Performing Department
(N/A)
Non Technical Summary
The American Peanut council has identified drought as the top challenge facing the peanut industry as only 35% of growers in the U.S. have irrigation capabilities. For this reason, breeding for drought tolerance is paramount for the peanut industry. In previous work, we have identified cultivars that use two different strategies (water spenders and water savers) to maintain high yields under drought. However, the physiological and genetic mechanisms controlling these two strategies are not known. In other crops, these two mechanisms resulted in increased yields under specific environmental conditions. In this project, we will perform detailed physiological and RNA-sequencing experiments in peanuts under two rain-out shelter facilities to fully understand the physiological and genetic mechanisms of water-saver and water-spender drought-tolerant cultivars. In addition, we will use a RIL population derived from the cross of a water saver with a water spender line to find genomic regions (QTL) that relate to water saving or spending strategies and that can be used to breed for drought tolerance using marker-assisted selection. We will also use the data produced in the detailed physiological experiments to modify a peanut model that can predict the performance of each variable type under current and future environments to determine environments that favor one mechanism over another. With this approach, we will facilitate the selection of cultivars with different drought-tolerant strategies that with the help of crop modeling, can be tailored to yield more under different environments in the Southeast U.S.
Animal Health Component
0%
Research Effort Categories
Basic
90%
Applied
10%
Developmental
(N/A)
Goals / Objectives
The long-term goal of this project is to assist breeders in selecting cultivars with different mechanisms of drought tolerance so growers can produce high-yielding peanuts with reduced irrigation or under rainfed conditions and therefore increasing the sustainability of peanut farming. To achieve this objective, we need to better understand the physiology and genetics of "water saver" and "water spender" drought tolerant strategies and by using models, learn where these cultivars may perform better in the Southern United States. For this reason, the supporting objectives of this proposal are:Objective 1: Discover underlying physiological mechanisms of water spender and water saver cultivars.Objective 2: Model water saver and water spender drought tolerant mechanisms to find the best environments to maximize yield.Objective 3: Identifying QTL and probable genes underlying water saving and spender drought tolerant traits.
Project Methods
This study will leverage detailed physiological experiments, transcriptomic data, genomic QTL identification, and process modeling information from a select group of peanut cultivars and a bi-parental population to increase our understanding of mechanisms behind water saver and water spender drought tolerant strategies. First, detailed physiological measurements will be taken in a select number of cultivars in two rain-out shelter locations in Alabama and Georgia to be combined with modeling to identify the ideal locations to maximize long-term yield under different climate change scenarios using this drought tolerant strategies in the peanut belt. Second, a bi-parental population created from the cross of a water saver and water spender drought-tolerant peanuts will be genotyped by next-generation sequencing (NGS) and phenotyped to find the QTLs related to these two drought-tolerant strategies. RNA sequencing from the detailed physiological experiment and from the extremes in the bi-parental population experiments will help to hypothesize which genes may be involved in the control of these two drought-tolerant mechanisms.Objective 1: Discover subjacent physiological mechanisms of water spender and water saver cultivarsObjective 1, Task 1: Grow water-saver and water-spender peanut cultivars under two rain-out shelter environments.Two previously selected water savers (Line-8 and AU-16-28) and two water spender (PI502120 and AU-NPL 17) drought-tolerant cultivars, along with one drought-sensitive cultivar (AP-3) used as a check will be grown under two different rainout shelter environments on the first two years of this grant (Summer 2024and 2025).Objective 1, Task 2: Collect physiological data to understand the underlying mechanisms of water users and water spender drought tolerant cultivars.All the measurements will be performed in both locations (NPL and EV-Smith), therefore in this description, we will not separate between locations. All the measurements performed in Objective 1 will be used in the modeling efforts in Objective 2 and therefore will not be described in that section. To make this section of the approach clearer, the physiological measurements will be divided into 2 different groups:(1) Finding photosynthetic and transpiration limitations or advantages at leaf and canopy level between water user and water saver cultivars.We know that the water-saver cultivars selected for this experiment show half the stomatal conductance compared to water spenders cultivars when measured at midday, however, we do not know if these differences are maintained during the whole day or during the whole season. For this reason, diurnal gas exchange measurements using 4 sets of LI-6800 (LICOR Biosciences, Lincoln Nebraska) will be performed every month during the whole experiment and every two weeks during the drought period (Sanz-Saez et al., 2017; Soba et al., 2020).(2) Studying C partitioning between shoot and root can explain differences in water acquisition and usage between water spender and saver cultivars.Phenological dates including vegetative growth stage (V-stage), date of first flower and first pod, and end of pod addition will be measured to understand how C partitioning changes based on the development stage. Root growth characteristics will be measured during the entire growing season by installing 3 mini-rhizotron accession tubes per plot as performed by Rowland et al., (2015). Root images will be taken with a mini-rhizotron CI-602 (CID Biosciences, Camas, WA) every two weeks, and root length, diameter, and density will be estimated using RootSnap (CID Biosciences, Camas, WA). This data will be used for model calibration and evaluation. In order to estimate aboveground biomass growth during the season, the leaf area index will be measured using an Accu-PAR LP-80 on the same day of root characteristics measurements.Objective 1 Task 3: Comparing RNA expression of water saver peanut lines versus water spenders in response to drought.To find underlying genetic mechanisms of water saver and water spender drought tolerant genotypes, RNA-sequencing will be performed to find differentially expressed genes between cultivars and drought conditions. Leaf samples will be taken in new fully expanded leaves at midday two times after drought (approximately 5 and 10 days after drought initiation) has started in four replications per cultivar.We will sample the first time when the stomatal conductance is reduced a 30% compared to the control (5 days approximately) and the second time when the stomatal conductance is reduced a 60% compared to the control (10 days approximately).Objective 2: Model water saver and water spender drought tolerant mechanisms to find the best environments to maximize yield.Objective 2, Task 1: Modify the CSM-CROPGRO-Peanut model to include water saver and water spender traits in peanut.We will use the CSM-CROPGRO-Peanut model and data collected from the rainout shelters and irrigated controls to test the different hypotheses for water saver and water spender traits. Each of these traits can be controlled by changing model inputs. Each cultivar will be calibrated using one year of data from each location and evaluated using the second year of data from each location. In addition, yield plots (20 feet long, 4-row plots) with the 5 studied cultivars will be placed in two other locations in Alabama (Wiregrass Research and Extension Center, Headland and Gulf Coast Research and Extension Center, Fairhope), one in Georgia (Dawson), and one in New Mexico (Clovis) during year 2 and year 3 to calibrate and evaluate the yield response in different environments.Objective 2, Task 2: Perform spatial modeling to find the best environments to grow water-saver and water-spender cultivars.Spatial modeling will be used to simulate the performance of each cultivar across the peanut belt using 30 years of historical weather data and climate change data for 2050 and 2080.The model will be run for each of the five cultivars on a 1-km grid scale across the peanut belt to develop maps of performance using historical and future weather data.The end result will be maps that show areas where water savers and water spenders have advantages over traditional genetics.Objective 3: Identifying QTL and probable genes underlying water saving and spender drought tolerant traits.Objective 3 3, Task 1: Grow a water saver x water spender recombinant inbred line population under two rain-out shelter environments. Co-PI Chen is currently developing a RIL population from the cross of a water saver (AU16-28) and a water spender (AU-NPL-17) cultivars. By the time of starting this project, we will have an F6 RIL mapping population including 200 RILs. Two hundred F6 RILs, along with the parental lines (AU-NPL-17 and AU16-28) and one drought-sensitive cultivar (AP-3) used as a checkwill be grown under two different rainout shelter environments on the third and fourth years of this grant.Objective 3, Task 2: Phenotyping efforts to find QTLs for water users and water spender cultivars.Parental lines AU16-28 (water saver) and AU-NPL-17 (water spender), differ in their stomatal conductance and carbon isotope discrimination (Δ13C) under drought conditions (Zhang et al., 2022). Therefore, we will phenotype the RIL population resulting from their cross to phenotype at least these traits.Objective 3, Task 3: Find QTLs related to water saver and water spender drought tolerant mechanisms.Genotyping RIL population will be carried out by 3X Illumina sequencing. Plant leaf samples will be collected from greenhouse-grown plants during the third year of the project and stored at -80°C for DNA isolation. Libraries will be sequenced on two lanes of Illumina Novaseq to yield 750 Gb of raw sequence and about 3X coverage per line. Genome-wide SNPs will be called using Khufu (Korani et al., 2021).