Papers by Timothy L. Setter
Cassava (Manihot esculenta) provides calories and nutrition for more than half a billion people. ... more Cassava (Manihot esculenta) provides calories and nutrition for more than half a billion people. It was domesticated by native Amazonian peoples through cultivation of the wild progenitor M. esculenta ssp. flabellifolia and is now grown in tropical regions worldwide. Here we provide a high-quality genome assembly for cassava with improved contiguity, linkage, and completeness; almost 97% of genes are anchored to chromosomes. We find that paleotetraploidy in cassava is shared with the related rubber tree Hevea, providing a resource for comparative studies. We also sequence a global collection of 58 Manihot accessions, including cultivated and wild cassava accessions and related species such as Ceará or India rubber (M. glaziovii), and genotype 268 African cassava varieties. We find widespread interspecific admixture, and detect the genetic signature of past cassava breeding programs. As a clonally propagated crop, cassava is especially vulnerable to pathogens and abiotic stresses.
This genomic resource will inform future genome-enabled breeding efforts to improve this staple crop.
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Journal of the American Society for Horticultural Science
Phalaenopsis plants are routinely shipped long distances in total darkness. To determine how thes... more Phalaenopsis plants are routinely shipped long distances in total darkness. To determine how these long dark periods affect photosynthetic status in Phalaenopsis Sogo Yukidian ‘V3’, changes of net CO2 uptake, photosystem II (PS II) efficiency, and abscisic acid (ABA) concentration after a long-term simulated dark shipping were investigated. Net CO2 uptake rate, malate concentration, and titratable acidity in potted Phalaenopsis Sogo Yukidian ‘V3’ decreased after a 21-day simulated dark shipping at 20 °C, but recovered gradually with time after shipping. It took 6 to 9 days to recover to a normal photosynthetic status after shipping. The value of Fv/Fm was little affected by shipping. Therefore, net CO2 uptake rate would be a better indicator for estimating the recovery time after shipping. After shipping, fresh weight loss, leaf ABA concentration, and number of yellowed leaves of bare-root plants were higher than those of potted plants, and increased with longer durations (7, 14, an...
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Annals of Botany
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Annals of Botany
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Environmental and Experimental Botany, Oct 29, 2014
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Tree physiology, 2003
Eight red maple (Acer rubrum L.) provenances, four each from wet and dry sites, were grown under ... more Eight red maple (Acer rubrum L.) provenances, four each from wet and dry sites, were grown under the same conditions and their physiological responses to soil water availability investigated. Under well-watered conditions, seedlings of wet-site provenances grew faster and had consistently higher net photosynthesis, leaf conductance, maximum carboxylation rate, maximum rate of coupled photosynthetic electron transport, apparent quantum use efficiency, light-saturated photosynthesis and dark respiration than seedlings of dry-site provenances. Under conditions of low soil water availability, only dry-site provenances responded with decreased osmotic potential at full hydration and at the turgor loss point; however, provenances from wet sites showed a smaller reduction in absolute growth rate, a greater reduction in gas exchange and a greater increase in abscisic acid concentrations than dry-site provenances.
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Annals of botany, 2003
Plants adjust their sink-organ growth rates, development and distribution of dry matter in respon... more Plants adjust their sink-organ growth rates, development and distribution of dry matter in response to whole-plant photosynthate status. To advance understanding of these processes, potato (Solanum tuberosum L.) plants were subjected to CO(2) and light flux treatments, and early tuber growth was assessed. Atmospheric CO(2) (700 or 350 micro mol mol(-1)) and light flux (shade and control illumination) treatments were imposed at two growth stages: tuber initiation (TI) and tuber bulking (TB). Elevated CO(2) increased accumulation of total net biomass when imposed at both stages, and increased tuber growth rate by about 36 %, but did not increase the number of tubers. Elevated CO(2) increased the number of cells in tubers at both TI and TB stages, whereas shade substantially decreased the number of cells at both stages. Generally, treatments did not affect cell volume or the proportion of nuclei endoreduplicating (repeated nuclear DNA replication in the absence of cell division), but t...
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Annals of botany, 2002
To further our understanding of the greater susceptibility of apical kernels in maize inflorescen... more To further our understanding of the greater susceptibility of apical kernels in maize inflorescences to water stress, abscisic acid (ABA) catabolism activity was evaluated in developing kernels with chirally separated (+)-[(3)H]ABA. The predominant pathway of ABA catabolism was via 8'-hydroxylase to form phaseic acid, while conjugation to glucose was minor. In response to water deficit imposed on whole plants during kernel development, ABA accumulated to higher concentrations in apical than basal kernels, while both returned to control levels after rewatering. ABA catabolism activity per gram fresh weight increased about three-fold in response to water stress, but was about the same in apical and basal kernels on a fresh weight basis. ABA catabolism activity was three to four-fold higher in placenta than endosperm, and activity was higher in apical than basal kernels. In vitro incubation tests indicated that glucose did not affect ABA catabolism. We conclude that placenta tissue...
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Advances in Molecular Breeding Toward Drought and Salt Tolerant Crops, 2007
Page 1. CHAPTER 28 RECENT ADVANCES IN MOLECULAR BREEDING OF CASSAVA FOR IMPROVED DROUGHT STRESS T... more Page 1. CHAPTER 28 RECENT ADVANCES IN MOLECULAR BREEDING OF CASSAVA FOR IMPROVED DROUGHT STRESS TOLERANCE TIM L. SETTER1 AND MARTIN A. FREGENE2 1Department of Crop and Soil Sci ...
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Annals of botany, 2004
Cassava (Manihot esculenta) is an important food crop in the tropics that has a high growth rate ... more Cassava (Manihot esculenta) is an important food crop in the tropics that has a high growth rate in optimal conditions, but also performs well in drought-prone climates. The objectives of this work were to determine the effects of water deficit and rewatering on the rate of expansion of leaves at different developmental stages and to evaluate the extent to which decreases in cell proliferation, expansion, and delay in development are responsible for reduced growth. Glasshouse-grown cassava plants were subjected to 8 d of water deficit followed by rewatering. Leaves at 15 developmental stages from nearly full size to meristematic were sampled, and epidermal cell size and number were measured on leaves at four developmental stages. Leaf expansion and development were nearly halted during stress but resumed vigorously after rewatering. In advanced-stage leaves (Group 1) in which development was solely by cell expansion, expansion resumed after rewatering, but not sufficiently for cell ...
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Drought is the single most common cause of severe crop production shortage in developing countrie... more Drought is the single most common cause of severe crop production shortage in developing countries, and global warming is predicted to further exacerbate drought's impact. This chapter describes how to best evaluate segregating germplasm under water-limited conditions, what are the secondary traits to be included in the selection and why is it important to identify key regulatory genes involved in
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Papers by Timothy L. Setter
This genomic resource will inform future genome-enabled breeding efforts to improve this staple crop.
This genomic resource will inform future genome-enabled breeding efforts to improve this staple crop.