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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY AND ECOLOGICALLY BASED KNOWLEDGE FOR INTEGRATED WEED MANAGEMENT SYSTEMS

Location: Global Change and Photosynthesis Research Unit

Title: Conidial Germination and Germ Tube Elongation of Phomposis Amaranthicola and Microsphaeropsis Amaranthi on Leaf Surfaces of Seven Amaranthus Species

Authors
item Ortiz Ribbing, Loretta
item Williams, Martin

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 10, 2006
Publication Date: June 15, 2006
Citation: Ortiz Ribbing, L.M., Williams, M. 2006. Conidial germination and germ tube elongation of Phomopsis amaranthicola and Microsphaeropsis amaranthi on leaf surfaces of seven Amaranthus species. Biological Control. 38(3):356-362.

Interpretive Summary: Previous research indicated that seedlings of several Amaranthus species are susceptible to infection by conidial suspensions of Microsphaeropsis amaranthi and Phomopsis amaranthicola in both controlled and field environments, and that these pathogens could potentially provide an alternative, biologically based method for managing certain weeds in the genus Amaranthus. In an effort to understand apparent relative susceptibility among seven Amaranthus species to these fungal organisms, a controlled environment study was conducted to estimate conidial germination and germ tube length ('m) on the weed leaf surfaces at 21° and 28° C. Weeds included Amaranthus rudis; A. palmeri; A. powellii; A. retroflexus; A. spinosus; A. hybridus; and A. albus. For P. amaranthicola, conidial germination and germ tube length varied among the seven weed species at both temperatures, while for M. amaranthi germ tube lengths were significant among weed species only at 21° C. Results indicate that P. amaranthicola may have greater host specificity for these weedy species than does M. amaranthi. In general, M. amaranthi had a higher percentage of conidial germination and longer germ tubes at both temperatures when compared to P. amaranthicola. While conidial suspensions of M. amaranthi and P. amaranthicola germinated on the leaf surfaces of all seven weed species, temperature appears to impact the number and length of germ tubes on the leaf surfaces. The percentage of germinated conidia and the length of germ tubes were often greater for M. amaranthi than P. amaranthicola, which could explain greater disease expression and control of some Amaranthus species. This research indicates the importance of host specific responses to germination and growth of M. amaranthi and P. amaranthicola on leaf surfaces of Amaranthus species and the influence that temperature may have on these processes. A greater understanding of host specificity of M. amaranthi and P. amaranthicola would help define the role of these organisms as bioherbicides for weedy Amaranthus species.

Technical Abstract: Previous research indicated that seedlings of several Amaranthus species are susceptible to infection by conidial suspensions of Microsphaeropsis amaranthi and Phomopsis amaranthicola in both controlled and field environments, and that these pathogens could potentially provide an alternative, biologically based method for managing certain weeds in the genus Amaranthus. In an effort to understand apparent relative susceptibility among seven Amaranthus species to these fungal organisms, a controlled environment study was conducted to estimate conidial germination and germ tube length ('m) on the weed leaf surfaces at 21° and 28° C. Weeds included Amaranthus rudis; A. palmeri; A. powellii; A. retroflexus; A. spinosus; A. hybridus; and A. albus. For P. amaranthicola, conidial germination and germ tube length varied among the seven weed species at both temperatures, while for M. amaranthi germ tube lengths were significant among weed species only at 21° C. Results indicate that P. amaranthicola may have greater host specificity for these weedy species than does M. amaranthi. In general, M. amaranthi had a higher percentage of conidial germination and longer germ tubes at both temperatures when compared to P. amaranthicola. While conidial suspensions of M. amaranthi and P. amaranthicola germinated on the leaf surfaces of all seven weed species, temperature appears to impact the number and length of germ tubes on the leaf surfaces. The percentage of germinated conidia and the length of germ tubes were often greater for M. amaranthi than P. amaranthicola, which could explain greater disease expression and control of some Amaranthus species. This research indicates the importance of host specific responses to germination and growth of M. amaranthi and P. amaranthicola on leaf surfaces of Amaranthus species and the influence that temperature may have on these processes.

Last Modified: 8/21/2014
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