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United States Department of Agriculture

Agricultural Research Service

2012 Annual Report

1a.Objectives (from AD-416):
Objective 1: Elucidate the role of fungal extracellular enzymes as virulence factors important in postharvest decay of fresh fruit including the effect of pathogen modification of the host environment on virulence factors.

Objective 2: Evaluate potential control strategies targeting fungal extracellular enzymes to reduce postharvest decay of fresh fruit. Sub-objective 2.A. Optimize the application of recombinant antibodies targeting extracellular enzymes of P. expansum and P. solitum to reduce postharvest decay of pome fruits. Sub-objective 2.B. Determine the effect of antioxidants and their analogs on decay development.

1b.Approach (from AD-416):
To elucidate the role of fungal extracellular enzymes as virulence factors in postharvest decay of apple and pear fruit, we will first compare the ability of several strains of a highly virulent and a weakly virulent pathogen of the same genus to produce extracellular enzymes (such as polygalacturonases and cellulases) during fruit infection and in response to fungal modification of the host/pathogen microenvironment. 'Golden Delicious' apple and 'Anjou' pear fruit will be infected with P. expansum or P. solitum and we will extract, purify, and characterize the extracellular enzymes produced by these organisms using standard procedures. We will develop and utilize recombinant antibodies specific for binding to and inactivating enzymes produced by the pathogens in vivo and in vitro. The antibodies will allow us to determine which specific enzymes play a major role in virulence of Penicillium species on pome fruit. Strategies incorporating recombinant antibodies against virulence factors, antioxidants known to have anti-fungal activity, and mild stress treatments will be tested for their ability to control postharvest decays of pome fruits caused by Penicillium species.

3.Progress Report:
Maintaining apple and pear fruit quality by eliminating decay during months of commercial storage is critical in preventing postharvest losses. Penicillium spp. fungi are the most destructive apple and pear fruit pathogens causing toxins which contaminate processed fruit products. A bridge project was implemented to address research from the terminating project that involved characterization of virulence factors produced by the blue mold fungus during postharvest decay of apple fruit with the new project identifying long term control measures. The Minimum Inhibitory Concentrations for several postharvest fungicides have been identified for Penicillium spp. that were isolated from decayed apple fruit to determine the efficacy of currently available control measures. This information can be used directly by apple and pear fruit growers to make informed decisions concerning fungicide use and rotation to ensure their prolonged efficacy. Progress contained in this report directly addresses the objectives contained in the current bridge project plan that is focused on postharvest decay of apple and pear fruit. This bridging project is under NP303 OSQR review.

Last Modified: 10/22/2014
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