Browsing by Subject "IDC"
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Item QTL mapping and GWAS identify sources of iron deficiency chlorosis and canopy Wilt Tolerance in the Fiskeby III X Mandarin (Ottawa) soybean population(2015-01) Butenhoff, Karl JosephAbiotic stresses are a major yield limiting component in soybean production that producers cannot directly control. Therefore, an increase in the understanding of how different abiotic stresses affect soybean, and the identification of sources of tolerance to these stresses will be critical for the continued increase of soybean productivity well into the future. Here I present three separate, but related, studies analyzing iron deficiency chlorosis and drought tolerance in several soybean populations. For the first and second studies, the objectives were to (i) characterize the Fiskeby III X Mandarin (Ottawa) recombinant inbred line (RIL) population for its tolerance to iron deficiency chlorosis (IDC) and drought; (ii) identify quantitative trait loci (QTL) via composite interval mapping for iron deficiency chlorosis and canopy wilt in the RIL population; and (iii) identify co-localization of abiotic stress QTL and putative candidate genes for iron deficiency chlorosis tolerance and delayed canopy wilt. Iron chlorosis and canopy wilt scores were significantly different across the three years tested between the RILs as well as the parents of the population. Fiskeby III consistently scored better than Mandarin (Ottawa) for tolerance to iron chlorosis and canopy wilt in all three years. Two QTL were discovered, one on chromosome five and one on chromosome six, that together accounted for approximately 25 percent of the phenotypic variation for IDC. Two QTL were also identified for canopy wilt, one on chromosome six and one on chromosome 12, that together accounted for approximately 13 percent of the phenotypic variation. The two QTL identified on chromosome six co-localized to the same confidence interval. Several previously identified QTL co-localized with the identified IDC and canopy wilt QTL in this study. In addition, a potential candidate gene was identified on chromosome five that may play a role in the soybean IDC response. The third study was undertaken to potentially validate the QTL identified for IDC in the first study in two independent soybean populations. The objectives of this study were to (i) utilize association mapping to detect markers significantly associated with IDC in two independent populations, (ii) compare significant identified markers with the QTL regions identified in the bi-parental RIL population, and (iii) validate the major QTL identified on chromosome five in the RIL population. Association mapping identified 12 significant markers that accounted for 27.2 percent and 8.9 percent of the phenotypic variation for IDC in the two populations, respectively. These markers co-localized with several known iron related QTL and genes. A significant cluster of 11 markers on chromosome five co-localized with the major IDC QTL identified in the bi-parental Fiskeby III X Mandarin (Ottawa) population. A second potential candidate gene was identified in this QTL region that may be related to IDC in soybean.Item QTL mapping of iron deficiency chlorosis tolerance in soybean using connected populations(2014-03) Jones, Ilene LouiseSoybean iron deficiency chlorosis or IDC is a yield limiting, abiotic stress condition common to calcareous soil types present in the Upper Midwest. Complex interactions among soil chemical and physical properties within these calcareous soils limit the amount of ferrous iron available to soybean plants. The subsequent nutrient deficiency leads to the classic chlorotic phenotype characterized by interveinal yellowing of new growth trifoliates. IDC is responsible for yield losses up to 0.8 Mg ha-1 amounting to an estimated economic loss of $120 million per annum. To mitigate yield losses, growers prefer to plant IDC tolerant cultivars; however, IDC tolerant cultivars have been known to yield less on non-chlorotic soils. In order to improve IDC tolerance without an associated reduction in yield, we evaluated yield and IDC performance using a network of 13 F4-derived recombinant inbred line (RIL) populations connected by common parents. Chlorosis severity was evaluated using two methods: visual chlorosis ratings and remote sensing via normalized difference vegetative index (NDVI) values collected from the GreenSeeker® RT100 System. NDVI values correlated strongly with visual chlorosis ratings with the largest negative Pearson's correlation coefficient of -0.89 (p-value < 0.0001) captured at the V4 growth stage. NDVI values collected at V4 were moderately correlated to yield with a Pearson's correlation coefficient of -0.61 (p-value < 0.0001), indicating that IDC tolerant lines yield less than IDC susceptible lines on non-chlorotic soils. Co-localization of IDC and yield QTL detected on linkage groups A1/5, J/16, and L/19 confirm that the correlations are in part due to genetically linked loci or pleiotropic effects of a single locus.