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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #264070
Title: Finalizing host range determination of a weed biological control pathogen with BLUPs and damage assessment

Author
item Berner, Dana
item Cavin, Craig

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2011
Publication Date: 8/13/2011
Citation: Berner, D.K., Cavin, C.A. 2011. Finalizing host range determination of a weed biological control pathogen with BLUPs and damage assessment. Biocontrol. DOI:10.1007/S10526-011-9399-X.

Interpretive Summary: We are evaluating a fungus for classical biological control of tumbleweed. In initial host range safety tests, a genetics approach was used to generate predictors of disease severity among 89 species of plants related to tumbleweed. The work provided: 1) disease reactions for rare and difficult or impossible to grow species; 2) environmentally independent measures of disease severity; 3) measures of disease severity for species versus only an average severity on limited material tested in a greenhouse; 4) indicators of susceptible and non-susceptible species; 5) a means to compare disease on tumbleweed versus plants related to the weed. Of the 89 species evaluated, eight native N. American species related to the weed were predicted to be susceptible. As a result of these predictions, these eight species were further evaluated to determine the amount of actual damage caused by the fungus. Results showed that none of the species had any damage to above-ground plant parts. This supports the genetic analysis in the initial host range determination tests. As a result of both analyses, there is no evidence that the fungus would cause any effects on the relatives in nature.

Technical Abstract: Colletotrichum gloeosporioides f. sp. salsolae (Penz.) Penz. & Sacc. in Penz. (CGS) is a facultative parasitic fungus being evaluated as a classical biological control agent of Russian thistle or tumbleweed (Salsola tragus L.). In initial host range determination tests, Henderson’s mixed model equations (MME) were used to generate best linear unbiased predictors (BLUPs) of disease severity reaction to CGS among 89 species of plants related to S. tragus. The MME provided: 1) disease assessments for rare and difficult or impossible to grow species; 2) environmentally independent measures of disease severity; 3) measures of disease severity for species versus a sample of material tested in a greenhouse; 4) objective indicators of susceptible and non-susceptible species; 5) a means to objectively compare disease on targets versus non-targets. Of the 89 species evaluated by the MME, eight native N. American species were predicted to be susceptible. As a result of these predictions, these eight species were further evaluated to determine the amount of actual damage caused by CGS. This was done by comparing root and shoot areas and weights between non-inoculated plants and plants inoculated with CGS. Results showed that several of the species exhibited some minor reduction in root weight and root area, but none of the species had any damage to above-ground plant parts. This supports the BLUP output in the initial host range determination tests. As a result of both analyses, there is no evidence that CGS would cause any non-target effects in nature.