Development Of Target QTL Near Isogenic Lines And Genetic Effect Of QTLs For Related Major Agronomic Traits

To increase maize production to meet the food, feed, and fuel needs,the traits affected maize yield always were the main improved objectives in maizebreeding. Genetic studies on these traits would be provided a theoretical and materialbasis for the genetic improvement of these traits. And now, a large number of QTLsrelated those traits have been detected, but most of them are statistically QTL with nopractical significance. In a previous study, several QTLs related plant architecture,yield, flowering were identified by a four-way cross mapping population crossed withthe four maize inbreds. Based on this, this paper developed a set of NILs of11QTLsrelated leaf angle, plant height, ear height, ear length, the day to silk emergence bybackcross breeding, with the marker interval mapped and their adjacent segment asthe target fragment screened and the genetic background of recurrent parent detectedby111-120SSR markers. The genetic effects of QTLs were verified by contiganalysis with the phenotype of NIL in three environments. The results were asfollowing:1.63NILs of11QTLs controlling the five traits were developed by the backcrosswith the inbred lines276,72, Jiao51respectively, assisted phenotypic screening andmaker-assisted selection. Among those,15NILs were developed by the backcrosswith the inbred line276,22with the inbred line72,26with the inbred line Jiao51.2. NILs derived from the inbred lines276and72were used to verify QTLs bycontig analysis with the phenotype of progeny in three environments. It indicated thatqLA1b, qLA2b, qLA4a, qPH1a, qEH1, qEH9existed on the QTL mapping intervals oradjacent intervals. On the intervals of qLA1b, qLA2b, qLA4a, qPH1a, qPH9, thegenomic segments of the inbred line276showed the negative genetic effect for leafangle, plant height, and ear height respectively. On the intervals of qPH9and qEH9,the genomic segments of the inbred line276showed the positive genetic effect forplant height and ear height respectively. On the intervals of qPH1a and qEH1, qPH9and qEH9, the genomic segments of the inbred line72show the positive and negativegenetic effect respectively. 3. NILs derived from the inbred lines A188and Jiao51were used to verify QTLsby contig analysis with the phenotype of progeny in three environments. It indicatedthat qLA4a, qLA5, qEL5, qSE4a existed QTL mapping intervals or adjacent intervals.On the intervals of qLA4a and qES4a, the genomic segments of the inbred line A188showed positive genetic effect for leaf angle and negative genetic effect for the day tosilk emergence. With nine NILs respectively, the interval of qLA5and qEL5wassplited into two minor QTL, showing positive genetic effect for leaf angle andnegative genetic effect for ear length.4. For dissecting qLA5and qEL5, two BC4F2plants with heterozygous segmenton bin5.02-5.06derived from the inbred lines A188and Jiao51were selfed to developF2population of188plants. Through the genetic map was fined with42SSR markers,qLA5and qEL5were mapped again with the phenotype of F2plants. It indicated thatonly two LA1QTL were detected. But QTL peaks of LA1, LA2, LA3, LAP, gatheredin two intervals, which of one provided positive additive effect, another providednegative additive effect. One EL QTL is detected, located umc1563-umc1591, withadditive genetic effect of2.9, provided by the inbred line A188. The QTL peaks of ELgathered in two intervals, which of one showed positive additive effect, anothershowed negative effect. Compared ear length of different genotypic F2plants, earlength of Jiao51/Jiao51genotype is least, and ear length of A188/Jiao51is largest.