Location: Crop Genetics and Breeding Research
2022 Annual Report
Objectives
Objective 1: Identify and characterize genes/Quantitative Trait Locus (QTLs) controlling resistance to major diseases (leaf spot, white mold, rhizoctonia limb rot, and nematodes) and drought stress, and use the information in marker-assisted breeding to develop improved high oleic (oleic/linoleic fatty acid ratio) peanut cultivars or germplasm with tolerance to biotic and abiotic stresses.
Sub-objective 1.A.: Conduct phenotypic evaluations of recombinant inbred line (RIL) populations to aid in the identification and characterization of genes/QTLs controlling resistance/tolerance to biotic and abiotic stresses.
Sub-objective 1.B.: Develop improved high oleic peanut cultivars or germplasm with resistance to nematodes and improved resistance to leaf spot.
Sub-objective 1.C.: Develop high oleic peanut germplasm with improved drought tolerance and reduced preharvest aflatoxin contamination (PAC).
Approach
1.A. Sixteen structured recombinant inbred line (RIL) populations were developed using parents that were selected to maximize genetic diversity while meeting practical breeding objectives. In-depth phenotyping and genotyping of the populations will be conducted to identify genetic markers that can be used in peanut cultivar development.
1.B. 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/or resistance to leaf spot. Marker assisted selection will be utilized to select early generation progeny that are homozygous for the desired characteristics (high oleic, nematode resistance, and/or leaf spot resistance). Selections in later generations will focus on field resistance to tomato spotted wilt virus, high yield, and other agronomic characteristics.
1.C. Breeding populations will be developed by hybridizing high-yielding, high-oleic cultivars with sources of resistance to preharvest aflatoxin contamination and sources of resistance to drought. 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 and/or relatively high pod yields.
Progress Report
Crosses were made by ARS researchers in Tifton, Georgia, to combine resistance to biotic and abiotic stresses with high yield, good grade, and high oleic fatty acid content. Populations were advanced to a more inbred state when marker assisted selection (MAS) was used to identify individuals that will breed true for high oleic fatty acid content and/or nematode resistance and/or leaf spot resistance. Progeny from these individuals were then evaluated for resistance to other biotic and/or abiotic stresses, yield, and other agronomic characteristics. Potential varieties with high levels of resistance to leaf spot were evaluated under different fungicide spray regimes. Growers should be able to use these varieties to reduce their input costs and increase profitability.
Accomplishments
1. Development of new sources of resistance to important peanut pathogens. Peanut is plagued by diseases and pests. Wild relatives of peanut harbor genes which confer strong resistance to disease and pest and adaptation to environmental stresses, traits which frequently cannot be found in the cultivated peanut species. Unfortunately, due to differences in numbers of chromosomes, the wild relatives are not cross compatible with the cultivated species. ARS researchers in Tifton, Georgia, along with collaborators crossed wild relatives and used a chemical treatment to double the chromosome of the resulting hybrids (tetraploids). These induced tetraploids are cross compatible with cultivated peanut, carry resistance to early and late leaf spot and root-knot nematode and are being used in breeding programs in the U.S. to produce resistant peanut varieties.
2. Identification of new genes for resistance to nematodes. Peanut root-knot nematode is a serious pathogen on peanut. The cultivated peanut species is highly susceptible to this nematode. Resistant peanut cultivars have been developed using a gene for resistance from a related wild peanut species. The identification of additional genes for resistance would be valuable incase the nematode overcomes the resistance from this gene. ARS researchers in Tifton, Georgia, along with collaborators have found near-immunity in a different peanut wild relative. The two genes controlling the resistance present in chromosomes A02 and A09 have been validated and have been shown to reduce nematode reproduction by up to 98.2%. We also identified molecular markers for these genes so that breeders can use marker assisted breeding to rapidly develop nematode resistant peanut cultivars using the new genes for resistance.
3. Development of a greenhouse method to screen for white mold resistance. Peanut stem rot (also known as white mold) is one of the most damaging soil borne pathogens for U.S. peanut production. The disease is typically controlled using fungicides and by the adoption of cultivars with moderate resistance. Field evaluation is the main approach for assessing plant resistance, but it is costly and labor-intensive. Reliable methods for in vitro or greenhouse evaluations are desirable. Greenhouse, growth chamber and in vitro methods have been tried to assess resistance, but they generally do not correlate well with field results. In this study, ARS researchers in Tifton, Georgia, along with collaborators tested several in vitro and greenhouse methods for evaluation. We devised a method that reliably assesses resistance to stem rot on stem cuttings in the greenhouse. Sixty-day old stem cuttings were transplanted into a cup filled with potting mix and inoculated with white mold. Inoculated cuttings were put in a mist chamber to keep humidity high. Evaluations taken at 3, 5, 7, and 9 days after inoculation (DAI) significantly correlated with field evaluations. This greenhouse assay is an important step forward to rapidly screen germplasm for stem rot resistance.
Review Publications
Holbrook Jr, C.C., Ozias-Akins, P., Chu, Y., Lamon, S., Bertioli, D.J., Leal-Bertioli, S., Culbreath, A.K., Godoy, I.J. 2021. Registration of TifGP-3 and TifGP-4 peanut germplasm lines. Journal of Plant Registrations. 16:120-123. https://doi.org/10.1002/plr2.20179.
Levinson, C.M., Chu, Y., Levinson, M., Marasigan, K., Stalker, H.T., Holbrook Jr, C.C., Ozias-Akins, P. 2021. Anatomical characteristics correlated to peg strength in Arachis. Peanut Science. 48:97-112. https://doi.org/10.3146/PS21-1.1.
Ballen-Taborda, C., Chu, Y., Ozias-Akins, P., Holbrook Jr, C.C., Timper, P., Jackson, S.A., Bertioli, D.J., Leal-Bertioli, S. 2022. Development and genetic characterization of peanut advanced backcross lines that incorporate root-knot nematode resistance from Arachis stenosperma. Frontiers in Plant Science. 12:785358. https://doi.org/https://doi.org/10.3389/fpls.2021.785358.
Janket, A., Vorasoot, N., Toomsan, B., Kaewpradit, W., Theerakulpisut, P., Holbrook Jr, C.C., Kvien, C.K., Jogloy, S., Banterng, P. 2021. Quantitative evaluation of macro-nutrient uptake by Cassava in a tropical savanna climate. Agriculture. 11(12):1199. https://doi.org/10.3390/agriculture11121199.
Chamberlin, K.D., Grey, T.L., Puppala, N., Holbrook, C.C., Isleib, T.G., Dunne, J., Dean, L.O., Hurdle, N.L., Payton, M.E. 2021. Comparison of field emergence and thermal gradient table germination rates of seed from high oleic and low oleic near isogenic peanut lines. Peanut Science. 48:131-143.
Bera, S.K., Rani, K., Kamdar, J.H., Pandey, M.K., Desmae, H., Holbrook Jr, C.C., Burow, M.D., Manivannan, N., Bhat, R.S., Jasani, M.D., Bera, S.S., Badigannavar, A.M., Sunkad, G., Wright, G.C., Janila, P., Varshney, R.K. 2022. Genomic designing for biotic stress resistant peanut. In: C. Kole (ed.) Genomic Designing for Biotic Stress Resistant Oil Seed Crops. Springer Nature Switzerland.. pp. 137-214. https://doi.org/10.1007/978-3-030-91035-8_9.
Chaimala, A., Jogloy, S., Vorasoot, N., Holbrook Jr, C.C., Kvien, C.K. 2021. The variation of relative water content, SPAD chlorophyll meter reading, stomatal conductance, leaf area, and specific leaf area of Jerusalem artichoke genotypes under different durations of terminal drought in tropical region. Journal of Agronomy and Crop Science. 00:1-15. https://www.doi.org/10.1111/jac.12561.
Chu, Y., Clevenger, J.P., Holbrook Jr, C.C., Isleib, T.G., Ozias-Akins, P. 2022. Registration of two peanut recombinant inbred lines (TifGP-5 and TifGP-6) resistant to late leaf spot disease. Journal of Plant Registrations. https://doi.org/10.1002/plr2.20242.
Mahakosee, S., Jogloy, S., Vorasoot, N., Theerakulpisut, P., Holbrook Jr, C.C., Kvien, C.K., Banterng, P. 2022. Light interception and radiation use efficiency of cassava under irrigated and rainfed conditions and seasonal variations. Agriculture. 12(5):725. https://doi.org/10.3390/agriculture12050725.
