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Bioregulators Induced Modulation of Leaf Physiological Attributes and Severity of Papaya Ring Spot Viral Disease Symptom expression in Papaya


                                The present study aimed to evaluate the influence of bioregulators onphysiological attributes and yield components of TNAU Papaya CO. 8 varietyduring 2017 - 2018. The study involved two factors viz., growth retardantsas factor I and stress tolerance promoting bioregulators as factor II. Thetreatments involving growth retardants (Factor I) were water spray (G1) ascontrol, 250 ppm of pro hexadione calcium (G2), 500 ppm of mepiquatchloride (G3) and 500 ppm of chlormequat chloride (G4). Similarly, the stresstolerance promoting bioregulators (Factor II) comprised of water spray ascontrol (S1), 100 ppm of methyl jasmonate (S2), 100 ppm of salicylic acid(S3) and 0.6 g/ L of strobilurins (S4). The bioregulators were applied as foliarspray at the fourth and eighth months after transplanting. Initially, growthretardants were sprayed and one week after that, the stress tolerancepromoting bioregulators were sprayed. Observations were recorded onnumber of leaves, leaf area index, leaf gas exchange parameters, papaya ringspot virusdisease incidence and yield components. Among the treatments,higher number of leaves (52.03) were observed in the combination involving250 ppm of prohexadione calcium and 100 ppm of salicylic acid (G2S3) andleaf area index (2.73) was highly influenced by 500 ppm of chlormequatchloride and 100 ppm of salicylic acid (G4S3). Leaf gas exchange parameterswere found to be superior with 250 ppm of prohexadione calcium and 100ppm of salicylic acid treatment (net photosynthetic rate - 16.46 µmol cm-2 s-1,stomatal conductance - 0.51 mol m-2s-1, transpiration rate - 7.58 mmol m-2s-1)as compared to control. Significant differences were also observed amongthe treatments for yield and yield components. The fruit yield was significantlyimproved by the treatment involving 500 ppm of mepiquat chloride and100 ppm of salicylic acid (G3S3 - 61.76 kg plant-1), indicating the possibilityfor enhancing papaya yield under field conditions where PRSV is prevalent.

Key words : papaya;bioregulators;LAI;leaf gas exchange;papaya ring spot virus;yield

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