Mapping and Epistatic Interactions of QTLs for Pericarp Thickness in Sweet Corn

Abstract

Pericarp thickness is of great importance to the sensory quality of sweet corn. Mining the gene for pericarp thickness and understanding its genetic mechanism can provide a base for instructing breeding. Quantitative trait locus(QTL) for pericarp thickness was detected based on two genetic models using a population comprising 190 BC1F2 families derived from the cross of Richao-1(thin pericarp, 56.57 μm) ×1021(thick pericarp, 100.23 μm) in the present study. Three QTLs for pericarp thickness were identified on bin 3.01, 6.01, and 8.05 using the Composite interval mapping(CIM) method, explained 8.6%, 16.0%, and 7.2% of phenotypic variation, respectively. Based on the MCIM(mixed-model based CIM) method, we identified five QTLs for pericarp thickness, comprising one additive QTL and two pairs of epistatic QTLs. The additive QTL was located on bin 8.05. Additive × additive epistatic effects for pericarp thickness were showed between QTL in 2.01 and QTL in 6.05 with estimated 6.63% of the phenotypic variation and between QTL in 5.06 and QTL in 6.01 with the estimated phenotypic variation of 12.48%. The results indicated that epistasis and additive effects play an important role in the genetic basis of pericarp thickness. The MCIM model with the ability to detect epistatic QTLs is more suitable for pericarp thickness QTL mapping. In addition, candidate genes encoding proteins that play important role for pigment biosynthesis and cell transformation in endosperm were contained in four QTL regions of all, suggesting the likely relations between the expressions of these candidate genes and pericarp thickness variation.