MSA - Ecology/Pathology
Bartz, Faith , Danehower, David , Taylor, Nick , Cubeta, Marc .
Investigation of the metabolic control over phenylacetic acid production by Rhizoctonia solani AG-3, and the physiological responses of a plant host .
The soil fungus Rhizoctonia solani can cause seedling diseases on many plants in natural and agricultural ecosystems. Production of the plant growth regulators phenylacetic acid (PAA) and its hydroxy (OH) and methoxy derivatives contributes to the host infection process. However, little is known about how these compounds affect host plant physiology. To determine if PAA and a derivative could cause plant responses similar to those of Rhizoctonia infection, PAA or 4-OH-PAA was added to Murishige and Skoog's medium in concentrations ranging from 0-7.5 mM. Four replicate vessels of each medium were sown with 5 tomato seeds, and seedlings were assessed for root necrosis over 12 days of development. The percent area of root necrosis was positively correlated with concentration of both PAA and 4-OH-PAA, though the severity and location of necrosis within the root system differed for the two compounds. This demonstrates that host responses to PAA and its derivative are consistent with Rhizoctonia disease symptoms. A second objective was to quantify the influence of carbon catabolism on production of PAA by R. solani. The biosynthetic pathway for PAA production shares two metabolic intermediates with the pathway for quinic acid (QA) catabolism. To test the hypothesis that induction of the QA pathway can lead to sequestration of these shared intermediates and reduce PAA production, 11 field isolates of R. solani AG-3 were grown in Vogel's minimal medium amended with either 25 mM QA or no QA. PAA and derivatives were quantified by gas chromatography. In support of our hypothesis, PAA production was reduced in the QA treatment, but varied with isolate. This shows that modifying the carbon content of this pathogenís growth environment can reduce production of PAA via metabolic regulation. Improved understanding of this mechanism may lead to novel approaches to suppress Rhizoctonia disease.
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1 - North Carolina State University, Plant Pathology, Campus Box 7612, Raleigh, NC, 27695, USA
2 - North Carolina State University, Crop Science, Campus Box 7620, Raleigh, NC, 26795, USA
3 - North Carolina State University, Plant Pathology, Campus Box 7612, c.o. Faith Bartz, Raleigh, NC, 27695, USA
4 - North Carolina State University, Plant Pathology, Campus Box 7567, Raleigh, NC, 27695, USA
plant growth regulator
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood B/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 8:45 AM