Jain, VeenaChawla, Shilpa2017-12-132017-12-132017http://krishikosh.egranth.ac.in/handle/1/5810037468During present investigations, guava fruits of variety Hisar Surkha harvested at mature stage and were analyzed for various physico-chemical, biochemical and molecular changes during storage. Pre-treatment of fruits with chitosan and CaCl2 alone and in combination significantly delayed decline in physiological loss in weight, total soluble solids and maintenance of fruit firmness, delay in loss of acidity, phenolics, ascorbic acid and total antioxidant activity during storage. Cell wall components viz. hemicellulose, cellulose and pectin decreased progressively throughout the storage at room temperature and low temperature. The decrease in cell wall components were in co-ordination with enhanced activities of cell wall degrading enzymes viz. PME, PG and cellulase. The storage of fruits at low temperature showed slow increase in their activities at all stages of storage thereby retaining the integrity of membrane. Oxidative stress indicies viz. superoxide radicals, hydrogen peroxide, malondialdehyde content and LOX activity increased progressively during storage at both conditions but fruit stored at low temperature showed lower oxidative stress. The activities of ROS scavenging enzymes viz. SOD, CAT, APX, POX and PPO and the content of antioxidative metabolite, ascorbic acid increased initially for few days of storage followed by decline at later stages of storage at both the temperatures. However, β-carotene content decreased continuously throughout the storage period. Ethylene production and ACC oxidase activity increased initially and decreased at later stages of storage. Pre-treatment of fruits with chitosan and CaCl2 alone and in combination resulted in significant inhibition of cell wall degrading enzymes, activation of ROS scavenging enzymes and reduction in ethylene production during storage. Transcript profiling of PG and ACO genes revealed the expression at 301 bp and 320 bp respectively. Fruits treated with combination of chitosan and CaCl2 was the most effective in inhibiting the expression of PG and ACO genes. The treatment of CaCl2 (1.5%)+chitosan (1.5%) was most effective treatment in modulating biochemical and molecular changes in guava fruits and enhancing keeping quality of guava during storage. Hence fruits given these treatments and stored at low temperature retained their quality for longer duration of time.ennullThesis