Plant growth regulators application time influences fruit quality and storage potential of young 'Kinnow' mandarin trees

Abstract

Poor fruit quality of young 'Kinnow' mandarin orchards limits its export potential and hence causes significant economic loss to the growers. Plant growth regulators (PGRs) are widely applied in mature citrus trees to improve fruit quality. However, their application in young orchards is scarce. The current study was designed to evaluate the influence of before and after color break (CB) applications of gibberellic acid (GA3) 10 mg L-1, 2, 4 dichlorophenoxy acetic acid (2, 4-D) 10 mg L-1, putrescine (Put) 0.1 mg L-1 and spermine (Spm) 0.1 mg L-1, on fruit quality of young 'Kinnow' orchards, at harvest, after seven days at ambient conditions (20±2°C and 60-65% relative humidity) and after 45 days at cold storage (4±1°C and 75-80% relative humidity). Application of 2, 4-D significantly reduced titratable acidity (TA) and improved TSS:TA ratio. The GA3 reduced fruit colour development and enhanced mass loss (%); Spm reduced juice mass (%) and increased rind mass (%). The GA3 application before CB significantly decreased reducing sugars (%) whereas, after CB application significantly increased rind mass (%) total soluble solids (TSS), total and non reducing sugars (%) in comparison with control. Polyamines (PAs) application after CB significantly reduced juice mass (%) and increased rind mass (%), TSS, total and non-reducing sugars (%). The 2, 4-D application after CB significantly decreased juice mass (%) and increased TSS, total and non reducing sugars (%) in comparison with control. After 45 days of cold storage 2, 4-D application significantly improved reducing sugars while, Put enhanced mass loss (%). In conclusion, 2, 4-D may be applied in young 'Kinnow' mandarin orchards after CB; however, PAs applications may be restricted due to their undesirable effect on fruit quality.