Tropical Agriculture Research Station

Mayagüez, Puerto Rico

Tropical Agriculture Research Station

Mayagüez, Puerto Rico
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Cuevas H.E.,Tropical Agriculture Research Station | Rosa-Valentin G.,Tropical Agriculture Research Station | Hayes C.M.,U.S. Department of Agriculture | Rooney W.L.,Texas A&M University | Hoffmann L.,Texas A&M University
BMC Genomics | Year: 2017

Background: The USDA Agriculture Research Service National Plant Germplasm System (NPGS) preserves the largest sorghum germplasm collection in the world, which includes 7,217 accessions from the center of diversity in Ethiopia. The characterization of this exotic germplasm at a genome-wide scale will improve conservation efforts and its utilization in research and breeding programs. Therefore, we phenotyped a representative core set of 374 Ethiopian accessions at two locations for agronomic traits and characterized the genomes. Results: Using genotyping-by-sequencing, we identified 148,476 single-nucleotide polymorphism (SNP) markers distributed across the entire genome. Over half of the alleles were rare (frequency < 0.05). The genetic profile of each accession was unique (i.e., no duplicates), and the average genetic distance among accessions was 0.70. Based on population structure and cluster analyses, we separated the collection into 11 populations with pairwise F ST values ranging from 0.11 to 0.47. In total, 198 accessions (53%) were assigned to one of these populations with an ancestry membership coefficient of larger than 0.60; these covered 90% of the total genomic variation. We characterized these populations based on agronomic and seed compositional traits. We performed a cluster analysis with the sorghum association panel based on 26,026 SNPs and determined that nine of the Ethiopian populations expanded the genetic diversity in the panel. Genome-wide association analysis demonstrated that these low-coverage data and the observed population structure could be employed for the genomic dissection of important phenotypes in this core set of Ethiopian sorghum germplasm. Conclusions: The NPGS Ethiopian sorghum germplasm is a genetically and phenotypically diverse collection comprising 11 populations with high levels of admixture. Genetic associations with agronomic traits can be used to improve the screening of exotic germplasm for selection of specific populations. We detected many rare alleles, suggesting that this germplasm contains potentially useful undiscovered alleles, but their discovery and characterization will require extensive effort. The genotypic data available for these accessions provide a valuable resource for sorghum breeders and geneticists to effectively improve crops. © 2017 The Author(s).

Porch T.G.,Tropical Agriculture Research Station | Harmsen E.W.,University of Puerto Rico at Mayaguez
Agronomy Journal | Year: 2011

Common bean (Phaseolus vulgaris L.) is extensively grown in production zones where water is limiting. Crop water use efficiency is the ratio of biomass or seed yield produced per unit of water evapotranspired in a particular environment. Transpiration efficiency (TE) is the ratio of yield per unit of water transpired. The objectives of this study were to: (i) determine the water use efficiency (WUE) for six common bean genotypes (BAT 477, Morales, SEN 3, SEN 21, SER 16, and SER 21) in the greenhouse and for two genotypes in the field (Morales and SER 16) and (ii) determine TE for two common bean genotypes using estimated evapotranspiration rates in the field. Three greenhouse trials and two field trials were conducted during 3 yr in Puerto Rico. Three water levels in the greenhouse and two in the field were applied. Actual evapotranspiration was estimated using the generalized Penman-Monteith model based on aerodynamic and surface resistance, and with drainage type lysimetersin the field. Differences among genotypes for WUE were found in the greenhouse experiments, with SEN 3 and SER 21 showing superior WUE in several treatments. In the field, TE and WUE were affected by water level, and TE was consistent with previously reported coefficients for common bean. © 2011 by the American Society of Agronomy. All rights reserved.

Jenkins D.A.,Tropical Agriculture Research Station | Epsky N.D.,U.S. Department of Agriculture | Kendra P.E.,U.S. Department of Agriculture | Heath R.R.,U.S. Department of Agriculture | Goenaga R.,Tropical Agriculture Research Station
Florida Entomologist | Year: 2011

Lures based on odors released by hydrolyzed protein were assessed for their attractiveness to Anastrepha obliqua and A. suspensa at 3 locations in Puerto Rico in Aug through Oct 2009. Lures compared included ammonium acetate combined with putrescine, hydrolyzed corn protein (Nulure) with borax, freeze-dried Nulure, freeze-dried Nulure in combination with ammonium acetate, freeze-dried Nulure in combination with ammonium acetate and putrescine, and the Unipak lure, a single lure containing ammonium acetate and putrescine. Where the distribution of trapped flies departed significantly from what would be expected given an equal attraction of the baits, Nulure and freeze-dried Nulure always attracted fewer flies than the other baits tested, regardless of species, sex, or location. Although all of the baits or bait combinations containing ammonium acetate attracted more flies than the Nulure or freeze-dried Nulure baits, there was a distinct trend of ammonium acetate and putrescine and the Unipak lures to attract more flies after the 4th week of the study and for the freeze-dried Nulure with ammonium acetate or in combination with ammonium acetate and putrescine to attract more flies in the 1st 4 weeks of the study. This trial is unique in that it was conducted in orchards of carambola, Averrrhoa carambola (Oxalidaceae), a poor host for both fly species. Our results are compared with other studies on lures of A. obliqua and A. suspensa and the implications for monitoring/detecting pest Tephritidae are discussed.

Irish B.M.,Tropical Agriculture Research Station | Goenaga R.,Tropical Agriculture Research Station | Zhang D.,U.S. Department of Agriculture | Schnell R.,U.S. Department of Agriculture | And 2 more authors.
Crop Science | Year: 2010

Cacao (Theobroma cacao L.) is an important cash crop in many tropical countries. Cacao accessions must be propagated vegetatively to conserve genetic integrity due to its allogamous nature and its seed recalcitrance (lack of dormancy). Therefore, cacao germplasm is usually maintained as living trees in field collections and has resulted in varying rates of misidentification and duplication. Using a high throughput genotyping system with 15 microsatellite loci, all 924 trees in the USDA-ARS Mayaguez cacao collection were fingerprinted. Nineteen accessions (12.3%) were found to have intraplant errors while 14 (9.1%) synonymous sets were identified that included replicates of 49 accessions. The average number of alleles (8.8; SE = 0.56) and gene diversity (HObs = 0.65; SE = 0.026) indicate a high allelic diversity in this collection. A distance-based cluster analysis and a Bayesian assignment test showed that the cacao accessions can be classified into four distinct clusters, with their geographical origins covering most of the cacao growing regions in the Americas. Assessment of the representative diversity of the collection led to the identification of several genetic gaps, including underrepresented genetic populations and particular traits of economic and agronomic value. The improved understanding of identities and structure in the USDA-ARS cacao collection will contribute to more efficient use of cacao in conservation and breeding. © Crop Science Society of America.

Goenaga R.,Tropical Agriculture Research Station | Jenkins D.,Tropical Agriculture Research Station
HortTechnology | Year: 2016

As consumers seek healthy and more diverse food products, the demand for tropical fruits has increased significantly during the last 15 years. There is a lack of formal experimentation to determine the yield performance and fruit quality traits of atemoya (Annona squamosa × 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, PR. ‘Geffner’ and ‘Lisa’ had the highest number of marketable fruit averaging 8542 fruit/ha, and the highest yield of marketable fruit, averaging 1507 kg·ha-1; they did not differ from each other, but were greater than all other hybrids. 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%; they did not differ from each other, but were greater than all other hybrids. © 2016, American Society for Horticultural Science. All rights reserved.

Erpelding J.E.,Tropical Agriculture Research Station
Plant Protection Science | Year: 2011

Sorghum anthracnose is a disease of worldwide importance and host-plant resistance is the most practical method of disease management. In this study, 154 sorghum accessions from the Botswana collection maintained by the United States National Plant Germplasm System were inoculated with Colletotrichum sublineolum and evaluated for disease resistance at the Tropical Agriculture Research Station in Isabela, Puerto Rico during 2007 and 2008. A resistant response was observed for 69 accessions in 2007 and for 48 accessions in 2008 with no acervuli development observed on inoculated leaves. The low frequency of resistant germplasm is expected from a region of low annual rainfall. However, disease severity was low for the susceptible accessions with a mean severity of 11% for the 85 susceptible accessions observed in 2007 and 17% for the 106 susceptible accessions identified in 2008. The highest frequency of resistant accessions was observed for the Ngamiland district with 58% of the accessions rated as resistant, whereas the frequency of resistant accessions ranged from 22% to 36% for the other districts. The lowest mean disease severity was also observed for the susceptible accessions from the Ngamiland district with the highest mean disease severity observed for susceptible accessions from the Kgatleng district. The resistant accessions identified in this study would be useful for the development of disease resistant varieties and the results indicated an ecogeographic association with disease resistance.

Goenaga R.,Tropical Agriculture Research Station
Journal of Agriculture of the University of Puerto Rico | Year: 2010

A major impediment to the development of a mangosteen (Garcinia mangostana L.) industry is the long pre-bearing stage that seedlings require to produce fruits. A field study was conducted to determine the effect of Promalin on the growth of mangosteen seedlings. Year-old seedlings were transplanted to the field in Santa Isabel, Puerto Rico. Four applications of Promalin were used as a foliar spray at concentrations of 0, 25, 50, 75, 100 and 125 mg/L beginning when seedlings were approximately 2.5 years old, and then every 10 to 15 weeks over a period of almost one year. Final measurements were made 10 weeks after the final application, and 353 days after treatment initiation, when seedlings were 3.5 years old. No significant differences were observed in plant height, stem diameter, or number of branches and leaves.

Goenaga R.,Tropical Agriculture Research Station
Journal of Plant Nutrition | Year: 2011

Little is known about the adaptability of rambutan (Nephelium lappaceum) to highly acidic soils rich in aluminum (Al). A 2-yr field study was conducted to determine the effects of various levels of soil Al on dry matter production, plant growth, and nutrient concentration in the leaves of four cultivars of rambutan. Cultivars and the cultivar x year interaction were not statistically significant for most variables measured in the study. Total, leaf, petiole, stem and root dry weights significantly increased at soil Al concentrations ranging from 0.67 cmol kg-1 to 11.0 cmol kg-1. At this range of soil Al, the concentrations of Al and manganese (Mn) in leaf tissue declined sharply. The results of this study demonstrate that rambutan is highly tolerant to acid soils and that tolerance may involve an Al- and Mn- exclusion mechanism.

Perez-Almodovar D.,Tropical Agriculture Research Station | Goenaga R.,Tropical Agriculture Research Station
Experimental Agriculture | Year: 2015

SUMMARY A randomized complete block design experiment with six aluminium (Al) concentrations was carried out to evaluate the effect of Al on nutrient content, plant growth, dry matter production and Al-induced organic acid exudation in rambutan (Nephelium lappaceum). One rambutan cultivar was grown in nutrient solution at pH 4.0 with (1.0, 2.3, 4.1, 6.7 and 10.2 mM Al) and without Al. The results of this study confirms that this crop is highly tolerant to Al in the rhizosphere as evidenced by: (1) a root tolerance index (RTI) of 0.85 when plant roots are exposed to Al concentrations as high as 3.5 mM; (2) root tissue Al concentrations as high as 6800 mg g-1 and the plants survived; (3) number of leaves, plant height and stem diameter being little affected when plants were grown at an Al concentration in the soil solution as high as 3.5 mM; (4) although plants exhibited leaf abscission, they were able to tolerate Al concentrations in the nutrient solution as high as 10.2 mM during the experimental period. No evidence of organic acid exudation was found in this study. Accumulation of Al in leaves, stems and roots suggests the existence of an Al-sequestration mechanism in rambutan which may involve an Al-ligand complex which translocates from roots to shoots, where it may accumulate in leaf vacuoles. © 2015 Cambridge University Press.

News Article | January 12, 2016

The staple banana variety available in U.S. supermarkets -- often the ONLY variety -- is threatened by a tropical fungus that is slowly killing it off as it spreads across the globe. The question is whether new, resistant varieties can be found and developed. "The bananas you find in the average U.S. grocery store are pretty much the same: They're the genetic variety known as Cavendish. In the market in Mayagüez, Puerto Rico, though, you have choices. Brian Irish, a scientist who has been working at the U.S. Department of Agriculture's Tropical Agriculture Research Station in Mayagüez, points out our options. There are Cavendish bananas, to be sure, but also red-skinned varieties, miniature ones and others that seem extra plump. Shop owners are also here, buying their bananas from farms on the island."

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