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Maricopa, AZ, United States

Wang M.,University of Arizona | Yu Y.,University of Arizona | Haberer G.,Helmholtz Center Munich | Marri P.R.,Dow AgroSciences | And 30 more authors.
Nature Genetics | Year: 2014

The cultivation of rice in Africa dates back more than 3,000 years. Interestingly, African rice is not of the same origin as Asian rice (Oryza sativa L.) but rather is an entirely different species (i.e., Oryza glaberrima Steud.). Here we present a high-quality assembly and annotation of the O. glaberrima genome and detailed analyses of its evolutionary history of domestication and selection. Population genomics analyses of 20 O. glaberrima and 94 Oryza barthii accessions support the hypothesis that O. glaberrima was domesticated in a single region along the Niger river as opposed to noncentric domestication events across Africa. We detected evidence for artificial selection at a genome-wide scale, as well as with a set of O. glaberrima genes orthologous to O. sativa genes that are known to be associated with domestication, thus indicating convergent yet independent selection of a common set of genes during two geographically and culturally distinct domestication processes. © 2014 Nature America, Inc. All rights reserved.

Perea H.,University of Nebraska - Lincoln | Strelkoff T.S.,Research Hydraulic Engineer | Adamsen F.J.,Urban Irrigation Water Testing and Consulting | Hunsaker D.J.,Us Arid Land Agricultural Research Center | Clemmens A.J.,Research Hydraulic Engineer and Center Director
Journal of Irrigation and Drainage Engineering | Year: 2010

A cross-section-averaged advection-dispersion equation (ADE) model was developed to simulate the transport of fertilizer in furrow irrigation. The advection and dispersion processes were solved separately at each time step by implementing a method of characteristics with cubic-spline interpolation and a time-weighted finite-difference scheme, respectively. The upstream boundary condition was a prescribed concentration. Downstream, a zero-flux boundary condition during advance and a concentration gradient following completion of advance were prescribed. Local pseudosteady state was assumed in order to apply Fischer's longitudinal dispersion equation under nonuniform and unsteady furrow flow conditions. Statistical parameters were used to evaluate the ADE model performance. © 2010 ASCE.

Chu Q.,China Agricultural University | Liu J.,China Agricultural University | Bali K.,University of California Cooperative Extension | Thorp K.R.,Us Arid Land Agricultural Research Center | And 3 more authors.
HortTechnology | Year: 2016

SUMMARY. The low availability and high cost of farm hand labor make automated thinners a faster and cheaper alternative to hand thinning in lettuce (Lactuca sativa). However, the effects of this new technology on the uniformity of plant spacing and size as well as crop yield are not proven. Three experiments were conducted in commercial romaine heart lettuce fields in 2013 and 2014 in Imperial Valley, CA, to compare the effects of automated thinning and hand thinning on uniformity of inrow spacing, plant size, and crop yield. Overhead images taken at 1 week after hand thinning indicate that thinning 8 to 11 days earlier by automated thinners did not affect plant size compared with the hand thinning treatment. However, lettuce plants in the automated thinning treatment were larger than plants in the hand thinning treatment 2 to 3 weeks after hand thinning. Automated thinners increased the uniformity of in-row spacing, increased the percentage of plants with the desired in-row spacing of 24 to 32 cm, and almost completely removed plants with an undesirable in-row spacing of 4 to 20 cm. As a result, individual lettuce plant weight and heart weight from the automated thinning plots was significantly greater and plants were more uniform compared with the hand thinned plants. Despite increases in lettuce plant size and uniformity in all three experiments, yield benefits of automated thinning were only significant in one of the three experiments due to larger plant populations resulting from hand thinning.This study suggests that automated thinning increases lettuce plant size and uniformity and makes it possible for growers to increase plant population and crop yield by optimizing in-row spacing. © 2016, American Society for Horticultural Science. All rights reserved.

Parsons E.P.,Purdue University | Popopvsky S.,Israel Agricultural Research Organization | Lohrey G.T.,Purdue University | Lu S.,King Abdullah University of Science and Technology | And 5 more authors.
Physiologia Plantarum | Year: 2012

To understand the role of fruit cuticle lipid composition in fruit water loss, an advanced backcross population, the BC2F2, was created between the Capsicum annuum (PI1154) and the Capsicum chinense (USDA162), which have high and low post-harvest water loss rates, respectively. Besides dramatic differences in fruit water loss, preliminary studies also revealed that these parents exhibited significant differences in both the amount and composition of their fruit cuticle. Cuticle analysis of the BC2F2 fruit revealed that although water loss rate was not strongly associated with the total surface wax amount, there were significant correlations between water loss rate and cuticle composition. We found a positive correlation between water loss rate and the amount of total triterpenoid plus sterol compounds, and negative correlations between water loss and the alkane to triterpenoid plus sterol ratio. We also report negative correlations between water loss rate and the proportion of both alkanes and aliphatics to total surface wax amount. For the first time, we report significant correlations between water loss and cutin monomer composition. We found positive associations of water loss rate with the total cutin, total C16 monomers and 16-dihydroxy hexadecanoic acid. Our results support the hypothesis that simple straight-chain aliphatic cuticle constituents form more impermeable cuticular barriers than more complex isoprenoid-based compounds. These results shed new light on the biochemical basis for cuticle involvement in fruit water loss. © 2012 Physiologia Plantarum.

White J.W.,Us Arid Land Agricultural Research Center | Dierig D.A.,National Center for Genetic Resources Preservation
Journal of Plant Registrations | Year: 2011

Descriptions of new germplasm published in the Journal of Plant Registrations (JPR), and previously in Crop Science, are important vehicles for informing researchers about advances in plant breeding. Launched in 2007, JPR introduced a format that allowed more detailed descriptions of registrations; however, an informal review suggests that further improvements are possible. This paper explores these suggestions. To support our arguments, we assessed the new format by reviewing 234 papers from JPR, focusing on 106 papers (53 each in the old-Crop Science-and new-JPR-formats) for cultivar releases in 14 self-pollinated crops. We examined genealogies (pedigrees), breeding processes, experimental techniques, phenotypes, and genotypes. In the new format, there was more extensive information on the chronology of the breeding process, the expected area of adaptation, experimental techniques, the quantification of phenotypes, and citation of web-based reports. Nonetheless, improvement appeared possible, including by (i) documenting genealogies in databases structured for breeding records; (ii) quantifying the degree of relatedness to other germplasm; (iii) describing the breeding process in tables that include key dates, population types and sizes, and numbers of test environments; (iv) describing adaptation through standardized scales, environmental classifications, or quantitative responses; (v) providing genotypic data; and (vi) providing access to supplementary materials from databases or Internet resources. © Crop Science Society of America.

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