Fruit Quality And Storability Of Kinnow Mandarin (Citrus Reticulata Blanco) In Relation To Tree Age

Rind quality is indispensable for the external appearance and marketability of citrus fruit especially for fresh consumption.Among many factors affecting citrus rind quality, tree age is the most important one, but remains unexplored so far.This study was carried out during 2007-11 and comprised of two parts.The first part of study includes the experiments exploring fruit quality in relation to different tree age, canopy position and fruit size.This study also revealed the cell number, cell size, endogenous nutrients and fruit pectin concentrations (rind and rag) in relation to tree age during fruit growth and development.A comparison of fruit quality of different age groups (3 year, 6 year, 18 year, 35 year) showed that fruit obtained from young trees (3-year-old) were poor in fruit quality such as having more rough rind, rind thickness, rind mass (%) and less juice mass (%), TSS and acidity.Moreover, fruit from young trees had lower rind macro nutrient concentrations (P, Ca) and higher rind micro-nutrient concentrations (Mn and Fe).Fruit in internal canopy position had significantly better fruit quality (smooth rind, less rind thickness, more juice contents) whereas, those in external canopy position were better in biochemical fruit quality such as (TSS), titratable acidity (TA), sugars and ascorbic acid (AA concentrations.Large sized fruit had more rind mass (%), rind thickness, and lower juice mass (%), TSS, TA (%) and TSS:TA ratio during ambient (20�2�C and 60 65% RH) and cold storage (4�1�C and 75-80% RH) conditions.From nutritional aspects, during fruit growth and development, fruit from sixyear old trees were nutrient deficient in rind (N, P and K), rag and leaf (N) concentrations, while 18-year-old trees were deficient in rag and leaf nutrient (P, K) concentrations.Pectin analysis showed that fruit from 6-year-old trees were deficient in rind total pectin, protopectin and rag protopectin concentrations, whereas fruit from 35-year-old trees were higher in rind water soluble pectin (WSP), total pectin and fruit from 18-year-old trees were higher in rind total pectin and rind and rag WSP. Anatomical studies of tissues from different age groups demonstrated increased cell number with lower cell size in rind tissue of 6-yearold trees in comparison with 18 and 35-year-old trees. Correlation analysis revealed that leaf N contents correlated positively with cell size in fruit from 18 and 35-year-old trees.Cell size was negatively correlated with rind P concentrations and positively correlated with leaf P concentrations in fruit from all tree age groups. In second part of the study, the potential of exogenous application of PGRs and nutrients were explored in improving fruit quality of young 'Kinnow' orchards. The PGRs like gibberellic acid (GA3), 2, 4 dichlorophenoxy acetic acid (2, 4-D), putrescine (Put) and spermine (Spm) were applied before and after colour break to young (3-4 years old) 'Kinnow' mandarin trees and their influence on fruit quality under ambient (20�2�C and 60-65% RH) and cold storage (4�1�C and 75-80% RH) conditions was determined. Only 2, 4-D significantly improved TA (%) and TSS:TA ratio during shelflife studies.GA3 and Put treated fruit exhibited maximum mass loss (%) during shelf studies and cold storage respectively. GA3 10 mg L-1 and cytokinins (kinetin and benzyladenine) 30 mg L-1 applications at fruit setting stage significantly improved juice (%) and reduced rag (%). In nutritional experiments, sulphate of potash (SOP), single super phosphate (SSP), urea, calcium ammonium nitrate (CAN), Wokozim and Isabion were applied to improve fruit quality. Wokozim application reduced rind thickness and improved reducing sugars of fruit, SSP improved juice contents, ascorbic acid (AA) and reduced rind mass (%) although not significant than control;SOP improved AA concentrations in "Kinnow' mandarin juice and CAN improved TSS and AA concentrations.In conclusion, tree age exhibited significant influence on 'Kinnow' mandarin fruit quality as fruit from young trees (3-years-old) showed inferior fruit quality. Moreover, rind of fruit from young trees had lower macro- (N, P and Ca) and higher micro-nutrient (Mn and Fe) concentrations. In young trees, macronutrients (P and Ca) and micronutrients (Cu, Mn, Fe and Zn) showed a negative correlation with fruit rind thickness.Large sized fruit from all tree age groups exhibited poor quality.Among PGRs, autumn application of 2, 4-D (10 ppm) to young 'Kinnow' mandarin trees significantly improved TA and TSS:TA ratio.Spring application of cytokinin especially kinetin, among nutrients SSP and CAN and among growth stimulator Wokozim (PGRs and nutrient solution) positively affected fruit physical (rind thickness, total seed, juice, rind and rag mass) and biochemical (TSS, reducing sugars, TA and AA) quality parameters (although some seasonal variations also exist) thus showing their potential for improving fruit quality of young 'Kinnow' mandarin orchards. An improvement in fruit quality of young orchards (3-6 years) can help extend the productive window of 'Kinnow' mandarin orchards