Fruit quality characterisation of papaya germplasm in uganda

Abstract

Cultivated papaya, Carica papaya L., is the most economically important fruit in the Caricaceae Family. Both female and hermaphrodite papaya plants are commercially useful for fruit production, while the males are solely used as a pollen source. Papaya fruit is also a potential source of proteolytic enzymes like papain and chymopapain. Nineteen accessions of papaya namely 16/5, 16/15, 16/16, 16/20, 16/1, 16/17 R+L (R), 16/18 R+L (L), 16/19, 16/6, 16/10, 16/3, 16/4, 18/10, 18/5, 18/25, 18/1, 18/4, 18/16 and 18/20 were evaluated. Fully mature hard papaya fruits of the selected were harvested at the appearance of yellow stripes indicating maturity of the fruit which were kept at the counter for a period of 7days for them to ripen and then were evaluated for the different parameters. The plant materials were obtained from locally available papaya varieties and landraces from all over Uganda. The collection was undertaken over the period of 2016 and 2018. The papaya germplasm collected consisted a total of 35 papaya plants, among these, some were males and a few had died off. Data was collected on the aforementioned accessions from the germplasm for Physical parameters of Fruit weight, External fruit firmness, Internal fruit firmness, Pulp thickness, Presence of hard lump pulp, Shelf life, Percentage dry matter (DM), Pulp colour, pH and Total Titratable Acidity (TTA). Accession 16/15 was recorded to have the highest average fruit weight of 3876g. Accession 16/16 exhibited an exceptionally high external firmness value of 9.73Kgf after 7days from the time of harvest. Accession 16/5 (2.23Kgf) showed the lowest external firmness. The highest internal fruit firmness recorded was 1.35Kgf (16/16) and the lowest was 0.20Kgf (16/6). Shelf life was determined by keeping the samples in the open at room temperature (at the counter) and observations made at 2 days’ interval until they are unfit for consumption and accession 18/16 and 16/16 recorded to stay longer of than all the other accessions (i.e. 12.7 and 12.3 days respectively). 16/5 and 16/6 stayed for the least number of days (i.e. 7.7days on average each) from physiological maturity. The highest average percentage DM value recorded was 19.2% exhibited by accession 18/16, while the lowest recorded was 14.4% exhibited by 18/25. The average pH for the different accessions ranged from 5.80 to 4.43 with the grand average pH of 4.93. Accession 16/18 R+L (L) had the lowest TTA of 0.030% while the highest (0.079%) was recorded in accession 18/4. Accessions 16/20, 16/4 and 18/10 exhibited the highest severity of hard lump pulp, accessions 16/5, 16/15 and 16/10 recoded no hard lump pulp. Pulp colour names were determined using the Royal Horticultural Society Colour Chart (RHS, 2015) (Table 2). Pulp colour ranged from yellow to red.