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United States Department of Agriculture

Agricultural Research Service

Research Project: Examination of Factors Influencing Virus Disease in Floriculture Crops

Location: Application Technology Research Unit

Project Number: 3607-21000-017-02
Project Type: Specific Cooperative Agreement

Start Date: Jul 01, 2011
End Date: May 31, 2016

Objective:
The objectives of this cooperative research project are: 1) to study interactions among Pelargonium flower break virus (PFBV) protein; 2) to examine the effects of silicon on virus infection; and 3) to determine the effects of silicon on copper (Cu) iron (Fe), and manganese (Mn) toxicity in ornamentals.

Approach:
Pelargonium flower break virus (PFBV) is the most common viral pathogen of geraniums. PFBV impairs growth and physical appearance, reducing their salability. To control PFBV, we are identifying interactions among the viral proteins, with the ultimate goal of interfering with these associations, thereby inhibiting the PFBV life cycle. Using yeast two-hybrid and affinity column pull-down approaches we are identifying protein interactions. We are writing two manuscripts on these interactions and will be testing viral protein binding molecules for their ability to interfere with PFBV infection. An advantage of this technology is that it could be employed quickly and easily by growers. We recently discovered that addition of soluble silicon (Si) delays Tobacco ringspot virus (TRSV) systemic symptoms in Nicotiana tabacum. TRSV infects a variety of food and ornamental crops, so our work has implications for both the agriculture and floriculture industries. The mechanism(s) by which Si caused this delay in viral symptoms is/are unclear. We will be investigating the mechanism(s) behind this “Si effect” by examining the accumulation of virus in inoculated leaves of plants treated with Si by ELISA and RT-PCR. We will also be studying the effects of Si on viral systemic spread by a leaf excision assay. Finally, we will be monitoring the expression of plant defense enzymes and genes in TRSV-inoculated and systemic leaves provided with Si. TRSV-infected tobacco leaves show a higher level of Si than in uninfected plants and this correlates with the delay in systemic symptom formation. To identify the potential signaling pathway(s) leaves on tobacco plants will be sprayed with a variety of molecules involved in responses to pathogens (such as salicylic acid, jasmonic acid, ethylene, etc.). The plants will then be monitored for Si uptake into leaves. We will also identify putative Si transporters in Nicotiana and apply this to ornamental crops. Si also helps plants resist abiotic stress as well, as reported in our first Si paper. Si alleviated the toxic effects of high levels of Cu (copper) in Arabidopsis. We are now exploiting this success to alleviate Cu toxicity in ornamental plants. The effects of Si on Cu toxicity are being investigated with zinnia (a Si accumulator) and snapdragon (a Si non-accumulator). We are also extending these studies to other metals (such as iron; Fe) in Si accumulator and non-accumulator plants. To perform this work, we examine: symptoms, fresh and dry weight, elemental analysis, and phenylalanine ammonia lyase (a stress enzyme) activity. Plant Fe metabolism is different from that for Cu. So if Si alleviates toxicity of both metals, this suggests a useful general strategy for helping plants cope with metal stress. In total, data generated from our studies will provide useful information regarding the use of Si for the alleviation of both abiotic and biotic stress to help inform growers to make better decisions regarding Si fertilization.

Last Modified: 4/20/2014
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