Characterization of Phytophthora and Pythium Species Associated with Root Rot of Olive Trees in Morocco

Ikram Legrifi, Abderrahim Lazraq, Jamila Al Figuigui, Zineb Belabess, Moussa El Jarroudi and Rachid Lahlali ()
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Ikram Legrifi: Phytopathology Unit, Department of Plant Protection, Ecole Nationale d’Agriculture de Meknès, Km 10, Rte Haj Kaddour, BP S/40, Meknes 50001, Morocco
Abderrahim Lazraq: Laboratory of Functional Ecology and Environmental Engineering, Sidi Mohamed Ben Abdellah University, Route d’Imouzzer, P.O. Box 2202, Fez 30000, Morocco
Jamila Al Figuigui: Laboratory of Functional Ecology and Environmental Engineering, Sidi Mohamed Ben Abdellah University, Route d’Imouzzer, P.O. Box 2202, Fez 30000, Morocco
Zineb Belabess: Plant Protection Laboratory, Regional Center of Agricultural Research of Meknes, National Institute of Agricultural Research, Km 13, Rte Haj Kaddour, BP 578, Meknes 50001, Morocco
Moussa El Jarroudi: Department of Sciences and Environmental Management, University of Liege, 6700 Arlon, Belgium
Rachid Lahlali: Phytopathology Unit, Department of Plant Protection, Ecole Nationale d’Agriculture de Meknès, Km 10, Rte Haj Kaddour, BP S/40, Meknes 50001, Morocco

Agriculture, 2025, vol. 15, issue 4, 1-15

Abstract: The olive tree is one of the most important fruit crops grown in Morocco, yet extensive decline associated with the root rot of this crop has been observed in many regions. This study aimed to identify and characterize the oomycetes associated with root rot disease in olive trees. During the 2021 and 2022 growing seasons, symptomatic root tissues and soil samples were collected for isolation. Based on morphological traits and the sequencing of the internal transcribed spacer ( ITS ) region of rDNA, 10 oomycete species were identified, belonging to the Phytophthora and Pythium sensu lato (s.l.) genera. Seven species were assigned to Phytophthora , namely, P. palmivora , P. plurivora , P. acerina , P. oleae , P. cactorum , P. gonapodyides , and P. megasperma . The Pythium s.l. genus was represented by three species, including P. schmitthenneri , P. aphanidermatum , and P. irregulare . A pathogenicity assay was conducted by soil infestation to evaluate the effect of these pathogens on one-year-old olive saplings (var. Picholine Marocaine ). Results revealed that all 10 species were pathogenic to olive saplings. Inoculated saplings exhibited symptoms, such as root rot, vascular discoloration, and wilting. The pathogens were successfully re-isolated from necrotic roots, thereby fulfilling Koch’s postulates. These findings highlight the complex etiology of root rot disease in olive trees, as multiple species can induce similar symptoms. This study represents the first detailed report of Phytophthora and Pythium s.l. species associated with olive root rot disease in Morocco.

Keywords: Olea europaea; oomycetes; root rot; Phytophthora spp.; Pythium s.l. spp.; ITS sequencing; pathogenicity (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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