The role of conidia in the dispersal of Ascochyta rabiei
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The role of conidia in the dispersal of Ascochyta rabiei Ihsanul Khaliq & Joshua Fanning & Paul Melloy & Jean Galloway & Kevin Moore & Daniel Burrell & Adam H. Sparks
Accepted: 30 September 2020 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2020
Abstract Ascochyta rabiei asexual spores (conidia) were assumed to spread over short distances (~10 m) in a combination of rain and strong wind. The potential distance of conidial spread was investigated in three rainfall and three sprinkler irrigation events. Chickpea trap plants were distributed at the distances of 0, 10, 25, 50 and 75 m from infected chickpea plots before scheduled irrigation and forecast rainfall events. Trap plants were transferred to a controlled temperature room (20 °C) for 48 h (100% humidity) after being exposed in the field for 2–6 days for rainfall events, and for 1 day for irrigation events. After a 48 h incubation period, trap plants were transferred to a glasshouse (20 °C) to allow lesion development. Lesions on all plant parts were counted after 2 weeks, which gave an estimate of the
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10658-020-02126-2) contains supplementary material, which is available to authorized users. I. Khaliq (*) : P. Melloy : D. Burrell : A. H. Sparks Centre for Crop Health, University of Southern Queensland, Toowoomba, Queensland 4350, Australia e-mail: [email protected] J. Fanning Agriculture Victoria, Horsham, Victoria 3401, Australia J. Galloway Department of Primary Industries and Regional Development (DPIRD), Northam, WA 6401, Australia K. Moore New South Wales Department of Primary Industries, 4 Marsden Park Rd, Tamworth, NSW 2340, Australia
number of conidia released and the distance travelled. Trap plants at all distances were infected in all sprinkler irrigation and rainfall events. The highest number of lesions on trap plants were recorded closest to the infected plots –the numbers decreased as the distance from the infected plots increased. There was a significant (p < 0.05) relationship between the amount of rainfall and the number of lesions recorded. A generalised additive model was developed that efficiently described spatial patterns of conidial spread. With further development, the model can be used to predict the spread of A. rabiei. This is the first systematic study to show that conidia distribute A. rabiei over longer distances than previously reported. Keywords Ascochyta blight . Epidemiology . Conidial spread . Wind-driven rain . Chickpea . Sprinkler irrigation
Introduction Chickpea (Cicer arietinum L.) is the second most important legume crop globally and is the most widely grown legume grain crop in Australia with >1,060,000 ha harvested in 2018 (FAOSTAT 2020). Ascochyta blight caused by Ascochyta rabiei (syn. Phoma rabiei) is one of the most devastating chickpea diseases worldwide (Pande et al. 2005). With the exception of the Ord region in northern Western Australia where it has never been introduced, A. rabiei is the major
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