European Journal of Plant Pathology (2014) 139, 625-640

Azza Rhaiem and Mohamed Cherif (2014)
Phenology of development of Didymella rabiei pseudothecia and modelling of ascospores discharge in Tunisia
European Journal of Plant Pathology 139 (3), 625-640
Abstract: Didymella rabiei development was investigated on naturally blight-infested debris in six Tunisian locations during two consecutive seasons. Pseudothecia initiated their development 2 months after their incubation on the soil surface. They reached their maturity earlier in the locations of Korba, Beja, Bizerte and Bousalem (March-April) than in Morneg and Tunis (June). After ascospore discharge, new asci and ascospores did not develop in empty pseudothecia, and the fungus survived during the second season by forming pycnidia. Pseudothecia maturity index (PMI) was determined based on internal developmental stages and a logistic model was proposed to establish an eventual correlation between PMI and Celsius degree days (CDD) cumulated over time during rainy days (for rain ≥1 mm). Results showed that PMI increased significantly over cumulative number of CDD in the six locations. In Korba, Beja, Bizerte and Bousalem locations, maximum rate of pseudothecia maturity occurred during an acceleration phase between 150 and 350 cumulated CDD during which pseudothecia reached the mature stage. The maturity rate of pseudothecia in Morneg and Tunis locations was slower as compared to the latter four locations and mature pseudothecia were observed at 450-500 cumulated CDD. The onset of pseudothecial maturity was also estimated by applying a pre-established model previously developed for Ascochyta disease management. Based on this model, which considers a combination of daily mean temperature and daily total rainfall, the number of suitable events required for pseudothecial maturity was determined at each location.
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Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ascochyta rabiei	Chickpea (Cicer arietinum)	Tunisia