PhD

Management of rhizome rot, the most destructive
disease of ginger incited by Pythium aphanidermatum
(Edson)Fitz. using native arbuscular mycorrhizal fungi (AMF)
and antagonists was attempted. The extensive survey in the
ginger growing belts of the state revealed a definite negative
relationship between AMF development and disease incidence.
Based on preliminary evaluation with six AMF species, Glomus
constrictum was selected as most efficient for disease
suppresion, growth enhancement and yield and used as reference
culture for the subsequent studies. The population of
Heloidogyne incognita, a pre disposing factor for the disease,
was reduced in the presence of all the six AMF species
particularly with G. fasciculatum. Characterization studies of
native AMF associated with ginger indicated that Glomus spp.
were more frequent and G. fasciculatum was the most predominent
species. Influence of soil types on the AMF occurrence in
ginger was evident.
Out of the fourteen native AMF developed from ginger
rhizosphere, Mi-l and Mi-4, identified as Glomus species, were
the most efficient isolates for rhizome rot suppression yield
increase and growth enhancement in ginger. Eleven native
antagonistic fungi, selected from in vitro evaluation, were
screened in the green house and Ai-12, identified as

Trichoderma viride, was the most effective isolate for
suppression of rhizome rot, growth enhancement and yield of
ginger. Ai-13 isolate, identified as Aspergillus fumigatus,
was also effective for disease suppression. The isolates,
Mi-l, Mi-4, Ai-12 and Ai-13 were tested for their combined
effect in the green house. Dual inoculation of Ai-12 with Mi-l
and Mi-4 resulted in remarkable synergistic interaction in
reducing the disease and enhancing biomass and yield. Both
single and dual inoculations of Ai-12, Mi-l and Mi-4
significantly reduced the disease and enhanced plant growth and
yield in the field also. Isolate Ai-13 inhibited AMF
development and increased disease in the green house and field.
Application of AMF inoculum on ginger rhizome after
starch coating was very effective for rapid and early
colonization of AMF. Out of the various plant protection
chemicals tested, thiram and carbofuran least affected the AMF
and antagonist development.
An effective management strategy of rhizome rot of
ginger is evolved in the present study by combining
appropriate native AMF (Mi-l and Mi-2) and antagonistic fungi
(Ai-12) for inoculation of seed rhizomes at planting time. The
present study forms the first report of detailed documentation
of native AMF associated with ginger and extensive study on the
utilisation of AMF. antagonists and their combined effect for
the management of rhizome rot.