Location: Crop Genetics and Breeding Research2010 Annual Report
1a. Objectives (from AD-416)
The long term objective for this project is the development of peanut germplasm with resistance to economically significant biotic and abiotic stresses. Over the next five years, we will focus on the following specific objectives: 1) Develop peanut germplasm with resistance to preharvest aflatoxin contamination; 2) Develop peanut germplasm with high oleic acid and resistance to the peanut root-knot nematode and tomato spotted wilt virus; 3) Develop peanut germplasm with improved drought resistance; and 4) Devise strategies to assess the genetic diversity for traits that will be important for the economical production of biodiesel from peanut.
1b. Approach (from AD-416)
Breeding populations will be developed by hybridizing high yielding cultivars with sources of resistance to preharvest aflatoxin contamination (1) and sources of resistance to drought (3). These populations will be evaluated under field conditions with drought and heat stress imposed by covering the entire test area with a mobile greenhouse. Aflatoxin contamination of the subsequent yield will be determined using the immunoaffinity column fluorometer method. Progeny will be selected based on relatively low aflatoxin contamination (1) and/or relatively high pod yields (3). 2) Breeding populations will be developed by hybridizing cultivars with high oleic acid with high yielding breeding lines with resistance to the peanut root-knot nematode and tomato spotted wilt virus. These populations will be tested for resistance to nematodes using a greenhouse screening technique. Progenies exhibiting nematode resistance will be field tested for virus resistance, and resulting selections will be analyzed for fatty acid composition. 4) A revised and updated core collection will be used to access genetic diversity for important characteristics for economical productions of biodiesel (pod yield, meat content, percent oil, and disease resistance).
3. Progress Report
Sources of resistance to preharvest aflatoxin contamination (PAC) were hybridized with high yielding cultivars in a continuing effort to develop breeding populations for selection. Over 100 late generation breeding lines were grown under heat and drought stressed field conditions and evaluated for aflatoxin contamination. Several showed at least a 70% reduction in aflatoxin contamination compared to susceptible controls. Some of these lines also had high yield and good resistance to tomato spotted wilt virus (TSWV). Sources of resistance to nematodes were hybridized with high yielding breeding lines with resistance to TSWV in a continuing effort to develop breeding populations for selection. Over 1000 late generation breeding lines were tested for nematode resistance in greenhouse trials, and for TSWV resistance in field studies. We identified over 100 breeding lines having resistance to both pathogens. Marker assisted selection was utilized in a backcrossing program and in segregating populations to develop breeding lines with high oleic acid and resistance to nematodes and TSWV. Sources of resistance to drought were hybridized with high yielding cultivars in a continuing effort to develop breeding populations for selection. Over 50 late generation breeding lines were grown under drought stressed field conditions and evaluated for pod yield. Several showed high yield relative to susceptible controls. Some of these lines also had high yield and good resistance to TSWV and PAC. Since the initial peanut core collection was selected, 821 accessions have been added to the U.S. germplasm collection of peanut. We evaluated these accessions for morphological characteristics and disease resistances and selected 151 representative accessions to add to the peanut core collection. Eighteen of these were added to the peanut mini core collection.
1. Breeding for Improved Fatty Acid Composition. Fatty acid composition is an important characteristic for oil seed crops such as peanut. High oleic fatty acid composition is favored because it confers health benefits and improved oil stability. The high oleic trait in peanut is controlled by two recessive mutations. Peanut has a normal oleic fatty acid composition unless both mutations are present. Plant breeding efficiency would be improved if we could identify the normal oleic peanut genotypes that contained one of the mutations. We developed a molecular marker that can identify those genotypes, and used it to survey the U.S. peanut germplasm collection for the frequency and distribution of the mutated gene. We discovered that almost one-third of the collection contained the mutant gene, and found that this mutation was much more prevalent in some area of the collection, and did not exist in other areas. This information will be very useful to plant breeders in making decisions on parents to use in variety development.
2. Drought Tolerant Peanut. The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought stress. Our objective was to examine the root growth of some drought tolerance peanut lines when grown under different levels of drought stress. Eleven peanut lines were grown in three soil moisture levels for two years. Root length was determined using a scanner and computer soft ware at three sampling dates. Pod yield was also recorded at harvest. Five of the peanut lines responded to increasing drought stress by increase rooting at deeper soil levels. Information on the ability of drought resistant peanut lines to alter root systems contributing to high yield under drought conditions might reveal avoidance mechanisms and could result in the development of improved breeding strategies for developing drought resistance in peanut.
Songsri, P., Jogloy, S., Vorasoot, N., Akkasaeng, C., Patanothai, A., Holbrook Jr, C.C. 2009. Root distribution of drought-resistant peanut genotypes in response to drought. Journal of Agronomy and Crop Science. 194:92-103.