Location: Tropical Crops and Germplasm Research2015 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 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; 2) In collaboration with scientists in Miami, Florida budwood of seven disease-resistant cacao accessions were received, grafted onto Amelonado rootstock for increase of propagating material. Once increased, accessions were grafted onto EET-400 rootstock again and field transplanted in a replicated experiment for evaluation of yield, pod index, and organoleptic quality traits. These accessions have never been evaluated in a replicated experiment; 3) Breadfruit budwood pieces of seven accessions were received from collaborating scientists in USDA-ARS in Hilo, Hawaii and grafted on breadnut rootstock. Grafting was successful with some accessions, but not with others. Different techniques were implemented to successfully graft difficult-to-graft cultivars. Accessions were field transplanted in a replicated experiment 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) Seedlings of eight papaya lines developed by collaborators at the University of the Virgin Islands Experiment Station 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; 5) An experiment to evaluate 12 dragon fruit (pitahaya) cultivars and lines continued in the field with the objective of determining yield of cultivars, fruit quality traits, and if fruit is host to Anastrepha spp. fruit flies; 6) In collaboration with scientists in Beltsville, Maryland, an experiment (Year 2) to screen cacao germplasm for acid soil tolerance was established in the field; 7) An experiment to evaluate for yield and fruit quality traits cultivar FHIA-17 (Sigatoka-tolerant banana cultivar) and FHIA-21 (Sigatoka-tolerant plantain cultivar) was completed and data is being analyzed; 8) An experiment (Year 2) to determine nutrient uptake of four rambutan cultivars grown at two locations in Puerto Rico was completed; 9) In collaboration with scientists at the University of Puerto Rico, Phytophthora root rot tolerant (PRR) rootstocks of four cultivars were purchased from a California nursery and grafted with Semil-34 budwood for field evaluation for productivity and tolerance to local PRR strains. Unfortunately, rootstock trees from the nursery, propagated using the Frolich-Platt grafting technique there did not root appropriately and a re-order had to be made. New material was successfully established and plants are expected to be transplanted to the field early in 2016; 10) Monitored aphid populations at three locations and identified the species composition of aphid populations during peaks; 11) Continued a survey for PRSV on the island, including genetic diversity and the impact of elevation on the incidence of infection; 12) An experiment to determine the host status of pitahaya was continued; 13) An experiment to determine the impact of lures and food attractants on atemoya yield and fruit size was continued; 14) An experiment was conducted to determine the impact various legumes (Canavalia sp., Cajanus cajan and Crotalaria juncea) have on growth, production and PRSV incidence in papaya orchards; 15) An experiment was conducted to look at the effects of photosynthetically active radiation (PAR) on Asian citrus psyllid longevity on Murraya exotica; 16) An experiment was conducted to determine the efficacy of the entomopathogenic fungus Isaria fumosorosea on the Asian citrus psyllid; 17) An experiment was continued to determine the efficacy of curry leaf (Bergera koenigii) as a sentinel plant for Asian citrus psyllid.
1. Bergera koenigii as a sentinel plant for Asian citrus psyllid. Preliminary trials conducted by ARS scientists in Mayaguez, Puerto Rico indicate that curry leaf, Bergera koenigii, is very attractive to the Asian citrus psyllid. This plant does not host the putative causal organism of citrus greening disease and so does not pose a threat as a source of infection. Trials by ARS scientists in Mayaguez, Puerto Rico in orchards indicate that potted curry leaf trees can draw psyllids from adjacent trees, increasing the ability to detect psyllids in and around orchards. This could be very useful in determining when to apply pesticides in citrus orchards.
2. Yield performance and bean quality of cacao propagated by grafting and somatic embryo-derived cuttings. Twelve cacao (Theobroma cacao) clones propagated by grafting and orthotropic rooted cuttings of somatic embryo-derived plants were grown on an Ultisol soil at Corozal, Puerto Rico, and evaluated by ARS scientists in Mayaguez, Puerto Rico for 6 years of production under intensive management. Propagation treatments had a significant effect on dry bean yield and pod index but not on number of pods produced. Dry bean yield of varieties propagated by grafting was 7% higher than those propagated by orthotropic rooted cuttings of somatic embryo-derived plants. This yield difference could not be attributed to grafted plants being more vigorous nor by differences in root architecture. With few exceptions, flavor characteristics were not significantly affected by propagation treatments. This study proves that the use of somatic embryogenesis is a viable propagation system for cacao. This is the first study reporting long-term production data, which compare yield performance and quality traits of cacao trees propagated by grafting and SE-ORC.
3. Papaya ringspot virus (PRSV) less prevalent in papaya at higher elevations. A survey of papaya plants carried out by ARS scientists in Mayaguez, Puerto Rico from sea level to 900 meters in elevation indicate that the incidence of PRSV is much lower at elevations above 400 meters. A model based on the data collected indicates that a one year old papaya tree has a 60% chance of being infected with the virus, while above 400 meters the predicted probability drops to less than 20%.
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Jenkins, D.A., Hall, D.G., Goenaga, R.J. 2015. Diaphorina citri (Hemiptera:Liviidae) abundance in Puerto Rico declines with elevation. Journal of Economic Entomology. 108(1):252-258.
Goenaga, R.J., Guiltinan, M., Maximova, S., Seguine, E., Irrizary, H. 2015. Yield Performance and bean quality traits of cacao propagated by grafting and somatic embryo-derived cuttings. HortScience. 50(3):358-362.
Irish, B.M., Cuevas, H.E., Simpson, S.A., Scheffler, B.E., Sardos, J., Ploetz, R., Goenaga, R.J. 2014. Musa spp. germplasm management: microsatellite fingerprinting of USDA-ARS National Plant Germplasm System (NPGS) collection. Crop Science. 54:2140-2151.
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Goenaga, R. 2014. Micro irrigation of tropical fruit crops. 2014. In: Goyal, M. R., editor. Research Advances in Sustainable Microirrigation: Sustainable Practices in Surface and Subsurface Microirrigation. Waretown, New Jersey: Apple Academic Press. p. 239-318.
Serrato-Diaz, L.M., Perez-Cuevas, M., Rivera-Vargas, L.I., Goenaga, R.J., French-Monar, R.D. 2015. First report of Fusarium decemcellulare causing inflorescence wilt, vascular and flower necrosis of rambutan (Nephelium lappaceum), longan (Dimocarpus longan) and mango (Mangifera indica). Plant Disease. Available: http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-09-14-0923-PDN.
Jenkins, D.A., Millan-Hernandez, C., Cline, A.R., Goenaga, R.J. 2015. Attraction of pollinators to atemoya (Annona squamosa x A. cherimola) in Puerto Rico using commercial lures and food attractants. Journal of Economic Entomology. doi: 10.1993/jee/tov136.