Location: Peanut and Small Grains Research Unit
2019 Annual Report
Objectives
The long-term objective of this research is to develop and release high oleic peanut cultivars with superior oil chemistry, disease resistance, and agronomic performance. Over the next 5 years this research proposal will address the following objectives:
OBJECTIVE 1: Identify new sources of resistance to industry-relevant peanut pathogens, and use improved marker assisted selection (MAS) methods and QTL analyses to incorporate those genes into existing and new peanut cultivars.
Subobjective 1A: Phenotype existing recombinant-inbred line (RIL) populations and the minicore collection from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) for Sclerotinia blight resistance and the U.S. mini-core germplasm collection for southern blight resistance in field trials.
Subobjective 1B: Genotype existing RIL populations and the U.S. and ICRISAT mini-core germplasm collections using a 48K SNP micro-array chip for tetraploid peanut; genotype existing RIL populations with SSR markers associated with Sclerotinia blight resistance. Analyze phenotypic and genotypic data collected in Subobjectives 1A and 1B to identify possible QTL for disease resistance and design molecular markers to be used in MAS breeding.
OBJECTIVE 2: Develop improved peanut varieties with superior genetic improvements and agronomic and plant health traits, including disease resistance, early maturity, elevated yield, oil, drought tolerance, and seed quality.
Subobjective 2A: Develop and release elite high-oleic, high-yielding, and/or early maturing runner, virginia, and spanish peanut cultivars with superior resistance to Sclerotinia blight, southern blight, drought and/or pod rot that are adapted for production in the SW United States.
Subobjective 2B: Phenotype U.S. peanut mini-core for drought tolerance and plant canopy architecture.
Subobjective 2C: Determine effects of cover crop mixtures and rotation crops on Pythium pod rot in susceptible commercial cultivars.
OBJECTIVE 3: Discover and characterize new genes from cultivated and wild Arachis species in the U.S. National Peanut Germplasm Collection for resistance to existing and emerging diseases, such as peanut smut.
Subobjective 3A: Phenotype the U.S. mini-core collection and other germplasm for resistance to peanut smut and develop new methodologies for high-throughput screening of peanut pods for the presence of peanut smut.
Subobjective 3B: Conduct crossing experiments between smut resistant germplasm and U.S. peanut cultivars to develop and release new smut resistant peanut varieties suitable for production in the Southwestern U.S.
Subobjective 3C: Phenotype wild Arachis species for resistance to Sclerotium rolfsii.
Approach
Objective 1: Two RIL populations (CAP and Sclerotinia marker) and germplasm collections will be evaluated for Sclerotinia blight resistance in separate field experiments for three years. The U.S. mini core collection will also be evaluated for Sc. rolfsii resistance for three years. Genotyping of RIL populations will also be conducted using the Axiom Arachis Custom Array for tetraploid peanut, covering 48K SNPs as well as SSR markers identified as flanking the region reported as a possible QTL for Sclerotinia blight resistance. Phenotype and genotypic data will be combined for quantitative trait loci (QTL) mapping. Multiple methods for QTL detection will be implemented including interval mapping, and composite interval mapping. Phenotypic coefficients of variation and heritabilities also will be estimated. Genetic maps will be constructed.
Objective 2: Parental lines being used in such crosses include Arachis hypogaea L. cultivars, advanced breeding lines, and plant introductions (PIs) with demonstrated disease resistance and/or drought tolerance. For each cross performed, a modified bulk selection breeding method will be used. Breeding lines will be advanced annually, screening for disease resistance, oil composition, and agronomic performance. F7 generation ines will be entered into advance performance trials such as the Oklahoma Peanut Variety Tests, advanced line disease resistance tests and the national Uniform Peanut Performance tests and tested by the USDA ARS Peanut Market Qualtiy lab before release. The U.S. mini-core collection will be evaulated for drough tolerance and canopy architecture by monitoring performance under water deficit irrigation and collecting data on leaf wilting, paraheliotropism, normalized difference vegetation index, upper canopy temperature, flower abundance, SPAD chlorophyll stability, and descriptive canopy traits. The canopy traits will be collected using a LiDAR camera. A four-year experiment to determine the effect of cover crops on pod rot persistence will be conducted. Experimental treatments will include combinations of three winter cover crops and two rotation crop sequences.
Objective 3: The U.S. mini-core collection and other selected genotypes will be evaluated for at least 3 years in T. frezzii-infested fields in Manfredi, Argentina. To incorporate newly found smut resistance into adapted peanut lines, crossing and early generation breeding line and cultivar development will be conducted. Prototypes of a new smut screening technology will be developed and shipped to Argentina and test. Seeds will be removed from pods and replaced with talcum powder to simulate T. frezzii spores. Acoustic measurements will be taken from twenty pods of each treatment. To discover new southern blight resistance among wild Arachis species, experimental treatments will include a total of 62 accessions representing 26 species of Arachis, in addition to the susceptible cultivar Florunner.
Progress Report
Subobjective 1A: Progress was made in continuing to increase seed from single-plant selections of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) mini-core collection in the field and greenhouse. The seed will be used to screen for Sclerotinia blight resistance in the field in 2020, and plants will be genotyped to identify genetic markers for resistance. Furthermore, the second year of phenotyping two recombinant inbred line (RIL) populations for resistance to Sclerotinia blight was completed, and both populations were planted in 2019 for a third year of testing.
Subobjective 1B: Two RIL populations were genotyped using the 48K SNP microarray developed for tetraploid peanut. Analysis of data identified potentially useful single-nucleotide polymorphisms (SNPS) and indicated a third year of phenotypic data was necessary to ensure SNP correlation with resistance to Sclerotinia blight.
Subobjective 1B: Five new advanced breeding lines (1 spanish and 4 runner types) were selected to enter advanced disease and performance trials. One runner-type was selected to for entry into the 2019 Uniform Peanut Performance Test. Progress was made in selecting elite lines advance to 2019 F3-F6 breeding nursery testing. Crosses were initiated to incorporate early leaf spot resistance and early maturity into cultivars currently being produced in Oklahoma and Texas.
Subobjective 2B: The second year of a 3-year, tri-state (Oklahoma, Texas, and Virginia) drought resistance study of the U.S. mini-core collection was conducted. Data were collected manually and with high-throughput methods such as unmanned aerial vehicle (UAV) and ground-based platforms.
Subobjective 2C: The first year of a 4-year study examining the effect of winter cover crops and summer rotation crops on Pythium pod rot was completed.
Subobjective 3A: Year 2 of phenotyping U.S. peanut germplasm in Argentina for resistance to peanut smut was completed. Fourteen new potential sources of smut resistance were identified and retained for testing in 2019-2020. Additionally, resistance was confirmed in 22 out of 35 entries retained from Year 1 of testing. Data on pod density were collected from nearly 2000 pods in Argentina. A considerable proportion of T. frezzii-infected pods were only partially infected, so more efficient methods for phenotyping smut resistance will be conducted using single pods, not bulked pod samples.
Subobjective 3B: Crosses were initiated with materials found to be potentially resistant to peanut smut in Argentine phenotyping trials. Approximately 300 F1 hybrid seed have been produced thus far. Back-crossing experiments with recurrent parents have been initiated.
Subobjective 3C: Progress was made by vegetatively propagating wild species of Arachis for Sclerotium rolfsii resistance studies. Disease screening requires many plants, but most wild Arachis species produce few seeds in the greenhouse in our environment.
Accomplishments
Review Publications
Chamberlin, K.D., Bennett, R.S., Damicone, J.P. 2019. Release of 'Contender' Peanut. Journal of Plant Registrations. 13(2):139-142. https://doi.org/10.3198/jpr2018.09.0060crc.
Yuan, H., Bennett, R.S., Wang, N., Chamberlin, K.D. 2019. Development of a peanut canopy measurement system using a ground-based LiDAR sensor. Frontiers in Plant Science. 10:203. https://doi.org/10.3389/fpls.2019.00203.
