STUDIES ON "BROWNING" ROOT ROT OF CEREALS: I. THE ASSOCIATION OF LAGENA RADICICOLA N.GEN.; N.SP., WITH ROOT INJURY OF WHEAT

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Abstract
A specific root rot of wheat and other cereals is described which is widespread over Saskatchewan, and occasions severe losses in some seasons. In early June, the outer leaves of the young plants become discolored, the number of tillers is reduced, growth delayed, and the yield considerably lessened. One of the chief diagnostic features is the presence of lesioned root tips containing oospores of the Pythium type. Although the disease is worst in a cool, wet spring, followed by warm, dry weather, the plants recover markedly when the remainder of the growing season is favorable. In preliminary work, "isolation strains" of various fungi from lesioned roots of field material collected in mid-summer failed to produce the disease under greenhouse methods of inoculation.A fungus belonging to the lower Phycomycetes, hitherto not described, was found associated with rootlet injury of wheat, barley, rye and maize seedlings grown in Regina clay soil from infested fields of southern Saskatchewan. Its life-history, morphology and physiological characters are given in detail; it is believed to be an obligate parasite which, under conditions favorable to its development, is capable of causing definite injury to wheat. It is not considered one of the major causes of browning root rot, but in the section where it is common it is likely one of the contributing causes in some seasons. It is regarded as belonging to the Ancylistaceæ, close to the genus Lagenidium, but the erection of a new genus Lagena is recommended. The binomial Lagena radicicola has been assigned to the fungus.More recently several "isolation strains" of Pythiaceous fungi have been secured from infected roots of wheat seedlings grown in soil collected from browning root-rot fields. A few of these in pot experiments in the greenhouse are shown to be definitely parasitic on the roots of wheat plants. There is some evidence that the particular root-rot concerned belongs to the Pythium root-rot complex type.

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