Antagonistic and plant growth promoting bacteria from organic growing substrates for controlling some soil borne fungal pathogens of melon
Author(s)
Sebaaly, Claudine
Date Issued
February 2, 2011
Type
Doctoral Thesis
Abstract
The two main fungal pathogens of melon (Cucumis melo L.) causing a critical problem and
economic losses in Central Italy are Monosporascus cannonballus (MC) and Fusarium
oxysporum f. sp. melonis (FOM). These pathogens are agents of collapse and vascular wilts of
the melon plants, respectively. Management strategies, for both pathogens are focused on
preventive measures; amongst those are the uses of biocontrol agents or the use of compost
soil amendments.
The objective of this study was to quantify and isolate the bacterial communities (fluorescent
pseudomonads and aerobic spore-forming bacteria) present in the bulk soil of a commercial
compost (ECOS), and in the bulk soil, rhizosphere and rhizoplane of melon plants grown in
an organic growing medium (MAIB-ECOS) and of melon plants grown in an infected field by
FOM. A large number of bacteria were obtained from the bulk soil, rhizosphere and
rhizoplane of the substrates. In addition, the positive effect of melon roots on bacterial
multiplication was studied.
Moreover, the ECOS compost was investigated in situ to detect the suppression effect of the
matured compost towards MC and FOM isolates, in which autoclaved and non-autoclaved
compost was placed onto the center of the fungi seeded plate’s surface. In situ results had
indicated considerable decrease in fungal growth in plates containing non-autoclaved compost
compared to the autoclaved one.
The representative isolated bacterial strains were characterized and, then, were in vitro tested
for their antagonism towards MC and FOM isolates and for their Plant Growth Promoting
ability. The results of in vitro assays were shown that few bacterial isolates expressed an
antagonistic feature against the assayed fungi; whereas a higher number of bacteria were able
to promote plant growth, in terms of Phosphorous solubilization and Siderophores production.
Based on the results obtained in the in vitro assays, eight bacterial isolates were selected to be
tested for their suppressive effect in further bioassays in vivo.
The findings reported here demonstrate that the use of microbial communities to induce a
disease suppressiveness of soil could be a potential tool for the management of soil borne
pathogens.
Additional information
Dottorato di ricerca in Protezione delle piante
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