Abstract
The present study aimed to evaluate the influence of bioregulators on physiological attributes and yield components of TNAU Papaya CO. 8 variety during 2017 - 2018. The study involved two factors viz., growth retardants as factor I and stress tolerance promoting bioregulators as factor II. The treatments involving growth retardants (Factor I) were water spray (G1) as control, 250 ppm of pro hexadione calcium (G2), 500 ppm of mepiquat chloride (G3) and 500 ppm of chlormequat chloride (G4). Similarly, the stress tolerance promoting bioregulators (Factor II) comprised of water spray as control (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 foliar spray at the fourth and eighth months after transplanting. Initially, growth retardants were sprayed and one week after that, the stress tolerance promoting bioregulators were sprayed. Observations were recorded on number of leaves, leaf area index, leaf gas exchange parameters, papaya ring spot virusdisease incidence and yield components. Among the treatments, higher number of leaves (52.03) were observed in the combination involving 250 ppm of prohexadione calcium and 100 ppm of salicylic acid (G2S3) and leaf area index (2.73) was highly influenced by 500 ppm of chlormequat chloride and 100 ppm of salicylic acid (G4S3). Leaf gas exchange parameters were found to be superior with 250 ppm of prohexadione calcium and 100 ppm 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 among the treatments for yield and yield components. The fruit yield was significantly improved by the treatment involving 500 ppm of mepiquat chloride and 100 ppm of salicylic acid (G3S3 - 61.76 kg plant-1), indicating the possibility for enhancing papaya yield under field conditions where PRSV is prevalent.
Highlights
Among the tropical fruits that contribute to economic growth, income, food security and nutrition in many developing countries, papaya occupies a key position
Each factor was with four sub treatments, including a control and totalof sixteen combinations were imposed.The growth retardants viz., prohexadione calcium (C 10 H 10 O 5 Ca), mepiquat chloride(C 7 H 16 Cl N) and chlormequat chloride (C 5 H 13 Cl 2 N, ) and the stress tolerance promoting bioregulators viz., methyl jasmonate (C 13 H 20 O 3 ), salicylic acid (C 7 H 6 O 3 ) and strobilurins [Tebuconazole(C 16 H 22 ClN 3 O) and Trifloxystrobin (C 20 H 19 F 3 N 2 O 4 )] were given as foliar spray as per the treatment details
The reduction was significant at 500 ppm of mepiquat chloride (G3) (34.79) as compared to control (G1S1) (38.00)
Summary
Among the tropical fruits that contribute to economic growth, income, food security and nutrition in many developing countries, papaya occupies a key position. It is a rich source of calcium and an excellent source of vitamins A, B1, B2 and C (Oliveira and Vitoria, 2011). Apart from other recognized bioregulators, strobilurinsare used globally to combat many diseases, but when formulated with triazoles, they are gaining so much attention It wasreportedto cause long-term changes in plant growth and metabolism, leading to higher biomass and yield (Bartett et al, 2001; Jeyakumar et al, 2014).Bioregulators may influence and modulate the physiological functions impaired by any stress, including biological stress. In the present study, the effects of foliar application of growth retardants and growth regulators on leaf physiological traits, yield components and PRSV disease expression in papaya variety TNAU Papaya CO. have been investigated to understand the modulation of leaf physiological parameters and PRSV disease incidence
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