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United States Department of Agriculture

Agricultural Research Service

Research Project: EMERGING FOREIGN FUNGAL PLANT PATHOGENS: DETECTION, BIOLOGY, AND INTERACTIONS WITH HOST PLANTS

Location: Foreign Disease-Weed Science

Title: Sporulation capacity and longevity of Puccinia horiana teliospores in infected chrysanthemum leaves

Authors
item Bonde, Morris
item Palmer, Cristi -
item Luster, Douglas
item Nester, Susan
item Revell, Jason -
item Berner, Dana

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 2013
Publication Date: August 23, 2013
Citation: Bonde, M.R., Palmer, C.L., Luster, D.G., Nester, S.E., Revell, J., Berner, D.K. 2013. Sporulation capacity and longevity of Puccinia horiana teliospores in infected chrysanthemum leaves. Plant Health Progress. doi:10.1094/PHP-2013-0823-01-RS.

Interpretive Summary: Chrysanthemum white rust is a significant fungal pathogen first discovered in the U.S. in 1977. The disease was eradicated and for many years successfully controlled by fungicides and strict regulatory measures, but more recently Chrysanthemum white rust has reappeared at an increasing frequency in the U.S., causing significant economic losses to chrysanthemum producers. Little is known about how the pathogen infects its chrysanthemum host and spreads between host plants. We initiated the present study to identify factors that affect how long leaves from infected plants remain capable of producing spores to spread the pathogen between chrysanthemum plants, and what factors influence the production of infectious spores. We demonstrated that infected leaves produce infectious spores beginning approximately 2 weeks after they become infected, and continued for the life of the leaf. We further demonstrated that the production of infectious spores on leaves was dramatically inhibited by light. These results have implications for understanding the disease cycle and should contribute to improved prediction of disease development, as well practical methods for control of the disease by growers.

Technical Abstract: PUCCINIA HORIANA is a quarantine-significant fungal pathogen and causal agent of Chrysanthemum white rust, first discovered in the U.S. in 1977. The disease was eradicated and for many years successfully controlled by fungicides and strict regulatory measures. However, recently Chrysanthemum white rust has reappeared at an increasing frequency. Because of lack of a reliable method to quantitate teliospore viability, we initiated the present study. Infected Chrysanthemum leaflets were scanned and total cross-sectional pustule areas determined for each leaflet. The leaflets were attached to the inside surface of the lid of a 5-cm diameter petri dish containing a 0.05 percent agar solution in the bottom of the dish to prevent basidiospores (sporidia) sticking to the dish. The dishes were incubated in the dark at 17 degrees C. Two days later, the basidiospores of that fell into the agar solution of each dish were counted by means of a hemocytometer. Based on numbers of basidiospores collected and total cross-sectional pustule area per leaflet, it was possible to determine numbers of basidiospores produced per mm2-pustule area. Results from the study showed that infected leaves sporulated beginning approximately 2 weeks after inoculation, and continued for the life of the leaf. We further demonstrated that sporulation on excised leaves was dramatically inhibited by light. These results have implications for understanding the disease cycle and should contribute to improved prediction of disease development, and practical methods for control.

Last Modified: 11/24/2014
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