Main conclusion α-Amylase synthesis by wheat aleurone during grain development (late maturity α-a... more Main conclusion α-Amylase synthesis by wheat aleurone during grain development (late maturity α-amylase) appears to be independent of gibberellin unlike α-amylase synthesis by aleurone during germination or following treatment with exogenous GA.
A method is described for the isolation of wheat endosperm cell walls free from non-endospermic c... more A method is described for the isolation of wheat endosperm cell walls free from non-endospermic cell walls in a 70 % ethanol medium which prevents the loss of watersoluble polymeric components.
The microscopy and ultrastructure of the interaction of Puccinia striiformis with a susceptible w... more The microscopy and ultrastructure of the interaction of Puccinia striiformis with a susceptible wheat cultivar was examined at intervals from the time of first haustorium formation to the onset of sporulation. At any particular point in the radially expanding area of infection a sequence of morphological changes occurred in the infected host cells and the fungus which were correlated with successive phases of active fungal growth, accumulation of reserves and finally export of reserves to the developing reproductive structures. The observations are compared with previous work on other host-rust interactions.
To examine the roles of epigenetic modulation on hair follicle regeneration, we generated mice wi... more To examine the roles of epigenetic modulation on hair follicle regeneration, we generated mice with a K14Cre-mediated loss of DNA methyltransferase (DNMT) 1. The mutant shows an uneven epidermal thickness and alterations in hair follicle size. When formed, hair follicle architecture and differentiation appear normal. Hair subtypes exist but hair fibers are shorter and thinner. Hair numbers appear normal at birth but gradually decrease to fewer than 50% of control in 1 year old mice. Sections of old mutant skin shows follicles in prolonged telogen with hyperplastic sebaceous glands. Anagen follicles in mutants exhibit decreased proliferation and increased apoptosis in matrix transient amplifying cells. Although K15 positive stem cells in the mutant bulge are comparable in number to the control, their ability to proliferate and become activated to form a hair germ is reduced. As mice age, residual DNMT activity declines further and the probability of successful anagen reentry decreases, leading to progressive alopecia. Paradoxically, there is increased proliferation in the epidermis which also shows aberrant differentiation. These results highlight the importance of DNA methylation in maintaining stem cell homeostasis during the development and regeneration of ectodermal organs.
Darkening in yellow alkaline noodles (YAN) was measured over 24 h in a high polyphenol oxidase (P... more Darkening in yellow alkaline noodles (YAN) was measured over 24 h in a high polyphenol oxidase (PPO) bread wheat ( Triticum aestivum L. cv. Tasman) and a very low PPO durum wheat ( Triticum durum cv. Kamilaroi). Over 24 h non-PPO darkening occurred across a range of pH 3.5-10.5, and in Tasman this was overlaid by darkening from PPO activity. The rate of darkening in YAN was separated into two main time periods, 0-4 and 4-24 h. The first 4 h of darkening was further divided into two stages using a composite first-order rate equation. Several specific inhibitors that partially inhibited non-PPO darkening were identified. These inhibitors, as well as the PPO inhibitors SHAM and tropolone, were used to analyze YAN darkening. The rate of the early stage of darkening was not altered by any inhibitors used; however, the magnitude of darkening was reduced by inhibitors specific for non-PPO darkening. Both the rate and extent of non-PPO darkening of the second stage of darkening were decreased in Tasman and Kamilaroi by inhibitors specific for non-PPO darkening, whereas both PPO inhibitors only decreased darkening in Tasman. The second and third stages of darkening showed similar characteristics. The third stage of darkening was examined in YAN made from Kamilaroi over a temperature range from -4 to 65 degrees C. It followed an Arrhenius relationship indicating non-PPO darkening during this stage was nonenzymatic. The inhibitor data suggested that the reactive component(s) was/were present in a reasonably high concentration(s) and that the soluble protein fraction was involved in the non-PPO darkening process.
A milling quality assessment protocol using a 10 g seed sample was developed. Its ability to disc... more A milling quality assessment protocol using a 10 g seed sample was developed. Its ability to discriminate between wheats differing in milling quality and its application to early generation selection were evaluated. The procedure reliably and accurately discriminated between the varieties Sunco, Hartog and Sunelg for the flour parameters yellow pigment content, Kent-Jones colour grade and yield. The procedure was applied to progeny of F2 single plant selections from five bread wheat crosses, and heritabilities and simulated response to selection measured in the F3 generation. Medium to high heritabilities were obtained for yellow pigment content and colour grade, while those for flour yield were generally lower and varied considerably between crosses. Results of simulated selection versus values for control varieties indicated that the protocol would result in positive response to selection for milling quality. The outcome for some crosses, however, was influenced by the comparative...
Freshly harvested grain from 14 varieties of wheat was stored in a deep-freezer at 15�C, or alter... more Freshly harvested grain from 14 varieties of wheat was stored in a deep-freezer at 15�C, or alternatively, in an air-conditioned seed room at 12�C for periods of up to 9 months. Freeze-storage preserved the germination rate of hand-threshed grain at the level observed at harvest, provided that the moisture content of the grain had reached 12%. When frozen grain was transferred to 12�C storage, its germination rate improved with time in parallel with changes observed in freshly harvested seed stored at 12�C from the time of harvest, i.e. after-ripening was not adversely affected by the freezing treatment. This technique should enable greater quantities of material to be screened for low germinability at harvest ripeness and for tolerance to pre-harvest sprouting damage. It also allows the provision of a continuous supply of uniform material for investigations of dormancy and grain after-ripening.
ABSTRACT Lutein is a naturally occurring plant carotenoid compound that is also an important micr... more ABSTRACT Lutein is a naturally occurring plant carotenoid compound that is also an important micro-nutrient for humans. While the biosynthesis of lutein in bread wheat (Triticum aestivum L.) is well understood, in contrast, there is little information on the mechanism or the genetic control involved in conversion of lutein to lutein esters during storage of wheat grain. The purpose of this research was to investigate the genetic control of lutein ester formation in wheat.
Main conclusion Dormancy in white-grained wheat is conditioned by the cumulative effects of sever... more Main conclusion Dormancy in white-grained wheat is conditioned by the cumulative effects of several QTL that delay the onset of the capacity to germinate during ripening and after-ripening. Abstract Grain dormancy at harvest-ripeness is a major component of resistance to preharvest sprouting in wheat ( Triticum aestivum L.) and an important trait in regions where rain is common during the harvest period. Breeding lines developed in Australia maintained their dormancy phenotype over multiple seasons and during grain ripening, the time between anthesis and the acquisition of the capacity to germinate, dormancy release, increased in line with the strength of dormancy. Genetic dissection of two dormant lines indicated that dormancy was due to the cumulative action of between one and three major genetic loci and several minor loci. This presents a significant challenge for breeders targeting environments with a high risk of sprouting where strong dormancy is desirable. Only around half of the difference in dormancy between the dormant lines and a non-dormant variety could be attributed to the major genetic loci on chromosomes 4A and 3A. A QTL that was mapped on chromosome 5A may be an orthologue of a minor QTL for dormancy in barley. At each locus, the dormancy allele increased the time to dormancy release during ripening. In combination, these alleles had cumulative effects. Embryo sensitivity to abscisic acid was related to the dormancy phenotype of the whole caryopsis, however, changes in concentrations of abscisic acid and gibberellins in embryo sections and de-embryonated grains during ripening and after-ripening could not be linked to the timing of dormancy release.
Preservation of lutein concentrations in wheat-based end-products during processing is important ... more Preservation of lutein concentrations in wheat-based end-products during processing is important both for product quality and nutritional value. A key constituent involved in lutein degradation is endogenous lipoxygenase. Lutein and lutein ester concentrations were compared at intervals during storage of noodle sheets prepared from flour of wheat varieties representing a range in lipoxygenase activity, as well as in different mill streams and in different grain tissues. Higher lipoxygenase concentration was associated with an increased loss of free lutein and lutein mono-esters whereas lutein diesters appeared to be more resistant to degradation. Lutein degradation was reduced in the presence of a lipoxygenase inhibitor, when noodle sheets were heated to destroy enzyme activity or when pH was increased. In addition, three populations were used to investigate the genetic control of lipoxygenase. A previously reported mutation of Lpx-B1.1 was associated with a reduction in activity fr...
Mapping of the late maturity α-amylase (LMA) gene using quantitative trait locus (QTL) analysis r... more Mapping of the late maturity α-amylase (LMA) gene using quantitative trait locus (QTL) analysis represents an important step in identification of potential molecular markers that would greatly improve efficiency and accuracy of screening for LMA. QTL controlling the expression of LMA in wheat were detected in a doubled haploid (DH) cross/population derived from wheat (Triticum aestivum L. em. Thell) cultivars Cranbrook (LMA source) and Halberd (non-LMA). The DH population and parents were sown in replicated trials at Narrabri with sowing times differing by 2 weeks. Cool temperature treatment of detached tillers was used to induce expression of LMA in lines carrying the defect. The number of grains in ripe, treated tillers that contained high pI (malt, germination type) α-amylase isozymes was measured using an ELISA antibody kit highly specific for high pI isozymes. QTL analyses were conducted separately for each sowing, but results from both sowings were consistent and indicated that there was a highly significant (P < 0.001) QTL on the long arm of chromosome 7B (accounting for 31% of the variation in the first experiment), with Cranbrook contributing the higher value allele. A second QTL that accounted for 13% of the variation was found close to the centromere on chromosome 3B. Although it was less important than the QTL on 7B it was nevertheless still significant (P < 0.05).
Main conclusion α-Amylase synthesis by wheat aleurone during grain development (late maturity α-a... more Main conclusion α-Amylase synthesis by wheat aleurone during grain development (late maturity α-amylase) appears to be independent of gibberellin unlike α-amylase synthesis by aleurone during germination or following treatment with exogenous GA.
A method is described for the isolation of wheat endosperm cell walls free from non-endospermic c... more A method is described for the isolation of wheat endosperm cell walls free from non-endospermic cell walls in a 70 % ethanol medium which prevents the loss of watersoluble polymeric components.
The microscopy and ultrastructure of the interaction of Puccinia striiformis with a susceptible w... more The microscopy and ultrastructure of the interaction of Puccinia striiformis with a susceptible wheat cultivar was examined at intervals from the time of first haustorium formation to the onset of sporulation. At any particular point in the radially expanding area of infection a sequence of morphological changes occurred in the infected host cells and the fungus which were correlated with successive phases of active fungal growth, accumulation of reserves and finally export of reserves to the developing reproductive structures. The observations are compared with previous work on other host-rust interactions.
To examine the roles of epigenetic modulation on hair follicle regeneration, we generated mice wi... more To examine the roles of epigenetic modulation on hair follicle regeneration, we generated mice with a K14Cre-mediated loss of DNA methyltransferase (DNMT) 1. The mutant shows an uneven epidermal thickness and alterations in hair follicle size. When formed, hair follicle architecture and differentiation appear normal. Hair subtypes exist but hair fibers are shorter and thinner. Hair numbers appear normal at birth but gradually decrease to fewer than 50% of control in 1 year old mice. Sections of old mutant skin shows follicles in prolonged telogen with hyperplastic sebaceous glands. Anagen follicles in mutants exhibit decreased proliferation and increased apoptosis in matrix transient amplifying cells. Although K15 positive stem cells in the mutant bulge are comparable in number to the control, their ability to proliferate and become activated to form a hair germ is reduced. As mice age, residual DNMT activity declines further and the probability of successful anagen reentry decreases, leading to progressive alopecia. Paradoxically, there is increased proliferation in the epidermis which also shows aberrant differentiation. These results highlight the importance of DNA methylation in maintaining stem cell homeostasis during the development and regeneration of ectodermal organs.
Darkening in yellow alkaline noodles (YAN) was measured over 24 h in a high polyphenol oxidase (P... more Darkening in yellow alkaline noodles (YAN) was measured over 24 h in a high polyphenol oxidase (PPO) bread wheat ( Triticum aestivum L. cv. Tasman) and a very low PPO durum wheat ( Triticum durum cv. Kamilaroi). Over 24 h non-PPO darkening occurred across a range of pH 3.5-10.5, and in Tasman this was overlaid by darkening from PPO activity. The rate of darkening in YAN was separated into two main time periods, 0-4 and 4-24 h. The first 4 h of darkening was further divided into two stages using a composite first-order rate equation. Several specific inhibitors that partially inhibited non-PPO darkening were identified. These inhibitors, as well as the PPO inhibitors SHAM and tropolone, were used to analyze YAN darkening. The rate of the early stage of darkening was not altered by any inhibitors used; however, the magnitude of darkening was reduced by inhibitors specific for non-PPO darkening. Both the rate and extent of non-PPO darkening of the second stage of darkening were decreased in Tasman and Kamilaroi by inhibitors specific for non-PPO darkening, whereas both PPO inhibitors only decreased darkening in Tasman. The second and third stages of darkening showed similar characteristics. The third stage of darkening was examined in YAN made from Kamilaroi over a temperature range from -4 to 65 degrees C. It followed an Arrhenius relationship indicating non-PPO darkening during this stage was nonenzymatic. The inhibitor data suggested that the reactive component(s) was/were present in a reasonably high concentration(s) and that the soluble protein fraction was involved in the non-PPO darkening process.
A milling quality assessment protocol using a 10 g seed sample was developed. Its ability to disc... more A milling quality assessment protocol using a 10 g seed sample was developed. Its ability to discriminate between wheats differing in milling quality and its application to early generation selection were evaluated. The procedure reliably and accurately discriminated between the varieties Sunco, Hartog and Sunelg for the flour parameters yellow pigment content, Kent-Jones colour grade and yield. The procedure was applied to progeny of F2 single plant selections from five bread wheat crosses, and heritabilities and simulated response to selection measured in the F3 generation. Medium to high heritabilities were obtained for yellow pigment content and colour grade, while those for flour yield were generally lower and varied considerably between crosses. Results of simulated selection versus values for control varieties indicated that the protocol would result in positive response to selection for milling quality. The outcome for some crosses, however, was influenced by the comparative...
Freshly harvested grain from 14 varieties of wheat was stored in a deep-freezer at 15�C, or alter... more Freshly harvested grain from 14 varieties of wheat was stored in a deep-freezer at 15�C, or alternatively, in an air-conditioned seed room at 12�C for periods of up to 9 months. Freeze-storage preserved the germination rate of hand-threshed grain at the level observed at harvest, provided that the moisture content of the grain had reached 12%. When frozen grain was transferred to 12�C storage, its germination rate improved with time in parallel with changes observed in freshly harvested seed stored at 12�C from the time of harvest, i.e. after-ripening was not adversely affected by the freezing treatment. This technique should enable greater quantities of material to be screened for low germinability at harvest ripeness and for tolerance to pre-harvest sprouting damage. It also allows the provision of a continuous supply of uniform material for investigations of dormancy and grain after-ripening.
ABSTRACT Lutein is a naturally occurring plant carotenoid compound that is also an important micr... more ABSTRACT Lutein is a naturally occurring plant carotenoid compound that is also an important micro-nutrient for humans. While the biosynthesis of lutein in bread wheat (Triticum aestivum L.) is well understood, in contrast, there is little information on the mechanism or the genetic control involved in conversion of lutein to lutein esters during storage of wheat grain. The purpose of this research was to investigate the genetic control of lutein ester formation in wheat.
Main conclusion Dormancy in white-grained wheat is conditioned by the cumulative effects of sever... more Main conclusion Dormancy in white-grained wheat is conditioned by the cumulative effects of several QTL that delay the onset of the capacity to germinate during ripening and after-ripening. Abstract Grain dormancy at harvest-ripeness is a major component of resistance to preharvest sprouting in wheat ( Triticum aestivum L.) and an important trait in regions where rain is common during the harvest period. Breeding lines developed in Australia maintained their dormancy phenotype over multiple seasons and during grain ripening, the time between anthesis and the acquisition of the capacity to germinate, dormancy release, increased in line with the strength of dormancy. Genetic dissection of two dormant lines indicated that dormancy was due to the cumulative action of between one and three major genetic loci and several minor loci. This presents a significant challenge for breeders targeting environments with a high risk of sprouting where strong dormancy is desirable. Only around half of the difference in dormancy between the dormant lines and a non-dormant variety could be attributed to the major genetic loci on chromosomes 4A and 3A. A QTL that was mapped on chromosome 5A may be an orthologue of a minor QTL for dormancy in barley. At each locus, the dormancy allele increased the time to dormancy release during ripening. In combination, these alleles had cumulative effects. Embryo sensitivity to abscisic acid was related to the dormancy phenotype of the whole caryopsis, however, changes in concentrations of abscisic acid and gibberellins in embryo sections and de-embryonated grains during ripening and after-ripening could not be linked to the timing of dormancy release.
Preservation of lutein concentrations in wheat-based end-products during processing is important ... more Preservation of lutein concentrations in wheat-based end-products during processing is important both for product quality and nutritional value. A key constituent involved in lutein degradation is endogenous lipoxygenase. Lutein and lutein ester concentrations were compared at intervals during storage of noodle sheets prepared from flour of wheat varieties representing a range in lipoxygenase activity, as well as in different mill streams and in different grain tissues. Higher lipoxygenase concentration was associated with an increased loss of free lutein and lutein mono-esters whereas lutein diesters appeared to be more resistant to degradation. Lutein degradation was reduced in the presence of a lipoxygenase inhibitor, when noodle sheets were heated to destroy enzyme activity or when pH was increased. In addition, three populations were used to investigate the genetic control of lipoxygenase. A previously reported mutation of Lpx-B1.1 was associated with a reduction in activity fr...
Mapping of the late maturity α-amylase (LMA) gene using quantitative trait locus (QTL) analysis r... more Mapping of the late maturity α-amylase (LMA) gene using quantitative trait locus (QTL) analysis represents an important step in identification of potential molecular markers that would greatly improve efficiency and accuracy of screening for LMA. QTL controlling the expression of LMA in wheat were detected in a doubled haploid (DH) cross/population derived from wheat (Triticum aestivum L. em. Thell) cultivars Cranbrook (LMA source) and Halberd (non-LMA). The DH population and parents were sown in replicated trials at Narrabri with sowing times differing by 2 weeks. Cool temperature treatment of detached tillers was used to induce expression of LMA in lines carrying the defect. The number of grains in ripe, treated tillers that contained high pI (malt, germination type) α-amylase isozymes was measured using an ELISA antibody kit highly specific for high pI isozymes. QTL analyses were conducted separately for each sowing, but results from both sowings were consistent and indicated that there was a highly significant (P < 0.001) QTL on the long arm of chromosome 7B (accounting for 31% of the variation in the first experiment), with Cranbrook contributing the higher value allele. A second QTL that accounted for 13% of the variation was found close to the centromere on chromosome 3B. Although it was less important than the QTL on 7B it was nevertheless still significant (P < 0.05).
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Papers by Daryl Mares