▪ Abstract  Research on impacts of climate change on plant diseases has been limited, with most work concentrating on the effects of a single atmospheric constituent or meteorological variable on the host, pathogen, or the interaction of the two under controlled conditions. Results indicate that climate change could alter stages and rates of development of the pathogen, modify host resistance, and result in changes in the physiology of host-pathogen interactions. The most likely consequences are shifts in the geographical distribution of host and pathogen and altered crop losses, caused in part by changes in the efficacy of control strategies. Recent developments in experimental and modeling techniques offer considerable promise for developing an improved capability for climate change impact assessment and mitigation. Compared with major technological, environmental, and socioeconomic changes affecting agricultural production during the next century, climate change may be less important; it will, however, add another layer of complexity and uncertainty onto a system that is already exceedingly difficult to manage on a sustainable basis. Intensified research on climate change-related issues could result in improved understanding and management of plant diseases in the face of current and future climate extremes.

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Pathogenic variability of 14 Septoria tritici isolates from different locations in the USA (California, Oregon, and Texas) was determined on seedlings of two sets of geographically diverse wheat cultivars under greenhouse conditions. Significant isolate effects, cultivar effects, and isolate × cultivar interactions were found, and a substantial amount of variation was accounted for by the interaction terms compared with the main effects of isolate and cultivar. All isolates were pathogenic on the cultivars tested but the degree of virulence on the individual cultivars varied among isolates. Linear contrasts between all homologous combinations (isolate × cultivar combination of same geographic location) and all heterologous combinations (isolate × cultivar combination of different locations) indicated that homologous combinations produced significantly more disease than heterologous combinations. The results demonstrate location‐specific adaptation of S. tritici. Implications of pathogenic variability and local adaptation in S. tritici are discussed.

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