Abstract:

Currently, a widely adopted strategy to estimate the position and effect of a mapped QTL more accurately is to create a new mapping population by crossing nearly isogenic line (NIL). In such a population, because of the absence of other segregating genetic background, the target QTL becomes the major genetic source of variation. Under such conditions, the QTL is considered as Mendel factor, and the distances between a QTL and the nearby molecular markers can be estimated more precisely. However, as a premise to perform the strategy, NILs that differ only at a short chromosome segment harboring QTL must be produced by marker assisted backcross introgression of one QTL allele into one or both parental genetic backgrounds. To develop two set of NILs covering whole genome of maize respectively, 87-1 and Zong 3(two parental lines of an elite maize hybrid Yuyu 22), and Hengbai 522(a waxy corn line derived from a local variety with short plant stature and disease resistance), were employed in the study. Two populations of link-up single segment introgression lines (SSILs) were developed with 87-1 and Zong 3 as the recurrent parents, Hengbai 522 as donor, respectively through 3–4 cycles advanced backcross. Foreground and background of populations were screened by SSR markers in each cycle of backcross. Genetic evaluation showed that 40 and 78 segments from the donor line were introgressed into 87-1 and Zong 3 SSILs, respectively. In population of 87-1 SSILs, the average length of a single introgressive segment was 91.1 cM, varying from 0.03 to 342.8 cM. The total segment length was 3 643.9 cM with coverage of 48.9% of chromosomes. In population of Zong 3 SSILs, the largest segment was 343.4 cM with an average and a total length of 75.5 cM and 5895.2 cM, respectively, and with the coverage of 79.2% of chromosomes. These developed SSILs could be widely used in fine mapping of QTLs and functional genomics researches of maize.

Key words: Maize (Zea mays L.), Single segment introgression line, Backcross, SSR marker