Search

Your search keyword '"Axtell, John"' showing total 50 results
Start Over Author "Axtell, John"
50 results on '"Axtell, John"'

11. Mutagenesis, selection, and allelic analysis of epicuticular wax mutants in sorghum

Author

Peters, Paul J., Jenks, Matthew A., Rich, Patrick J., Axtell, John D., and Ejeta, Gebisa

Subjects
Mutagenesis -- Research, Plant genetics -- Research, Sorghum -- Properties, Agricultural industry, Business
Abstract

Epicuticular wax forms an outer coating on the aerial surfaces of many crop plants and is implicated in tolerance to several environmental stresses including drought. Advances in knowledge of biosynthesis and secretion of these leaf surface waxes could lead to improvements in crop-stress tolerance. To study the genetics of epicuticular wax deposition, we screened for bloomless (bm) and sparse-bloom (h) mutants with reduced glaucousness of abaxial sheath surfaces within chemically mutagenized populations of Sorghum bicolor (L.) Moench. We screened over 3974 segregating [M.sub.2] head rows with over 160,000 plants and identified 38 putative recessive epicuticular wax mutant alleles. We grouped 31 of these into allelic groups associated with one existing and 18 new epicuticular wax loci. The overall epicuticular wax mutation frequency was 0.88%. In addition, analysis of the mutant segregation frequencies within the [M.sub.2] rows allowed us to calculate the existence of five target meristem cells in a dormant ([M.sub.0]) seed embryo. The high epicuticular wax mutation rate and identification of 19 epicuticular wax loci indicate the presence of a complex genetic system of epicuticular wax production in sorghum as has been shown in other species. The new bloomless and sparse-bloom mutants identified here have a wide range of phenotypes and constitute a valuable resource for studies of the genetics and biosynthesis of epicuticular waxes and their effects on tolerance to environmental stresses such as drought.

Published
2009

13. Genotypic variation for glycinebetaine in Sorghum. (Crop Physiology & Metabolism)

Author

Yang, Wen-Ju, Rich, Patrick J., Axtell, John D., Wood, Karl V., Bonham, Connie C., Ejeta, Gebisa, Mickelbart, Michael V., and Rhodes, David

Subjects
Sorghum -- Genetic aspects -- Physiological aspects -- Research -- Methods, Plant breeding -- Methods -- Genetic aspects -- Physiological aspects -- Research, Agricultural industry, Business, Physiological aspects, Genetic aspects, Research, Methods
Abstract

Glycinebetaine (GB) accumulation has been suggested to be an adaptive response to several abiotic environmental stresses. Genetic and metabolic studies of GB accumulation in maize (Zea mays L.) indicate that recessive alleles of a single locus are responsible for the phenotype of GB nonaccumulation. The present study was undertaken to determine whether a similar genetically determined range of GB levels exists in the related [C.sub.4] species Sorghum bicolor (L.) Moench. In a preliminary analysis of 240 sorghum genotypes, sampled at the postflowering stage, total quaternary ammonium compound (QAC) levels in the betaine fraction of the flag leaves were found to range from as low as 0.1 µmol [g.sup.-1] FW to as much as 33 µmol [g.sup.-1] FW. Stable isotope dilution desorption chemical ionization mass spectrometry of six genotypes with high QAC levels and five genotypes with low QAC levels confirmed that this variation could be attributed almost exclusively to genetic variability for GB level. GB-nonaccumulating sorghum genotypes were confirmed to be GB-non-accumulating in a second year or field-testing, and in greenhouse studies under salinized and non-salinized conditions. GB levels increased with seedling age and/or salinization in GB-accumulating genotypes. Also, GB levels were highest in the youngest leaves of GB-accumulating sorghum genotypes. This work shows that GB is the major QAC in sorghum, that genetic differences in GB accumulation exist in sorghum as they do in maize, and that the level of GB in GB-accumulating fines is developmentally and environmentally regulated. A list of GB levels of publicly available lines of sorghum is also provided., THE BREEDING of crop plants for environmental stress tolerance has been difficult and slow. The quantitative nature of stress tolerance and the problems associated with developing appropriate and replicable testing [...]

Published
2003

16. Evidence for an evolutionarily conserved interaction between cell wall biosynthesis and flowering in maize and sorghum

Author

Thompson Karen J, Vermerris Wilfred, McIntyre Lauren M, and Axtell John D

Subjects
Evolution, QH359-425
Abstract

Abstract Background Factors that affect flowering vary among different plant species, and in the grasses in particular the exact mechanism behind this transition is not fully understood. The brown midrib (bm) mutants of maize (Zea mays L.), which have altered cell wall composition, have different flowering dynamics compared to their wild-type counterparts. This is indicative of a link between cell wall biogenesis and flowering. In order to test whether this relationship also exists in other grasses, the flowering dynamics in sorghum (Sorghum bicolor (L.) Moench) were investigated. Sorghum is evolutionarily closely related to maize, and a set of brown midrib (bmr) mutants similar to the maize bm mutants is available, making sorghum a suitable choice for study in this context. Results We compared the flowering time (time to half-bloom) of several different bmr sorghum lines and their wild-type counterparts. This revealed that the relationship between cell wall composition and flowering was conserved in sorghum. Specifically, the mutant bmr7 flowered significantly earlier than the corresponding wild-type control, whereas the mutants bmr2, bmr4, bmr6, bmr12, and bmr19 flowered later than their wild-type controls. Conclusion The change in flowering dynamics in several of the brown midrib sorghum lines provides evidence for an evolutionarily conserved mechanism that links cell wall biosynthesis to flowering dynamics. The availability of the sorghum bmr mutants expands the germplasm available to investigate this relationship in further detail.

Published
2002
Full Text
View/download PDF

19. Evidence for an evolutionarily conserved interaction between cell wall biosynthesis and flowering in maize and sorghum

Author

Thompson Karen J, Vermerris Wilfred, McIntyre Lauren M, and Axtell John D

Subjects
Time Factors, Evolution, fungi, food and beverages, Flowers, Models, Biological, Zea mays, Body Height, Cell Wall, Mutation, QH359-425, Linear Models, Sorghum, Research Article
Abstract

Background Factors that affect flowering vary among different plant species, and in the grasses in particular the exact mechanism behind this transition is not fully understood. The brown midrib (bm) mutants of maize (Zea mays L.), which have altered cell wall composition, have different flowering dynamics compared to their wild-type counterparts. This is indicative of a link between cell wall biogenesis and flowering. In order to test whether this relationship also exists in other grasses, the flowering dynamics in sorghum (Sorghum bicolor (L.) Moench) were investigated. Sorghum is evolutionarily closely related to maize, and a set of brown midrib (bmr) mutants similar to the maize bm mutants is available, making sorghum a suitable choice for study in this context. Results We compared the flowering time (time to half-bloom) of several different bmr sorghum lines and their wild-type counterparts. This revealed that the relationship between cell wall composition and flowering was conserved in sorghum. Specifically, the mutant bmr7 flowered significantly earlier than the corresponding wild-type control, whereas the mutants bmr2, bmr4, bmr6, bmr12, and bmr19 flowered later than their wild-type controls. Conclusion The change in flowering dynamics in several of the brown midrib sorghum lines provides evidence for an evolutionarily conserved mechanism that links cell wall biosynthesis to flowering dynamics. The availability of the sorghum bmr mutants expands the germplasm available to investigate this relationship in further detail.

Published
2001

29. Genotypic Variation for glycinebetaine in Sorghum.

Author

Wen-Ju Yang, Rich, Patrick J., Axtell, John D., Wood, Karl V., Bonham, Connie C., Ejeta, Gobisa, Mickelbart, Michael V., and Rhodes, David

Subjects
GLYCINE, CORN, CROP science
Abstract

Glycinebetaine (GB) accumulation has been suggested to be an adaptive response to several abiotic environmental stresses. Genetic and metabolic studies of GB accumulation in maize (Zea mays L.) indicate that recessive alleles of a single locus are responsible for the phenotype of GB nonaccumulation. The present study was undertaken to determine whether a similar genetically determined range of GB levels exists in the related C[sub 4] species Sorghum bicolor (L.) Moench. In a preliminary analysis of 240 sorghum genotypes, sampled at the postflowering stage, total quaternary ammonium compound (QAC) levels in the betaine fraction of the flag leaves were found to range from as low as 0.1 µmol g[sup -1] FW to as much as 33 µmol g[sup -1] FW. Stable isotope dilution desorption chemical ionization mass spectrometry of six genotypes with high QAC levels and five genotypes with low QAC levels confirmed that this variation could be attributed ahnost exclusively to genetic variability for GB level. GB-nonaccumulating sorghum genotypes were confirmed to be GB-non-accumulating in a second year of field-testing, and in greenhouse studies under salinized and non-salinized conditions. GB levels increased with seedling age and/or salinization in GB-accumulating genotypes. Also, GB levels were highest in the youngest leaves of GB-accumulating sorghum genotypes. This work shows that GB is the major QAC in sorghum, that genetic differences in GB accumulation exist in sorghum as they do in maize, and that the level of GB in GB-accumulating lines is developmentally and environmentally regulated. A list of GB levels of publicly available lines of sorghum is also provided. [ABSTRACT FROM AUTHOR]

Published
2003
Full Text
View/download PDF

30. Evidence for an evolutionarily conserved interaction between cell wall biosynthesis and flowering in maize and sorghum.

Author

Vermerris, Wilfred, Thompson, Karen J., McIntyre, Lauren M., and Axtell, John D.

Subjects
PLANT cell walls, BIOSYNTHESIS, FLOWERING of plants, CORN flowering, SORGHUM
Abstract

Background: Factors that affect flowering vary among different plant species, and in the grasses in particular the exact mechanism behind this transition is not fully understood. The brown midrib (bm) mutants of maize (Zea mays L.), which have altered cell wall composition, have different flowering dynamics compared to their wild-type counterparts. This is indicative of a link between cell wall biogenesis and flowering. In order to test whether this relationship also exists in other grasses, the flowering dynamics in sorghum (Sorghum bicolor (L.) Moench) were investigated. Sorghum is evolutionarily closely related to maize, and a set of brown midrib (bmr) mutants similar to the maize bm mutants is available, making sorghum a suitable choice for study in this context. Results: We compared the flowering time (time to half-bloom) of several different bmr sorghum lines and their wild-type counterparts. This revealed that the relationship between cell wall composition and flowering was conserved in sorghum. Specifically, the mutant bmr7 flowered significantly earlier than the corresponding wild-type control, whereas the mutants bmr2, bmr4, bmr6, bmr12, and bmr19 flowered later than their wild-type controls. Conclusion: The change in flowering dynamics in several of the brown midrib sorghum lines provides evidence for an evolutionarily conserved mechanism that links cell wall biosynthesis to flowering dynamics. The availability of the sorghum bmr mutants expands the germplasm available to investigate this relationship in further detail. [ABSTRACT FROM AUTHOR]

Published
2002
Full Text
View/download PDF

32. Digestibility and Utilization of Protein and Energy from Nasha, a Traditional Sudanese Fermented Sorghum Weaning Food

Author

Graham, George G., MacLean, William C., Morales, Enrique, Hamaker, Bruce R., Kirleis, Allen W., Mertz, Edwin T., and Axtell, John D.

Abstract

Whole grain sorghum flour was fermented into Nasha, a traditional Sudanese food, and freeze-dried or drum-dried. It was cooked and fed to convalescent malnourished infants and small children as 61% of total diet calories and all of 6.4% protein calories, with (Lys+) and without lysine supplementation to 3% of protein. Apparent absorptions of nitrogen were 73 ± 5 and 74 ± 6% of intake, significantly (P< 0.01) less than those from preceding (Cas-1, 86 ± 3%) and following (Cas-2, 85 ± 3%) isonitrogenous casein diets. Apparent retentions of nitrogen from Nasha (26 ± 10%) were significantly lower than those from Lys + (34 ± 9%, P< 0.05), Cas-1 (35 ± 11%, P< 0.01) or Cas-2 (49 ± 9%, P< 0.01). Retentions from Cas-2 were higher than those from Cas-1 or Lys + (P< 0.01). Fecal wet and dry weights were higher (P< 0.02) during both Nasha diets and Cas-2 than during Cas-1. Fecal energy and carbohydrate were significantly (P< 0.01) higher from either Nasha diet than from either casein diet; fecal fat was not different. Two children received drum-dried Nasha without further cooking; digestibilities were not different from those of the cooked product but biological value was much lower. When properly cooked and consumed along with small amounts of a good source of lysine, Nasha is a satisfactory weaning food.

Published
1986
Full Text
View/download PDF

33. High Lysine Mutant Gene (hlthat Improves Protein Quality and Biological Value of Grain Sorghum1

Author

Singh, Rameshwar and Axtell, John D.

Abstract

Seeds from over 9,000 lines in the world sorghum [Sorghum bicolor(L.) Moench] collection were classified for endosperm phenotype to identify floury endosperm lines and evaluate each for potential increases in lysine concentration. Sixty‐two floury endosperm lines were selected and analyzed for protein and lysine composition. Two floury lines of Ethiopian origin, IS 11167 and IS 11758, were exceptionally high in lysine at relatively high levels of protein. The average whole grain lysine concentration of high lysine lines IS 11167 and IS 11758 was 3.34 and 3.13 (g/100g protein) at 15.7 and 17.2% protein, respectively. Both lines were also high in percent oil. Carbohydrate analyses of whole grain samples of the two high lysine lines were similar to that of normal sorghum grain except for a twofold increase in sucrose concentration. The high lysine gene altered the amino acid pattern in hl hl hlendosperm tissue relative to normal endosperm checks. The major changes were increased lysine, arginine, aspartic acid, glycine, and tryptophan concentrations and decreased amounts of glutamic acid, proline, alanine, and leucine in the hl hl hlendosperm. Inheritance studies suggest that the increased lysine concentration of each line is controlled by a single recessive gene, although it is not known whether the genes from both lines are allelic. The high lysine gene(s) present in IS 11167 and IS 11758 from Ethiopia is (are) herein designated as hl. The endosperm of kernels homozygous for the hlgene is partially dented. The biological value of the high lysine lines was much higher than that of average sorghum lines. In a 28‐day isonitrogenous feeding experiment the weight gain of weanling rats was three times higher on an IS 11758 ration and twice as high on an IS 11167 ration as weight gains on rations prepared from normal sorghum lines. When fed rations without any dilution except the usual 2% vitamin and 4% mineral supplementation, rats gained 94 g on high lysine sorghum (IS 11758) and 28.5 g on our current best nutritional quality sorghum line (IS 2319), versus 91.5 g on opaque‐2 corn (Zea maysL.) and 30.2 g on normal corn in a 28‐day feeding trial. Feed efficiency ratios for this trial were 3.0 for high lysine sorghum, 6.8 for IS 2319, 3.4 for opaque‐2 corn, and 7.4 for normal corn.

Published
1973
Full Text
View/download PDF

34. Interactive.

Author

Powell, Jonathan, Samworth, Roger, Axtell, John, Lowe, Michael, Smith, Derek, Ritter, Bill, Moss, Tony, Strand, Adrian, Alexander, Roy, Grace, Sandra, Walker, Kayleigh, McCarthy, Peter, Wickham, William, Brown, Kari, Wilson, Julia, Higgs, Al, Phillips, Scott, and Brown, Steve

Published
2018

45. WHAT SHORTAGE?

Author

Axtell, John

Subjects
LETTERS to the editor, LABOR supply, STEM education
Abstract

A letter to the editor is presented in response to John Levesque's Final Analysis column in the November 2012 issue which claimed there is a lack of science, technology, engineering, mathematics talent.

Published
2013

46. LETTERS.

Author

Axtell, John, McKenzie, Chuck, and Burgess, Sid

Subjects
LETTERS to the editor, LEADERSHIP, BUDGET, EDUCATIONAL finance
Abstract

Several letters to the editor are presented in response to articles in previous issues including one on Ignatian principles of leadership by John Leveque in the August 2011 issue, another on Oklahoma city by Bill Virgin in the August 2011 issue, and another on annual budget allocated to K-12 education by Rob McKenna in the August 2011 issue.

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results