2009 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).
Sources of resistance to preharvest aflatoxin contamination 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.
Sources of resistance to nematodes were hybridized with high yielding breeding lines with resistance to tomato spotted wilt virus 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 tomato spotted wilt virus 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 tomato spotted wilt virus.
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 tomato spotted wilt virus and preharvest aflatoxin contamination.
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 41 representative accessions to add to the peanut core collection.
Drought Tolerant Peanut. Unpredictable rainfall creates conditions of drought stress which reduced the yield of peanut in areas throughout the World. Breeding peanut varieties with improved water use efficiency would help in alleviating this problem. The objective of this study was to evaluate a select group of peanut genotypes to identify those with improved water use efficiency. Genotypes with improved water use efficiency were identified. These genotypes should be valuable parents to use in peanut breeding programs. Different mechanisms for improved water use efficiency were also evident. Some genotype had larger root systems for extracting more of the available soil moisture. Other genotypes appear to be able to maintain a higher level of photosynthesis under drought stressed conditions. It may be possible to combine these mechanisms together to develop new peanut varieties with improved water use efficiency.
Nematode Resistance Reduces Severity of Other Diseases. Cylindrocladium black rot (CBR) and the peanut root-knot nematode both cause significant losses to peanut production, and losses are greatest in fields that have both pathogens. USDA-ARS has recently release Tifguard, a variety with resistance to nematodes. The objective of this study was to evaluate the potential impact of nematode resistance on Cylindrocladium black rot disease. The addition of nematode eggs increased Cylindrocladium black rot disease and reduced yield for two nematode susceptible varieties; however, Tifguard did not show increased disease, and there was no yield reduction. Tifguard should be a valuable variety for peanut growers who need to manage both root-knot nematode and Cylindrocladium black rot.
Dong, W.B., Brenneman, T.B., Holbrook Jr, C.C., Timper, P., Culbreath, A.K. 2009. The interaction between Meloidogyne arenaria and Cylindrocladium parasiticum in runner peanut. Plant Pathology 58:71-79.
Songsri, P., Jogloy, S., Holbrook Jr, C.C., Kesmala, T., Vorasoot, N., Akkasaeng, C., Patanothai, A. 2009. Association of root, specific leaf area and SPAD chlorophyll meter reading to water use efficiency of peanut under different available soil water. Agricultural Water Management 96:790-798.
Pimratch, S., Jogloy, S., Vorasoot, N., Toomsan, B., Patanothai, A., Holbrook Jr, C.C. 2008. Relationship between biomass production and nitrogen fixation under drought stress conditions in peanut genoytpes with different levels of drought resistance. Journal of Agronomy and Crop Science 194:15-24..
Pimratch, S., Jogloy, S., Vorasoot, N., Toomsan, B., Kesmala, T., Patanothai, A., Holbrook Jr, C.C. 2009. Heritability of N2 fixation traits, and phenotypic and genotypic correlations between N2 fixation traits with drought resistance traits and yield in peanut under different water regimes. Crop Science 49:791-800.