30 A STUDY IN CEREAL RUSTS 



ESTIMATED PERCENTAGES OF RUST ON VARIETIES GROWN IN 1911 AND 1912 



1911 1912 



Per Per 



Variety Cent Variety Cent 

 Einkorn 2433 



Dickinson 1910 Ped. No. 4.. 92 Minnesota No. 169 15 



No. 6 90 lumillo 1736 98 



No. 7 93 Minnesota No. 188 30 



No. 8 95 Einkorn 2433 96 



lumillo 1736 95 Khapli 95 



Kubanka 1516 No. 8 15 Minnesota No. 169 35 



Kubanka 1516 No. 9 10 Arnautka 288 97 



Minnesota No. 163 10 Arnautka 1431 67 



It will be noticed that in 1912 the resistance was slightly greater 

 than in 1911. This may be accounted for by the fact that in 1911 the 

 grains were sown late, giving the rust ample opportunity to develop 

 fully. 



EXPERIMENTAL 



GREENHOUSE TRIALS 



The varieties tested for resistance in the greenhouse were : Minne- 

 sota No. 163, Minnesota No. 169, Kubanka 1516, Nos. 8 and 9, Ku- 

 banka 2094, lumillo 1736, einkorn 2433, Nos. 4, 6, 7, and 8, emmer 

 1522, Arnautka 288, and Khapli. Of these, Minnesota No. 163, Min- 

 nesota No. 169, Kubanka 1516 did not prove resistant. The behavior 

 of einkorn has already been discussed under adaptation of biologic 

 forms. Very careful observations were made on the others to deter- 

 mine as accurately as possible their comparative resistance. The inocu- 

 lations were made with fresh, viable spores and the plants put under 

 bell jars 48 hours after inoculation. 



The incubation period varies with temperature conditions, both 

 high and low temperatures lengthening the period very perceptibly. 

 No experiments with this particular object in view were made, but 

 numerous observations brought the fact out very clearly. Under the 

 same conditions on Minnesota No. 163 the incubation period is shorter 

 than on any of the resistant forms. With an average temperature of 

 about 65 degrees Fahrenheit and a variation of from 40 to 75 degrees 

 and a relative humidity of about 55 per cent, pustules appear on Minne- 

 sota No. 163 in 7 or 8 days. In case of lumillo the period is usually 

 about 2 days longer, although considerable variation was found. Em- 

 mer has an incubation period of about 11 days, Arnautka, 12 days, and 

 Khapli, 14 days. Arranged in order of their susceptibility these vari- 

 eties are as follows : 



