EFFECTIVE FACTORS ON ONION BACTERIAL SOFT ROT DISEASE INCIDENCE DURING STORAGE

Seven bacterial isolates were isolated and identified from green onion and mature bulb (Allium cepa L.) that showing naturally infected soft rot disease. Onion samples used for isolation were collected from different super markets and store houses of Abou-Hamad District, Sharkia Governorate, during 2016/2017 seasons. Seven isolates showed different degree of aggressive pathogenic capability on onion bulbs. Morphological, physiological and biochemical diagnostic properties of the seven bacterial isolates confirmed that one isolate identified as Bacillus polymyxa, three isolates as Pseudomonas cepacia and three isolates as Pectobacterium carotovorum subsp. carotovorum. The seven identified bacterial isolates were compared for their degree of pathogenic capabilities in some different plant hosts. With the exception of chili fruits, the seven bacterial isolates were able to infect fruits, tubers, pods and roots of seventeen host plant species related to seven plant genera. Percentage of rotted onion bulb during storage significantly affected by the packing materials that used in preparing storage package, onion cultivar, maturity of bulb, type of cultivated soil and storage time. Results revealed that good control against onion soft rot could be obtained when mature bulbs of resistant cultivar cultivated in clay soil conducted to good cure program and stored under low temperature and high ventilation conditions.