Snapdragon rust-resistance trials 1937-1938

Abstract does not appear. First page follows.

Introduction

Through the efforts of a number of workers, especially of Mains4 and Emsweller and Jones,5 it appeared in 1934 and 1935 as though the serious problem of rust on snapdragons would soon be solved. Some valuable commercial strains6 had been released to the seed trade in 1931 and 1932, and development of others was proceeding at a rapid pace. Mains had warned of the possibility of the occurrence of physiologic forms7 in the Antirrhinum rust (Puccinia antirrhini D. and H.), but when in 1936 the so-called “resistant” snapdragons began to show severe symptoms of rust, especially in the Salinas Valley, the question was raised by commercial seed growers as to whether this was due to a “breakdown” in the resistance resulting from breeding and cultural practices. Yarwood,8 however, clearly demonstrated that the susceptibility of the resistant strains was due to the presence of one or more different forms of the rust, which evidently had not been prevalent before that time in the district where the earlier work had been done.

The purpose of this paper is to place on record the results of trials conducted during the seasons of 1937 and 1938, in an attempt to locate species, varieties, or strains of Antirrhinum immune, or at least highly resistant, to new as well as old forms of rust. It was hoped that, if such an Antirrhinum strain could be found, it might be used in the breeding of resistant or immune types suitable for floriculture and ornamental gardening.