Location: Application Technology Research2012 Annual Report
1a. Objectives (from AD-416):
The objective is to detect and evaluate the early stress response of seed geranium following exposure to Pythium, a microorganism that is ubiquitous in greenhouse setting, and can easily spread through the use of infested soil and reuse of contaminated irrigation water. The implementation of non-destructive or minimally invasive techniques to detect and evaluate plant performance early in the interaction process has become possible through the use of portable and computer-based devices. The techniques allow for real time monitoring and evaluation of periodical progression of stress response of the same plant or the same part of the plant. Data generated from the study should give us insight into developing strategies that could be implemented in order to lessen the biotic stress from such pathogens and to improve and optimize plant quality and profitability.
1b. Approach (from AD-416):
Geranium seed cv. Red Maverick will be sown in Oasis Cubes for ~2 weeks before being transplanted into 6” pots containing soilless medium into either greenhouse or growth chamber environments. Controlled environmental conditions such as light level of 200-400 micromol m-2 s-1 PAR, and temperature at 23 C will be maintained throughout the duration of the study. Other aspects of plant maintenance such as watering, fertilization, and insect control will be implemented as required. The system will utilize computer-based data monitoring and recording of temperature, humidity, light, and soil moisture. Pythium ultimum and P. aphanidermatum will be utilized, and were originally isolated from infected plants and kept in Potato Dextrose Agar (PDA) in Toledo. Tested pathogens will be cultured in artificial media (PDA) for 1-2 weeks prior to inoculation at 23 C. The inoculum density will be adjusted to 104 spores ml-1. The inoculation procedure will be done by adding 100 ml of spore suspension from each of the tested pathogen to each pot. Two major control treatments will be included. One is the negative control where no pathogen will be tested. And the other will include treating of the plants with the fungicide Subdue Maxx prior to adding the spore suspension of each of the pathogen. Periodic response of the challenged plants to treatments will be evaluated using non-destructive techniques which include visual inspection of symptom development and disease severity, chlorophyll content using a hand-held chlorophyll content meter (CCM200), leaf fluorescence with a portable fluorometer (OP-30), soil moisture, and whole-plant gas exchange with a system developed at Ohio State.
3. Progress Report:
The goal of this project was to use minimally invasive, minimally destructive approaches to evaluate the stress responses of zonal geraniums following exposure to two water mold pathogens (Pythium ultimum and Phytophthora nicotianae). The implementation of non-destructive or minimally invasive techniques allows for real time monitoring and evaluation of periodical progression of stress response of the same plant or the same part of the plant. Data generated from the study should give us insight into developing strategies that could be implemented in order to lessen the biotic stress from such pathogens and to improve plant quality and profitability. To summarize this project, we established an experimental procedure, and developed instrumentation for the project. A preliminary study was conducted under environmentally controlled growth conditions that included appropriate light level, temperature, fertilization, watering, and pest control. The study was conducted to fine tune the plant growing, pathogen inoculation/introduction, and disease evaluation procedures. A weekly visual evaluation was used to rate symptom development and disease severity of Phythium on the geranium. The plants were started, transplanted, and inoculated with the pathogens and transferred to the 12-chamber phytotron facility, and the stress symptoms were evaluated weekly. At week 4 of this study, the plants challenged with Pythium ultimum showed slightly more visual disease severity than the ones treated with Phytophthora nicotianae. The observation was somewhat counter intuitive that warrants further investigation. Also collected was plant canopy temperature, and chlorophyll fluorescence as potential indicators of root damage due to the pathogen attack. Higher canopy temperature and higher fluorescent signal were expected as root damage severity increased. Another major effort during this time period was to improve our gas exchange measurement and data acquisition capability. We were successful in acquiring a CO2/H2O analyzer to improve our gas exchange analysis capability for this project. This project relates to two sub-objectives in the parent project. Sub-objective 1a: Elucidate the optimal level of selected nutrients required for major production species and their interaction with potential biotic and abiotic stresses and Sub-objective 2a: Evaluate the use of non-destructive sensor technology and develop new molecular probes to measure and predict the impact of biotic and abiotic stresses on ornamental crops.