AbstractsBiology & Animal Science

Studies on the role of the toxic substances produced by helminthosporium sativum P.K. & B. in its parasitism.

by Robert Vernon. Clark

Institution: McGill University
Department: Department of Plant Pathology.
Degree: MS.
Year: 1952
Keywords: Plant Pathology.
Record ID: 1527481
Full text PDF: http://digitool.library.mcgill.ca/thesisfile124028.pdf


Grain crops are often afflicted with a disease commonly referred to as root rot or foot rot. Because root rot diseases are very variable in their symptom expression, they are frequently overlooked as the abnormal condition is often attributed to drought, wind, frost or other causes. For these reasons it is difficult to estimate the damage caused exclusively by root rots. It is generally agreed that the fungus Helminthosporium sativum P.K. & B. is of prime importance in the root rot complex affecting barley and wheat. By plating tests of seed samples of barley and wheat grown in representative areas of Canada, Greaney (1944) showed that the most important pathogen present was H. sativum. Oswald (1950) in California found the four primary pathogenic fungi attacking barley and wheat, in their order of apparent economic importance, to be Helminthosporium sativum, Fusarium roseum f. cerealis, Ophiobolus graminis and Fusarium nivale. Simard and Ludwig (1946) found that, in the years 1942 and 1943, 65 per cent of the Quebec grown barley seed samples examined by them carried H. sativum. The significance or Helminthosporium sativum in the barley and wheat growing areas is indicated by estimates of the damage caused by this fungus. Maohaeek (1943) concluded from the results of a three year survey in Manitoba that barley and wheat yields are reduced by as much as 12 per cent because of root rot.[...]