Location: Crop Protection and Management Research2012 Annual Report
1a. Objectives (from AD-416):
(1) Develop peanut genomic tools and strategies to elucidate the molecular mechanisms that define crop defense pathways and regulation of resistance to diseases such as tomato spotted wilt virus (TSWV), leaf spots and aflatoxin contamination in peanut. (2) Evaluate corn germplasm that harbors resistance genes that reduce aflatoxin contamination and understand the responding genes and pathways in corn.
1b. Approach (from AD-416):
(1) Replicated laboratory and field screening and evaluation of peanut accessions for disease resistance will be conducted in order to identify the “resistant” germplasm for further genomic studies. The resistant germplasm will be utilized in molecular marker development for marker-assisted breeding. (2) ESTs (expressed sequence tags) will be generated from cDNA libraries constructed from seed and leaf tissues of two genotypes, Tifrunner and GT-C20. EST-derived SSR markers will be developed and peanut oligo-microarray will be produced for gene expression study. (3) Genetic mapping populations (RILs, recombinant inbred lines) will be produced from crosses of Tifrunner and GT-C20, and SunOleic 97R x NC94022. QTL mapping will be conducted for resistance to tomato spotted-wilt virus (TSWV) and leaf spots, and aflatoxin contamination. (4) Microarray experiments will be used to identify candidate genes in corn-Aspergillus flavus and drought stress interactions that are turned on or off during corn kernel development. The candidate genes identified from microarray will be verified or confirmed through real time PCR or other well established methods. Another goal is to develop a macroarray tool (membranes) using these candidate genes from microarray to assess resistance or drought tolerance in corn germplasm for their stability of expression in native crops under environmental conditions (e.g., drought) known to be conducive to aflatoxin contamination. The genes identified in corn kernels also will be applied in searching possible ‘orthologs’ in peanut genome and peanut germplasm.
3. Progress Report:
Peanut production and consumer acceptability are adversely affected by several biotic/abiotic stresses and poor oil quality. In order to deal with these concerns, the developed genetic map from one peanut population derived from SunOleic 97R × NC94022 by Qin et al. (2012) using 190 subset with 172 markers was further advanced with additional 77 polymorphic marker loci on all 353 lines. The saturated genetic map possesses 249 loci distributed on 23 linkage groups with total map distance of 3,433.5 cM. Multiple phenotyping data of all lines on several economically important traits was used for quantitative trait loci (QTL) analysis, resulting in identification of a total of 155 QTLs with phenotypic variance (PVE) that ranged from 1.48 to 65.2% and the log-of-odds (LOD) ranged from 2.51 to 83.68. One major Quantitative Trait Loci (QTL) (16.7% PVE) for Tomato spotted wilt virus (TSWV) resistance, three major QTLs for late leaf spot (12.42 -20.59%), two major QTLs for growth habit (11.90 - 14.05% PVE) while one major QTL each for leaf color (10.43% PVE), pod shape (11.55% PVE) and pod reticulation (14.01% PVE), and four QTLs for seed color (10.12-18.45% PVE) were identified. QTL analysis also revealed that FAD2B gene contributes up to 74.03% PVE while FAD2A gene could contribute only 11.13% PVE for high oleic/linoleic (O/L) ratio. Interestingly, the A- and B-genome mutations of FAD2 were also found to contribute to other fatty acids, such as palmitic acid (PVE 21.26 and 27.77%) and gadoleic acid (PVE 13.73 and 10.32%), respectively. The markers linked to major QTLs could be utilized for peanut genetic improvement through molecular marker-assisted selection in breeding.
Jiang, T., Fountain, J., Davis, G., Kemerait, R., Scully, B.T., Lee, R.D., Guo, B. 2012. Root morphology and gene expression analysis in response to drought stress in maize (Zea mays). Plant Molecular Biology Reporter. 30:360-369.