Epsilon Archive for Student Projects

Abstract

Stem rust, Puccinia graminis, has caused enormous yield losses throughout history which have had significant consequences for oat and wheat production. Today in Sweden stem rust is only reported from rye, oats and wild grasses. Stem rust infections in wheat have become unusual due to the general use of resistant wheat varieties and also due to the eradication of barberry, Berberis vulgaris, the alternate host for P. graminis. According to international sources, new races of P. graminis f. sp. tritici will eventually be dispersed from Africa to the northern parts of the world including Sweden. The new race, Ug99, is very virulent even in resistant wheat and can cause enormous yield losses. The aim of this work was to investigate the current epidemiology of stem rust in oats, P. graminis f. sp. avenae, and identify the most effective control methods against the pathogen in the future, bearing in mind that Ug99 could arrive to Sweden.

This study contains investigations of the development rate of the pathogen in the field, the yield loss it causes, and if there are any differences in susceptibility between oat cultivars. Microclimate in the field was studied as a tool for a rust forecast. Race identification was also done on a set of oat differential lines.

The results from this study show that the development of stem rust in fields is very rapid. This means that even if the first rust infection comes late in the season, the disease can still cause significant yield losses. To be effective, the timing of application of fungicides as a control method is very important. Results from the field trials show that a late treatment yields the best results. Using fungicides as preventive control was shown to be less effective. The basis for the most effective control relies on careful monitoring of the appearance of stem rust.

There are some indications of variation in susceptibility between different oat cultivars; however these indications are not statistically significant. Experiment arrangement and implementation for this type of experiments could be revised in order to better consider stem rust.

Measurements of microclimate are not reliable as a forecasting method. Our experiments show that the temperature and humidity throughout the growing season are favorable for spore germination and development of rust pustles. Rather, stem rust attacks are determined by the occurrence and dispersal of spores.

The race identification was inconclusive. It appears that the gene material in the differential lines contained unknown resistance genes. Only a few races of P. graminis f. sp. avenae were identified.

In the event that Ug99 appears in Sweden, it is important to consider the role of barberry in the dispersal of P. graminis. Preventive measures such as the reintroduction of the barberry eradication law can arrest the dispersal and development of stem rust. As such, the use of fungicides can be decreased when integrated plant protection is applied.