INHERITANCE OF REACTION TO RACE 7A AND OTHER RACES OF OAT STEM RUST, PUCCINIA GRAMINIS AVENAE

Publisher Website
Google Scholar
Abstract
Prior to 1952, oat varieties with the Hajira type of resistance to all the known races of oat stem rust in North America, such varieties as Garry and Rodney, were thought to have identical rust resistance. In 1952, slight amounts of stem rust occurred in one field of Rodney. This rust was identical with race 7 except for its ability to attack Rodney and some sister strains. Other sister strains of Rodney as well as Garry were highly resistant to it. Therefore, Garry and Rodney, which derived their resistance from the same source, did not, as had been assumed, contain identical factors for rust resistance. The new rust strain was regarded as a biotype of race 7 and was designated race 7A. Studies were made on F3 lines derived from crosses involving Hajira to determine the reaction of the plants to stem rust races, including race 7A. These studies indicate that resistance to the various rust races is conditioned by three genes. Gene A (present in varieties such as Richland, Vanguard, Ajax, and Green Russian) conditions resistance to races 1, 2, 3, 5, 7, 7A, and 12. A second gene B (present in varieties such as Canuck and Rodney) conditions resistance to races 1, 2, 3, 5, 7, and 12 but is not effective against race 7A. A third gene C conditions resistance to races 4, 6, 8, 10, 11, and 13. Varieties such as Rodney, Canuck, and R.L. 1225 presumably contain genes B and C, whereas varieties such as Garry and R.L. 1574 contain genes A, B, and C.