VARIETAL TRIALS, PHYSIOLOGIC SPECIALIZATION, AND BREEDING SPRING WHEATS FOR RESISTANCE TO TILLETIA TRITICI AND T.LEVIS

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Abstract
There has been a considerable increase in the amount of bunted wheat in western Canada recently. One hundred and forty-nine varieties and selections of spring wheat showed all gradations in reaction to this disease when inoculated artificially, varying from apparent immunity to high susceptibility. The increase in bunt can be accounted for in part by the use of certain varieties that are more susceptible than some of those grown formerly. There has also been an increase in the number and virulence of physiologic forms. One physiologic form of T. tritici and five of T. levis were obtained from six collections of bunt in this study. The isolation and study of relatively pure forms of the organism will be necessary for a study of the genetic factors in the host governing the reaction to bunt. Inheritance studies at present indicate that multiple factors, the exact nature of which has not yet been determined, govern the reaction to this disease. Production of resistant varieties suitable for the prairie provinces of Canada offers a very promising means for reducing the losses due to bunt of wheat.