Recessive genes for resistance to Puccinia striiformis f. sp. hordei in barley

Barley genotypes Abyssinian 14, BBA 2890, Grannelose Zweizeilige, PI 548708 , PI 548734, PI 548747, and Stauffers Obersulzer are resistant to all races of Puccinia striiformis f. sp. hordei identified thus far in North America . Astrix, BBA 809, Bigo, Cambrinus, Emir, Heils Franken, Hiproly, I5, Mazur ka, Trumpf, and Varunda have specific resistance to certain races, whereas Topper and Steptoe are susceptible to all races. Seedlings of parents and F -1, F-2, and F-3 progeny from crosses of resistant genotypes with Topper an d Steptoe were tested for resistance to North American F1 striiformis f. sp . hordei races PSH-1, PSH-4, PSH-10, PSH-13, and PSH-20. When tested with P SH-1, one recessive gene was detected in BBA 809, BBA 2890, Bigo, Hiproly, and Grannelose Zweizeilige; two recessive genes were detected in Emir, 15, PI 548708, PI 548734, PI 548747, Varunda, and Astrix; and one dominant gene and one recessive gene were detected in Abyssinian 14 and Stauffers Obersu lzer. In tests with PSH-4, one recessive gene was detected in BBA 809, two recessive genes were detected in Trumpf, and two partially recessive genes were detected in Astrix. in tests with PSH-13, one recessive gene was detec ted in BBA 2890, Grannelose Zweizeilige, 15, and PI 548708 and two recessiv e genes were detected in Abyssinian 14, Hiproly, Pi 548734, and PI 548747. In tests with PSH-20, one recessive gene was detected in Bigo and a recessi ve gene and a dominant gene were detected in Heils Franken. A gene in Cambr inus for resistance to PSH-10 and a gene in Mazurka for resistance to PSH-2 0 were dominant on the basis of the response of the first seedling leaf but recessive on the basis of the response of the second leaf. Four different types of epistasis were detected. Information on the number of genes, mode of inheritance, and nonallelic gene interactions should be useful in unders tanding the host-pathogen interaction and in breeding barley for resistance to stripe rust.