Location: Tropical Crops and Germplasm Research2017 Annual Report
1. Devise optimum production practices for tropical and subtropical fruit crops that help expand local and export markets. 1.A. Evaluate, across various agroenvironments, the performance of cultivars of cacao, breadfruit, dragon fruit, mandarin orange, and papaya for yield, fruit quality traits and abiotic stress tolerance. 1.B. Determine nutrient requirements of rambutan and dragon fruit so as to optimize nutrient applications. 1.C. Evaluate trap-and-kill technology as a tool to suppress fruit fly populations in and around orchards. 1.D. Determine host status of dragon fruit to the fruit flies Anastrepha suspensa and A. obliqua. 2. Evaluate the performance of selected cultivars of tropical/subtropical fruit crops for tolerance to economically-limiting diseases, including, but not limited to black Sigatoka, and the Puerto Rican strain of Papaya ringspot virus (PRSV). 2.A. Evaluate plantain and banana cultivars for productivity under pressure of black Sigatoka disease. 2.B. Evaluate avocado rootstocks for productivity and tolerance to Phytophthora root rot. 2.C. Evaluate the performance of suitable papaya varieties and assess their response to PRSV for optimized productivity in Puerto Rico and surrounding ecosystems. 2.D. Identify potential intercrop candidates for papaya that reduce the propensity for the aphid vector to transmit PRSV in orchards. 3: Evaluate and develop new means for reducing or eliminating the threat and impact of key insect pests and the ability of insect vectors to transmit specific diseases. 3.A. Determine effect of altitude gradients on Asian citrus psyllid (ACP) populations and citrus greening incidence. 3.B. Survey ACP populations in Puerto Rico to identify parasitoids and predators for potential use in biocontrol. 4. Develop means of increasing the effectiveness of pollinators that maximize crop productivity. 4.A. Determine differences in biotic and abiotic factors associated with colony collapse disorder of Apis mellifera in Puerto Rico and mainland U.S. 4.B. Assess the efficacy of nitidulid pheromones or other pollinator attractants in increasing pollination, fruit set, and yield in atemoya.
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. Rootstocks will be field-evaluated for tolerance to acid soil conditions or root diseases. Sustainable management strategies, including biological control and orchard layout, will be developed for plant pathogens of tropical and subtropical fruit crops and their arthropod vectors. Strategies to increase pollinator visits to Annonaceae, thus increasing fruit set and fruit quality, will be developed. Pollinator health will be examined, including identifying important factors contributing to the decline in honey bee population.
Progress was made on all four objectives and their subobjectives. The following research was conducted: 1) In collaboration with ARS scientists in Fort Pierce, Florida, certified, disease-free budwood pieces of seven mandarin cultivars were received, grafted onto a common rootstock, increased, grafted again onto three rootstocks and established in August 2015 in a replicated trial at two locations for field evaluation for yield, fruit quality traits, and citrus greening incidence. These accessions have never been evaluated in a replicated experiment. Determination of citrus greening incidence using enzime-linked immunosorbent assay (ELISA) tests so far are confirming that the disease is not a problem at elevations above 600 meters; 2) Seven disease-resistant cacao accessions grafted onto EET-400 rootstock were established in a replicated experiment for evaluation of yield, pod index, and organoleptic quality traits. These accessions have never been evaluated in a replicated experiment. Two years after planting, some genotypes are showing precocity and are already producing pods and yield data were collected; 3) Seven breadfruit accessions grafted onto breadnut rootstock were established in a replicated experiment at two locations in August 2015 for evaluation of yield, disease and insect response, canopy volume, and organoleptic quality traits. These accessions have never been evaluated in a replicated experiment. Yield data collection was initiated; 4) Eight papaya lines developed by collaborators at the University of the Virgin Islands Experiment Station and ARS scientists were established in a replicated experiment at three locations for field evaluation of yield, fruit quality traits, and papaya ringspot virus (PRSV) tolerance. These accessions have never been evaluated in a replicated experiment. Year 2 has been planted. One line (Line 41) shows great potential. This line is also being evaluated in commercial orchards in Florida and Puerto Rico; 5) A 3-yr experiment to evaluate 12 dragon fruit (pitahaya) cultivars and lines with the objective of determining yield of cultivars and fruit quality traits was completed and data is being analyzed; 6) In collaboration with scientists in Beltsville, Maryland, a 3-yr experiment to screen cacao germplasm for acid soil tolerance was completed and data is being analyzed; 7) In collaboration with scientists at the University of Puerto Rico, Semil-34 avocado grafted onto five avocado rootstocks were established in a replicated experiment for field evaluation for productivity and tolerance to local strains of Phytophthora root rot (PRR). Unfortunately, rootstock trees propagated using the Frolich-Platt grafting technique from the California nursery where they were purchased did not root appropriately and a re-order had to be made. New material had to be established again and trees were transplanted to the field in November 2015. Preliminary data have shown severe susceptibility even in the most tolerant clones; and 8) An experiment (Year 2) to determine nutrient uptake of four dragon fruit continued. During FY 16, a total of 12 distributions of the nine cacao selections released in 2009 were made to farmers in Puerto Rico. These received 400 budwood pieces, 4 fruit and 6 plants of cacao from these clones. Thanks to this effort a completely new cacao industry is being established in Puerto Rico with clones exclusively developed by ARS scientists in Mayaguez, Puerto Rico. These same clones were requested by scientists at the "Centro Agronómico Tropical de Investigación y enseñanza" (CATIE; Tropical Agricultural Research and Higher Education Center) and budwood sent for grafting and field evaluation in Costa Rica. The results from these experiments help to fill the knowledge gaps on cropping management systems for tropical/subtropical fruit crops.
1. Yield performance of six lychee cultivars grown at two locations in Puerto Rico. The globalization of the economy, increased ethnic diversity, and a greater demand for healthy and more diverse food production has increased the demand for tropical fruits. There is a lack of formal experimentation to determine yield performance and fruit quality traits of lychee (Litchi chinensis) cultivars. Six lychee cultivars (Bosworth-3, Brewster, Groff, Mauritius, Kaimana, Salathiel) grown on Mollisol and Inceptisol soils were evaluated for 8 years at the Adjuntas Agricultural Experiment Station of the University of Puerto Rico (UPR-Adjuntas) and La Balear farm, Adjuntas, Puerto Rico, respectively by ARS scientists in Mayaguez, Puerto Rico. At UPR-Adjuntas and La Balear, cultivar Groff had a significantly higher production (257,296 fruit/ha) of total fruit than other cultivars, whereas Salathiel had the lowest. However, total fruit production of ‘Groff’ was not significantly different from ‘Kaimana’ and ‘Bosworth-3’at La Balear. At UPR-Adjuntas, cultivars 'Groff' and 'Bosworth-3' had significantly higher number of marketable fruit than the rest of the cultivars averaging 171,760 fruit/ha. At La Balear, ‘Kaimana’ had a higher number of marketable fruit, but it was not significantly different from ‘Groff’, ‘Bosworth-3’, and ‘Mauritius’, averaging 291,360 fruit/ha. At both sites, individual fruit weight of marketable fruit was higher in ‘Kaimana’ than the rest of the cultivars. However, at La Balear farm, there were no significant differences between ‘Kaimana’ and ‘Mauritius’. At both locations, cultivars exhibited erratic production patterns, which were characterized by lower production during 1 or 2 successive years following heavy cropping. At current farm gate prices and fruit yield reported in this study, cultivars 'Groff', 'Bosworth-3', and 'Kaimana' can generate a good income for growers, and allow them to diversify crops as part of their farm operations.
Serrato-Diaz, L., Latoni-Brailowski, E., Rivera-Vargas, L., Goenaga, R.J., Bayman, P., French-Monar, R. 2017. First report of Colletotrichum fructicola and C. queenslandicum causing fruit rot of rambutan (Nephelium lappaceum L.). Phytopathology. Available: http://dx.doi.org/10.1094/PDIS-11-16-1557-PDN.
Goenaga, R.J., Jenkins, D., Marrero Soto, A.R. 2016. Yield Performance of six lychee cultivars grown at two locations in Puerto Rico. HortTechnology. 26(6):748-753.
Irish, B.M., Goenaga, R.J. 2016. Register of new fruit and nut cultivars list 48. Banana, cacao, plantain. HortScience. 51:622-628.