Biophysical and Biochemical Basis of induced Resistance Against Soybean Pests Nourished with Organics
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Date
2011
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UAS, Dharwad
Abstract
The studies on the biophysical and biochemical basis of induced resistance as
influenced by organic, inorganic, integrated nutrient management (INM) and natural
farming practices in soybean against defoliators and pod borer were undertaken
during kharif 2010-11 at the Main Agricultural Research Station (MARS), University
of Agricultural Sciences, Dharwad. The results indicated that least larval population
of Spodoptera litura (Fab.) and Thysanoplusia orichalcea (Fab.) (0.08 and 2.50 l/m
row, respectively at 6 WAS) and minimum per cent pod damage by Cydia ptychora
(Meyk.) (3.32%) were recorded in the treatment that received 100 per cent organics
followed by 75% organics (2.51, 0.00 l/m row, 3.37%, respectively). The RPP
recorded higher larval population (0.17and 3.28 l/m.row, respectively at 6 WAS) and
pod damage (5.86%) followed by fully inorganic, natural farming, INM which were
on par with each other. The studies on biophysical factors at 45 DAS revealed lower
leaf succulency (78.28%) and higher leaf thickness (5.69 mg/cm2) imparted induced
resistance against pest infestation in plants receiving organic nourishment compared
to inorganic (82.49% and 4.86 mg/cm2 respectively). The biochemical constituent,
phenol recorded higher amount (0.61 mg/g fr.wt-1 at 60 DAS) in plants nourished with
organics resulting into lower pest incidence owing to induced resistance. The lower
amounts of sugars, free amino acids, soluble proteins and prolines also imparted
resistance to the plants receiving organics whereas higher quantities recorded in
inorganic treatments resulted in susceptibility to pests. Morphological characters like
plant height, number of leaves, leaf area index, number of pods, number of nodules
etc. were enhanced in organically nourished plants. Also, plants under organic
nutrition recorded higher nodule dry weight, 100-seed weight, seed weight/plant and
grain yield (2994.25 kg/ha) which were comparable to RPP (3375.75 kg/ha).
Microbial activity especially of heterotrophs in soil receiving organics was higher
which induced the resistance capacity of plants through the production of antibiotics,
psederophores etc., than in other treatments.
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Keywords
Agricultural Entomology