|DI GIAMBATTISTA, GIUSEPPE|
Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2007
Publication Date: 3/12/2008
Citation: Riccioni, L., Inman, A., Magnus, H.A., Valvassori, M., Di Giambattista, G., Porta-Puglia, A., Hughes, K., Coates, M., Bowyer, R., Barnes, A., Sansford, C.E., Razzaghian, J., Prince, A., Peterson, G.L. 2008. Susceptibility of European bread and durum wheat cultivars to Tilletia indica. Plant Pathology. doi 10.1111/j 1365-3059.2008.01830.X
Interpretive Summary: The most prevalently grown European winter, spring and durum wheat lines were tested for their susceptibility to infection from the fungal plant pathogen, Tilletia indica, which causes the disease Karnal bunt of wheat. Tilletia indica has not been reported in Europe and is considered a quarantine pest. Two studies were conducted in containment growth chambers, replicated in Italy and the United Kingdom. In the first, pre-emerging wheat heads were inoculated by injection with a suspension of infective spores in order to assess physiological disease resistance. In the second, emerging wheat heads of selected cultivars were inoculated by spraying them with an infective spore suspension to determine if host morphology played a role in disease resistance. At maturity, plants were harvested and the number and severity of infected seeds was determined. Thirty five of the forty-one European cultivars tested became infected. The infection severity across all wheat cultivars ranged from highly susceptible to resistant based on international rating standards for Karnal bunt resistance screening. This broad range of disease resistance was also observed in similar field studies conducted with regionally grown cultivars in India and Mexico, and in greenhouse studies in the United States. Results suggest that many European wheat cultivars had some level of disease resistance which would limit the agronomic severity of the disease, however, most were susceptible to infection and therefore would not present a significant barrier to the establishment and spread Karnal bunt in the European Union.
Technical Abstract: Representative European wheat cultivars were tested under quarantine containment for their susceptibility to Tilletia indica, the cause of Karnal bunt (or partial bunt) of wheat. Fifteen winter, 15 spring wheat (Triticum aestivum) and 11 durum wheat cultivars (Triticum durum) were inoculated by ‘boot’ injection just prior to ear emergence, to test their physiological susceptibility. Selected cultivars were then re-tested by spray inoculation after ear emergence to determine their morphological susceptibility, which is a better predictor of field susceptibility. At maturity, the ears and seeds were assessed for incidence and severity of disease. For the physiological susceptibility tests, 13/15 winter wheat cultivars were infected and the percentage infected seeds ranged from 1 to 32%. For spring cultivars, 13/15 cultivars were infected and the percentage infected seeds ranged from 1 to 48%. For the durum cultivars, 9 /11 were infected and the percentage infected seeds ranged from 2 to 95%. Across all cultivars, 35/41 were infected, with 1 cultivar classed as ‘highly susceptible’, 3 as ‘moderately susceptible’, 11 as ‘susceptible’, 20 as ‘resistant’ and only 6 as ‘highly resistant’, based on historical Karnal bunt susceptibility categories using coefficients of infection. The spray-inoculation morphological susceptibility tests broadly confirmed the physiological susceptibility results, although lower levels of infection were observed. Overall, the range of susceptibility was similar to that found in cultivars grown in ‘Karnal bunt’ countries. The results demonstrated that European wheat cultivars are susceptible to T. indica and that they would not limit establishment of T. indica if introduced into Europe.