Location: Tropical Crops and Germplasm Research2016 Annual Report
1a. Objectives (from AD-416):
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.
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. 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.
3. Progress Report:
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. One year after planting, some genotypes are showing precocity and are already producing pods; 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; 4) Eight papaya lines developed by collaborators at the University of the Virgin Islands Experiment Station and former 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 1 is almost completed and the experiment will be repeated a second year in FY 17; 5) An experiment to evaluate 12 dragon fruit (pitahaya) cultivars and lines continued in the field (Year 3) with the objective of determining yield of cultivars and fruit quality traits; 6) In collaboration with scientists in Beltsville, Maryland, an experiment (Year 3) to screen cacao germplasm for acid soil tolerance was established in the field; 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; 8) A study to monitor aphid populations at three locations and to identify the species composition of aphid populations during peaks was completed; 9) A survey on PRSV prevalence on the island, including genetic diversity and the impact of elevation on the incidence of infection was completed and results will be published soon; 10) An experiment to determine the fruit fly host status of pitahaya was completed; 11) An experiment to determine the impact of lures and food attractants on atemoya yield and fruit size was completed; 12) An experiment to determine the impact various legumes (Canavalia sp., Cajanus cajan and Crotalaria juncea) have on growth, production and PRSV incidence in papaya orchards was completed. The intercrops did not prevent or slow development of PRSV; 13) An experiment to study the effects of photosynthetically active radiation (PAR) on Asian citrus psyllid longevity on Murraya exotica was completed and results will be published soon; 14) An experiment to determine the efficacy of the entomopathogenic fungus Isaria fumosorosea on the Asian citrus psyllid (ACP) was completed. No successful entomopathogen to control ACP was found; 15) An experiment to determine the efficacy of curry leaf (Bergera koenigii) as a sentinel plant for Asian citrus psyllid was completed and results will be published soon; and 16) An experiment (Year 1) to determine nutrient uptake of four dragon fruit was initiated. The results from these experiments help to fill the knowledge gaps on cropping management systems for tropical/subtropical fruit crops.
1. Yield and fruit quality traits of atemoya (Annona squamosa x A. cherimola) hybrids grown in Puerto Rico. As consumers seek healthy and more diverse food products the demand for tropical fruits has increased significantly during the past 15 years. There is a lack of formal experimentation to determine yield performance and fruit quality traits of atemoya (Annona squamosa x A. cherimola) hybrids. Six atemoya hybrids (Bradley, Geffner, Priestly, Lisa, 47-18, and 75-9) grown on an Oxisol soil were evaluated for 4 years at Isabela, Puerto Rico. There were no significant differences in marketable fruit production between ‘Geffner’ and ‘Lisa’ which averaged 8,542 fruit/ha. Significantly higher yield of marketable fruit was obtained by ‘Geffner’ and ’Lisa’, averaging 1,507 kg/ha. Individual weight of marketable fruit was significantly higher in ’75-9’ and ‘Priestly’ which averaged 264.8 g. Significantly higher soluble solids concentration values were obtained from fruit of ’75-9’, ‘Bradley’ and ‘Geffner’ which averaged 23.8%. This study provides for the first time valuable information to growers and Extension specialists on yield and fruit quality traits of atemoya hybrids.
5. Significant Activities that Support Special Target Populations:
1. Scientists participated in activities targeting minority, historically under-served operators/stakeholders by providing information on alternative high-cash crops and best management practices to Hispanic producers in rural areas through farm visits, hosting growers at experimental sites, and on-farm research at Martex Farms, La Balear Farm, Rainforest Fruits Farm in Santa Isabel, Adjuntas, and Jayuya, Puerto Rico, respectively. Also, new lines of papaya were provided for field testing to growers at Robert Is Here, Unity Farm, and Farmers’ Bob Farm, all small tropical fruit growers in Homestead, Florida. 2. Provided propagation material of superior varieties of rambutan, lychee, cacao, banana, plantain, mango, mangosteen and papaya from ARS research, hands on training on grafting and other propagation procedures, and technical expertise on crop nutrition to socially disadvantaged growers of tropical fruits in Puerto Rico, Florida and Hawaii. 3. Assisted science and agricultural science Hispanic teachers as part of the Future Scientists Program funded by the National Science Foundation. This is an educational outreach program in collaboration with Texas A&M University whose purpose is to introduce high school teachers to learn about ARS research and take that information back to the classroom to benefit their students. 4. Hosted six minority students from the University of Puerto Rico as part of their summer practice course designed to obtain experience in laboratory and field plot techniques. 5. Hosted six minority students from the University of Puerto Rico at Mayaguez (5) and Interamerican University (1) as part of an internship for students seeking to gain experience in crop physiology, entomology, chemistry. 6. Hosted five student interns from the Computer Science Department of the Business Administration School of the University of Puerto Rico as part of a program leading to provide students with real life work skills which may help them once they become part of the labor force after graduation. 7. Hosted an Agricultural Education teacher from a secondary science and mathematics magnet public high school (CROEM or Residential Center of Educative Opportunities of Mayaguez) and Future Farmers of America leader, to bring her Agricultural Science class to the station for one day in order to provide them with hands-on experience in various areas pertaining to agricultural research. These areas included: chemistry, tissue culture, entomology and genetics. 8. Served as member of Master’s graduate committee of three students from the University of Puerto Rico at Mayaguez working in various disciplines related to tropical fruit production. 9. Scientists established contact with regulatory agencies responsible for risk assessment of export fruit. There is now a dialog between growers in Puerto Rico and offices of risk assessment.