Dimuth Siritunga
University of Puerto Rico Rio Piedras, Biology, Chemistry, Faculty Member
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Research Interests: Agronomy, Biology, Tropics, Cultivar, Cutting, and 3 moreManihot esculenta, Crop, and Perennial Plant
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Research Interests: Food Science and Carotene
<p>H<sub>O</sub>: Observed heterozygosity.</p><p>H<sub>T</sub>: Total heterozygosity.</p><p>SSR Source: <sup>a</sup> Buteler <i>et al.</i><a... more
<p>H<sub>O</sub>: Observed heterozygosity.</p><p>H<sub>T</sub>: Total heterozygosity.</p><p>SSR Source: <sup>a</sup> Buteler <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116184#pone.0116184-Buteler1" target="_blank">[12]</a>; <sup>b</sup> Tseng <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116184#pone.0116184-Tseng1" target="_blank">[15]</a>; <sup>c</sup> Yañez <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116184#pone.0116184-Yaez1" target="_blank">[18]</a>; <sup>d</sup> Benavides (unpublished data; 2002–2003 at CIP); <sup>e</sup> Solis <i>et al.</i> (unpublished data; 2005–2006 developed at CIP); <sup>f</sup> Yada <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116184#pone.0116184-Yada1" target="_blank">[17]</a>.</p><p>Twenty-three SSR marker primers with their respective sequence, annealing temperatures, repeat motifs and allele size.</p
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<p>(NoA: Number of Alleles, H<sub>o</sub>: Observed Heterozygosity, H<sub>T</sub>: Total Heterozygosity, G<sub>is</sub>: Inbreeding Coefficient).</p><p>Summary statistics of genetic... more
<p>(NoA: Number of Alleles, H<sub>o</sub>: Observed Heterozygosity, H<sub>T</sub>: Total Heterozygosity, G<sub>is</sub>: Inbreeding Coefficient).</p><p>Summary statistics of genetic diversity estimators at 23 SSR loci for 167 sweet potato samples.</p
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<p>Eight accessions are from the agricultural experimental station in Gurabo, Puerto Rico (GAES), 22 from the plant genetic resources conservation unit (PGRCU) in Griffin, GA (12 PR accessions and 10 known US commercial cultivars)... more
<p>Eight accessions are from the agricultural experimental station in Gurabo, Puerto Rico (GAES), 22 from the plant genetic resources conservation unit (PGRCU) in Griffin, GA (12 PR accessions and 10 known US commercial cultivars) and 137 Puerto Rico landraces across the island were analyzed. The eight groups (Group 1: olive green, Group 2: pink, Group: navy blue, Group: orange, Group: purple, Group: lime green, Group: red, and Group: blue) were determined based on STRUCTURE and Evanno <i>et al</i>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116184#pone.0116184-Evanno1" target="_blank">[26]</a> analysis. The colors of the branches in the dendrogram also indicates the groups while the highlight of the name refers to PRGCU (olive green), GAES (pink), US cultivars (navy blue) and PR landraces (light gray).</p
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and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the continent’s and the world’s largest producer (fao, 00 ). SubSaharan africa produced over million tons of fresh roots of cassava in 00 , of which no... more
and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the continent’s and the world’s largest producer (fao, 00 ). SubSaharan africa produced over million tons of fresh roots of cassava in 00 , of which no less than 95% was consumed as food; the starch provides > 5% of dietary energy for an estimated 00 million africans (Dorosh, 00 ). frequent consumers of cassava are at greater risk for malnutrition—especially deficiencies in vitamin-a, iron, and zinc—than consumers of other diets, particularly those that are cereal-based (Gegios et al., 0 0). a nutrition survey in cassava-consuming areas of nigeria and Kenya revealed inadequate intake of vitamin a in 3% and % and inadequate iron intake in 3% and % of pre-school-aged children, respectively (Gegios et al., 0 0). vitamin-a deficiency causes a loss of 9 ,000 disability-adjusted life years (DaLYs1) in nigeria and ,000 DaLYs in Kenya annually; iron deficiency causes loss of 59 ,000 DaLYs in nigeria and...
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An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Research Interests: Genetics, Plant Biology, Forecasting, Plant Molecular Biology, Genetic Engineering, and 15 moreCassava, Tissue culture, Plant diseases, Insect Resistance, Animals, Insects, Key words, Genetic transformation, Cyanogenesis, Plant viruses, Manihot esculenta Crantz, Insect pests, PLANT PROTEINS, Biochemistry and cell biology, and Gene Transfer
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Cassava (Manihot esculenta) is the most important root crop in the tropics and due to its drought tolerance, ability to grow in poor soils, and resistance to herbivore, cassava is well suited for cultivation by subsistence farmers.... more
Cassava (Manihot esculenta) is the most important root crop in the tropics and due to its drought tolerance, ability to grow in poor soils, and resistance to herbivore, cassava is well suited for cultivation by subsistence farmers. However, its use and expansion is constrained by ...
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More than 250 million Africans rely on the starchy root crop cassava (Manihot esculenta) as their staple source of calories. A typical cassava-based diet, however, provides less than 30% of the minimum daily requirement for protein and... more
More than 250 million Africans rely on the starchy root crop cassava (Manihot esculenta) as their staple source of calories. A typical cassava-based diet, however, provides less than 30% of the minimum daily requirement for protein and only 10%–20% of that for iron, zinc, and vitamin A. The BioCassava Plus (BC+) program has employed modern biotechnologies intended to improve the health of Africans through the development and delivery of genetically engineered cassava with increased nutrient (zinc, iron, protein, and vitamin A) levels. Additional traits addressed by BioCassava Plus include increased shelf life, reductions in toxic cyanogenic glycosides to safe levels, and resistance to viral disease. The program also provides incentives for the adoption of biofortified cassava. Proof of concept was achieved for each of the target traits. Results from field trials in Puerto Rico, the first confined field trials in Nigeria to use genetically engineered organisms, and ex ante impact ana...
Research Interests: Plant Biology, Biology, Puerto Rico, Plant biotechnology, Nigeria, and 6 moreMedicine, Vitamin A, Nitriles, Zinc, Iron, and Nutritive Value
Today, more minority students are entering undergraduate programs than ever before, but they earn
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Key message Among the five cassava isoforms (MeAPL1–MeAPL5), MeAPL3 is responsible for determining storage root starch content. Degree of storage root postharvest physiological deterioration (PPD) is directly correlated with starch... more
Key message Among the five cassava isoforms (MeAPL1–MeAPL5), MeAPL3 is responsible for determining storage root starch content. Degree of storage root postharvest physiological deterioration (PPD) is directly correlated with starch content. Abstract AGPase is heterotetramer composed of two small and two large subunits each coded by small gene families in higher plants. Studies in cassava (Manihot esculenta) identified and characterized five isoforms of Manihot esculenta ADP-glucose pyrophosphorylase large subunit (MeAPL1–MeAPL5) and employed virus induced gene silencing (VIGS) to show that MeAPL3 is the key isoform responsible for starch and dry matter accumulation in cassava storage roots. Silencing of MeAPL3 in cassava through stable transgenic lines resulted in plants displaying significant reduction in storage root starch and dry matter content (DMC) and induced a distinct phenotype associated with increased petiole/stem angle, resulting in a droopy leaf phenotype. Plants with r...
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The Solanaceae family is one of the largest and well-distributed plant families in the world. It contains species of agricultural and economical importance, such as Solanum tuberosum, Solanum melongena, Solanum lycopersicum, Nicotiana... more
The Solanaceae family is one of the largest and well-distributed plant families in the world. It contains species of agricultural and economical importance, such as Solanum tuberosum, Solanum melongena, Solanum lycopersicum, Nicotiana tabacum, and Capsicum annuum. In Puerto Rico, there are ≈46 species of Solanaceae of which six are endemic: Brunfelsia densifolia, Brunfelsia lactea, Brunfelsia portoricensis, Goetzea elegans, Solanum ensifolium, and Solanum woodburyi. Our objective was to use DNA barcoding to identify the Solanaceae species in Puerto Rico, including the endemics, and to assess the species relationships between them. To accomplish our objective, two chloroplast regions (psbA-trnH and matK) and a nuclear region [internal transcribed spacer (ITS)] were assessed. Pairwise distance and phylogenetic analysis demonstrate that DNA barcoding can be used to discriminate at the species level among these taxa in Puerto Rico. For all three markers, the genus that showed the highes...
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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)... more
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 is...
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Native to Central America, papaya (Carica papaya) is one of the most cultivated fruit crops in the tropical areas of the world. Genetic diversity analyses are an important aspect of conservation of plant genetic resources. In the island... more
Native to Central America, papaya (Carica papaya) is one of the most cultivated fruit crops in the tropical areas of the world. Genetic diversity analyses are an important aspect of conservation of plant genetic resources. In the island of Puerto Rico, where papaya has been consumed for centuries, knowledge on the genetic diversity of papaya is lacking. Therefore, 162 papaya accessions were evaluated using 23 simple sequence repeat (SSR) markers. Of these accessions, 139 were farmer-held samples from Puerto Rico, 13 were U.S. Department of Agriculture (USDA) repository samples, and 10 were commercial varieties. A total of 214 alleles were identified with a mean observed heterozygosity (Ho) of 0.219. Inbreeding coefficient (F) was 0.565, and when evaluating the population structure of these accessions, 2 groups (k = 2) were identified. Unweighted pair group method with arithmetic mean (UPGMA) dendrogram showed no geographical organization within the unknown Puerto Rican samples. This...
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Plant tissue culture is an important tool in both basic and applied studies as well as in commercial applications. Plant tissue culture is based upon the theory of totipotency, that is, the genetically based ability of a cell or a... more
Plant tissue culture is an important tool in both basic and applied studies as well as in commercial applications. Plant tissue culture is based upon the theory of totipotency, that is, the genetically based ability of a cell or a nonembryonic organ to form all the cell types in the adult organism. Here we present the methodology and assessment results of the implementation of a multi-week laboratory module conducted in the introductory botany course. In this module, spread throughout the semester, the students used African violet (Gloxinia sp., Fam. Gesneriaceae) to gain experience in plant tissue culture techniques. The objective was for the students to learn how to take part of the plant from in vivo to in vitro culture. This required the establishment of aseptic techniques and the use of different media components to multiply plants under in vitro conditions. This lab module was initially pilot tested in one lab section and currently impacts approximately 140 minority students p...
Being involved in hands-on independent research as an undergraduate student has been positively correlated to the pursue of careers in science. A well-established method of students gaining such experiences has been by conducting an... more
Being involved in hands-on independent research as an undergraduate student has been positively correlated to the pursue of careers in science. A well-established method of students gaining such experiences has been by conducting an independent project in a research laboratory of a faculty member of their home institution. Unfortunately, only a fraction of students are able to participate due to reasons ranging from a lack of knowledge of opportunities, lack of faculty resources, lack of space in research labs, lack of exposure to research, family commitments, etc. Recognizing these limitation and the benefits of engaging students in the scholarship of science as early as possible, faculty and departments have begun to successfully implement research- or inquiry-based laboratory exercises in small-, medium- or large-enrollment courses throughout different curriculums. Here, we present a model for the large-scale implementation of guided-research on a topic of cultural relevance to i...
Protection of crop genetic resources is a key approach for securing food sources for the future generations. Crop diversity in part is maintained by farmers who share plant material, introduce new varieties and even select improved... more
Protection of crop genetic resources is a key approach for securing food sources for the future generations. Crop diversity in part is maintained by farmers who share plant material, introduce new varieties and even select improved genotypes. Also the farmers keep and, in some cases without knowing, protect the wild relatives of many different species. The establishment of genetic relations within a crop is an important component in crop improvement programs. Correct assessment of genetic diversity is invaluable in any crops’ conservation and for diverse applications including the identification of new combinations with maximum genetic variability for further selection and introgression of desirable genes from diverse germplasm into the available genetic base. In this study, we report the first genetic diversity assessment of lima beans (Phaseolus lunatus L.) in the Caribbean. Lima bean, known as ‘pois souche’ in Haiti and ‘haba’ in Puerto Rico (PR) and the Dominican Republic (DR), ...
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ABSTRACT Thesis (M.S.)--Ohio State University, 1996. Includes bibliographical references (leaves 114-121).
... especially Estelle Devillard, for her tireless support, loving companionship and constant encouragement and my two roommates through the years, Indika Kotakadeniya and Sumedha De Silva, for their friendship. Page 8. viii VITA ...
ABSTRACT Micronutrient deficiencies affect millions of children in sub-Saharan Africa. Vitamin A deficiency alone renders 250,000-500,000 children blind annually, while 23% of pre-school aged children suffer from iron deficiency anemia.... more
ABSTRACT Micronutrient deficiencies affect millions of children in sub-Saharan Africa. Vitamin A deficiency alone renders 250,000-500,000 children blind annually, while 23% of pre-school aged children suffer from iron deficiency anemia. Though cassava contains very low levels of pro-vitamin A and micronutrients it is the staple food in sub-Saharan Africa due to agronomic and caloric benefits coupled with cultural preferences. With the intention of ameliorating malnourishment in Africa, ‘BioCassava Plus Program’ has generated genetically enhanced cassava fortified with β-carotene and Iron. To properly gauge the engineered trait’s performance under natural environmental conditions, confined field trials of these transgenic plant lines are being conducted in the fields at the University of Puerto Rico Mayaguez. Adhering to all biosafety regulation of the Animal Health and Plant inspection Services of the USDA, 66 transgenic lines have been evaluated so far. The primary biosafety criteria been observed in conducting transgenic field trials are ‘confinement’ and ‘isolation’. Confinement is being achieved by restricting access for animals and unauthorized personnel while isolation is being achieved by having a minimum separation distance from other planted cassava, removal of flowers prior to anthesis and by the addition of a border row of non-transgenic cassava plants of the same age and variety. Furthermore, all excess plant material is being mechanically shredded and buried on-site immediately after harvest. The platform built, through many years of field evaluation of transgenic cassava, has also been utilized to conduct field trials with transgenic cowpea and sweet potato as well.
ABSTRACT Due to its accuracy, sensitivity and reproducibility, real-time PCR has emerged as a key technique to measure changes in expression of target genes. But to obtain reliable results using real-time PCR, gene transcripts that do not... more
ABSTRACT Due to its accuracy, sensitivity and reproducibility, real-time PCR has emerged as a key technique to measure changes in expression of target genes. But to obtain reliable results using real-time PCR, gene transcripts that do not alter its expression under different conditions need to be identified. These transcripts can then be used as references to normalize the expression of target genes. Only a few studies have been conducted so far in the identification of such reference genes in plants. In an effort to identify appropriate reference genes, cassava, an important food source in the tropics and an excellent crop against famine and drought, was assessed for its capacity to express eight housekeeping genes in leaves, stems and roots at four different stages of development under field conditions. The eight candidate genes tested were rRNA18S(18S), β-tubulin(TUB), actin 11(ACT), elongation factor 1α(EF1), translation initiation factor 5A(F5A), ubiquitin protein ligase E3-2a(UBI), ubiquitin conjugating enzyme E2-10(U10) and ubiquitin conjugating enzyme E2-35(U35). Data analysis was performed using four approaches commonly employed in identifying the reference genes and consensus rankings were generated using the output of each independent approach. EF1 and TUB were the most stable genes when all tissues and developmental stages were analyzed together. At different stages of development, UBI/18S, EF1/U35, TUB/U35 were the most stable genes in roots, leaves and stem tissues, respectively. Our results suggest the use of more than one reference gene in gene expression studies involving different tissues at different developmental stages.
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Storage roots of cassava, a major subsistence crop of sub-Saharan Africa, are calorie-rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots... more
Storage roots of cassava, a major subsistence crop of sub-Saharan Africa, are calorie-rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots were enhanced by co-expression of transgenes for deoxy-D-xylulose-5-phosphate synthase (DXS) and bacterial phytoene synthase (crtB), mediated by the patatin type-1 promoter. Storage roots harvested from field-grown plants accumulated carotenoids to ≤50 μg/g DW, 15- to 20-fold increases relative to roots from non-transgenic plants. Approximately 85-90% of these carotenoids accumulated as all-trans-β-carotene, the most nutritionally efficacious carotenoid. β-Carotene-accumulating storage roots displayed delayed onset of post-harvest physiological deterioration, a major constraint limiting utilization of cassava products. Large metabolite changes were detected in β-carotene enhanced storage roots. Most significantly, an inverse correlation was observed be...
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Storage roots of cassava, a major subsistence crop of sub-Saharan Africa, are calorie-rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots... more
Storage roots of cassava, a major subsistence crop of sub-Saharan Africa, are calorie-rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots were enhanced by co-expression of transgenes for deoxy-D-xylulose-5-phosphate synthase (DXS) and bacterial phytoene synthase (crtB), mediated by the patatin type-1 promoter. Storage roots harvested from field-grown plants accumulated carotenoids to ≤50 μg/g DW, 15- to 20-fold increases relative to roots from non-transgenic plants. Approximately 85-90% of these carotenoids accumulated as all-trans-β-carotene, the most nutritionally efficacious carotenoid. β-Carotene-accumulating storage roots displayed delayed onset of post-harvest physiological deterioration, a major constraint limiting utilization of cassava products. Large metabolite changes were detected in β-carotene enhanced storage roots. Most significantly, an inverse correlation was observed be...
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Cassava (Manihot esculenta, Crantz) roots are the primary source of calories for more than 500 million people, the majority of whom live in the developing countries of Africa. Cassava leaves and roots contain potentially toxic levels of... more
Cassava (Manihot esculenta, Crantz) roots are the primary source of calories for more than 500 million people, the majority of whom live in the developing countries of Africa. Cassava leaves and roots contain potentially toxic levels of cyanogenic glycosides. Consumption of residual cyanogens (linamarin or acetone cyanohydrin) in incompletely processed cassava roots can cause cyanide poisoning. Hydroxynitrile lyase (HNL), which catalyses the conversion of acetone cyanohydrin to cyanide, is expressed predominantly in the cell walls and laticifers of leaves. In contrast, roots have very low levels of HNL expression. We have over-expressed HNL in transgenic cassava plants under the control of a double 35S CaMV promoter. We show that HNL activity increased more than twofold in leaves and 13-fold in roots of transgenic plants relative to wild-type plants. Elevated HNL levels were correlated with substantially reduced acetone cyanohydrin levels and increased cyanide volatilization in proc...
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For cassava to become a safe and acceptable crop, it is necessary to reduce the cyanogen levels in cassava foods. While this objective can be achieved by processing procedures, recent findings have shown that it is also possible to... more
For cassava to become a safe and acceptable crop, it is necessary to reduce the cyanogen levels in cassava foods. While this objective can be achieved by processing procedures, recent findings have shown that it is also possible to achieve it by suppression of cyanogen synthesis or by accelerating cyanogen turnover and volatilization. In 2003, cyanogen-free cultivars were generated by selective inhibition CYP79D1/D2 gene expression. The CYP79D1/D2 enzymes catalyze the first-dedicated step in cyanogen synthesis. Tissue-specific inhibition of CYP79D1/D2 expression in leaves lead to a 99% reduction in root cyanogen levels, indicating that the cyanogenic glycoside, linamarin, is synthesized in leaves and transported to roots. An alternative strategy to the reduce cyanogen content is to enhance cyanogen detoxification and cyanide volatilization during processing. This strategy has the advantage that cyanogen levels in unprocessed roots are not altered, potentially providing protection ag...