JOlim OF AGMOILTiAL RESEARCH 
Voi,. XXIV Washington, June 23, 1923 No. 12 
THE MODE OF INHERITANCE OF RESISTANCE TO 
PUCCINIA GRAMINIS WITH RELATION TO SEED 
COLOR IN CROSSES BETWEEN VARIETIES OF 
DURUM WHEATS 
By J. B. Harrington, Graduate Student in Plant Breeding^ University of Minnesota^ 
and O. S. AamodT, Assistant Pathologist, Office of Cereal Investigations, Bureau 
of Plant Industry, United States Department of Agriculture ^ 
INTRODUCTION 
It has long been recognized that the production of economically desir¬ 
able varieties of wheat resistant to Puccinia graminis tritici Erikss. 6* 
Henn. would be of great value. Until recently, hybridization experi¬ 
ments with this end in view were based upon a very incomplete knowledge 
of both the exact nature of the pathogene and the nature of the inherit¬ 
ance of resistance, and consequently, satisfactory results were not 
obtained. A knowledge of the mode of inheritance of certain desired 
economic characters of wheat together with the discovery that there are 
several biologic forms of stem rust of wheat has been of much importance 
in placing breeding studies on a definite basis. Several varieties belong¬ 
ing to different species or subspecies of wheat have been found to be resist¬ 
ant to certain biologic forms. It is hoped that by hybridization, resistance 
to all biologic forms may be combined in one variety. The present 
problem was attacked chiefly for the purpose of determining whether the 
resistance of two varieties, having different factors for resistance, may be 
combined in the progeny of a cross between them. 
REVIEW OF PREVIOUS INVESTIGATIONS 
Since 1894, when Eriksson (7)® discovered biologic specialization in 
the black stem rust, numerous investigators (6, 9, -25) have corroborated 
his work. The reports of Ward, Evans, and others (j^, <^, 9) indicated 
that biologic forms might change rather rapidly as a result of host in¬ 
fluence but more recent work by Stakman and others (27, jo) showed 
that biologic forms were apparently quite stable. Previous to 1916, it 
was generally believed that only one form of black rust attacked wheat* 
^Accepted for publication Feb. 20,1923. Cooperative investigations between the Sections of Plant Breed¬ 
ing and Plant Pathology, Minnesota Agricultural Experiment Station, and the Ofi&ce of Cereal Investi¬ 
gations, Bureau of Plant Industry, U. S. Department of Agriculture. 
Published with the approval of the Director of the Miimesota Agricultural Experiment Station as paper 
No. 349, Journal Series of the Minnesota station. 
* The authors wish to express their appreciation for the assistance rendered by Dr. H. K. Hayes and Dr. 
E. C. Stakman. both of the Minnesota Agricultural Experiment Station, and to thank Mr. M. N. Levine, 
Assistant Pathologist, Office of Cereal Investigations, U. S. Department of Agriculture, for certain biologic 
forms of wheat rust which he furnished. 
® Reference is made by number (italic) to “ Literature cited,” p. 995-996. 
Journal of Agricultural Research, 
Washington, D. C. 
afd 
Vol. XXIV. No. 12 
Jtme 23, 1923 
Key No. G-313 
43326—23—I 
(979) 
