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Leaf‐Spot Of Oats, Helminthosporium Avenae (Bri. And Cav.) Eid.
Author(s) -
TURNER D. M.,
MILLARD W. A.
Publication year - 1931
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1931.tb02324.x
Subject(s) - biology , seedling , mycelium , scutellum , germination , spore , fungus , horticulture , inoculation , leaf spot , hypha , botany
S ummary . 1. The symptoms of the disease are defined. There are two well‐marked phases as described by Ravn (1) on the seedling, (2) on the mature piant. The fist of these is responsible for considerable loss in seedling oats. The second brings about the infection of the grain. Both spot and “stripe” lesions are produced. 2. The disease is especially dependent upon climatic factors. Under adverse conditions the extent and degree of infection is greatly increased, whilst with favourable conditions even plants from infected seed may escape the disease. It is for this reason that the disease assumes serious proportions in northern districts, where an inclement spring is the rule rather than the exception. 3. The causative organism of the disease has been isolated and its pathogenicity verified. It is not pathogenic to wheat or barley. 4. The disease is seed borne by adherent spores and resting mycelium within the pericarp. The percentage infection by spores on a number of commercial samples of Scottish grown oats ranged from 6 to 62 per cent.; the resting mycelium, however, is the more common and the more dangerous type of infection. 5. The infection of the seedling by the fungus has been investigated. The mycelium within the pericarp penetrates the scutellum and the epiblast during the early stages of germination, and this is followed by the invasion of the first, second and third leaves. If the growing point is reached the seedling is killed. Spores are produced abundantly on the dead leaves and initiate the secondary stage on the fifth and subsequent leaves. No parallel has been found between the mode of infection described and that stated to occur in the smuts. The production of a “stripe” is due to the coalescence of individual spots, and there is, therefore, no analogy between the formation of such lesions and those of stripe on barley as described by Smith. 6. The morphological and cultural characters of the causative fungus have been described and compared with those of other workers. The conclusion is drawn that it is identical with the H. avenae (Bri. and Cav.) Eid., and that whilst its close relationship to H. teres is admitted there are certain morphological and considerable cultural differences between the two species. 7. Control measures for the disease are discussed.