Regulation of flower initiation for out-of-season harvest of tropical and subtropical fruits

Abstract There is much growing interest in the expansion of tropical and subtropical fruit production in the tropics, and in particular in the control of season and timing of flowering and fruit production. In the lowland tropics, temperatures are favourable year round for biomass production, and with increasing altitude, the available growing season is curtailed only by suboptimal cool temperatures; hence, an understanding of the control of flowering and fruiting is paramount in enabling major fruit harvest for key markets. Most of the tropical and subtropical fruits are available in the summer-rainy season (April–August) in Asian markets. A number of fruits like mango, lychee, guava, dragon fruit, jackfruit, pineapple and many minor fruits are available during this time of the year, sometimes causing market glut, and growers cannot get a good market price. Because of the high water content in most tropical and subtropical fruits, they are highly perishable, causing a high wastage in the supply chain from harvesting to consumers. On the other hand, most of these fruits are not available in the rest of the year, especially during winter. Management of phenology and the timing of flowering, therefore, is paramount to the productivity and success of production and marketing. Management of the timing of flowering and fruiting contributes to both over- and under-supply of fruit. Hence, out-of-season production of tropical and subtropical fruits is definitely more remunerative where it is possible by manipulating flowering time. In this review, four fruit crops (guava, pineapple, longan and dragon fruit) were selected because each fruit crop responded with a particular treatment for FI and/or YRP. Successfully off-season production of longan can be achieved by use of potassium chlorate as a FI chemical, guava by training of shoots in particular time of the year, pineapple with ethephon and calcium carbide and dragon fruit by supplemental lighting. Significance of the study What is already known in this subject? The technology developed for off-season production of various tropical fruits is not new; however, each fruit crop responds more to a particular treatment. Identifying the most appropriate technology for the growers of a particular crop or growers of composite orchards will ensure higher return. What are the new findings? The article does not present new information but compares the available technologies and suggests the best one for each of the four tropical fruits covered in this review. What is the expected impact on horticulture? Hopefully, the growers will adopt the technology to regulate flowering and out-of-season harvest according to market demand and to have more income.