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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 Research

Title: Observations of the germination behavior of Tilletia indica teliospores on the soil surface under varying simulated environmental conditions

Author
item Peterson, Gary
item Glenn-parrish, Deborah
item Berner, Dana
item Phillips, John

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Karnal bunt of wheat is a minor wheat disease that can have a potentially significant economic impact due to wheat import/export regulations. In 1996, the disease was first reported in the United States in Arizona, California and Texas resulting in regional quarantines in those states. The disease is spread through contaminated seed and equipment that carry resilient Karnal bunt spores. Under favorable environmental conditions, which have not been fully defined, Karnal bunt spores on the soil surface will germinate and the resulting product produce a secondary fragile spore form that can infect the wheat head at flowering time. The resulting infection then partially converts the infected seed into a black powdery mass of new Karnal bunt spores. Earlier studies showed that teliospores can live more than 3 years in the soil. This study looked only at the behavior of teliospores on the soil surface under a varying set of environmental temperatures and soil moisture. Spores on the soil surface are capable of infecting wheat during that particular growing season. Our results suggest that in wheat growing regions subjected to early season rainfall, the majority of Karnal bunt spores will germinate before wheat reaches a susceptible state. However, a lesser portion of the spores will remain dormant until flowering and still pose a risk if favorable conditions for both spore germination and wheat infection occur. These results will be useful to federal and state regulatory officials in refining policies on Karnal bunt quarantine and eradication.

Technical Abstract: A series of replicated growth chamber studies were conducted to investigate the effects of soil type and simulated 5-yr average minimum/maximum European temperature conditions from the time of planting until anthesis in Hungary, United Kingdom, Italy and Norway on the initiation of Tilletia indica teliospore germination on the soil surface. A concurrent study was conducted with a simulated temperature profile for Ciudad Obregon and Mexico, where Karnal bunt is known to occur. Three soil moisture treatments were studies; 40.5 percent WHC, 16.2 percent WHC and weekly fluctuation of soil WHC. Results suggest that soil type would not have a significant effect on germination during the season. Under all conditions tested, some portion of the teliospore population remained dormant but viable throughout the entire simulated seasons. In comparing Mexican and Hungarian temperature profile we observed the greatest soil surface germination at 40.5 percent WHC during the first 30 days of the simulation of the Hungarian profile (30 days after planting date) while the greatest germination for the 16.2 percent WHC treatment occurred using the Mexican profile during the last 30 days of the study (time of anthesis).

Last Modified: 09/25/2017
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