Pathogenic variation in Drechslera teres in New Zealand

Abstract

Drechslera teres f sp teres causes net blotch of barley While it is usually controlled adequately by fungicides episodes of fungicide insensitivity have led to periodic outbreaks of severe net blotch in New Zealand Disease resistance is an alternative control method but resistance may not be durable due to the development and spread of new pathotypes of D teres In New Zealand the use of disease resistance has been hampered by a lack of information on pathogenic variation in D teres Samples of net blotch were collected from barley crops and field trials and single conidium isolates of D teres f sp teres were produced These were inoculated onto internationally recognised differential barley cultivars Disease reactions were assessed and pathogenic variation in the New Zealand D teres population determined Some differential cultivars were resistant to all isolates tested but others were susceptible to one or more of the isolates While pathogenic variation was identified in the New Zealand D teres f sp teres population the extent of variation was less than indicated in some overseas studies