Abstract：To investigate the genetic basis of heterosis in maize seedling traits, highly heterotic maize(Zea mays L.) hybrid Yuyu22 and RILs(recombinant inbred lines) were used as basic population to construct TTC(triple testcross) population, which included 312 testcross progenies by using TTC genetic mating design. Thirty QTLs were detected for the longest root length(LRL), shoot height(SH), primary root number(RN), root dry matter weight(RDW) and shoot dry matter weight(LDW) by using composite interval mapping. And some QTLs for different seedling traits were found to be located on the same chromosome regions, and a total of 4 regions were detected, which distributed on chromosome 2, 3 and 7, respectively. Further analysis indicated that 22 QTLs were detected by using Z1 and Z2 data, which were classified as overdominant(11), additive(5), partially dominant(5) and dominant(1). Furthermore, 8 genome regions of QTL× genetic background interactions and 16 markers pairs with epistatic effects were detected. Collectively, we propose that overdominance and epistasis are the main genetic basis of maize seedling traits and their heterosis.
