LIBRARY 



NEW VORk 

 BOTANIC A I 



JOMAL OF AGKICHTDRAl ffiSEARCH 



Vol. XIX Washington, D. C, September i, 1920 No. 11 



GENETICS OF RUST RESISTANCE IN CROSSES OF VA- 

 RIETIES OF TRITICUM VULGARE WITH VARIETIES 

 OF T. DURUM AND T. DICOCCUM ^ 



By H. K. H.AYUS, Head of Section of Plant Breeding , Division of Agronomy and Farm 

 Managem,ent, Department of Agriculture, University of Minnesota, John H. Parker, 

 Scientific Assistant, and Carl KurtzwEil,^ Assistant Pathologist, Office of Cereal 

 Investigations, Bureau of Plant Industry, United States Department of Agriculture 



INTRODUCTION 



The black stemrust (Puccinia graminis) of small grains causes enor- 

 mous losses. Reduction in yield of from 10 to 50 per cent of the wheat 

 crop is common. At irregular intervals the black stemrust of wheat 

 causes almost complete failure, especially in the spring-wheat area of the 

 upper Mississippi Valley. Control of this disease, which develops into 

 such terrific epidemics, is impossible by any method now available to the 

 individual grower. For this reason the development of resistant varie- 

 ties assumes great importance. While the barberry eradication cam- 

 paign now being carried on over a wide area Vill certainly reduce the 

 amount of rust, local outbreaks may perhaps be expected even after 

 barberries have apparently been eradicated. The attempt to develop 

 resistant varieties, therefore, should continue. There is every reason to 

 hope that the stemrust problem can be solved by barberry eradication 

 and the development of resistant wheat varieties. 



When the present study was outlined, the evidence seemed to show that 

 parasitic action of the rust was constant. Recent extensive studies 

 {22, 2sY have confirmed this view and indicate that the bridging hypothe- 

 sis (jj), which was supposed to account for the increase or decrease in 



' Published with the approval of the Director as Paper 187, Journal Series, Minnesota Agricultural 

 Experiment Station. Cooperativ(f investigation between the Minnesota Agricultural Experiment Station 

 and the Office of Cereal Investigations, Bureau of Plant Industry, United States Department of Agriculture. 

 ^ The breeding of spring wheat for rust resistance was begun by Dr. E. M. Freeman and E. C. Johnson 

 in 1908 and has been continued without interruption until the present time. The present cooperative 

 arrangement between the Division of Plant Pathology and Botany and the Section of Plant Breeding, 

 Division of Agronomy and Farm Management, of the University of Minnesota, was made in the spring 

 of 1916. The writers wish to acknowledge the helpful cooperation of Dr. E. M. Freeman and Dr. E. C. 

 Stakman in this investigation. 



t^, ' Reference is made by number (italic) to "Literature cited," pp. 541-542. 



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O^ Journal of Agricultural Research, Vol. XIX, No. 11 



Washington, D. C. Sept. i, 1920 



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