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Influence of Bioregulators on Latex Yield and Proteolytic Activity of Papain Extracted from Field-grown TNAU Papaya CO. 8 under the Natural Incidence of Papaya Ring Spot Virus


                                he cultivation of papaya for both fruits and commercial papain extractiondrastically suffers often due to the devastating incidence of papaya ringspotvirus disease. The present study aimed to find out whether the papain yieldand quality are influenced when bioregulators are applied to manage papayaring spot virus (PRSV) incidence or as a measure to limit the height of the cropin TNAU Papaya CO.8 variety grown in the open field with the natural incidenceof PRSV. Three growth retardants [250 ppm of prohexadione calcium (G2),500 ppm of mepiquat chloride (G3) and 500 ppm of chlormequat chloride(G4)] and three stress tolerance promoting bioregulators [100 ppm of methyljasmonate (S2), 100 ppm of salicylic acid (S3) and 0.6 g/ l of strobilurins (S4)]were employed in the study. Water spray (G1 and S1) was kept as control. Thetreatments were imposed at 4th and 8th months after planting. The growthretardants were initially sprayed and, in the subsequentweek ,the stresstolerance promoting bioregulators were sprayed as per the recommendeddoses. Among the combinations tried, spraying 250 ppm of prohexadionecalcium followed by water spray (G2S1) a week later recorded the lowestplant height (140.79 cm) at the time of fruiting. The treatment combinationG2S2 involving 250 ppm of prohexadione calcium and 100 ppm of methyljasmonate registered a higher number of fruits (42.17). The combinationof 250 ppm of prohexadione calcium along with 100 ppm of salicylic acid(G2S3) was found to be the most effective combination to manage PRSVwithout compromising papain production and to enhance the proteolyticactivity significantly (44378.36 TU g-1) as compared to other combinations.The treatment combination of 500 ppm of mepiquat chloride and 100 ppmof salicylic acid (G3S3) favored higher dry latex yield apart from a significantreduction in PRSV symptoms. Both these treatment combinations (G2S3 andG3S3) merit due consideration in PRSV management for commercial fruit andpapain production in papaya.

Key words : Papaya; Bioregulators; Prohexodione calcium; Mepiquat chloride; Salicylic acid; Methyl jasmonate; Papain; Latex yield; Proteolytic activity

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