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.
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.
This report documents progress for Project Number 3072-21220-008-00D, which started in January 2018 and continues research from Project Number 3072-21220-007-00D, entitled “Development of Improved Peanut Cultivars and Germplasm for the Southwest Peanut Region of the United States”. Progress was made toward the completion of all objectives. For Objective 1A, both the Peanut Genomics Initiative (PGI) RIL and Sclerotinia marker RIL populations are undergoing year 2 of phenotyping for resistance to Sclerotinia blight. Genotyping of the Sclerotinia marker RIL population has begun. Also, under Objective 1A, we made progress in screening the U.S. peanut mini-core in the field for resistance to Sclerotium rolfsii. Moderately low levels of disease were observed, allowing the identification of susceptible genotypes. However, high levels of web blotch, caused by Phoma arachidicola, were observed in 2017 and 39 accessions exhibited high levels of resistance. Progress towards completion of Objective 2A includes conducting five (5) separate studies on advanced breeding lines to determine agronomic potential. These included the Uniform Peanut Performance Test (UPPT), Oklahoma Peanut Variety Trials, and Advanced Line Disease Trials. Early generation breeding lines (F2-F5) were also evaluated in the breeding nursery (600 entries total). For Objective 2B, a drought resistance study of the U.S. mini-core collection was initiated in 2017 using replicated trials in Oklahoma, Texas and Virginia. Data were collected manually and with high-throughput methods such as unmanned aerial vehicle (UAV) and ground-based platforms equipped with various sensors. A subset of twenty contrasting mini-core accessions were identified for use in more detailed experiments to find genetic markers associated with drought resistance and to validate high-throughput technologies. For Objective 3, year one of field work on the testing of the U.S. mini-core collection for peanut smut resistance has been completed and phenotyping of pods is currently underway. New entries that will replace eliminated susceptible genotypes are currently being readied for shipment to Argentina.
1. Release of Contender peanut cultivar. Virginia-type peanuts are grown on approximately 35% of peanut acres in Oklahoma and Texas and a large percentage of those harvested enter the U.S. export market, which has different pod size distribution requirements than the domestic market. The high oleic cultivar VENUS, released by this program in 2016, is currently being produced and marketed domestically, but it does not consistently meet export market preferences. Therefore, Contender, which has larger percentage of extra-large kernels (ELK), pods and seed than VENUS, was developed and released. The cultivar Contender is unique among cultivars developed for the Southwestern U.S. due to its enhanced market quality characteristics, which include large, bright pods averaging 9 per ounce, and large seed size averaging 104 g/100 seed. Contender was developed for optimal performance in Oklahoma and Texas, and production of this cultivar will provide producers with Virginia-type peanuts that can be sold into export, increasing their marketing options and the U.S. economy by an estimated $20M annually.
Chamberlin, K.D., Puppala, N. 2018. Genotyping of the Valencia peanut core collection with a molecular marker associated with Sclerotinia blight resistance. Peanut Science. 45(1):12-18.