In vivo studies
Pot and field experiments were carried out at January 2010 in Dakahlyia governorate,
Egypt, in order to investigate the effect of actinomycete isolate No. HHFA2, as the most potent isolate, in controlling onion bacterial rot diseases. The pot experiment was
carried under artificial inoculation condition with the pathogenic bacteria, while the field
experiment was dependent on the natural infection of the field. Onion transplants of
Giza red cultivar were used, and their root systems soaked overnight in liquid culture
containing 106 spore/ml of the actinomycete isolate No. HHFA2, and another group
soaked in water as control then allowed to air dry, immediately before planting. In the
pot experiment, transplants were planted in plastic pots of 17 cm diameter, which previously
filled with clayey/sandy soil (2:1). Each pot was planted with two transplants.
One month before the harvest, the pots were divided into three groups; group 1 was
inoculated with liquid culture of Ecc, group 2 was inoculated with liquid culture of Bc
and group 3 was treated with water (control). The field experiment was carried out in a
field of disease history for the bacterial rot at storage; the field was naturally infected
with bacterial rot pathogens. The treated and the control onion transplants were distributed
randomly in the field plots before planting. In the middle of the growing period
(after two months from planting), a second treatment of actinomycete isolate No.
HHFA2 was applied in the pots and field by irrigating the soil with its liquid culture.
All the suitable cultural practices were carried out through the growing period. Onion
was harvested after four months from planting (when 50% of the onion necks fallen
down). Then, onion was leaved in the open air for two weeks before being stored as
common.