonhost plants, other fruits, and microorganisms on the fruit carposphere that participate in host-pathogen interactions. We also seek to determine the mode of action of patulin-mediated cell death in the fruit and if it is conserved across kingdom Fungi. By elucidating the mechanism for patulinmediated cell death in fruit, and impacts on nonhosts, intervention technologies can be applied to improve postharvest storage regimes and shift the carposphere composition to a disease-suppressive situation serving as next-gen class of postharvest decay control measures

Biography:

Holly P. Bartholomew is a postdoctoral researcher with the USDA-ARS Beltsville Agricultural Research Center with Drs. Wayne M Jurick II and Jorge M. Fonseca in the Food Quality Lab . Her fellowship is supported by an appointment to the Agricultural Research Service (ARS) Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA). She holds a B.S. in Microbiology and a Ph.D. in Biological Sciences from Virginia Polytechnic Institute and State University. She is passionate about improving food quality and reducing waste through understanding postharvest storage practices and pathogen proliferation.

Title: Advanced diagnosis of pre and post-harvest fruit Diseases and their management to education

Abstract:

The diseases are severely affected multibillion-dollar fruits industry by plant pathogens including fungi, bacteria, and viruses. Many of the diseases in fruits have similar signs and symptoms, making it difficult to diagnose the specific problem pathogen. Incorrect diagnosis leads to the delay of treatment and excessive use of post-harvest chemicals. Proper identification of damage, defects, diseases, and disorders is the first step in solving the issue and producing quality fruit. There are many methods for diagnosing pathogens on fruit. Traditional methods include symptoms, morphology, and microscopy identification. These have been followed by nucleic acid detection and onsite detection techniques. Many of these methods allow for rapid diagnosis, some even within the field without much expertise. There are several methods that have great potentials, such as high-throughput sequencing and remote sensing. The utilization of these techniques for disease diagnosis allows for faster and accurate disease diagnosis and a reduction in damage and cost of control. Understanding each of these techniques can allow researchers to select which method is best suited for their pathogen of interest. Almost 90% of fruit diseases are caused by fungi; however other groups cause damage, including bacteria, and viruses. Blue and gray mold caused by Penicillium expansum and Botrytis cinerea, respectively are the most prominent postharvest diseases on pome fruit. Control of this devastating pathogen mainly relies on the use of fungicides but the development of resistance has become an important factor in limiting the efficacy and useful lifetime of fungicides. Thus, there is an urgent need for an alternative fungicide or fungicides for controlling these post-harvest pathogens.

Title: Plant diseases pose a serious threat for sustainable agriculture

Abstract:

Plant diseases pose a serious threat for sustainable agriculture. In this study we establish RAV1, an ethylene responsive transcription factor as a master transcriptional regulator of defense genes. The overexpression of AtRAV1 provided resistance against necrotrophic fungal pathogen (Rhizoctonia solani) in Arabidopsis thaliana whereas the atrav1 mutant demonstrated hyper-susceptibility to the infection. Several defense genes including AtMPK3, AtMPK4 and AtMPK6 were induced in the AtRAV1 overexpression (OE) lines but not in the atrav1 mutant, upon R. solani infection. The AtMPK3/AtMPK6 proteins seems essential for AtRAV1 mediated disease resistance, as knocking out AtMPK3/AtMPK6 in OE1 background, rendered plants susceptible to infection. We demonstrate that AtMPK3 (but not AtMPK6) phosphorylates AtRAV1 and the phospho-defective variants of AtRAV1 are unable to impart disease resistance in A. thaliana. Considering that AtRAV1 orthologs are conserved in diverse plant species, we hypothesize that they can be gainfully deployed to control economically important diseases. Indeed, overexpression of tomato ortholog of AtRAV1 provided broad spectrum disease resistance against bacterial (Ralstonia solanacearum), fungal (R. solani) and viral (Tomato leaf curl virus) infections in tomato.