QTL mapping of iron deficiency chlorosis tolerance in soybean using connected populations

Abstract

Soybean 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.