|Development of Integrated Systems for Tropical/Subtropical Fruit Crop Production|
The increase in ethnic diversity in the U.S., as well as changes in the diet habits of the public for health considerations, have opened a large market for tropical/subtropical fruits. Increased production of many tropical fruits, however, is hindered by a lack of basic information on how physiological, horticultural, environmental, entomological and pathological variables affect tropical fruit production systems and how these interact to influence harvestable yield.
Promising germplasm of mangosteen (Garcinia mangostana), mamey sapote (Pouteria sapota), papaya (Carica papaya), lychee (Litchi chinensis), longan (Dimocarpus longan), carambola (Averrhoa carambola), rambutan (Nephelium lappaceum) and sapodilla (Manilkara sapotilla) are being introduced and evaluated at various ecological zones for tolerance to pests and diseases, yield, acid soil tolerance, drought tolerance, nutrient use efficiency, and scion/rootstock compatibility. The development of a tropical fruit industry will allow for an expanded trade between the U.S. and other markets. The research conducted in this project directly impact "small farms" and "social disadvantaged/ limited resource" producers in rural areas by providing growers in these regions alternative high-cash crops and best management practices which should result in improved socio-economic conditions for rural families.
The project is a component of National Program 301, Plant, Microbial, and Insect Genetic Resources, Genomics and Genetic Improvement.
Evaluation of longan trees on an Oxisol soil. Top: Two year old trees at an experimental site. Bottom: Plant Physiologist Ricardo Goenaga and Agronomist Edmundo Rivera inspect an early flowering tree; Right: longan fruits from an early bearing clone.
Evaluation of mamey sapote clones. Top: two-year mamey sapote trees in an experiment designed to test six clones for high yield, fruit quality traits and disease and insect resistance. This study is conducted in replicated experiments on an Ultisol an d an Oxisol.
This project was created in 1997. Initial efforts were devoted to the introduction of germplasm, hiring of scientists and establishment of field, screenhouse and laboratory experiments.
A 3-year study was recently completed to determine water requirement, yield, and fruit quality traits of the plant crop and two ratoon crops of two banana cultivars subjected to five levels of irrigation based on crop evapotranspiration. A 2-year study t o determine papaya water requirement, yield and fruit quality demonstrated that irrigating plants with 125% of the water lost through evapotranspiration (WLET) increased fruit yield by 129%, 85%, 41%, and 37% more than when irrigated with 25, 50, 75 and 1 00% of the WLET, respectively.
A study was conducted to evaluate yield and fruit quality traits of new commercial hybrids of papaya grown under intensive management at two locations in Puerto Rico. Hybrid Tainung 3 produced greater number of fruits but these were smaller than that of other hybrids; there were no significant differences in weight of marketable fruit per hectare among hybrids Red Lady, Known You 1, Tainung 1 and Tainung 2 at both locations, however, Tainung 1 had the greatest brix (sweetness) value. This study provides useful information to Extension Agents and growers about yield and fruit quality traits of new commercial hybrids of papaya.
A multi-location experiment was conducted to provide baseline information on the papaya/aphid/ringspot virus complex and test the efficacy of reflective mulch to repel aphids and in turn decrease the incidence of papaya ringspot virus and increase yield. Very few aphids were caught in traps within the fields during the first three months after transplanting with the majority captured 90-150 days after transplanting. This pattern of aphid capture has several implications related to the use of the reflect ive mulch: 1) protection of plants during the first three months may be unnecessary because of the lack of aphids landing in the fields; 2) when protection of the plants is necessary (after three months), plant cover and a deterioration of the mulch inhib it the reflective capability of the mulch; 3) no difference in incidence of virus or yield was found between plots with or without the mulch. Mechanisms other than reflective mulch must be studied as a means to prevent/reduce ringspot virus transmission by aphids during the long growth cycle of papaya.