| Abstrakt: |
Introduction. Citrus canker, caused by the bacterium Xanthomonas axonopodis pv. citri, is a serious disease of most commercial citrus cultivars and some citrus relatives. Surveys were conducted in small-scale farms, commercial plantations, backyard orchards and nurseries in order to quantitatively study the occurrence and distribution of the disease and determine the intensity and field host range. Materials and methods. Seventeen locations in four regional states of Ethiopia were surveyed. Incidence on leaves was determined by counting total number of leaves and expressed as a proportion of leaves with at least one lesion. Incidence on fruits was determined on attached fruits, recorded as presence or absence of the symptoms. Severity was also measured on leaves and fruits. The identity of the pathogen was confirmed by morphological, biochemical and physiological characterization and detached leaf tests of representative isolates. Results. The surveys indicated the occurrence of citrus canker in Ethiopia. Overall incidence on leaves was 71.4% of leaves with at least one lesion and severity was 26.8% of leaf area infected. Incidence on fruits was 30% of fruits infected and severity was 21.25% fruit area infected. Morphological, biochemical and physiological characterization and detached leaf tests of isolates indicated characteristics similar to X.?axonopodis pv. citri. The host range for citrus canker in Ethiopia was limited to Mexican lime (C.?aurantifolia) and sour orange (C.?aurantium). Based on the field host range and detached leaf tests, it appears that the X. axonopodis pv. citri variant that occurs in Ethiopia has similar host ranges to that of atypical Asiatic (Xac-A*) form. Canker severity significantly correlated with temperature but not with rainfall, elevation or tree age. Conclusion. This is the first confirmed report of the disease in Ethiopia.Introduction. Le chancre citrique, provoqu? par la bact?rie Xanthomonas axonopodis pv. citri, est une maladie s?rieuse de la plupart des cultivars commerciaux d?agrumes et d?autres genres voisins. Des prospections ont ?t? conduites en exploitations de petite taille, en plantations commerciales, en vergers de case et en p?pini?res afin d??tudier quantitativement l?occurrence et la distribution de la maladie et d?en d?terminer l?intensit? et les h?tes. Mat?riel et m?thodes. Dix-sept lieux r?partis dans quatre ?tats d??thiopie ont ?t? visit?s. L?incidence sur feuilles a ?t? exprim?e par la proportion de feuilles portant au moins une l?sion parmi l?ensemble des feuilles ?chantillonn?es. L?incidence sur fruits a ?t? d?termin?e sur les fruits sur arbre, en notant la pr?sence ou l?absence des sympt?mes. La s?v?rit? a ?t? ?galement mesur?e sur feuilles et fruits. L?identit? du pathog?ne a ?t? confirm?e par caract?risation morphologique, biochimique, physiologique et par tests des isolats sur feuille d?tach?e. R?sultats. Les prospections ont indiqu? la pr?sence du chancre citrique en ?thiopie. Sur feuilles, l?incidence globale a ?t? de 71,4?% de feuilles avec au moins une l?sion et la s?v?rit? a ?t? de 26,8?% de surface foliaire infect?e. Sur fruits, l?incidence a ?t? de 30?% de fruits infect?s et la s?v?rit? a ?t? de 21,25?% de surface de fruit infect?e. Les tests morphologiques, biochimiques, physiologiques et d?isolats sur feuille d?tach?e ont indiqu? des caract?ristiques semblables ? X. axonopodis pv. citri. La gamme d?h?tes du chancre citrique en ?thiopie a ?t? limit?e ? la lime mexicaine (C. aurantifolia) et ? l?orange am?re (C.?aurantium). Sur la base de cette gamme d?h?tes et des tests sur feuille isol?e, il s?av?re que le variant de X. axonopodis pv. citri qui s?exprime en ?thiopie a les m?mes h?tes que ceux de la forme asiatique atypique (Xac-A*). La s?v?rit? du chancre a ?t? significativement corr?l?e ? la temp?rature mais pas aux pr?cipitations, ? l?altitude ou ? l??ge de l?arbre. Conclusion. C?est la premi?re fois que la pr?sence de cette maladie est confirm?e en ?thiopie. [ABSTRACT FROM AUTHOR] |
