Development Of Single Segment Introgression Lines And Primary Identification Of QTLs In Maize (Zea Mays L.)

Single segment introgression lines (SSILs) was a permanent mapping population, which was developed using advance-backcross and marker-assisted selection, which is a novel materials for quantitative trait locus (QTLs) genetic analysis. Comparing with the traditional population, there were more advantages in SSILs, such as:1) There were knowable genetic background and steady genetic base in SSILs.2) the accuracy and sensitivity of QTL.mapped and identified were improved using SSILs.3) Genetic effects of QTLs can be exactly analyzed and study on the interaction of QTL and environment or QTL were go along using SSILs.At present, SSSLs was developed and applied on tomato and rice. 87-1 and Zong 3 were parental lines of an elite corn hybrids Yuyu 22, Hengbai 522 is a waxy corn line separated from local variety with special traits such as low plant height, disease resistance, lodging resistance, etc. In this study, two single segment introgression lines (SSILs) were developed using 87-1 and Zong3 (Z3) as the recurrent parent respectively, Hengbai522 as donor through 3⁴ cycles advanced backcross and 1 cycle self-cross. Foreground and background of populations were selected by SSR marker in each cycle of backcross generation. The QTLs of mostly agronomic characters were primarily identified using BC3F1 population. The results were as follows:1 General genome DNA were extracted using CTAB, SSR markers came from http://maizegdb.org, and detected using PAGE. It has respectively screened 134 and 121 SSR locus from 87-1 and HB522, Z3 and HB522, polymorphic locus were used for foreground selection and background selection.2 Doing foreground selection of BC₁F₁ with polymorphic locus, 161 donor segment were detected, and doing background selection and backcross for plants containing donor segment. Based on the detecting results of BC₁F₁ by DNA markers, planting BC₂F₁ had high regress rate and contained donor segment. 128 donor segment were detected from BC₂F₁ and 118 donor segment from BC3F1. 87-lHBSSILs and Z3HBSSILs which contained 40 and 78 donor segment respectively were constructed through 3⁴ generation backcross and 1 generation self-cross.3 After foreground selection, there were 80 plants composing 87-lHBSSILs population and 115 plants composing Z3HBSSILs population. After background selection, in theBC3F1 population of 87-1, the minimal recoverage was 98.21% , the average recoverage was 99.09%, and the maximal recoverage was 100%;in the BC3F1 population from Z3, the minimal of regress rate was 97.77% , the average rate was 99.27%, and the maximal rate was 99.74%.4 According to genetic analysis of the two SSILs, it showed that the average length of a single introgressed segment was 91.10 cM, varying from 0.03 to 342.86 cM. Total length was 3643.92 cM with coverage of 48.96 % of chromosomes in 87-lHBSSILs. In Z3HBSSILs, the largest segment was 343.42cM with an average and a total length of 75.58cM and 5895.26cM respectively with coverage of 79.21%.5 QTLs of some agronomic traits were elementarily identified, which included plant height, ear height, leaf area and number of tasser branch in BC3F1 population. It detected twenty-one of plant height, thirty QTLs of ear height, seven QTLs of leaf area, and sixteen QTLs of number of tasser branch.The two SSILs could be used to identify and map QTLs, to study inheritance of QTLs and to pyramid of QTLs, et al. Those also provided valuable materials for constructing sub-NILs to fine map and clone QTLs.