Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2009
Publication Date: 6/23/2009
Citation: Peterson, G.L. 2009. Susceptibility of selected winter wheat cultivars from Europe and the United States to Karnal bunt. European Journal of Plant Pathology. DOI 10.1007/s10658-009-9498-z. Interpretive Summary: In 1996, Karnal bunt of wheat, a fungal pathogen of regulatory significance, was found in the Southwestern U.S., in Arizona and California. Globally the disease appeared to be limited in distribution; generally confined to regions growing fall planted spring wheat cultivars under irrigation. In 1997, Karnal bunt was found for the first time on non-irrigated winter wheat cultivars in Central and Northern Texas. This region is the southern most beginning of the U.S. winter wheat belt that stretches continuously north into Canada. Extensive studies have been conducted in Mexico and India to evaluate disease susceptibility in existing spring wheat cultivars and resistance has been identified and utilized. Because Karnal bunt has not been observed in regions growing winter wheat, little work has been conducted to assess the vulnerability of this germplasm. The aim of our study was to test selected U.S. and European winter wheat germplasm for resistance to Karnal bunt. In total, 50 cultivars were tested for physiological (syringe injection of spores into plants) as well as morphological (spores sprayed on plants) resistance. The study was repeated three times. All cultivars tested for physiological resistance were susceptible to KB, though most to a lesser degree than the highly susceptible spring wheat cultivar WL711 used as a comparative control. Cultivars showed varying levels of morphological resistance with none scoring as susceptible or highly susceptible based on our criteria. One cultivar, “Eltan” scored highly resistant for both physiological and morphological resistance. The variability in resistance encountered among the cultivars tested was similar to that reported in spring wheat studies.
Technical Abstract: A study was conducted to determine the susceptibility of popular U.S. and European winter wheat cultivars to the fungal pathogen Tilletia indica. Historically, the disease has been limited to fall-sown spring-habit wheat regions and had not been associated with winter-habit wheat (requiring vernalization). In 1997, Karnal bunt was observed on winter wheat in limited regions of Texas. This region marks the southern end of the contiguous U.S. central winter wheat belt, which extends north into Canada. The aim of this study was to assess the levels of disease resistance in winter wheat. Fifty U.S. and European winter wheat cultivars were tested using two different greenhouse inoculation procedures. For each cultivar, 12 spikes in boot were inoculated by boot-injection with a sporidial suspension (1.0 ml/boot, 10,000/spores per ml), and 12 other emerged spikes were spray-inoculated with the same concentration. The experiment was repeated for three seasons. Among cultivars, mean seed infection ranged from 2.1 to 87.2 percent and 0 to 15.6 percent for boot-injected and spray-inoculated treatments, respectively. Results suggest that, in the presence of the pathogen, winter wheat in areas with favorable environmental conditions could develop the disease.