Location: Peanut and Small Grains Research Unit
2021 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 and/or early leaf spot 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 and/or early leaf spot 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
Progress was made on all three objectives. For Subobjectives 1A and 1B, progress was made by completing the phenotyping of 2 recombinant inbred line (RIL) populations for resistance to Sclerotinia blight. Each population member was also genotyped using the Axiom single nucleotide polymorphism (SNP) array developed for tetraploid peanut. Correlation of phenotypic and genotypic data was completed, and analyses identified at least 3 quantitative trait loci (QTL) strongly associated with Sclerotinia blight resistance. Further steps to sequence the population and develop a Kompetitive allele specific PCR (KASP) marker system to screen for Sclerotinia blight resistance in breeding populations and/or germplasm collections are in progress.
For Subobjective 2A, field evaluation of all breeding lines was completed. Breeding lines were identified for all generations that will be moved forward to further testing and advanced line performance trials. Greenhouse testing of F1 and F2 hybrids was completed and selections were made to advance to field testing. A new high-oleic Virginia peanut cultivar, Comrade, was developed in cooperation with North Carolina State University and released. This new cultivar has enhanced market quality due to its high percentage of super-jumbo pods. Plant Variety Protection (PVP) approval is pending. Progress was also made on Subobjective 2C, related to the effects of cover and rotation crops on peanut pod rot. The first year of winter cover crop treatments and summer rotation crops was planted after soilborne inoculum was increased with a pod rot-susceptible genotype.
Progress was made for Subobjectives 3A and 3B, year 3 of phenotyping for resistance to peanut smut was completed. To date, we have evaluated 209 peanut genotypes comprised of germplasm accessions, breeding lines, and cultivars, in the field for resistance to T. frezzii. Among those evaluated for three years, 8 entries appeared immune to the disease, averaging 0% incidence. Because the germplasm used in this study was purified by single seed descent and increased before evaluation, these smut-resistant entries are a valuable resource for peanut breeding programs. The 8 entries are currently being used to incorporate smut resistance into elite breeding lines to develop smut-resistant cultivars suitable for U.S. production. These breeding lines are being advanced for further testing and seed will be increased prior to evaluating for smut resistance in Argentina. In addition, the X-ray system for phenotyping peanut smut is currently being constructed.
Accomplishments
1. Release of 'Comrade' peanut. Approximately 35% of the peanut acreage in Oklahoma and Texas are Virginia-type peanuts. Most of the southwestern Virginia peanuts enter the U.S. export market, which requires larger pods than the domestic market. The high oleic cultivar Contender, released by ARS in 2019 and produced and marketed domestically, does not have the high percentage of super jumbo pods attractive to foreign markets. Comrade, the newly released Virginia peanut by ARS researchers in Stillwater, Oklahoma, in collaboration with colleagues at North Carolina State University, fills this market void. Comrade has significantly more super jumbo pods than Contender (47% compared to 11%), while matching Contender’s high oil quality, yield, and seed grade. Comrade peanut will allow producers in the Southwest to be highly competitive in the export market and increase producer profit by $3-5M, annually.
Review Publications
Kulkarni, R., Chopra, R., Chagoya, J., Simpson, C.E., Baring, M.R., Hillhouse, A., Puppala, N., Chamberlin, K., Burow, M.D. 2020. Use of targeted amplicon sequencing in peanut to generate allele information on allotetraploid sub-genomes. Genes. 11(10). Article 1220. https://doi.org/10.3390/genes11101220.
Bennett, R., Harting, A.D., Simpson, C.E., Tallury, S.P., Pickering, A.B., Wang, N., Dunne, J.C. 2021. A note on a Greenhouse evaluation of wild Arachis species for resistance to Athelia rolfsii. Peanut Science. 48(1):40-48. https://doi.org/10.3146/PS20-21.1.
Bennett, R.S., Rodriquez, A.V., Baldessari, J.J., Chamberlin, K.D., Payton, M.E., Wang, N. 2021. A note on the association between Thecaphora frezzii infection and peanut pod density. Peanut Science. 48(1):54-60. https://doi.org/10.3146/PS20-27.1.
Otyama, P.I., Kulkarni, R., Chamberlin, K., Ozias-Akins, P., Chu, Y., Lincoln, L.M., MacDonald, G.E., Anglin, N.L., Dash, S., Bertioli, D.J., Fernandez-Baca, D., Graham, M.A., Cannon, S.B., Cannon, E.K.S. 2020. Genotypic characterization of the U.S. peanut core collection. G3, Genes/Genomes/Genetics. 10(11):4013-4026. https://doi.org/10.1534/g3.120.401306.
