Ecofriendly management of rhizoctonia leaf blight of amaranthus
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Date
2003
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Department of Plant Pathology, College of Agriculture, Vellayani
Abstract
The present investigation was undertaken at College of Agriculture,
Vellayani during the year 2002-2003 to evolve an ecofriendly practice for the
management of foliar blight of amaranthus caused by Rhizoctonia so/ani.
Biocontrol agents like Trichoderma harzianum, Pseudomonas jluorescens,
a newly discovered root endophyte, Piriformospora indica and indigenous
materials like turmeric powder-baking soda and rice husk ash were used in
the study.
From among the ten isolates of R. so/ani, the isolate R3 (Vellayani)
which produced maximum disease symptoms W?3 selected for the study.
Among the four fungal antagonists tested against R. so/ani, T. harzianum
emerged as the most potential one. The fungus, P. indica when subjected
to dual culture with R. so/ani did not cause any inhibition on its growth.
Among the four isolates of P. jluorescens tested against R. so/ani, the
isolate B3 showed maximum inhibition followed by the isolate KK16. The
culture filtrate of the isolate of P. jluorescens viz., B3 alone exerted
inhibitory effect on the growth of R. so/ani. The different combinations of
turmeric powder-baking soda and rice husk ash did not inhibit the growth
of R. so/ani .
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Pot culture experiments were conducted to assess the efficacy of
biocontrol agents and indigenous materials in managing the disease and
enhancing the growth of amaranthus. Among the three concentrations of
rice husk ash used, the highest concentration of 1000 g produced
maximum disease suppression and enhancement of growth. Rice husk ash
exerted significant effects on all the growth parameters. The fungal
antagonist T. harzianum and bacterial isolates B3 and KK16 were found to
be highly effective in reducing the disease and enhancing growth. 10 : I
combination of turmeric powder-baking soda was found to enhance the
growth significantly and there was a reduction in the disease incidence
also. The highest concentration of P. indica (2.00 per cent) recorded the
maximum root colonization and exerted significant effects on root length
and root dry weight.
Changes in the level of total phenols, amino acids carbohydrates and
enzymes like PAL, PO and PPO due to the above treatments were
estimated. Soil application followed by foliar spray of fungal and
bacterial antagonists significantly enhanced the activity of the defense
related enzymes. The level of total phenol was found to be higher for
plants treated with T. harzianum. There was no significant increase in
amino acid and carbohydrate content due to these treatments. The results
of this study indicate that the efficient strains of T. harzianum and
P. fluorescens (soil or foliar application) can be used in tandem with rice
husk ash to evolve a suitable ecofriendly disease management strategy to
combat foliar blight of amaranthus.
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PG
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Citation
172205