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Seedborne Fungal Contamination: Consequences in Space-Grown Wheat

November 1997 , Volume 87 , Number  11
Pages  1,125 - 1,133

Deborah L. Bishop , Howard G. Levine , Bradley R. Kropp , and Anne J. Anderson

First, third, and fourth authors: Department of Biology, Utah State University, Logan 84322-5305; second author: Dynamac Corporation, DYN 3, Kennedy Space Center, Cape Canaveral, FL 32899

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Accepted for publication 5 July 1997.

Plants grown in microgravity are subject to many environmental stresses that may promote microbial growth and result in disease symptoms. Wheat (cv. Super Dwarf) recovered from an 8-day mission aboard a NASA (National Aeronautics and Space Administration) space shuttle showed disease symptoms, including girdling of leaf sheaths and chlorosis and necrosis of leaf and root tissues. A Neotyphodium species was isolated from the seed and leaf sheaths of symptomatic wheat used in the spaceflight mission. Certain isozymes of a peroxidase unique to extracts from the microgravity-grown plants were observed in extracts from earth-grown Neotyphodium-infected plants but were not present in noninfected wheat. The endophytic fungus was eliminated from the wheat seed by prolonged heat treatment at 50°C followed by washes with water at 50°C. Plants from wheat seed infected with the Neotyphodium endophyte were symptomless when grown under greenhouse conditions, whereas symptoms appeared after only 4 days of growth in closed containers. Disease spread from an infected plant to noninfected plants in closed containers. Dispersion via spores was found on asymptomatic plants at distances of 7 to 18 cm from infected plants. The size and shape of the conidia, mycelia, and phialide-bearing structures and the ability to grow rapidly on carbohydrates, especially xylose, resembled the characteristics of N. chilense, which is pathogenic on orchard grass, Dactylis glomerata. The Neotyphodium wheat isolate caused disease symptoms on other cereals (wheat cv. Malcolm, orchard grass, barley, and maize) grown in closed containers.

Additional keywords: fungal endophyte.

© 1997 The American Phytopathological Society