Effect of temperature on growth of Colletotrichum lupini and on anthracnose infection and resistance in lupins

The impact of temperature was assessed on mycelial growth of Colletotrichum lupini on agar and on anthracnose expression in lupin cultivars with varying degrees of resistance. Growth rate of C. lupini was determined at temperatures from 5 to 3°C. Fungal growth was observed at temperatures from 10 to 30°C with maximum growth rate occurring at 25°C. In growth cabinet experiments, the impact of temperatures ranging from 10 to 26°C was observed on anthracnose development in the Lupinus angustifolius cultivars Myallie (susceptible), Merrit (moderately susceptible) and Wonga (resistant) and the L. albus cultivar Kiev Mutant (extremely susceptible). At 10°C, disease incidence was very low (0–12%) in all cultivars, reflecting the slow in vitro growth of the fungus at this temperature. Increasing temperature from 12 to 26°C reduced the latent period by more than 50% and increased disease incidence, sporulation incidence and lesion severity. Latent period response to temperature was independent of cultivar resistance. However, cultivar×temperature interactionswere evident for disease incidence, sporulation incidence and lesion severity responses. Anthracnose resistance in cv.Wonga was temperature sensitive. At 12 and 18°C, disease incidence and severity inWonga were significantly lower than other L. angustifolius cultivars tested but at 26°C disease incidence and severity were similar to other cultivars.