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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF IMPROVED PEANUT GERMPLASM AND RESISTANCE TO DISEASE AND NEMATODE PESTS
2011 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.

Accessions in the peanut mini core collection were evaluated for disease resistance and agronomic characteristics to identify potential candidates for biodiesel production.


4.Accomplishments
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. Using marker assisted selection in an accelerated backcross breeding program we completed the development of ‘Tifguard High O/L’ in less than 3 years. Growers will benefit from the fact that Tifguard High O/L is a high yielding variety with excellent resistance to the peanut root-knot nematode and tomato spotted wilt virus. Other segments of the peanut industry, and consumers will benefit from the fact that this variety is high oleic which results in a longer shelf life, and a healthier food.

2. Drought tolerant peanut. A large root system can be an important character for drought tolerance in peanut. Unfortunately, measuring root characteristics in soil is difficult and labor intensive. The objective of this study was to attempt to develop an easier system for measuring root characteristics. Twelve peanut genotypes were planted in a hydroponic study, a small pot, and a large pot experiment. Shoot dry weight, root dry weight, root-to-shoot ratio, root length, root surface, average diameter of roots, and root volume were measured. Root characteristics of peanut genotypes grown in hydroponics were positively correlated with those of peanut genotypes grown in pot conditions. The development of this hydroponic system should be useful in breeding peanut for larger root systems.


Review Publications
Chu, Y., Wu, C.L., Holbrook Jr, C.C., Tillman, B., Person, G., Ozias-Akins, P. 2011. Marker-assisted selection to pyramid nematode resistance and the high oleic trait in peanut. The Plant Genome. 4:110-117.

Girdthai, T., Jogloy, S., Vorasoot, N., Akkasaeng, C., Wongkaew, S., Holbrook Jr, C.C., Patanothai, A. 2010. Association between physiological traits for drought tolerance and aflatoxin contamination in peanut genotypes under terminal drought. Plant Breeding. 129:693-699.

Guo, B., Chen, C.Y., Chu, Y., Holbrook Jr, C.C., Ozias-Akins, P., Stalker, H. 2011. Advances in Genetics and Genomics for Sustainable Peanut Production. Sustainable Agriculture. In: Benkeblia, N., editors. Sustainable Agriculture and New Biotechnologies. Boca Raton, FL:CRC Press. p. 341-368.

Knoll, J.E., Ramos, M., Zeng, Y., Holbrook Jr, C.C., Chow, M., Chen, S., Maleki, S.J., Bhattacharya, A., Ozias-Akins, P. 2011. TILLING for allergen reduction and improvement of quality traits in peanut (Arachis hypogaea L.). Biomed Central (BMC) Plant Biology. 11:81.

Li, Y., Chen, C.Y., Knapp, S.J., Culbreath, A.K., Holbrook Jr, C.C., Guo, B. 2011. Characterization of simple sequence repeat (SSR) markers and genetic relationships within cultivated peanut (Arachis hypogaea L.). Peanut Science. 38:1-10.

Chen, X., Wang, M.L., Holbrook Jr, C.C., Culbreath, A., Liang, X., Brennenman, T., Guo, B. 2010. Identification and characterization of a multigene family encoding germin-like proteins in cultivated peanut (Arachis hypogaea L.). Plant Molecular Biology Reporter. 29:389-403.

Last Modified: 12/19/2014
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