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Changes in Carbon Dioxide Levels During Sclerotial Formation by Phymatotrichum omnivorum. Stuart D. Lyda, Associate Professor, Department of Plant Sciences, Texas A&M University, College Station, Texas 77843; Earl Burnett, Research Soil Scientist, USDA, ARS, Blackland Conservation Research Center, Temple, Texas 76501. Phytopathology 61:858-861. Accepted for publication 23 February 1971. DOI: 10.1094/Phyto-61-858.

Carbon dioxide was monitored over a 12-week period from pint-sized culture chambers supporting sclerotial formation by Phymatotrichum omnivorum on a sterile soil-sorghum seed substrate. Carbon dioxide accumulated rapidly during the first 2 weeks after inoculation with the fungus, and declined rapidly during the period of maximum sclerotial development. Sclerotial initiation coincided with the elevated CO2 concentration, whereas maximum sclerotial dry weight was obtained in 8 weeks. Apparently, CO2 or the dissolved bicarbonate ion influences sclerotial formation in P. omnivorum. Soils with the capacity to absorb or otherwise accumulate high concentrations of CO2 or bicarbonate might be suitable for sclerotial development of P. omnivorum and support the cotton disease caused by this fungus. There were no significant changes in O2 and N2 levels during the 12-week study period.

Additional keywords: fungus, sclerotia, soil microbiology.