Abstract
Benomyl (methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate) inhibited growth of Phymatotrichum omnivorum in culture at concentrations of 0.5 μg/ml or higher. Concentrations of 0.25, 0.5, and 1 μg/ml benomyl did not inhibit respiration of P. omnivorum in the Warburg respirometer. When aqueous benomyl solutions were applied to the stem bases of cotton plants in green house soil-temperature tanks, the incidence of Phymatotrichum root rot was reduced 85 - 87% with 24mg active material/plant, applied in either 1.5 or 3.0 ml. Similar field treatments with naturally infested soil at two locations gave 74-91% reduction of Phymatotrichum root rot in cotton. Histological examination of cotton roots grown under controlled environmental conditions revealed that primary tissues were lost naturally due to the development of secondary growth 20 days after emergence. Phymatotrichum mycelium was not found associated with the cotton roots until the secondary growth had been initiated. The periderm, which comprises part of the secondary growth, was the site of extensive intercellular penetration by P. omnivorum. When the first visual symptoms of Phymatotrichum root rot were present (wilting), microscopic examination of the roots revealed extensive mycelial invasion of the xylem parenchyma and plugging of the metaxylem without extensive damage in the periderm. The fatty acid content of Phymatotrichum mycelium grown in liquid cultures under different CO₂ environments was determined. The two predominant fatty acids were palmitic and linoleic. Concentrations of palmitic acid were not significantly altered in mycelium grown in 0.3, 0.5, 5, or 50% CO₂. Concentrations of linoleic were decreased four-fold in the 50% CO₂ environment, but not at the other CO₂ concentrations. There was no difference between the palmitic and linoleic acid concentrations of infected and non-infected cotton roots.
Rivers, James Robert (1972). Chemical and histological studies on Phymatotrichum omnivorum (Shear) Duggar and its interaction with Gossypium hirsutum L. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -186039.