Variability of recombination frequencies in the Iowa Stiff Stalk Synthetic (Zea mays L.)

Abstract

Variability in recombination frequency has been reported in several plant populations. The objectives of the present research were to establish the range in variability in recombination among genotypes in the important corn population Iowa Stiff Stalk Synthetic and to identify individual genotypes which produced increased or decreased recombination frequencies. Approximately 150 individual S0 plants were testcrossed to measure male recombination frequency on three chromosomes: 4, sul-c2; 5, a2-btl-pr1; and 9, sh1-bz1-wx1. Although the variance component for individuals accounted for only 20-33% of the total variation, highly significant variability among individuals was present at all chromosome regions. Thus the environmental effects did not prevent measurement of differences between S0 individuals. At each chromosome region, individual genotypes with recombination frequencies at least two standard deviations above or below the population mean were isolated. Reports in the literature suggest that the variability reported here for the BSSS population should be representative of that present in other corn breeding populations. Recombination frequencies were positively correlated between adjacent regions of chromosome 9 and also between adjacent regions of chromosome 5. Recombination frequencies were positively correlated between both regions on chromosome 5 with the su1-c2 region of chromosome 4. Negative correlations were observed between chromosome 9 recombination and recombination in each region of chromosomes 4 and 5. Thus rankings of S0 individual recombination frequencies were not consistent for all three chromosomes.

The effects of trans modifiers and tandem duplications on meiotic recombination in maize

“…Even so, recombination frequencies were correlated between some regions on different chromosomes (FATMI et al 1993). These results suggest polygenic regulation of recombination within a genome.…”

“…These cis and trans-acting modifiers are polymorphic within maize germplasm, evidenced by the significant differences in genetic map sizes among diverse mapping populations. However, in these previous studies (FATMI et al 1993;TULSIERAM et al 1992) the effects of cis-and trans-acting genetic modifiers could not be separated. The second goal of this research was to determine how polymorphic trans-acting genetic modifiers, in the absence of polymorphic c «-acting elements, affect the distribution of recombination breakpoints across an interval containing both genie and non-genic regions (Chapter 3).…”

“…Indeed, there is often no correlation between recombination frequencies in either adjacent or genetically unlinked genomic intervals in maize mapping populations (BEAVIS and GRANT 1991;FATMI et al 1993;TULSIERAM et al 1992). Even so, recombination frequencies were correlated between some regions on different chromosomes (FATMI et al 1993).…”

“…For example, in Arabidopsis the distribution of recombination breakpoints along chromosomes differs among accessions (SANCHEZ-MORAN et al 2002). In maize, recombination frequencies can vary greatly among mapping populations, as evidenced by genetic maps generated in cornbelt (BEAVIS and GRANT 1991;TULSIERAM et al 1992), cornbelt x exotic germplasm (TULSIERAM et al 1992), synthetic (FATMI et al 1993), exotic and teosintemaize hybrid (WILLIAMS et al 1995) populations. Average recombination distances between genetic markers were highly variable in mapping populations of diverse and even similar maize germplasm (WILLIAMS et al 1995).…”

“…In Arabidopsis, recombination rates vary among accessions (SANCHEZ-MORAN et al 2002). In maize, heterogeneity in recombination frequencies has been well documented within combelt (BEAVIS and GRANT 1991;TULSIERAM et al 1992), combelt x exotic germplasm (TULSIERAM et al 1992), synthetic (FATMI et al 1993), exotic and teosinte-maize hybrid (WILLIAMS et al 1995) mapping populations and has often confounded the generation of composite genetic maps. Recombination rates in intervals with heterogenous frequencies varied two-to-three fold among diverse mapping populations (WILLIAMS et al 1995).…”