1a. Objectives (from AD-416)
The long-term objective of this project is to improve the genetics of peanut for disease resistance and the oleic acid content of oil. Objective 1. Develop peanut germplasm that is high-oleic in nature with improved resistance to Sclerotinia blight and southern blight. Objective 2. Develop molecular markers for peanut associated with resistance to Sclerotinia blight and southern blight. Objective 3. Develop improved methodology to characterize the reaction of Sclerotinia minor and Sclerotium rolfsii on inoculated peanut germplasm and breeding lines under greenhouse conditions.
1b. Approach (from AD-416)
Parental lines being used in such crosses include Arachis hypogaea L. cultivars, advanced breeding lines, and plant introductions (PIs) with demonstrated Sclerotinia disease resistance and high oleic acid content. New and existing potential parent lines with high oleic acid content are continually tested in the greenhouse and field plots for resistance to Sclerotinia blight and southern blight and are readily available for use in the peanut breeding program. Included in our annual screening of germplasm for disease resistance are cultivars, breeding lines, and germplasm accessions. Also, collaborators include the curator of the U.S. peanut germplasm collection as well as other breeders who are continually evaluating accessions for value added traits. Molecular markers for Sclerotinia resistance will be identified and verified by phonotypic reaction.
3. Progress Report
The long-term objective of this project is to improve the genetics of peanut for disease resistance and the oleic acid content of oil. Progress towards attaining that objective was substantially made when this program released a new high oleic runner type cultivar, "Red River Runner". This new variety has acceptable resistance to Sclerotinia blight, excellent oil chemistry and sensory attributes, acceptable yield and superior grade which will increase the peanut producers' profit margin by $50-$100 per acre. Further progress will be made by the development of a superior high oleic Spanish peanut breeding line that has been identified and targeted for release in 2013. Additionally, advanced breeding lines with improved genetics for the high oleic trait as well as resistance to Sclerotinia blight are now in their third year of performance trials, and these trials have been expanded to include 4 locations in Oklahoma and the national Uniform Peanut Performance Test (UPPT). Analysis of the results of year 2 trials allowed the identification of breeding lines for further advancement, and also resulted in the removal of poor performing lines from the program. We are using a newly developed non-destructive technique using capillary electrophoresis to determine the concentration of oleic and linoleic acid in a single peanut seed and are currently developing a technique for high throughput sample processing using a refractometer. This technique will allow rapid screening of early generation breeding lines for those individual seeds possessing the desired high oleic acid trait while maintaining sample integrity. The development of new high oleic Virginia market-type lines with resistance to Sclerotinia blight has resulted from this process, and coupled with generation increase in the Puerto Rico Winter Nursery has allowed those lines to enter advanced trials earlier than expected. Progress was also made toward placing the molecular marker for Sclerotinia blight resistance on the tetraploid peanut map. Genotypic and phenotypic data from one mapping population was gathered, and another population is currently being generated (now in the F2:F4 stage of development). Due to an unfortunate natural disaster, much of the original population was lost.
1. Release of "Red River Runner" peanut. Peanut producers in the southwestern U.S. are in need of peanut varieties that reduce their input cost and/or produce a more desirable (by the industry) product. Cooperative research between ARS, Texas AgriLife Research, and Oklahoma State University resulted in the release of a superior runner-type peanut that will increase profits for producers by $50-$100 per acre, due to its superior seed quality. Red River Runner is high in oleic acid, has acceptable disease resistance and yield, and consistently out-grades other varieties by 3-5 percentage points. Peanut producers will benefit by producing Red River Runner because it will consistently increase their profit margin.
2. Identification of new germplasm with potential resistance to Sclerotinia blight. Due to the nature of cultivated peanut genetics (narrow genetic base), few sources of resistance to Sclerotinia blight are available for breeding programs and new sources are always needed. The molecular marker discovered by this project, that is linked to Sclerotinia blight resistance, was used to screen the ICRISAT peanut mini-core collection and was successful in identifying 67 accessions spanning hypogaea, vulgaris, and fastigiata botanical varieties as potential new sources of Sclerotinia blight resistance. Peanut breeders, and ultimately the peanut producer, will benefit from this accomplishment because new sources of resistance to Sclerotinia blight will be incorporated into new peanut varieties that are released for production.
3. Improvement of greenhouse screening for Sclerotinia blight. Acceleration of a plant breeding program in general depends on the availability of realistic greenhouse protocols to quantify resistant reaction to plant pathogens as a supplement to field evaluation for purposes related to release of resistant germplasm and breeding lines. A greenhouse protocol was improved by defining the shortest time (days) at post-inoculation with the Sclerotinia fungus where 100% relative humidity is required for attaining a realistic, not overwhelming, disease progress over a 7-day period of incubation. This protocol will potentially shorten the time required to develop resistant peanut cultivars by 2 years. This technology will benefit peanut breeders and Plant Pathologists.
Barkley, N.L., Chamberlin, K.D., Wang, M.L., Pittman, R.N. 2011. Genotyping and fatty acid composition analysis in segregating peanut (Arachis hypogaea L.) populations. Peanut Science. 38:11-19.