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1. Introduction
Onion (Allium cepa L.), is one of the oldest
vegetables, has been used as spice and
medicine for thousands of years (Keusgen,
2002). Fusarium basal rot of onion is an
economically important disease to which onion
bulbs and shallots are sensitive during all their
growth stages (Cramer, 2000). To manage the
disease, chemical control is very effective, but
it is not economical and pollutes the
environment. Use of resistant cultivars is
another acceptable strategy of control however
onion cultivars with acceptable level of
resistance are limited. Researchers have
recently considered biological control as a
complementary approach for controlling this
disease. Yeasts treatments were suggested to
play a beneficial role in cell division and cell
enlargement (Freimoser et al., 2019). yeasts
were demonstrated to be effective biocontrol
agents of seedlings onion post-emergence
damping off. Various yeast species have been
reported as active biological control agents.
Some effectively saccharomyces cerevisiae
was used as bioagents root rot pathogens under
greenhouse conditions (Abd El-kader et al.,
2012). Candida glabrata and C. maltosa
significantly reduced the incidence of late
maize wilt disease when applied by seed
inoculation (El-Mehalawy et al., 2004). Pichia
guilliermondii gave hence possess potential to
control wilt disease in tomato crop (Nguyen et
al., 2011). Shalaby and El-Nady (2008) found
that seed soaking, or soil inoculation with S.
cerevisiae increased germination rate, survival
of plants and reduction of pre and post
emergence damping off and inhibited
Fusarium oxysporum liner growth in vitro.
Also, they found that pre- and post- emergence
damping off was reduced significantly when
seeds of faba bean were coated with a water
suspension of the yeast (109 CFU ml-1). The
beneficial effects of these microorganisms last
longer than that of chemicals and can therefore
protect the plant throughout all growth stages.
Under greenhouse and field conditions, control
of plant diseases using antagonistic yeasts can
be effective. Also, biological control can limit
the instances of basal rot of onion caused by F.
oxysporum and reduced probability of disease
development. If pathogen attacks the host plant
late in the season, the symptoms may not
appear until onion bulbs are in storage (Ozer et
al., 2003) Present study found that biological
agents inhibit the growth of F. oxysporum.
Fusarium oxysporum f. sp. cepae (Hanz) Snyd
attack onion bulbs in storage and cause rotting
of onion bulbs during storage. In storage, onion
bulbs appear spongy or sunken, infected bulbs
are softened, brown and watery when cut open
during storage bulbs are affected by many
microorganisms leading to rot being
commercially important crop of the state; it
was felt necessary to carry out investigations
on storage rot of onion. Despite the
achievement in production technology and
availability of good varieties of onion, the post
harvest losses during storage is still an ailing
cause which leads to significant qualitative and
quantitative losses during storage up to 25-
30%. The onion postharvest losses were
estimated worth Rs 600 crores is found to be
due to desiccation, decay and sprouting,
(Kumar et al., 2015). The rationale behind such
post-harvest losses till today is the
unavailability of good storage facilities during
post-harvest storage phase. There seems a big
gap between the storage facility and the storage
capacity which is ultimately leading to the
unforeseeable postharvest decay and
deterioration of onion bulbs. Therefore, the
main objectives of this study were attempted to
apply a of some antagonistic yeasts, enhanced
the biocontrol of onion basal rot and studied
the suppressive effect of some free yeast
strains against Fusarium oxysporum, under
greenhouse, field and storage conditions.
2. Materials and methods
2.1 Isolation of the causal pathogen of onion
basal rot disease
Bulb samples of onion showing typical basal