A study of speckled leaf blotch of wheat and its causal organism (Septoria tritici Rob.), in Canterbury, New Zealand

Abstract

The available evidence suggests that speckled leaf blotch of wheat is increasing in severity in Canterbury. Prior to 1947 it was practically unknown in the province, but in November of that year a wheat crop at Lincoln College was found to have a high percentage infection. In November of 1948 a preliminary survey of wheat crops in North Canterbury was made by the writer, and of forty fields inspected, all except two were found to be infected. This evidence, together with the known potential importance of the disease as illustrated by the severity of attacks in overseas countries has emphasised the need for fundamental studies of the disease and its causal organism under New Zealand conditions. This thesis embodies the results of a two year study conducted at Canterbury Agricultural College, Lincoln, during 1948-49 and is intended to contribute to our understanding of the disease. The aims were 1. To isolate and prove pathogenicity of Septoria tritici Rob. as causal organism of speckled leaf blotch under Canterbury conditions. 2. To study signs and symptoms as they occur in the field and under glasshouse conditions. 3. To study the causal organism in pure culture. 4. To study host range of the causal organism in New Zealand. 5. To study varietal resistance to the disease in New Zealand wheats. 6. To determine the mode of perpetuation of the causal organism in New Zealand.