Location: Water Management and Systems Research
Project Number: 3012-13210-001-001-N
Project Type: Non-Funded Cooperative Agreement
Start Date: Oct 1, 2019
End Date: Sep 30, 2022
Objective:
Characterize the genetic architecture of hydraulic performance under cold temperatures in sunflower. The proposed work includes robust phenotypic characterization of cultivated and wild sunflowers under controlled and field conditions, genome-wide mapping to identify candidate genes that are associated with agriculturally relevant phenotypic traits, and targeted approaches for specific genes likely to orchestrate adjustments that confer high productivity in challenging environments.
Approach:
We will utilize the Sunflower Association Mapping (SAM) population and also a set of 22 wild H. annuus accessions originating from the species’ native range. Plants will be grown from seed using eco-physiological approaches in two phases. Initially, all accessions will be grown to seedlings in triplicate in climate-controlled growth chambers at the USDA–ARS Fort Collins, CO. We will assess hydraulic architecture (e.g., conduit diameter and frequency), hydraulic function at low water potential (e.g., cavitation resistance), and growth, as well as the plasticity of these traits in response to cold temperatures. To characterize phenotypic plasticity in the H. annuus accessions, we will grow one set of seedlings at warm (25°C) air temperature and an additional set of seedlings will be grown at cold (8°C) air temperature under otherwise similar conditions. Large-scale field trials will be performed with USDA–ARS researchers in Fargo, ND. We will translate findings from initial studies in controlled environments to performance in the field. At this time, we will also implement methods for high-throughput phenotyping of relevant traits, which will be developed based on findings from studies under controlled conditions. Furthermore, we will characterize how phenotypic traits of seedlings correlate with relevant agricultural traits (e.g., seed quantity and quality) of mature plants. Genotypic variation across the SAM population and wild accessions will be assessed using whole-genome sequence libraries previously sequenced with Illumina HiSeq from 100-bp reads and assembled by collaborators. We will define genotypic variation as single-nucleotide polymorphisms (SNPs) based on available reference sequences from the HA412 genome. Genome-wide association mapping will use these SNPs as the genetic basis to which phenotypic data can be compared. In addition, we will use targeted approaches to investigate candidate genes, such as those encoding DREB transcription factors, that coordinate whole-plant responses to cold temperatures. In addition to obtaining the protein sequences of these genes in all accessions, we will look for SNPs in the regulatory elements of DREB-like genes that could serve as a basis for differential expression. We will also perform whole-genome searches of all accessions to identify copy-number variation as well as variation of the DREB regulon—target genes containing the DRE (ACCGAC) and CRT-element (GCCGAC) sequences to which DREB transcription factors bind.
