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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Hard Winter Wheat Genetics Research » Research » Research Project #432516

Research Project: Validation, characterization and deployment of QTL for grain yield components in wheat

Location: Hard Winter Wheat Genetics Research

Project Number: 3020-21000-010-36-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Dec 15, 2016
End Date: Dec 14, 2017

Objective:
Overall hypothesis or goal: The overall goals for this project are the validation, characterization and deployment of QTL for grain yield components in wheat and the training of a new generation of plant breeders. Specific objectives: 1) Validation and characterization of QTL for grain yield and identification of the underlying genes using a combination of map-based cloning. 2) Identification and validation of candidate genes using sequenced mutants and transgenic approaches. 3) Deployment of useful QTL in public wheat breeding programs. 4) Development of new genomic and informatics tools to accelerate candidate gene identification. 5) Training a new integrated cohort of 15 plant breeders.

Approach:
General Strategy for QTL cloning: The cloning of a QTL using a map-based approach requires a precise mapping of the QTL effect, which can be achieved by reducing the genetic and environmental variability in segregating populations. To reduce the genetic variability among lines we will use heterogeneous inbred families or HIFs (Barrero et al. 2015, Genome Biol 16:93). Once a QTL is validated in a bi-parental population, lines heterozygous for the target regions will be selected from advanced generations. For example, in the sixth generation of sellfing in a SSD population, 1.5% of the markers are still in heterozygous state, and likely heterozygous families can be identified. If not, we will use F5 lines where the probability is higher (3.1%). We will use more than one HIF to be prepared for strong epistatic interactions resulting in better detection of the QTL in some genetic backgrounds than others. During the project, we will continued to self-pollinated the parental lines of the HIFs, selecting the QTL flanking markers for heterozygocity. This will allow us to generate more isogenic progenies for the high-density mapping as the project progress. The segregation of the QTL in an isogenic background eliminates most of the epistatic interactions and results a smaller variation within the two allelic classes, and consequently in improved statistical power. To reduce the environmental variability we will use a large number of replications. Based on the observed variability between and within the isogenic lines we will adjust the number of replication to have a low type I error with reasonable probability of detecting the differences (power >90%). Since this usually results in a large number of replication (we have used 10-20 replications in the cloning of previous QTL {Uauy, 2006 #2470}), the number of lines evaluated at each stage needs to be kept reasonable (e.g. 50 lines with 10 replications each, result in a large but reasonable plot experiment). Only the lines carrying recombination events between flanking markers are informative, so the number of informative lines that will need to be tested in the field can be estimated from the genetic distance between the flanking markers and the number of lines screened for recombination.