Aug. 4, 1923 
Resistance in Rye to Leaf Rust 
251 
of accuracy. The results obtained by crossing the two plants, 8 and 9, 
resistant to leaf rust, however, are suggestive. The appearance of two 
highly susceptible and seven susceptible plants in the progeny from 
this cross strongly indicates that resistance is dominant. The appear¬ 
ance of so many different types in the offspring is confusing. Whether 
more than one pair of factors is involved, or one main pair with modify¬ 
ing factors, as Puttick (10) has suggested as an explanation for the 
appearance of different types of susceptibility to Puccinia graminis in 
segregates from a Marquis-Mindum wheat cross, or whether we have a 
number of segregating strains of rye which in homozygous condition 
may differ in respect to type of susceptibility, must be determined by 
future study. It is evident, however, that the problem of obtaining 
rust-resistant strains of rye is complicated not only by the high degree 
of self sterility and the consequent slow progress which can be made 
by selfing, but also by the dominance, as seems probable, of the desired 
quality of resistance and the consequent longer process of breeding 
before it is certain that a pure homozygous strain has been obtained. 
SUMMARY 
(1) Rye plants have been found which show high resistance to and 
in some cases practically complete immunity from the leaf rust of rye, 
Puccinia dispersa Erikss. 
(2) Sixty-eight selections and varieties of rye, including such varieties 
as Abruzzes, Giant Winter, Henry, Invincible, Ivanov, Mammoth Win¬ 
ter, Mexican, Petkus, Rosen, St. John, Star, Von Ruemker, Wisconsin 
No. 2 (Schlanstedt selection), and a number of unnamed introductions, 
were studied as to susceptibility to leaf rust. 
(3) None of these varieties or selections was uniformly resistant. 
(4) All of these varieties or selections showed at least a few individuals 
having high resistance. 
(5) Crosses made by bagging heads of two highly resistant plants 
together showed gradation in the susceptibility of the plants produced, 
varying from high susceptibility through intermediate grades of resis¬ 
tance to complete immunity. 
(6) The production of susceptible individuals from a cross between 
resistant ones indicates that resistance probably is dominant. The 
production of intermediate types, however, would indicate complicating 
factors. 
literature cited 
(1) Arthur,. Joseph Charles, and Fromms, Fred Denton. 
1920. dicaEoma ON poaceae. In North American Flora, v. 7, p. 269-404. 
(2) Bary, Anton de. 
1866. NEUS unTErSuchungEn ubER urEdinEEn. In Monatsber. K. Preuss. 
Akad. Wiss. Berlin, 1866, p. 205-215, 1 pi. 
(3) BaudyS, E. 
1913. sin bsitrag zur Obsrwintsrung dsr rostpilze durch ursdo. In 
Ann. Mycol., Jahrg. 11, p. 30-43, illus. Literatur, p. 42-43. 
(4) CarlSTon, Mark Alfred. 
1899. CEREAL rusts op ths unitsd statss: a physiological invsstigation. 
U. S. Dept. Agr., Div. Veg. Phys. and Path. Bui. 16, 74 p., 1 fig., 4 col. 
pi. Bibliography, p. 70-73. 
(5) Christman, A. H. 
1905. obsSrvation on ths wintering op grain rusts. In Trans. Wis. 
Acad. Sci., v. 15 (1904), p. 98-107. 
