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First Report of Leaf Blight Caused by Alternaria mali and A. arborescens on Date Palm ( Phoenix dactylifera ) in Tunisia

2019; American Phytopathological Society; Volume: 103; Issue: 11 Linguagem: Inglês

10.1094/pdis-05-19-1121-pdn

1943-7692

Ahmed Namsi, Samia Gargouri, Amal Rabaoui, Nasihah Mokhtar, M.L. Takrouni, Antonio Moretti, Mario Masiello, Touil Souhila, L. Dieb, Stefaan Werbrouck,

Forest Insect Ecology and Management

HomePlant DiseaseVol. 103, No. 11First Report of Leaf Blight Caused by Alternaria mali and A. arborescens on Date Palm (Phoenix dactylifera) in Tunisia PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Leaf Blight Caused by Alternaria mali and A. arborescens on Date Palm (Phoenix dactylifera) in TunisiaA. Namsi, S. Gargouri, A. Rabaoui, N. Mokhtar, M. L. Takrouni, A. Moretti, M. Masiello, S. Touil, L. Dieb, and S. P. O. WerbrouckA. NamsiCentre Régional de Recherches en Agriculture Oasienne, Laboratoire de Phytopathologie, Degache, TunisiaSearch for more papers by this author, S. GargouriLaboratoire de Protection des Végétaux, Institut National de la Recherche Agronomique de Tunisie, Ariana, TunisiaSearch for more papers by this author, A. RabaouiCentre Régional de Recherches en Agriculture Oasienne, Laboratoire de Phytopathologie, Degache, TunisiaSearch for more papers by this author, N. MokhtarCentre Régional de Recherches en Agriculture Oasienne, Laboratoire de Phytopathologie, Degache, TunisiaSearch for more papers by this author, M. L. TakrouniCentre Régional de Recherches en Agriculture Oasienne, Laboratoire de Phytopathologie, Degache, TunisiaSearch for more papers by this author, A. MorettiNational Research Council of Italy, Institute of Sciences of Food Production, CNR-ISPA, Bari, ItalySearch for more papers by this author, M. MasielloNational Research Council of Italy, Institute of Sciences of Food Production, CNR-ISPA, Bari, ItalySearch for more papers by this author, S. TouilCentre Technique de Dattes, Kébili, TunisiaSearch for more papers by this author, L. DiebCommissariat Régional de Développement Agricole de Kébili, Kebili, TunisiaSearch for more papers by this author, and S. P. O. Werbrouck†Corresponding author: S. P. O. Werbrouck; E-mail Address: [email protected]http://orcid.org/0000-0001-5195-7054Ghent University, BelgiumSearch for more papers by this authorAffiliationsAuthors and Affiliations A. Namsi1 S. Gargouri2 A. Rabaoui1 N. Mokhtar1 M. L. Takrouni1 A. Moretti3 M. Masiello3 S. Touil4 L. Dieb5 S. P. O. Werbrouck6 † 1Centre Régional de Recherches en Agriculture Oasienne, Laboratoire de Phytopathologie, Degache, Tunisia 2Laboratoire de Protection des Végétaux, Institut National de la Recherche Agronomique de Tunisie, Ariana, Tunisia 3National Research Council of Italy, Institute of Sciences of Food Production, CNR-ISPA, Bari, Italy 4Centre Technique de Dattes, Kébili, Tunisia 5Commissariat Régional de Développement Agricole de Kébili, Kebili, Tunisia 6Ghent University, Belgium Published Online:4 Sep 2019https://doi.org/10.1094/PDIS-05-19-1121-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Date palm cultivation constitutes the main horticultural activity in the southern region of Tunisia. In June 2017, an unknown disease caused spectacular damages and affected approximately 12,000 ha, representing 30% of the total area, mainly planted with ‘Deglet Nour’. The first symptoms appear in summer as a drying out of the apex of the leaflets. This zone spreads quickly, leaving behind a light brown, dry area. Forward of this area, small yellow spots appear on the remaining leaflet and spine surface. Finally, the affected leaflets become brown and completely wither. The number of dried leaflets per tree can exceed 60%, which has a negative influence on the photosynthetic activity and consequently on date production. Symptoms reappear in autumn as a dry leaf top and particularly dry margins but evolve at a slower rate. Then a larger number of elongated, rectangular, reddish-brown foliage spots with a burnt appearance, delineated by the veins, develop on the remaining portion of the leaflet and rachis. They show a rusty and dry center, and they sometimes regroup. First the basal crown is infected, and then the fungus colonizes leaflets of the middle crown. The youngest leaves of the erect crown are not affected. Small leaflet fragments, taken from infected tissue at the “burned” margin, were cut and disinfected with diluted bleach (2%) and ethanol (80%) (2 min) and then rinsed with sterile distilled water, dried, and finally plated in Petri dishes containing potato dextrose agar. After 7 days at 30°C, a thick, fluffy, cotton-like mycelium developed. The color was olive to gray-black and the reverse side dark brown to black. The conidia were greenish brown, catenary, ovoid or obese, multicellular, and 12 to 32 μm long × 6 to 12 μm wide, with two to six transverse and one to two longitudinal septa (n = 40). Based on the symptoms and morphology, Alternaria mali (Roberts) (Woudenberg et al. 2013) was suspected. The ITS, gpd, calmodulin, and Alt-1a regions of the three isolates were amplified with the primer pairs ITS1/ITS4, gdp1/gdp2, CALDF1/CALDR1, and Alt-for/Alt-Rev and sequenced. Multilocus sequence analyses proved that the strains belong to the Alternaria section of Alternaria. Phylogenetic tree analysis showed that I10.1 and I3 share 100% homology with A. arborescens (BMP 0308) and I20 showed 100% homology with A. mali (BMP 3064). GenBank deposits were as follows: for I10 and I20, MG722800, MG744601, and MK430424 (ITS); and for I10, I20, and I3, MK399416, MK399417, and MK399418 (Alt-1a); MK399419, MK399420, and MK399421 (gpd); and MK399422, MK399423, and MK399424 (calmodulin). A suspension of 106 conidia/ml was each sprayed on 13 potted date palm seedlings, which were enclosed in plastic bags for 3 weeks in a greenhouse. The plants showed similar symptoms as observed on infected date palms in June. The fungus was reisolated and was identical to the one isolated from leaflets infected in the open field, confirming Koch’s postulates. Control plants had no symptoms. Strains of Alternaria genus caused date palm fruit and inflorescence diseases in Spain, Saudi Arabia, and Egypt (Al-Sheikh 2009; Farrag and Abo-Elyousr 2011; Palou et al. 2013). According to Woudenberg et al. (2013), A. mali belongs to the A. alternata species complex. Although A. arborescens has been reported to be isolated from date palm root (Al-Sadi et al. 2012), to our knowledge, this is the first report of A. mali and A. arborescens causing “leaf blight” symptoms on P. dactylifera in Tunisia, threatening a quasi-monoculture of one sensitive variety.The author(s) declare no conflict of interest.References:Al-Sadi, A. M., et al. 2012. Crop Prot. 37:1. https://doi.org/10.1016/j.cropro.2012.02.011 Crossref, ISI, Google ScholarAl-Sheikh, H. 2009. Res. J. Microbiol. 4:208. https://doi.org/10.3923/jm.2009.208.213 Crossref, Google ScholarFarrag, E. S. H., and Abo-Elyousr, K. A. 2011. Plant Pathol. J. 10:154. https://doi.org/10.3923/ppj.2011.154.160 Crossref, Google ScholarPalou, L., et al. 2013. Plant Dis. 97:286. https://doi.org/10.1094/PDIS-08-12-0742-PDN Link, ISI, Google ScholarWoudenberg, J. H. C., et al. 2013. Stud. Mycol. 75:171. https://doi.org/10.3114/sim0015 Crossref, ISI, Google ScholarA. Namsi and S. Gargouri contributed equally.The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 103, No. 11 November 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionAdvanced symptoms of bacterial blotch disease on mushroom caps (Osdaghi et al.). Photo credit: C. Bull. Powdery mildew caused by Golovinomyces neosalviae on Salvia fruticosa (Soylu et al.). Photo credit: S. Soylu. Metrics Article History Issue Date: 4 Nov 2019Published: 4 Sep 2019First Look: 19 Jun 2019Accepted: 16 Jun 2019 Pages: 2962-2962 Information© 2019 The American Phytopathological SocietyKeywordstree fruitsepidemiologydisease development and spreadpathogen detectionThe author(s) declare no conflict of interest.Cited bySpecies of the Genera Neopestalotiopsis and Alternaria as Dominant Pathogen Species Attacking Mastic Trees (Pistacia lentiscus var. 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