Uptake of soil applied paclobutrazol in mango cv. Dashehari and its persistence in soil, leaves and fruits.
Bhattacherjee A. K., Singh V. K.
Author Affiliation: Central Institute for Subtropical Horticulture, Rehmankhera, P.O. Kakori, Lucknow 226 101, UP, India.
Indian Journal of Plant Physiology 20 : 39-43
Abstract : 'Dashehari' mangoes from Lucknow region of Uttar Pradesh, India are popular in domestic as well as international markets. Paclobutrazol, a plant growth regulator, has been successfully used on a commercial scale in soil application to counter the alternate bearing habit of mango all over the country. The persistence of paclobutrazol residues in soil and its subsequent uptake in mango leaves and fruits were studied using high performance liquid chromatography after its application to tree basin soil of mango cv. Dashehari @ 0.8 and 1.6 g a.i. tree-1. The residues of paclobutrazol dissipated in soil from its initial values of 3.51 and 7.04 to 0.01 and 0.03 mg kg-1 after 300 days of application from normal and higher concentrations, respectively. The rate of dissipation in soil followed first order kinetics with half life values of 41.5 and 43.0 days from normal and double doses, respectively. Initially paclobutrazol residues were not detected in leaf samples, which gradually increased to 0.95 and 1.69 mg kg-1 after 240 days of its application to soil and then decreased with time. The amounts of paclobutrazol residues noticed in mango inflorescence after 150 days of its application were 0.27 and 0.39 mg kg-1 from normal and double doses, respectively. Residues of paclobutrazol were detected in premature mango fruits, harvested between 40 and 70 days after fruit set, at levels below permissible limit (0.5 mg kg-1), but the same was not found in fully mature fruits at harvest after 85 days of fruit set. Though paclobutrazol persisted in the soil for a longer period (up to 300 days after its application) but the mature fruits harvested from treated trees were free from its residue and safe for consumption.