ARS | Publication request: HOST SPECIFICITY OF MICROSPHAEROPSIS AMARANTHI AND PHOMOPSIS AMARANTHICOLA, BIOHERBICIDE CANDIDATES FOR AMARANTHUS SPECIES

Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2005
Publication Date: December 15, 2005
Citation: Ortiz-Ribbing, L., Williams, M. 2005. Host specificity of microsphaeropsis amaranthi and phomopsis amaranthicola, bioherbicide candidates for amaranthus species [abstract]. North Central Weed Science Society US Proceedings. 60:140.

Technical Abstract: Weeds of the Amaranthus genus have variable susceptibility to two indigenous fungal organisms, Microsphaeropsis amaranthi and Phomopsis amaranthicola. In an effort to explain host specific responses, M. amaranthi and P. amaranthicola conidial germination and germ tube length were quantified on the leaf surfaces of seven Amaranthus species at 21° and 28° C. Weeds included common waterhemp, Palmer amaranth, Powell amaranth, redroot pigweed, spiny amaranth, smooth pigweed, and tumble pigweed. Host-specific responses were greater for P. amaranthicola than M. amaranthi, as evidenced by weed species effects on conidial germination and germ tube elongation. Conidia of M. amaranthi had higher germination and germ tube elongation than P. amaranthicola. Assuming disease severity of host plants increases with conidia germination and germ tube elongation, these results are largely consistent with seedling biomass reduction and mortality reported for these weed species in previous work. However conidial germination and germ tube elongation are only two processes of disease expression; the ability of the fungal organism to penetrate and infect leaf tissue warrants further study.