Recipient Organization
TENNESSEE STATE UNIVERSITY
3500 JOHN A. MERRITT BLVD
NASHVILLE,TN 37209
Performing Department
Agricultural and Environmental Sciences
Non Technical Summary
Certain ornamental crops are limited in the range of their landscape use due to biotic and abiotic stresses. This project examines the effects of biotic and abiotic stresses on selected economically important ornamental crops, crop response to stresses, and identification of forms that are stress tolerant for superior landscape performance.
Animal Health Component
25%
Research Effort Categories
Basic
50%
Applied
25%
Developmental
25%
Goals / Objectives
The purpose of this study is a more complete understanding of the effects of biotic and abiotic stresses on selected economically important ornamental crops, how the crops respond to stresses, and identification of forms that are stress tolerant for superior landscape performance. Specific objectives are as follows: Objective 1. (Aziz) To develop genetic characterization data and genetic maps of phlox and beebalm using AFLP molecular markers. Objective 2. (Sauve) To evaluate 20 commercially available cultivars of phlox for susceptibility to powdery mildew, and evaluate efficacy of traditional and non-traditional fungicides. Objective 3. (Hayslett) To evaluate 20 commercially available cultivars of beebalm for susceptibility to powdery mildew, and evaluate efficacy of traditional and non-traditional fungicides. Objective 4. (Dumenyo) To evaluate the effects of selected bacterial pathogens on a range of phlox and beebalm cultivars, screen for tolerance and perform
characterization of host-pathogen interaction in susceptible forms. Objective 5. (Catanzaro) To screen 10 commercially available cultivars each of phlox (including mildew resistant), beebalm (including mildew resistant) and grasses at two developmental stages to quantify their whole-plant tolerance to short term high temperature stress events. Objective 6. (Zhou) To characterize expression of heat shock proteins in cultivars of phlox, beebalm and grasses found to be differentially heat tolerant at the whole plant level.
Project Methods
Objective 1. AFLP molecular markers will be used for genetic characterization and mapping of selected forms of phlox and beebalm. AFLP markers will be identified using sequencing gel electrophoresis. Non-linked AFLP markers will segregate following 1:1 Mendelian segregation, while segregation ratios that differ from the expected value will be classified as distorted. A genetic mapping program that calculates map distances will be used for linkage analysis. Map distances will be estimated by conversion of recombination frequencies through the Kosambi mapping function. Objectives 2,3. Field and container-grown plants (20 cultivars each of phlox and beebalm) will be evaluated for degree of incidence of powdery mildew. Development of visual symptoms will be rated monthly between June and September. The overall performance of each cultivar over the study will be determined by averaging the highest disease readings over the three-year period. The cultivars will be
categorized as resistant, moderately resistant, moderately susceptible or susceptible. At the end of the season, shoots will be harvested to obtain shoot biomass data. Phlox and beebalm will also be rated on their cultural adaptability to the soils and conditions of USDA zone 6A for winter hardiness, and rated on ornamental traits and response to shearing after flowering. A susceptible cultivar of each species will also be used to evaluate effectiveness of traditional and non-traditional (antibacterial detergent) fungicides, with weekly ratings of disease severity as described above. Objective 4. A range of phlox and beebalm cultivars will be screened in greenhouse and laboratory tests to quantify effects of one strain each of Pseudomonas, Xanthomonas and Ralstonia. Plants will be screened for tolerance to selected pathovars and strains. Where a compatible reaction results, a pathosystem will be established for molecular characterization of host-pathogen interaction. Objective 5. Ten
cultivars each of container-grown phlox, beebalm and grasses will be screened over a time course starting at two developmental stages (seedling, mature growth) to quantify their tolerance to short term and season-long high temperature stress events. For short term stress, recovery of plants (visual ratings, growth rates) will be recorded. For season-long evaluation, vegetative growth and flowering data will be recorded over time, and final shoot and root biomass data will be collected. Results will be used to classify each cultivar as to its degree of thermotolerance. Whole-plant results will be correlated with results at the subcellular level. Objective 6. Expression of heat shock proteins will be characterized in selected phlox, beebalm and grass cultivars found to be differentially heat tolerant at the whole plant level. Leaf samples will be taken from plants exposed to short term high temperature stress events and protein extraction performed. Samples will be stored at -80C until
SDS-PAGE can be performed on groups of samples and Western blotting performed. Results with heat shock proteins for cultivars of each species will be correlated with thermotolerance response at the whole-plant level.