Abstract Detail

Mycological Section

Franke, JanaLynn [1], Meyer, Susan E. [2], Geary, Brad  [1].

Bleach Blonde Syndrome, a New Disease of Bromus tectorum Implicated in Cheatgrass Die-offs.

With the accidental introduction of Bromus tectorum into the Western United States, came a massive shift in the ecosystem, resulting in complete monocultures of B. tectorum. Undescribed soilborne microorganisms in the Great Basin are beginning to surface as plant pathogens on Bromus tectorum. Recently, we have identified a pathogen that could potentially play an important role in the cheatgrass die-off phenomenon. The disease manifests itself late in flowering; the seeds fail to fill, the plant is stunted, and turns prematurely chlorotic “bleach blonde”. These plants also tend to lodge very quickly and easily, so that patches look matted down compared to the litter left standing from healthy current-year stands. Symptomatic plant samples were taken from the Whiterocks study site in Skull Valley, Utah in summer 2012 and putative causal organisms were isolated onto water agar. The prevalent microorganism, identified using molecular-genetic techniques, is undescribed, but is most closely related to Stromatinia gladioli, and is also a close relative of Roetstromia henningsiana and Sclerotinea homeocarpa. In a greenhouse pathogenicity test, this fungal isolate was inoculated into a low-nutrient soil and non-dormant B. tectorum seeds were planted. Initial height measurements showed that inoculated plants were significantly shorter than uninoculated plants. Final results showed that 17% of the plants in the study exhibited most or all of the following symptoms: failure to set viable seed, lodging, stunted growth, and premature bleach blonde coloring. Plants with these symptoms were also abundant at Whiterocks in 2011-2012. In summer 2012, six permanent transects were installed, each with twenty-five 0.10 m² plots. After seed dispersal was complete but before any germination, a baseline data set was collected that included the density of fertile tillers as well as semi-quantitative indices of bleach blonde abundance and litter cover and depth. Seed bank samples were also collected. An average of 60% of the potential seed production on these plots in 2011-2012 was destroyed by the bleach blonde pathogen. Data collected in May 2013 showed that there was a six-fold drop in average fertile tiller density from 2012 to 2013 (350 to 64 plants-m^-2).  In addition, 26 plants-m^-2 were rendered sterile by the bleach blonde disease in 2012-2013 for an estimated disease incidence of 29%.  These results suggest that the bleach blonde pathogen not only had a major impact on seed production but apparently also interacted with other pathogens to create a cheatgrass die-off.

1 - Brigham Young University, 263 widb, PWS, Provo, Utah, 84602, United States
2 - UNITED STATES DEPARTMENT OF AGRICULTURE, USFS SHRUB SCIENCES LABORATORY, 735 NORTH 500 EAST, Provo, UT, 84606, USA

Keywords:
Bromus tectorum
Western United States
fungal plant pathogen
cheatgrass die-off .

Presentation Type: Oral Paper:Papers for Sections
Session: 36
Location: Cottonwoods North/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 9:15 AM
Number: 36004
Abstract ID:446
Candidate for Awards:None