Abstract:

In order to get rid of the linkage drag of target gene and get more selected individuals with better genetic recovery, two backcrossing populations (SCBC₁F₁ and HCBC₁F₁ ) of maize were constructed with its size up to 1 416 and 1 627 individuals each. Five SSR markers which are localized in and linked closely to opaque2 (o2) gene (Fig.1) were employed to analyze linkage drag of o2 in SCBC₁F₁ and HCBC₁F₁ populations. Foreground and background selection were processed in the two populations by those five SSR markers (Fig.2－5). Compared with the computer simulation results proposed by Ribaut (Table 2), the MAS results were more exercisable and convictive. It suggests that, when the MAS program is put in practice of plant backcrossing breeding process, to make sure the size of the backcrossing F₁ population is appropriate, not only the number of the selected individuals ultimately (N_i), but also the number of the selected individuals ultimately with enough seeds (N_j) need to be considered (Table 1). Moreover, the length of the linkage drag is also an important parameter to estimate the size of BC₁F₁ population.

Key words: Maize, Marker-assisted selection, opaque2 gene, Linkage drag