The role of seedling infection in epiphytotics of ascochyta blight on chickpea |
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Authors: | R B E Kimber D Shtienberg M D Ramsey E S Scott |
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Institution: | (1) School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Glen Osmond, SA, 5064, Australia;(2) South Australian Research and Development Institute (SARDI), GPO Box 397, Adelaide, SA, 5001, Australia;(3) Department of Plant Pathology, Agricultural Research Organisation, The Volcani Center, P.O. Box 6, Bet-Dagan, 50250, Israel;(4) Animal and Plant Control Commission, GPO Box 2834, Adelaide, SA, 5001, Australia |
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Abstract: | Didymella rabiei, the causal agent of ascochyta blight, survives on infected seeds and seedlings. Diseased seedlings originating from infected
seeds occasionally serve as the source for primary infection in chickpea crops. Experiments carried out independently in Australia
and in Israel provided quantitative information on the temporal and spatial distribution of ascochyta blight from initial
infections and on the relationship between the amount of initial infection and the intensity of subsequent epiphytotics for
cultivars differing in susceptibility to the pathogen. Disease spread over short distances (<10 m) from individual primary
infections, was governed by rain and wind, and was up to five times greater down-wind than up-wind. Cultivar response to D. rabiei significantly affected the distance and area over which disease spread and the intensity of the disease on infected plants.
At onset of the epiphytotic, the relationship between disease spread and time was exponential (P < 0.05; R
2 > 0.95) and the area of the resulting foci was over 10 times greater in susceptible cultivars than in resistant cultivars.
Regression equations showed the relationship between disease severity and the distance from the focus-plants was inverse-linear
for all cultivars tested (P < 0.05). A simulation model based on the experimental data revealed that even if primary infection is infrequent (less than
1% of plants), the consequences are potentially devastating when susceptible cultivars are used. The epidemiological information
and simulation model generated by this study provide an increased understanding of the development of an epiphytotic in which
the primary foci of disease originate from infected chickpea seedlings. |
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Keywords: | Ascochyta rabiei Gram blight Quantitative epidemiology |
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