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Ricardo Goenaga and David Jenkins

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 (Nephelium lappaceum). There is a lack of formal experimentation to determine yield performance and fruit quality traits of rambutan cultivars. Eight rambutan cultivars (Benjai, Gula Batu, Jitlee, R-134, R-156Y, R-162, R-167, and Rongren) grown on an Ultisol and an Oxisol soils were evaluated 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−1, respectively, at Corozal and 167,504 fruit/ha and 5149 kg·ha−1, 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.

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Ricardo Goenaga and David Jenkins

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.

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Ricardo Goenaga and David Jenkins

The demand for tropical fruits has increased significantly during the last decade as consumers seek healthy and more diverse food products. There is a lack of formal experimentation to determine yield performance and fruit quality traits of mamey sapote (Pouteria sapota) cultivars. Six mamey sapote cultivars (Copan, Magaña, Mayapan, Pace, Pantin, Tazumal) grown on Ultisol and Oxisol soils were evaluated 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 25,929 fruit/ha and 16,527 kg·ha−1 at Corozal and 17,887 fruit/ha and 11,920 kg·ha−1 at Isabela. ‘Tazumal’ had the highest 5-year mean number and weight of fruit per hectare, but fruit of this cultivar was very small and contained several seeds, which could reduce its marketability. At Corozal, cultivars Tazumal and Magaña had significantly higher fruit yield per hectare than the rest of the cultivars, whereas ‘Magaña’, ‘Tazumal’, and ‘Pantín’ had the highest fruit yield at Isabela. At both locations, ‘Pantin’ had relatively high yield, above-average soluble solids concentration values, and adequate fruit size and weight for domestic and export markets (650–900 g), making this cultivar suitable for planting at various agroenvironments typical of the humid tropics.

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Ricardo Goenaga, David Jenkins and Angel Marrero

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. 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, 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.

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Ricardo Goenaga, Heber Irizarry, David Jenkins, Debbie Boykin and Angel Marrero

Research on sapodilla (Manilkara zapota) has been very limited. A field study was conducted to determine the yield potential, fruit quality traits, leaf nutrient composition, and scion/rootstock compatibility of ‘Prolific’ sapodilla grafted onto 16 sapodilla rootstock seedlings. For this purpose, seedlings (maternal half-sibs) of cultivars Adelaide, Arcilago, Aruz, Blackwood, Blocksberg, Guilbe, Hanna, Jamaica-1, Larsen, Mendigo-1, Gallera, Morning Star, Russel, Prolific, Timothe, and Vasallo-1 were used as rootstock seedlings and evaluated during 7 years of production at Isabela, PR. Year showed a significant effect on the number of fruit per hectare, yield, individual fruit weight, fruit length and diameter, and total soluble solids. Rootstock seedlings had a significant effect on the number of fruit per hectare, yield, and individual fruit weight but had no effect on other fruit traits. The year × rootstock interaction was not significant for any of the variables measured in the study. Rootstock seedlings ‘Timothe’, ‘Vasallo-1’, ‘Larsen’, and ‘Aruz’ had the highest 7-year mean for number and the yield of fruit averaging 4479 fruit/ha and 1245 kg·ha−1, respectively. ‘Timothe’ and ‘Vasallo-1’ significantly out yielded the ‘Prolific’ rootstock seedling. The number of fruit per hectare and corresponding yield obtained in this study were very low probably as the result of wind exposure, the presence of the fungus Pestalotia causing floral necrosis, or both. Scion/rootstock incompatibility was not the cause of the low yield performance of grafted trees. The average individual weight of fruit was 282 g and ranged from 264 to 303 g. Averaged over rootstock seedlings, leaf tissue nutrient concentration did not vary greatly over time. Moreover, tissue nutrient concentration was similar before and after fertilization events.

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Cristina Zambrana-Echevarría, Lorriane De Jesús-Kim, Rocio Márquez-Karry, Dimuth Siritunga and David Jenkins

Papaya ringspot virus (PRSV) devastates papaya production worldwide. In Puerto Rico, papaya fields can be completely infected with PRSV within a year of planting. Information about the diversity of the Puerto Rican PRSV (PR-PRSV) population is relevant to establish a control strategy in the island. The coat protein gene (cp) of PRSV was sequenced from 62 isolates from different regions in Puerto Rico. The viral population of PRSV in Puerto Rico has 4% nucleotide and 5% amino acid diversity. Analysis of the coat protein (CP) amino acid sequence showed a variable amino terminal (N-terminal) region with a conserved aphid transmission motif and a variable EK repeat region. The core and carboxyl terminal (C-terminal) region were conserved. In the phylogenetic analysis, Puerto Rican isolates grouped independently of their geographical origin, with the exception of southern isolates that formed two separate subgroups and were the most divergent. Sequences of the cp from the Puerto Rican isolates, when compared with sequences from other countries, showed least genetic distance with isolates from the United States and Australia, followed by other American and Caribbean isolates. The U.S. and Australian isolates are sister taxa to the Puerto Rican isolates in the phylogenetic tree. This suggests that PRSV from Puerto Rico and the isolates from the United States and Australia have a common origin thought to be from a Mexican population.