Abstract
Background: Dynamic regulations of QTLs still remain mysterious. Single segment substitution lines and conditional QTL mapping, functional QTL mappings are ideal materials and methods to explore epistatic interactions, expression patterns and functions of QTLs for complex traits.Results: Based on single segment substitution lines five QTLs on plant height in rice were identified first in this paper, and then their epistatic interactions, expression patterns and functions were systemmatically studied by tailing after each QTL. Unconditional QTL mapping showed the five QTLs were with significant effects at one or more stages, all of which increased plant height except QTL1. They interacted each other as homeostatic mechanisms to regulate plant height with negative effects before 72d after transplanting and positive since then. Conditional QTL mapping revealed the expression quantities and periods for the five QTLs and their epistases. Temporal expression pattern was verified again by selective expressions of QTLs in specific periods. QTL1 expressed negatively while QTL2 and QTL4 positively, mainly occurring in the periods from 35 to 42d and from 49 to 56d after transplanting. Epistatic expressions were dispersedly in various periods, mainly with negative effects before 35d while positive since then. Functional QTL mapping discovered the five QTLs brought the inflexion point ahead of schedule, accelerated the growth and the degradation, and changed the peak of plant height, while their interactions had the opposite effects approximately. This paper uncovered the dynamic rules of five QTLs and their interactions on plant height systematically, which will be helpful to understand the genetic mechanism for developmental traits.Conclusions: Five single segment substitution lines were tested with significant additive, dominant and epistatic effects of QTLs on plant height. Additive and dominant expressions were mainly in two periods, while epistasis dispersedly. The five QTLs and their interactions significantly regulated the developmental trajectory of plant height.
Localization of quantitative trait loci for cucumber fruit shape by a population of chromosome segment substitution lines
