The inheritance of resistance to rust in the snapdragon

Abstract does not appear. First page follows.

Introduction

The rust (Puccinia antirrhini D. and H.) of the cultivated snapdragon (Antirrhinum majus Linn.), was first observed by Blasdale⁽²⁾4 in 1896. For some time thereafter it was apparently confined to the Pacific Coast, but in 1913 it suddenly appeared in the vicinity of Chicago, Illinois, whence it has spread rapidly to all sections of this country, to Mexico, and to Canada. Within recent months it has appeared in England where it will probably become widespread because of the very favorable climatic conditions.

The work of Mains⁽⁴⁾ indicates that the rust is heteroecious and that it probably has pycnia and aecia on an alternate host. All his attempts to infect snapdragon plants with germinating teliospores were unsuccessful. He predicts that the alternate host will probably be found in California on native species of Antirrhinum in localities where those plants are naturally infected with rust.

When the disease first appeared in the Middle West, florists were unable to control or check it, so that the growing of snapdragons under glass became exceedingly hazardous. The rapid spread of the rust was probably caused by the method of propagation then in use. Many florists had their own strains, which they increased by cuttings from a desirable plant. The shade and high moisture conditions of the cutting bench afforded ideal conditions for rust, and interstate shipments of rooted cuttings probably caused its wide distribution.