The genetics of winterhardiness in barley : perspectives from genome-wide association mapping

Fall-planted barley makes the best use of available precipitation in the Pacific Northwest of the United States. This growth habit is also suitable to many other areas of the world. A prerequisite for production in most of these areas is tolerance of low temperature during the vegetative growth stages. Fall-planted barley is often equated with winter habit barley. Winter habit type cereals require vernalization: a period of low temperature necessary to trigger the vegetative to reproductive transition. Facultative growth habit defines germplasm that is tolerant of low temperature but do not require vernalization. Cereals achieve their greatest cold tolerance during vegetative stages, and a vegetative condition can be maintained by vernalization sensitivity or sensitivity to short days. As global climate changes and temperatures fluctuate without warning, vernalization sensitivity becomes an unreliable trait for maintaining a vegetative condition, and thus maximizing cold tolerance. Hence the interest in short day sensitive facultative types – provided that maximum cold tolerance can be achieved without vernalization sensitivity. Facultative cereals have the additional advantages that they can be fall or spring planted and they are amenable to rapid cycling breeding methods. In barley, winterhardiness loci have been identified using bi-parental QTL approaches. Candidates for the FR-H1 and FR-H2 QTL are VRN-H1 and a cluster of CBF family members respectively. VRN-H1, which interacts epistatically with VRN-H2 and VRN-H3, is also a major player in vernalization sensitivity. FR-H1 and FR-H2 are approximately 30 cM apart on the long arm of chromosome 5H. The candidate genes for the PPD-H1 and PPD-H2 photoperiod sensitivity QTL are HvPRR7 on chromosome 2H and HvFT3 on chromosome 1H respectively. Genome-wide association mapping provides a complementary or alternative approach to bi-parental mapping. In this research, we explored the genetics of winterhardiness in barley germplasm through genome-wide association mapping. We identified the same FR-H1, FR-H2, VRN-H2, PPD-H1 and PPD-H2 QTL identified via bi-parental QTL mapping. We found that FR-H1/FR-H2/VRN-H2 haplotypes predict maximum cold tolerant facultative germplasm with high certainty and that facultative germplasm is as cold tolerant as vernalization sensitive germplasm

Genetic analysis of BYVD resistance and low temperature tolerance in winter x spring barley crosses

The development of winter 6-row malting barley varieties is an objective of the OSU program. The program's winter germplasm is quite susceptible to Barley Yellow Dwarf Virus (BYDV). The program recently released the spring 2-row variety Orca, which carries the Yd2 gene for BYDV resistance. The objective of this project was to transfer the Yd2 gene from Orca to the winter varieties Strider and Kold. A molecular marker tightly linked to the Yd2 locus was used to facilitate the introgression of this gene from the spring to the winter ger nplasm pool In 1998, six-row plants were selected in F2 populations derived from crosses of Orca x Kold and Orca x Spider. DNA was extracted from these plants for genotyping with the molecular marker YLM, which is tightly linked to the Yd2 locus on the long arm of chromosome 3 (311). In order to encourage natural infection by BYDV-infected aphids, the F3 families tracing to selected F2 plants were planted one month before the usual planting date in the fall of 1998. Unusually low temperatures in December 1998 led to significant winter injury, leading to the loss of approximately 70% of the F3 families in each of the two populations. Phenotype data (visual rating of BYDV symptoms on F2 plants and F3 families, and visual rating of winter survival in F3 families) and genotype data (allelic structure of each F2 plant at the YLM locus) were collected to determine the genotype of the F3 phenotypic selections and to assess the utility of the marker locus as tools for rapidly introgressing target alleles from spring to winter germplasm

金融不安定性の分析

研究科: 千葉大学大学院社会文化科学研究科修了年:2000.09学位:経済

学生との連携による市民社会に開かれた「学び」の創造 : 「在宅での看取り」から持続可能な福祉社会を捉える

千葉大学公共研究センター21世紀COEプログラム「持続可能な福祉社会に向けた公共研究拠点

Structural and functional characterization of candidate vernalization genes in barley

Vernalization - the requirement of a period of low temperature to induce the transition from a vegetative to a reproductive state - is an evolutionarily and economically important trait in the Triticeae. The genetic basis of vernalization in barley (Hordeum vulgare subsp. vulgare), a model crop for the Triticeae, was first defined in terms of a three-locus epistatic model. Candidate genes for two of the vernalization loci (Vrn1 and Vrn2) were recently cloned in diploid and polyploid Triticurn species. The sequence and expression of HvBM5A, a candidate for Vrn-H1, were characterized in a panel of ten barley germplasm accessions, including one accession of the wild progenitor (Hordeum vulgare subsp. spontaneum). Differences in vernalization requirement are most likely due to allelic variation at the HvBM5A promoter and/or intragenic sites rather than in the coding region. An analysis of promoter and intron 1 polymorphisms showed that differences in the sequence of the latter are most consistent with growth habit classifications. HvBM5A expression patterns correlate with growth habit and meristem development. HvBM5A maps to the predicted position of Vrn-H1 on chromosome 5H. All available evidence suggests that HvBM5A is Vrn-H1. The presence/absence of the tightly linked ZCCT-H gene family members on chromosome 4H is perfectly correlated with growth habit in the germplasm array: all spring forms show a complete deletion of the ZCCT-H gene family. All available evidence suggests that a ZCCT-H gene family member is Vrn-H2. All QTL for vernalization requirement reported for barley in the literature can be explained by a two-locus model involving the Vrn-H1 and Vrn-H2 candidates. The data from this study provide a rigorous definition for "facultative growth habit": facultative genotypes have the Vrn-H2 deletion and signature "winter" habit alleles at Vrn-H1. These data lay the foundation for determining if the coincidence of Vrn-H1 with QTL for multiple winter hardiness-related phenotypes is due to linkage and/or pleiotropy

High-throughput Phenotyping and Genomic Selection: The Frontiers of Crop Breeding Converge

Genomic selection (GS) and high-throughput phenotyping have recently been captivating the interest of the crop breeding community from both the public and private sectors world-wide. Both approaches promise to revolutionize the prediction of complex traits, including growth, yield and adaptation to stress. Whereas high-throughput phenotyping may help to improve understanding of crop physiology, most powerful techniques for high-throughput field phenotyping are empirical rather than analytical and comparable to genomic selection. Despite the fact that the two methodological approaches represent the extremes of what is understood as the breeding process (phenotype versus genome), they both consider the targeted traits (e.g. grain yield, growth, phenology, plant adaptation to stress) as a black box instead of dissecting them as a set of secondary traits (i.e. physiological) putatively related to the target trait. Both GS and high-throughput phenotyping have in common their empirical approach enabling breeders to use genome profile or phenotype without understanding the underlying biology. This short review discusses the main aspects of both approaches and focuses on the case of genomic selection of maize flowering traits and near-infrared spectroscopy (NIRS) and plant spectral reflectance as high-throughput field phenotyping methods for complex traits such as crop growth and yield