Abstract:
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.
