Australasian Plant Pathology (2021) 50, 179-192

Noura Omri Ben Youssef, Hatem Chaar, Zayneb Bessaidi, Imen Halila, Noura Jammezi, Ahlem Mbazia, Mohamed Kharrat and Christophe Le May (2021)
Temporal and spatial dynamics of ascochyta blight caused by Ascochyta fabae Speg. In faba bean fields in Tunisia
Australasian Plant Pathology 50 (2), 179-192
Abstract: Ascochyta blight of faba bean, caused by Ascochyta fabae (teleomorph: Didymella fabae) is one of the most destructive diseases of faba bean in Tunisia. Temporal and spatial development of ascochyta blight were studied and characterized during 2010–2011 and 2011–2012 in three faba bean fields located in Oued Mliz, Oued Beja and Mornag, using mathematical and geostatistical analyses. Mass Disease Index (MDI) was assessed every two weeks in each quadrat located around the central source of inoculum. Richards' function well described disease progress in all sites except for Oued Beja in 2011–2012, the shape parameter m is significantly close to 1 placing the model in its particular form of Gompertz and confirming the polycyclic characteristic of the epidemic. Empirical analysis showed that the effect to locations on epidemic dynamics was explained by highly significant environmental effect (temperature, rain events). These differences in epidemic dynamics were confirmed by the analysis of parameters estimated by the Richards' model (average relative disease progression rate (r_w), proportional average relative disease progression rate (r_wp), maximum disease progression rate at inflection point (r_i), time at inflection point (t_i), MDI at the inflection point (y_i)). Analyzing the spatial structure dynamics of the disease using Lloyed Index of Patchiness (LIP) and the mapped disease distribution at different dates showed that LIP was estimated by an exponential functionthat decreased over time in all sites and seasons. LIP dropped below 1 (limit value for aggregated distribution) after 12, 25, 30, 36 and 48 daysat Oued Beja and Oued Mliz during both seasons and during the second season in Mornag. After these periods, the disease distribution is randomly distributed. However, according to the mapping, disease distribution was aggregated in terms of severity even at the end of the epidemics, indicating different temporal dynamics such as changes in distance from the inoculum source.
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Link to article at publishers website
Database assignments for author(s): Mohamed Kharrat, Christophe Le May

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ascochyta fabae	Broad/faba bean (Vicia faba)	Tunisia