A study of Tranzschelia pruni-spinosae on Prunus species in California

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Introduction

The genus Prunus comprises a heterogeneous collection of plants originating in many different parts of the world. The foliage of these plants is at times attacked by plant rust caused by various species of Tranzschelia.

The plant-rust genus Tranzschelia, as established by Arthur (1)4 in 1906, consisted of a number of macrocyclic and microcyclic species, one of the macrocyclic species being the heteroecious rust of Prunus spp., T. pruni-spinosae (Pers.) Diet., formerly described as Puccinia pruni-spinosae Pers., but now separated from Puccinia because of differences in morphological characters.

This rust of Prunus is world wide in its distribution and probably occurs wherever Prunus species are grown. It is widely distributed in Europe and occurs in Asia (China, India, and Japan), Africa (Egypt and Uganda), Australia, and New Zealand. In South America this rust is found where Prunus is indigenous, in the mountains of Brazil, Colombia, Uruguay, and Venezuela. It is also reported from Mexico and Central America. In the United States it is found in the eastern states and is especially prevalent in the southeastern states and along the Pacific coast.

Other species of Tranzschelia found on the foliage of Prunus spp. and described by Tranzschel and Litvinov ⁽¹¹⁾ should be listed: T. japonica on P. armeniaca var. Ansu and on P. mume; T. microcerasi on P. microcarpa and on six other species of Prunus, all from Central Asia; and T. arthurii on P. serotina, in the United States “(Michigan, leg. C. H. Hicks; Iowa, leg. Holway).”

The present study concerns observations of the rust Tranzschelia prunispinosae, both natural infection and that induced by artificial inoculation, on different species of Prunus in California. The study has extended over a series of years, though many of the artificial inoculations were made during the years 1942 and 1943.