Genetic Analysis Of Heterosis For Seeding Traits Under The Nitrogen Stress In Maize

Heterosis is an important biological genetic mechanism to improve crop yield,enhance the resistance and improve the quality.Therefore,it is important to clarify the genetic mechanism of maize heterosis to select the new maize varieties.A set of single segment substitution lines(SSSLs)population,which derived for an elite inbred line Xu 178 as recurrent parent and inbred line Zong3 as nonrecurrent parent,were used as marital for constructing test populations with Recurrent parent Xu 178.By using 171 single segment substitution lines and their crosses,QTL and heterotic loci of the root related traits in Seedling were analyzed in two nitrogen treatments.The main results were as follows:1?1?QTLs for root and related traits of seedling roots were analyzed by SSSL inbred population.95 root-related QTLs were detected under two nitrogen conditions.22 root roots QTLs were detected under high nitrogen condition and low nitrogen condition QTLs for controlling root surface area,QTLs for controlling root diameter,11 QTLs for controlling dry weight of shoots,15 QTLs for controlling dry weight parts of underground,16 QTLs for plant height were detected,The QTLs of q RL6 a,q RAD4,q RDW1 a and q PH4 were detected under two nitrogen conditions,which indicated that the QTLs specific expression under low nitrogen conditions might exist in the nitrogen efficient gene.Six QTLs were found under high nitrogen condition,and eight QTLs under low nitrogen conditions controlled multiple traits of roots.Control of seedling roots of various traits may have a common genetic control,that is,a pleiotropism.2?A total of 91 HL were identified by using SSSL ×178 cross population under the condition of two nitrogen.Among the HL,19 HL for root length traits?20HL for root surface area traits?14HL for shoot dry weight traits? 16 HL for plant height traits were detected under the two nitrogen treatments,h RL1b?h RL7?h RL9?h RSA7?h RSA9?h RAD1b?h SDW7a?h SDW7b?h PH6 a were detected under the two nitrogen treatments simultaneously,Under the condition of high nitrogen,7HL control the root related traits,and under the condition of low nitrogen,10 HL control e root related traits.The results showed that the Heterosis loci of maize seedling traits also had the interaction between genetic and environment.3?Among the 91 HL for root related traits,only 17(18.8%)had a corresponding QTL(18.1%)sharing the same chromosomal region.These result illustrated that heterosis and performance was controlled by different genetic mechanisms.Meanwhile,Under the condition of two nitrogen conditions,the common root traits HL was detected.HRL1 b,h RAD1 b showed partial-dominant effect.HRL7,h RL9,h RSA7,h RSA9,h SDW7 a,h SDW7 b,h PH6 showed over-dominant effect.The results implied that over-dominance was important of heterosis in maize main related traits in the present testcross population.