Botany and Plant Sciences
Non Technical Summary
This project will contribute new knowledge concerning the inheritance, genetic control, and breeding of traits important for agricultural production in the face of unpredictable climates. The aim is to study responses to heat during reproductive development using cowpea, a warm-season legume with a legacy as a model for studying heat tolerance. A broad assessment of allelic variation important for tolerance to heat during reproductive development will be captured using an unstructured diversity panel, SNP genotyping, and knowledge of legume synteny. This knowledge will be reconciled with previously developed marker-trait associations to design breeding indices and mating schemes aimed at developing enhanced varieties of cowpea. Furthermore, knowledge gained from cowpea will be used to help describe heat-tolerance associated regions in related crop genomes including soybean and common bean.
Animal Health Component
Research Effort Categories
Goals / Objectives
Professional Development Design critical elements of a plant breeding initiative. Attend and participate in conferences including PAG and CSSA meetings. Comunicate research strategy and findings by publication and presentation. Research Survey heat tolerance among a diversity panel of cowpea samples during a greenhouse trial. Perform a genome-wide association study to identify allelic variation important for the inheritance of heat tolerance. Reconcile marker-trait associations to design a breeding scheme. Pursue marker-assisted breeding. Describe genomic regions important for heat tolerance.
Approach A diversity panel of ~200 cowpea lines will be chosen from the UCR collection and grown under hot greenhouse conditions in the fall of 2013. These lines will be chosen among a larger group of ~700 lines which were already genotyped using an EST-derived SNP genotyping platform developed by our group and some lines which are interesting but have yet to be genotyped. An experimental trial will be conducted during short days in order to mitigate potentially different photoperiod responses. Plants will be deconstructed at maturity and evaluated for tolerance to heat during reproductive development (stage II) by measuring the number of pods per peduncle. DNA will be gathered from lines yet to be genotyped and sent to a service provider for finger printing. Genotype data for the diversity panel will be used to identify population structure including genepools, migrants, admixture, duplicates, and to develop coancestry estimates (Pritchard et al., 2000; Earl and vonHoldt, 2012; Evanno et al., 2005; Jakobsson and Rosenberg, 2007; and Rosenberg, 2004) to be used as a covariate in association mapping provided by TASSEL (Bradbury et al., 2007). Marker-trait associations identified using the diversity panel will be combined with associations I previously identified using a recombinant-inbred population (Lucas et al., 2012a) to identify SNP haplotypes associated with tolerance to heat during reproductive development. These trait-associated regions will also be compared to knowledge of other trait-associated regions including seed size (unpublished), resistance to foliar thrips (Lucas et al., 2012b), and resistance to fungi (Pottoroff et al., 2012; Muchero et al., 2011). Haplotype variation at heat tolerance associated regions will be assessed by surveying previously genotyped materials. An index weighted in favor of heat tolerance will be developed to calculate genome estimated breeding values for lines yet to be phenotyped. Lines with the highest breeding values will eventually be tested and incorporated into a mating design capable of stacking trait determinants. Broader diversity provided by an unstructured population will provide a more comprehensive assessment of allelic variation contributing to the inheritance of tolerance to heat when compared to a bi-parental population. Such a design would facilitate the discovery and tagging of novel trait-determinants. This project will also aim to capture favorable allelic diversity using marker-assisted approaches to selection including genomic selection and marker-assisted backcrossing. If relatively few genes with major effect are identified a backcrossing approach will be pursued to combine heat tolerance into high-quality grain and biotic stress resistant backgrounds. If several genes contributed by several sources with minor phenotypic effects are identified genomic selection will be designed and pursued in order to breed a variety with the highest predicted breeding values based on known marker-trait associations. Twelve milestones will be used to verify the project is on schedule and to assure that objectives are being met. The targeted timeframe for the completion of these milestones within the life of the funded project are provided in TABLES 1 and 2 for fiscal years 2014 and 2015, respectively. Milestones for Objective 1 are those concerning professional development which includes experimental design, networking, and communication of findings and strategy of the project. Milestones for Objective 2 contribute to the development of technical competence by primarily focusing on the utilization of genomic technologies to help develop new crop varieties capable of enhanced production in marginal environments typically affected by unpredictable climates. *Milestones for Objective 1 1a) Design critical elements of a modern plant breeding scheme. 1b) Attend and participate in conferences, including PAG and CSSA meetings in 2013 - 2015. 1c) Communicate research strategy and findings by publication and presentation. Milestones for Objective 2 2a) Conduct a greenhouse trial using a diversity panel to measure agronomically important traits. 2b) Utilize service providers to obtain genotype data. 2c) Identify and account for population structure of the diversity panel. 2d) Identify marker-trait associations through GWAS. 2e) Reconcile knowledge with previous association studies. 2f) Describe genomic regions of related crops likely to harbor trait determinants. 2g) Plant parents for mating, make crosses, and advance to F2. 2h) Make selections based on genotype knowledge. * See original application for timeline of milestones.