Location: Forage Seed and Cereal Research UnitTitle: Field trials to study choke spread and evaluate orchardgrass germplasm for choke resistance
|MERLET, LEA - Oregon State University|
|BOREN, PAT - Western Farm Service|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2019
Publication Date: N/A
Technical Abstract: Choke in orchardgrass (Dactylis glomerata L.), caused by Epichloë typhina (Pers.) Tul & C. Tul, was first reported in western Oregon in 1997. The pathogen quickly spread within and between fields and by 2003, wherein 90% of the fields tested were infected with choke. Yield loss in orchardgrass seed production fields were reported as great as 30%. Epichloë typhina infects orchardgrass systemically with a low density of hyphae found in leaves and stems. Infected plants remain asymptomatic during most of the year. As reproductive tillers elongate, and just prior to seed head emergence, a rapid and dense growth of the fungus within and among leaf sheaths effectively blocks the emergence of seed heads. In most grasses, E. typhina typically infects host ovaries during flowering, which results in infected seed and subsequent infected plants. However, in orchardgrass, E. typhina has not been found in, or transmitted through seed, and very little is known about how infections occur in the field. Currently, there is no effective management for choke in orchardgrass seed production fields. The best long-term solution to disease management includes host genetic resistance. Using a semi-natural inoculation method to look at Epichloë transmission in orchardgrass, we showed that infection can occur in young plants. Furthermore, disease spread does not appear to rely on wounding during harvest, however wounding might improve its transmission. Recent cultivar and germplasm trials identified potential lines and plants that appear to demonstrate potential resistance to the disease. Currently we are screening 27 orchardgrass lines in a multi-year field trial to identify cultivars resistant to infection in field conditions. Artificially inoculated plants were included to detect tolerant cultivars, which produce less or no stromata upon infection.