Papers by Margaret Pallotta
TAG Theoretical and Applied Genetics, 2000
In many cropping regions of the world, yield is limited by the availability of micronutrients, an... more In many cropping regions of the world, yield is limited by the availability of micronutrients, and micronutrient-efficient cultivars provide a yield advantage. Traditional methods of testing cultivars for micronutrient efficiency are time-consuming and laborious. Molecular markers linked to loci controlling micronutrient efficiency will allow more rapid and efficient selection and introgression of these traits than is currently possible. Using a pot-based bioassay and bulked segregant analysis of an F 2 population, we have identified several RFLPs (grouped distally on chromosome 4HS) linked to a locus for manganese efficiency in barley. This manganese efficiency locus has been designated Mel1. Pot bioassay analysis of intercrosses suggests that three useful sources of manganese efficiency are likely to be allelic at the Mel1 locus. Field evaluation of marker selected F 4 progeny supports the major role of Mel1 in the genetic control of manganese efficiency. Adoption of marker assisted selection for this trait in the Southern Australian barley breeding program has occurred. This has been facilitated by the demonstration that the Mel1 allele of Amagi Nijo can be distinguished from 95 other locally useful varieties and breeder's lines on the basis of RFLPs identified by just two molecular markers.
Centric fusion between nonhomologous rye chromosomes in wheat
Genome
ABSTRACT
Allelic Variation and Gene Duplication Determine Boron Toxicity Tolerance in Bread and Durum Wheat
Boron has the narrowest range between deficient and toxic soil solution concentration of all plan... more Boron has the narrowest range between deficient and toxic soil solution concentration of all plant nutrients, and boron deficiency and toxicity both severely limit crop production worldwide. In wheat, genetic variation exists for tolerance to soil boron, and the utilisation of a locus on the long arm of chromosome 7BL named Bo1 has been a long term priority for marker assisted selection in wheat breeding programs in Australia. To assist breeding for this trait we defined the tolerance locus using a population of 2100 individuals derived from a cross between Cranbrook (boron intolerant) and Halberd (boron tolerant) and used a map based cloning approach to identify the Bo1-locus gene. We generated independent Halberd EMS mutations to confirm the identity of the tolerance protein as a membrane bound boron efflux transporter, which is similar but not orthologous to a barely boron tolerance gene HvBot1. An allelic series of genes at the locus was identified from a panel of bread and duru...
Validation of molecular markers for wheat breeding
Australian Journal of Agricultural Research, 2001
... Brown GN (1997) The inheritance and expression of leaf chlorosis associated with gene Sr2 for... more ... Brown GN (1997) The inheritance and expression of leaf chlorosis associated with gene Sr2 for adult plant resistance to wheat stem rust. ... McIntosh RA, Wellings CR, Park RF (1995) 'Wheat rusts: an atlas of resistance genes.' (CSIRO: Australia) Naik S, Gill KS, Prakasa Rao VS ...
Nature, 2014
Environmental constraints severely restrict crop yields in most production environments, and expa... more Environmental constraints severely restrict crop yields in most production environments, and expanding the use of variation will underpin future progress in breeding. In semi-arid environments boron toxicity constrains productivity, and genetic improvement is the only effective strategy for addressing the problem 1 . Wheat breeders have sought and used available genetic diversity from landraces to maintain yield in these environments; however, the identity of the genes at the major tolerance loci was unknown. Here we describe the identification of near-identical, root-specific boron transporter genes underlying the two major-effect quantitative trait loci for boron tolerance in wheat, Bo1 and Bo4 (ref. 2). We show that tolerance to a high concentration of boron is associated with multiple genomic changes including tetraploid introgression, dispersed gene duplication, and variation in gene structure and transcript level. An allelic series was identified from a panel of bread and durum wheat cultivars and landraces originating from diverse agronomic zones. Our results demonstrate that, during selection, breeders have matched functionally different boron tolerance alleles to specific environments. The characterization of boron tolerance in wheat illustrates the power of the new wheat genomic resources to define key adaptive processes that have underpinned crop improvement.
Theoretical and Applied Genetics, 2009
Frost at Xowering can cause signiWcant damage to cereal crops. QTL for low temperature tolerance ... more Frost at Xowering can cause signiWcant damage to cereal crops. QTL for low temperature tolerance in reproductive tissues (LTR tolerance) were previously described on barley 2HL and 5HL chromosome arms. With the aim of identifying potential LTR tolerance mechanisms, barley Amagi Nijo £ WI2585 and Haruna Nijo £ Galleon populations were examined for Xowering time and spike morphology traits associated with the LTR tolerance loci. In spring-type progeny of both crosses, winter alleles at the Vrn-H1 vernalization response locus on 5H were linked in coupling with LTR tolerance and were unexpectedly associated with earlier Xowering. In contrast, tolerance on 2HL was coupled with late Xowering alleles at a locus we named Flt-2L. Both chromosome regions inXuenced chasmogamy/ cleistogamy (open/closed Xorets), although tolerance was associated with cleistogamy at the 2HL locus and chasmogamy at the 5HL locus. LTR tolerance controlled by both loci was accompanied by shorter spikes, which were due to fewer Xorets per spike on 5HL, but shorter rachis internodes on 2HL. The Eps-2S locus also segregated in both crosses and inXuenced spike length and Xowering time but not LTR tolerance. Thus, none of the traits was consistently correlated with LTR tolerance, suggesting that the tolerance may be due to some other visible trait or an intrinsic (biochemical) property. Winter alleles at the Vrn-H1 locus and short rachis internodes may be of potential use in barley breeding, as markers for selection of LTR tolerance at 5HL and 2HL loci, respectively. Communicated by J. Snape.
TAG Theoretical and Applied Genetics, 2000
Boron is an essential plant micro-nutrient which can be phytotoxic to plants if present in soils ... more Boron is an essential plant micro-nutrient which can be phytotoxic to plants if present in soils in high concentration. Boron toxicity has been recognised as an important problem limiting production in the low rainfall areas of southern Australia, West Asia and North Africa. Genetic variation for boron toxicity tolerance in wheat has been well-characterised. The efficiency of breeding for boron toxicity tolerance could be greatly enhanced by the development of molecular markers associated with QTLs for tolerance in wheat. A population of 161 doubled haploids from a cross between the tolerant cultivar Halberd and the moderately sensitive cultivar Cranbrook was used to identify chromosomal regions involved in boron tolerance. A combined RFLP and AFLP linkage map of the Cranbrook x Halberd population was used to identify chromosomal regions involved in the boron tolerance traits measured. Regions on chromosome 7B and 7D were associated with leaf symptom expression. The region on chromosome 7B was also associated with the control of boron uptake and with a reduction in the effect of boron toxicity on rootgrowth suppression. RFLP markers at the chromosome 7B and 7D loci were shown to be effective in selecting for improved boron tolerance in an alternative genetic background. Halberd alleles at the chromosome 7B locus were associated with the concentration of boron in whole shoots and grain. The concentration of boron in whole shoots and in grain were both related to grain yield in a field trial conducted on soil containing toxic levels of boron. Implications relating to marker-assisted selection for boron toxicity tolerance in wheat are discussed.
Theoretical and Applied Genetics, 2009
Rye is a diploid crop species with many outstanding qualities, and is important as a source of ne... more Rye is a diploid crop species with many outstanding qualities, and is important as a source of new traits for wheat and triticale improvement. Rye is highly tolerant of aluminum (Al) toxicity, and possesses a complex structure at the Alt4 Al tolerance locus not found at the corresponding locus in wheat. Here we describe a BAC library of rye cv. Blanco, representing a valuable resource for rye molecular genetic studies, and assess the library's suitability for investigating Al tolerance genes. The library provides 6 £ genome coverage of the 8.1 Gb rye genome, has an average insert size of 131 kb, and contains only »2% of empty or organelle-derived clones. Genetic analysis attributed the Al tolerance of Blanco to the Alt4 locus on the short arm of chromosome 7R, and revealed the presence of multiple allelic variants (haplotypes) of the Alt4 locus in the BAC library. BAC clones containing ALMT1 gene clusters from several Alt4 haplotypes were identiWed, and will provide useful starting points for exploring the basis for the structural variability and functional specialization of ALMT1 genes at this locus.
Plant Molecular Biology, 2009
The TaPR60 gene from bread wheat encodes a small cysteine-rich protein with a hydrophobic signal ... more The TaPR60 gene from bread wheat encodes a small cysteine-rich protein with a hydrophobic signal peptide, predicted to direct the TaPR60 protein to a secretory pathway. It was demonstrated by heterologous expression of recombinant TaPR60 protein that the signal peptide is recognized and cleaved in yeast cells. The full-length gene including promoter sequence of a TaPR60 orthologue was cloned from a BAC library of Triticum durum.
Plant Biotechnology Journal, 2012
An HD-Zip IV gene from wheat, TaGL9, was isolated using a Y1H screen of a cDNA library prepared f... more An HD-Zip IV gene from wheat, TaGL9, was isolated using a Y1H screen of a cDNA library prepared from developing wheat grain. TaGL9 has an amino acid sequence distinct from other reported members of the HD-Zip IV family. The 3¢ untranslated region of TaGL9 was used as a probe to isolate a genomic clone of the TaGL9 homologue from a BAC library prepared from Triticum durum L. cv. Langdon. The full-length gene containing a 3-kb-long promoter region was designated TdGL9H1. Spatial and temporal activity of TdGL9H1 was examined using promoter-GUS fusion constructs in transgenic wheat, barley and rice plants. Whole-mount and histochemical GUS staining patterns revealed grain-specific expression of TdGL9H1. GUS expression was initially observed between 3 and 8 days after pollination (DAP) in embryos at the globular stage and adjacent to the embryo fraction of the endosperm. Expression was strongest in the outer cell layer of the embryo. In developed wheat and barley embryos, strong activity of the promoter was only detected in the main vascular bundle of the scutellum, which is known to be responsible for the uptake of nutrients from the endosperm during germination and the endosperm-dependent phase of seedling development. Furthermore, this pattern of GUS staining was observed in dry seeds several weeks after harvesting but quickly disappeared during imbibition. The promoter of this gene could be a useful tool for engineering of early seedling vigour and protecting the endosperm to embryo axis pathway from pathogens during grain desiccation and storage.
Genetics, 2008
Aluminum toxicity is a major problem in agriculture worldwide. Among the cultivated Triticeae, ry... more Aluminum toxicity is a major problem in agriculture worldwide. Among the cultivated Triticeae, rye (Secale cereale L.) is one of the most Al tolerant and represents an important potential source of Al tolerance for improvement of wheat. The Alt4 Al-tolerance locus of rye contains a cluster of genes homologous to the single-copy Al-activated malate transporter (TaALMT1) Al-tolerance gene of wheat. Tolerant (M39A-1-6) and intolerant (M77A-1) rye haplotypes contain five and two genes, respectively, of which two (ScALMT1-M39.1 and ScALMT1-M39.2) and one (ScALMT1-M77.1) are highly expressed in the root tip, typically the main site of plant Al tolerance/susceptibility. All three transcripts are upregulated by exposure to Al. High-resolution genetic mapping identified two resistant lines resulting from recombination within the gene cluster. These recombinants exclude all genes flanking the gene cluster as candidates for controlling Alt4 tolerance, including a homolog of the barley HvMATE Al-tolerance gene. In the recombinants, one hybrid gene containing a chimeric open reading frame and the ScALMT1-M39.1 gene each appeared to be sufficient to provide full tolerance. mRNA splice variation was observed for two of the rye ALMT1 genes and in one case, was correlated with a 400-bp insertion in an intron.
Functional Plant Biology, 2013
Tolerance to boron (B) toxicity in barley (Hordeum vulgare L.) is partially attributable to HvNIP... more Tolerance to boron (B) toxicity in barley (Hordeum vulgare L.) is partially attributable to HvNIP2;1, an aquaporin with permeability to B, as well as to silicon, arsenic and germanium (Ge). In this study, we mapped leaf symptoms of Ge toxicity in a doubled-haploid barley population (Clipper  Sahara 3771). Two quantitative trait loci (QTL) associated with Ge toxicity symptoms were identified, located on Chromosomes 6H and 2H. These QTL co-located with two of four B toxicity tolerance loci previously mapped in the same population. The B toxicity tolerance gene underlying the 6H locus encodes HvNIP2;1, whereas the gene(s) and mechanisms underlying the 2H locus are as yet unknown. We provide examples of the application of Ge in studying specific aspects of B toxicity tolerance in plants, including screening of wheat (Triticum aestivum L.) and barley populations for altered function of HvNIP2;1 and related proteins. In particular, Ge may facilitate elucidation of the mechanism and gene(s) underlying the barley Chromosome 2H B tolerance locus.
New eSSR and gSSR markers added to Australian barley maps
Australian Journal of Agricultural Research, 2006
Résumé/Abstract To enhance genetic maps of barley previously developed in Australia for identifyi... more Résumé/Abstract To enhance genetic maps of barley previously developed in Australia for identifying markers useable in molecular breeding, a new set of simple sequence repeat (SSR) and indel markers was added to the maps. These markers were developed through ...
Australian Journal of …, 2003
Two populations between the German malting variety Alexis and the Australian malting variety Sloo... more Two populations between the German malting variety Alexis and the Australian malting variety Sloop were constructed, mapped, phenotyped, and subjected to quantitative trait loci analysis. One population consisted of 153 F 4 -derived recombinant inbred lines and the other of 111 doubled haploid lines. This paper describes 18 field and laboratory experiments conducted with the populations and summarises the traits mapped and analysed. The genetic basis of 5 traits (malt extract, resistance to leaf rust, resistance to powdery mildew, early flowering, plant stature) important to Australian efforts to improve malting barley varieties was elucidated. Detailed maps for these populations are shown in this paper, while a consensus map incorporating these maps and further experiments on the populations are described elsewhere in this issue.
Uploads
Papers by Margaret Pallotta