AN ABERRANT STRAIN OF PUCCINIA HELIANTHI SCHW.

Abstract

The aberrant strain of rust here discussed was first observed in haploid infections arising from germinating teliospores of the tuberosus strain of Puccinia Helianthi. The teliospores occurred on a single leaf of Helianthus tuberosus. Teliospores on several other leaves of the same collection were induced to germinate, but their sporidia produced only normal infections. This strain of rust differed from the parent strain in colour, pathogenicity, spore viability, and host range, and was parctically intersterile with it. It also differed in urediospore size, shape, and echinulation, and in ability to withstand warm temperatures. It is suggested that these differences were probably due to a mutation in which the loss or gain of chromatin carrying more than one gene was involved.