Time course studies of temperature and soil depth mediated sporangium production by Phytophthora cinnamomi

• Published in: Australasian plant pathology 2014-05, Vol.43 (3), p.235-244
• Main Author: Shearer, B. L.
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Ecology; Entomology; Life Sciences; Phytophthora cinnamomi; Plant Pathology; Plant Sciences
• ISSN: 0815-3191; 1448-6032
• DOI: 10.1007/s13313-013-0258-3

This study examines the effects of temperature on Phytophthora cinnamomi sporangium production and soil-seasonal population dynamics of the pathogen. Response surfaces from time-course studies of the effects of temperature and soil depth on sporangium in ex-situ soil extracts, were used to predict sporangium production. Regression equations explained 65–97 % of the variation in observed sporangium production. Number of sporangia increased rapidly as temperatures rose from 16 °C to 30 °C and incubation period increased from 2 to 12 days. Changes of number of sporangia with temperature was relatively flat after a 2 day incubation period compared to the steep sporangia-temperature response curve after 6 days incubation. No sporangia formed at 12 °C and optimal temperatures were between 26 °C to 30 °C. A significantly greater number of sporangia formed in extract from near-surface soil than in extract from soil sampled at 60 and 90 cm depth. Determination of K max of the temperature-sporulation progress curves enabled combination of temperature and soil depth of sampling in the one equation. Increases in predicted sporangium production in autumn (May) was followed by increases in observed surface soil inoculum in winter (June) and sporulation in spring (September and October) followed by increases in observed surface soil inoculum in October. The temperature-response surfaces confirm that temperature is a determining factor for sporulation of P. cinnamomi in the soils of south-western Australia, when soil water is not limiting. A hierarchy of abiotic and biotic factors influences seasonal population dynamics of P. cinnamomi in the soil profile.