Studies of germination and physiologic races of stripe rust (Puccinia striiformis Westend.): A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours in the University of Canterbury

Abstract

Stripe rust, caused by Puccinia striiformis Westend., is a serious disease of wheat (Triticum aestivum L.) in many parts of the world. This disease was first located in Southland, New Zealand, in November, 1980 (Harvey, 1981), and since then, has spread throughout other wheat growing areas. Many New Zealand cultivars currently grown have proved to be very susceptible to the disease, e.g. Rongotea, Tiritea, and Takahe, and fungicides are used for disease control. The study of epidemiology is an important aspect of disease control, and a knowledge of the factors affecting disease development is essential to implement economic control measures. Spore germination is one component of a disease cycle which contributes to an epidemic of stripe rust. Various factors affect spore germination which influence the rate at which an epidemic develops. A knowledge of these factors is also necessary for accurate disease forecasting. Host resistance is one method of stripe rust control, and in the long term, is the most effective and simplest control method (National Academy of Sciences, 1968; Strobel and Mathre, 1970). To effectively screen cultivars for resistance to stripe rust, it is ·necessary to study the genetic variation of the pathogen, particularly with respect to factors for virulence. Thus physiologic surveys which monitor the distribution of pathogenic races and identify shifts in the pathogen population are necessary (Dinoor, 1973). The objectives of this study were: i) To investigate factors influencing urediniospore germination of Puccinia striiformis in vitro. ii) To identify physiologic races of Puccinia striiformis using world, European, and Australasian differentials.