العزل والتشخيص والشدّة الإمراضية للفطرPythium sp. المسبب لمرض سقوط بادرات البندورة في البيوت المحمية
Abstract
أجريت هذه الدراسة للتحري عن مرض سقوط بادرات البندورة، ولعزل الفطور المسببة وتشخيصها لهذا المرض ولاختبار قدرتها الإمراضية في منطقة الساحل السوري المتمثلة بمحافظتي اللاذقية وطرطوس؛ إذ اختيرت للدراسة أربعة مواقع مختلفة هي جبلة ورأس العين وحريصون ومجدلون البحر. أظهرت النتائج وجود المرض في جميع المواقع المدروسة ضمن المشاتل والبيوت المحمية. تراوحت نسبة البذور غير النابتة في المشاتل من 1,91% إلى 4,61% في حين تراوحت نسبة إصابة البادرات من 0,57% إلى 1,47% أما في البيوت المحمية فقد تراوحت نسبة الإصابة من 1,74% إلى 10,2%. أظهرت نتائج العزل الفطري وجود ستة أجناس مصاحبة للبادرات المصابة، كان أعلاها تردداً جنس الفطر Pythium spp. بنسبة (38%) يليه الفطر Fusarium spp. (18%) ثم الفطرRhizoctonia spp. (13%) يليه كلٌّ من الفطورAlternaria sp.(12%) وVerticillium sp. (12%) وأخيراً الفطر Phoma sp. بنسبة (7%). تمّ عزل ثماني عزلات وشخصت على أنها تابعة للجنس Pythium spp. اعتماداً على المفاتيح التصنيفية المعروفة، ووجد بأن أربع منها (P1, P2, P5, P6)، تابعة للنوع
P. aphanidermatum ، واثنتان (P3, P4) تابعتان للنوع P. ultimum var. ultimum واثنتان (P7, P8) تابعتان للنوع P. paroecandrum. أظهر اختبار القدرة الإمراضية تبايناً بمستوى شراسة العزلات ؛ إذ كانت العزلة P6 التابعة للنوع
P. aphanidermatum هي الأكثر شراسة بشدّة مرضية بلغت 68,33% وأقلها شراسة كانت العزلة P4 التابعة لنوع
P. ultimum var. ultimum بشدة إمراضية تساوي 38%، مع وجود فروقات معنوية للعزلة P4 مع العزلات P1, P2, P5, P6، في حين لم تكن الفروقات معنوية مع العزلات P3, P7, P8 .
This study was conducted in the Syrian coastal area to detect tomato seedlings damping-off disease, to identify and isolate fungi responsible of the disease and to evaluate their pathogenicity. Samples were collected from nurseries and greenhouses from four locations (Jableh and Ras Elain from Lattakia and Hressoun and Majdalon Elbahr from Tartous). Results demonstrated the presence of seedling damping-off disease in all screened sites, where the incidences ranged from 0.57% to 1.47% in the nurseries and from 1.74% to 10.2% in the greenhouses. The proportion of non-germinating seeds in the nurseries ranged from 1.91% to 4.61%. Six fungal genera were isolated from the infected seedlings with different level of frequency. Pythium spp. was present in the highest percentage (38%), followed by Fusarium spp. (18%), Rhizoctonia spp. (13%), Alternaria spp. (12%), Verticillium spp. (12%) and Phoma spp. (7%). Eight isolates were subsidiary diagnosed as belonging to Pythium spp., four of them (P1, P2, P5 and P6) were of P. aphanidermatum, the two isolates P3 and P4 were of P. ultimum var. ultimum and the isolates P7 and P8 are from P. paroecandrum. The pathogenicity test showed that the P6 was the most virulent isolate ( pathogenicity = 68.33%) and P4 was the least virulent one (pathogenicity = 38%). P4 had significant differences with P1, P2, P5 and P6 and non-significant differences with P3, P7 and P8 isolates.
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