Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
(N/A)
Non Technical Summary
The proposed research aims at providing genetic solutions to mitigate the limitations to producing alfalfa on acid soils. It addresses the Alfalfa Seed and Alfalfa Forage Systems Research Program (AFRP) priority area # 1: Increasing alfalfa forage and seed yields and forage quality through improved management practices, plant breeding, and other strategies to reduce biotic and abiotic stresses and costs of production. Despite the efforts made over several decades to understand the mechanisms of low pH and Al stress in alfalfa, nothing has translated into cultivars with acceptable yield and persistence in field conditions, leaving growers to rely on costly management or avoid growing alfalfa. The proposed project integrates research and extension objectives and represents a multi-state collaboration of four states from the Southeast (Georgia, Alabama, and South Carolina) and North Central (Minnesota). This project uses a diverse germplasm panel of 200 accessions to 1) identify QTLs or genes associated with yield, low-pH, and high-Al tolerance across four different locations. 2) Identify the top five germplasms for each region for breeding to stack low-pH tolerance and yield genes. 3) Improve stakeholder knowledge of the challenges to grow alfalfa on acid soils and the value of low-pH tolerant cultivars through Extension programming. The alfalfa industry and producers will benefit from this research through access to the germplasm and resources developed in this project to develop elite alfalfa cultivars and expand alfalfa acreage to regions with acid soils, and provide profitable economic opportunities for rural communities.
Animal Health Component
50%
Research Effort Categories
Basic
15%
Applied
50%
Developmental
35%
Goals / Objectives
The overarching aim of the proposed project is to identify alfalfa germplasm with optimal yield and stand persistence in low pH soils and develop genomic resources and strategies to improve the resilience and sustainable production of alfalfa in regions with low pH soils in the USA in order to expand alfalfa acreage.The specificgoals of the project are:1. Identify QTLs or genes associated with yield, low-pH, and high-Al tolerance across different environments.2. Identify the top five germplasms for each region based on the differential acid soil performance index, taking into consideration regional adaptation, forage yield, and persistence traits.3. Pre-Breeding to create new populations and novel germplasm and incorporate low pH tolerance in elite germplasm.4. Improve stakeholder knowledge and awareness of challenges and management to grow productive alfalfa on acidic soils and the value of low pH-tolerant cultivars by developing regional workshops and field days, extension publications, and online media.
Project Methods
Experimental ApproachObjective 1: Identify QTLs and genes associated with yield, low-pH, and high-Al tolerance across different environments using GWAS A GWAS panel of 200 germplasm accessions that underwent tandem selection for yield and stand count in low pH, followed by selection for yield under neutral pH among 1,200 accessions evaluated for four years in a field with soil pH of 4.9 and Al content of 87 mg Kg-1 in GA will be used in this study, in addition to 10 commercial checks (Figure 4). One hundred twenty-eight clones from eight plants within each accession will be propagated by stem cuttings (eight clones per replication, two replications under low pH, and two replications under adjusted pH) for testing in four locations (Georgia, Alabama, South Carolina, and Minnesota). The Georgia location will be planted in November 2025 at the University of Georgia J.P.C. Research and Education Center on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludults) with a pH of 5.2. The control set will be planted at the same location, where the surface soil pH has been adjusted to 7.0 to an 8-inch depth using lime. The experimental design will be a randomized complete block (RCBD) with two replications. Eight plants will be transplanted in each row with a spacing of 7" between plants in a row and 2 feet between the rows. The same layout will be used at the four locations.Differential Acid Performance Index (DAPI): Each space-planted row plot with eight plants will be harvested at 10 to 25% bloom with intervals of 25 to 30 days between cuts through the growing season. Dry weights will be determined by drying samples in a convection dryer. Relative yield (RY) expressed as the ratio (Yield in adjusted pH - Yield in low pH)/ Yield in adjusted pH) will be used for non-linear regression analysis to detect site, year, and genotype effects on the relationship of RY with pH. Tolerance of the alfalfa accessions to low pH soil will be assessed as a Differential Acid Performance Index (DAPI) similar to Howeler (1991), as follows: DAPI = (Yl × Ya)/(µl × µa) where: Yl = yield in low pH condition, Ya = yield in adjusted pH condition, µl = average yield in low pH condition, µa =average yield in adjusted pH condition.Identify QTLs associated with low-pH tolerance and biomass yield across different environments using genome-wide association studies (GWAS), genomic prediction, and machine learning.Genotyping using the universal genotyping platform from Breeding Insight (BI):The selected 200 germplasm accessions were genotyped by the universal 3,000 SNPs and will be genotyped by an additional 3,000 SNPs by the end of 2023 for genome-wide association mapping, marker-assisted selection, and genomic selection in alfalfa.Association analysis: The phenotypic data consisting of forage yield, fall dormancy, forage quality, cold tolerance, and stand count in low pH, in addition to the acid soil adaptation index of the GWAS panel of 200 accessions, will be analyzed across the four locations and will be evaluated for geospatial autocorrelation for quality control.Objective 2: Identify the top five germplasm for each region based on the differential acid soil performance index, forage yield and persistence traits. The field data generated from the four locations will be used to investigate the effect of the environment on the response to low soil pH and fall dormancy of the 200 germplasm accessions, together with 10 commercial checks, along a gradient spanning latitudes from Alabama to Minnesota. A cross-location and years analysis will be conducted on the combined data (locations × years). This information will be used to streamline information for alfalfa cultivar development for low pH soils in different environments. Identification of genotype × environment (G×E) interactions of low-pH, yield, and fall dormancy will assist alfalfa breeders in decision-making to develop cultivars that are widely adapted or with region-specific adaptation.Genomic prediction to select the best-performing parents and advance elite germplasm: Genomic prediction models will be applied to conduct estimates of genomic breeding values and selection of the best genotypes to advance for pre-breeding and incorporation of low pH tolerance in adapted germplasm using the various data types collected from this proposal.Objective 3: Pre-breeding to create new populations and novel germplasm and incorporate low pH tolerance in elite germplasm.The execution of this objective will continue beyond the three-year timeline of this proposal. At the end of the evaluation cycle, the surviving plants from each of the top 5 selected genotypes at each location will be dug and multiplied by stem cuttings to increase the number of plants for intermating in bee cages. Initially, each selection will be seed-increased individually in bee cages, and the seed is saved for potential crosses and for sharing with interested researchers. In a second phase, the 5 selections from each location will be intermated in bulk to create new half-sibs that will be further evaluated and advanced through recurrent selection to generate new adapted parental germplasm and low pH-tolerant cultivars. The selections will also be intermated with elite germplasm within each region to incorporate low pH tolerance into the existing adapted elite germplasm.Objective 4: Improve stakeholder knowledge and awareness of challenges and management to grow productive alfalfa on acidic soils and the value of low pH-tolerant cultivars by developing regional workshops and field days, extension publications, and online media. Extension faculty in Alabama and South Carolina will collaborate to create or update print and web-based educational resources related to alfalfa production in low-pH soils. Two regional Extension publications will be written on alfalfa establishment and production related to acidic Southeastern soils. One to two on-farm demonstrations will be established in each state. These demonstrations will be used to promote the novel cultivars developed during this grant (Years 2 and 3) and provide field day locations, and gather producer testimonials. We will also develop a mobile alfalfa demonstration that will include 3 - 4 alfalfa varieties (including conventional and low-pH tolerant) planted in acidic soil. This demonstration can be taken to multiple venues throughout the Southeast (e.g., Sunbelt Ag Expo, State Cattleman's Conventions, American Forage and Grassland Council Meeting) to demonstrate and promote the cultivars developed as part of this grant. In Years 2 and 3, videos will be developed to highlight concepts and experiences from researchers, Extension agents, and producers with experience managing alfalfa in acidic soils. These videos will be released during National Forage Week (June of each year) as part of the national campaign to promote forages in the US.Producer workshops will be conducted using already established, multi-state programs (i.e., Alfalfa in the South) to develop regional and statewide workshops to promote alfalfa production in the Southeast. Since 2018, the "Alfalfa in the South Program" has provided in-person and virtual Extension workshops for producers related to alfalfa cultivar selection, soil fertility management, and harvest management.