The experiment was conducted at Bangladesh Agricultural University Germplasm Centre (BAUGPC), Mymensingh, during May 2018 to September 2019. The experimental site was located between 24.43° N latitude, 90.25° E longitude and 18m altitude from the sea level. The soil of the experimental area was sandy loam type and belonging to the old Brahmaputra Flood Plain Alluvial Tract of AEZ 9 having non calcareous dark grey flood plain soil. The selected area was a medium high land. It was fertile and well drained and slightly acidic with pH varying from 5.4 to 6.7. During the study period, the average maximum and minimum temperature were 34.010 C and 25.300 C, respectively. While the average relative humidity was 85.61%.
The two-factor experiment was conducted following Randomized Complete Block Design (RCBD) with three replications. The experimental treatments were two varieties of Dragon fruit viz., V1 : BAU dragon fruit-1 (White flesh) and V2 : BAU dragon fruit-2 (Red flesh), and three bagging time viz.,T1 : Fruit bagging at 7 days after fruit setting (DAFS), T2 : Fruit bagging at 12 DAFS and T3 : Fruit bagging at 17 DAFS.
Regular observation during flowering time was continued to find out fruit setting time after anthesis and fruits were tagged for recording days after fruit setting. Black polythene bag was used for bagging of selected fruits in the month of May, 2019. The fruits were wrapped by black polythene bag at 7, 12 and 17 days after fruit setting. A small portion of two corners of each bag was cut off in order to prevent water deposition inside the bag. The bags were tightly tied with the help of rope so that water and insect-pest could not enter into the bag. Fruits were harvested at full mature stage, a common index of maturity is skin color change to almost full red (Nerd et al., 1999). Five fruits were randomly selected from each replication of each treatment and counted days required to maturity (days). Fresh weight was recorded immediately after harvesting of fruits thereafter fruit length and diameter were measured using digital slide calipers. Fruit peel and flesh were separated carefully and recorded the weight for calculation of flesh-peel ratio and % edible rate. The peel thickness was measured by using digital slide calipers.
Determination of moisture and dry matter content Fifty grams (50g) of fresh fruit sample of each treatment was taken and cut into small pieces on an aluminum foil and oven dried at 700 C until the constant weight was attained. Percent moisture content was calculated according to the following formula:
% dry matter content was calculated as % dry matter content =100 - %moisture content
Determination of fruit pH The pH of dragon fruit was recorded by using an electric pH meter. The pH meter was standardized using buffer solutions described by Ranganna (1994). Samples of 10 g fresh pulp was homogenized in 10 ml de-ionized water pH 7.0 and the flesh of homogenate was measured with the pH meter.
Determination of Total Soluble Solids (0 Brix) Total soluble solids (TSS) content of dragon fruit was estimated using digital refractometer (Model N-1 á, Atago Company Ltd., Japan). A drop of juice was squeezed from the dragon fruit flesh and taken on the prism of refractometer. TSS content was recorded from the direct reading of the instrument. Temperature correction was made using the temperature correction chart.
Shelf life (days) Five fruits of each variety and treatment were stored in an ambient condition (30±20 C) to observe the storage life. Fruits were monitored regularly and the shelf life of fruits was counted from the date of harvesting to the last edible stage.
Statistical analysis The collected data on various parameters were statistically analyzed using MSTATC statistical package program. The means for all the treatments were calculated and analysis of variances (ANOVA) for all the parameters was compared by least significant difference (LSD) test at 5% and 1% levels of probability (Gomez and Gomez, 1984).