Location: Tropical Crops and Germplasm Research2011 Annual Report
1a. Objectives (from AD-416)
Evaluate tropical/sub-tropical fruit production systems and germplasm for broad agro-environmental adaptation, high yield and productivity, and ability to produce fruits of superior quality. Develop efficient and sustainable monitoring and/or control methods for key pests that limit tropical/subtropical fruit production and quality.
1b. Approach (from AD-416)
Field evaluations for yield and fruit quality traits of selected tropical fruit crop scion and/or rootstock germplasm will be conducted in various agro-environments. Nutrient requirements and utilization efficiency studies will be conducted to optimize nutrient applications. Control strategies for plant pathogens of tropical and subtropical fruit crops will be developed using systemic acquired resistance agents. Strategies to increase pollinators in Annonaceae will be developed. Field evaluation of biological agents for biocontrol of important insect pests of tropical and subtropical fruit crops will be conducted.
3. Progress Report
The following research was conducted: 1) an experiment to evaluate six lychee cultivars for yield and fruit quality traits at two locations in Puerto Rico continued; 2) an experiment to evaluate six atemoya clones for yield and fruit quality traits was completed; 3) an experiment to evaluate 12 dragon fruit (pitahaya) cultivars and lines continued; 4) an experiment to screen mamey sapote germplasm for acid soil tolerance was harvested and biomass production for each accession determined; 5) a greenhouse experiment was established to determine the effect of soil pH and various concentrations of iron on early growth of mangosteen trees; 6) an experiment to evaluate three longan cultivars as rootstocks and in combination with three scions continued with trees producing fruit for the first time; 7) an experiment to evaluate 16 sapodilla cultivars as rootstocks continued; 8) an experiment to study the performance of 12 cacao accessions propagated by grafting and somatic embryogenesis continued; 9) the first year of an experiment to evaluate cultivar FHIA-17, a Sigatoka-tolerant banana, for yield and fruit quality traits was completed. We established an experiment to evaluate nutrient uptake, yield and fruit quality traits of four mamey sapote cultivars grown at two locations in Puerto Rico; a similar experiment with carambola was completed and tissue is being processed for nutrient analyses. Establishment of commercial pheromone of Nitidulids in orchards of atemoya increased yields, and surveys of visitors to atemoya flowers identified pollinators not previously reported in the literature. The first year of a field experiment to determine the effect of induced systemic acquired resistance (SAR) agents on reducing the incidence of the papaya ringspot virus (PRSV) was completed. We gathered evidence showing that protein lures typically used for the detection and monitoring of fruit flies in the genus Anastrepha showed that lures that were a month old outperformed fresh lures, suggesting the lower doses of the lures are more attractive, or, conversely, that higher doses of the lures are repellent. We demonstrated that tall grass barriers, such as rows of sorghum, around an orchard impede migration of the May beetle into these orchards. We identified entomopathogenic nematodes that were effective in controlling the root weevil of Diaprepes abbreviatus but not against Phyllophoga vandinei. We surveyed populations of lychee scale in orchards. Parasitoids and predators were too low in number to successfully rear and assay their effectiveness in the laboratory. We demonstrated that abundance of winged aphids, the vector of papaya ringspot virus, is cyclical in Puerto Rico, with population peaks occurring more or less every two months. The results from these experiments help to fill knowledge gaps on cropping management and production systems for tropical/subtropical fruit crops.
1. Evaluation of rambutan cultivars for yield and fruit quality traits. The globalization of the economy, increased ethnic diversity, and a greater demand for healthy and more diverse food products have opened a window of opportunity for the commercial production and marketing of tropical fruit, including rambutan. There is a lack of formal experimentation to determine yield performance and fruit quality traits of rambutan cultivars. ARS researchers in Mayaguez, PR evaluated eight rambutan cultivars (Benjai, Gula Batu, Jitlee, R-134, R-156Y, R-162, R-167, and Rongren) grown on Ultisol and Oxisol soils for 5 years at Corozal and Isabela, PR, respectively. There was a significant difference in the number and weight of fruit per hectare between locations, averaging 415,103 fruit/ha and 13,826 kg/ha, respectively, at Corozal and 167,504 fruit/ha and 5149 kg/ha, respectively, at Isabela. At Corozal, R162 had the highest 5-year mean for number and weight of fruit per hectare, but this cultivar was not significantly different from the rest except for Benjai and R-156Y, which had significantly lower values. At Isabela, cultivars Gula Batu and R-162 had significantly higher number of fruit per hectare but the latter was not different from Benjai. Overall, there were no differences in soluble solids concentration except for cultivars Gula Batu and R-156Y, which had significantly lower values at both locations. Cultivar R-162 had higher number and weight of fruit per hectare and high soluble solids concentration at both locations, making it suitable for planting in various agroenvironments particularly on Ultisols typical of the humid tropics. This study provides for the first time valuable information to growers and Extension specialists on yield, fruit quality traits and adaptability of rambutan cultivars grown in various agroenvironments.
2. Demonstration of natural barriers to fruit fly dispersal in Puerto Rico. Fruit flies are important economic pests of fruits. The presence of a given fruit fly in a region can drastically decrease potential markets for exported fruit or require that the fruit is subjected to potentially harsh and expensive post-harvest treatments. Traps deployed in orchards and adjacent natural areas demonstrated that host availability is extremely important for fruit fly dispersal. The biggest predictor of number of flies caught in a trap was not its proximity to an orchard, but proximity to a host tree, which are lacking in most natural areas in southern Puerto Rico (no fruit collected from natural areas so far have proved to be suitable hosts for these fruit flies). All natural areas, including those immediately adjacent to orchards with fruit flies, had vanishingly low populations of fruit flies and some sites never produced a single fly. Also, collections of fruit from different regions indicate that fruit are consistently differentially infested by region; fruit from some areas consistently yield more larvae per kg of fruit than fruit from other areas. These facts suggest that natural barriers to fruit fly dispersal exist in Puerto Rico and may be exploited by farms growing fruit susceptible to fruit flies. If extended to an area-wide application, there is potential that the economically important fruit fly species could be eradicated from Puerto Rico entirely, allowing growers to expand exports to more markets and do away with post-harvest measures.Osuna-Garcia, J.A., Doyon, G., Salazar-Garcia, S., Goenaga, R.J., Gonzalez-Duran, I.J. 2010. Effect of Harvest date and ripening degree on quality and shelf life of 'Hass' avocado in Mexico. Fruits. 65:367-375.