Durability of resistance to stripe rust in the wheat cultivar 'Claire' in New Zealand

Abstract

Host resistance is the most economical way to manage wheat stripe rust caused by Puccinia striiformis f. sp. tritici. The cultivar 'Claire' was released in 1999, and until recently, remained highly resistant to the disease in the United Kingdom. While 'Claire' was considered durably resistant to stripe rust in New Zealand, it is now categorised as moderately susceptible. The present study investigated whether race-specific resistance was responsible for this 'break-down' in resistance, and whether cv. 'Claire' retains useful durable resistance. A rust culture from cv. 'Claire' was compared with a pre-2005 culture on a set of differential cultivars. The seedling resistance in cv. 'Claire' was race-specific. Greenhouse and field experiments suggest that the adult plant resistance in cv. 'Claire' has been reduced in the presence of a more virulent stripe rust population. Remaining adult plant resistance is insufficient to provide adequate control of stripe rust in New Zealand wheat crops.