Effect of hand pollination to increase yield of papaya (Carica papaya) cv. ‘Yellow Krang’ grown in Thailand

Abstract

This research aimed to determine if the time of the year and the practice of hand pollination affected the yield of papaya. The experiment was done on papaya cultivar ‘Yellow Krang’ grown in northeastern Thailand. The experiment was arranged in a 12 × 2 factorial in a randomized complete block design with 5 replications and 10 trees per replication. The first factor tested was the time of the year. Seeds were planted each month, from January to December 2017. The second factor was pollination method, i.e., hand pollination versus natural pollination. The results showed that the number of days to flowering (range 90.8–110.2 days), flesh thickness of fruit (range 1.3–2.4 cm), flesh firmness (range 0.44–0.76 kg/cm²) and perceived crispness of the fruit (range 4.3–4.8 on a scale of 1–5) were similar across all months of the year, and no significant differences in these variables were observed between fruit obtained from natural pollination and those from hand pollination. However, there were statistically significant differences (0.05) in mean number of flowers per tree, percentage of fruit set, number of fruit per tree, and mean fruit weight between the trees planted in different months and comparing hand to natural pollination. Trees that began flowering in the cooler months, between October and January, bore the most flowers per tree (180.1–189.6 flowers over the data collection period of 3 months), while those that began flowering in the hottest month of April bore fewer flowers (mean 124.2 flowers per tree over 3 months). Notably, the percentage of fruit set was 90.1–100% in trees that were hand pollinated, compared to 56.2–98.2% for naturally pollinated trees. The number of fruit per tree from hand pollinated trees was 241.5–305.6, more than double the number of fruit harvested from naturally pollinated trees (62.7–132.2). The mean fruit weight from hand-pollinated trees was also greater, ranging from 1.20–2.56 kg, compared to a range of 0.72–1.84 kg from naturally pollinated trees. Pollination success is dependent on many factors including cultivar, existence/population density of insect pollinators, temperature, humidity, and precipitation. A hand pollination technique might hold promise for increasing yield of ‘Yellow Krang’ papaya for growers with the time to invest in this procedure.