Reduced recombination and distorted segregation in aSolanum tuberosum(2x) ×S.spegazzinii(2x) hybrid

Abstract

In this paper we describe the reduced recombination and distorted segregation in an interspecific hybrid between Solanum tuberosum and Solanum spegazzinii. To study these phenomena, a cross was made between a (di)haploid S. tuberosum, used as a female parent, and a diploid wild potato species, S. spegazzinii, used as a male parent. Next, a backcross (BC) population was made with F1 genotype 38 that was backcrossed to S. tuberosum. In the backcross, S. tuberosum was used as the male parent. RFLP linkage maps were made using the F1 and the BC populations, yielding linkage maps of the interspecific hybrid, S. spegazzinii, and S. tuberosum from which male and female linkage maps could be constructed. The computer program JOINMAP was used to construct and combine the separate linkage maps. Subsequently, the separate linkage maps were compared with each other, and reduced recombination was observed in the linkage maps of the male S. tuberosum and the interspecific hybrid. The reason for this reduced recombination is discussed. Another common feature in linkage maps is the observation of distorted segregation. The distorted segregation of alleles from the interspecific hybrid was studied in more detail in the BC population. Most of the distortion was probably caused by gamete selection, but for 3 loci, on chromosomes 2, 3, and 4, we found evidence for the presence of a strong selection force acting at the zygote level against homozygous genotypes.

Can the QTL for late blight resistance on potato chromosome 5 be attributed to foliage maturity type?

“…This was not the result of our method of evaluation, since the residuals were distributed normally (data not shown) and therefore the data did not require transformation. Skewness caused by distorted segregation due to gamete or zygote selection (Kreike and Stiekema 1997) was not supported by the segregation of molecular markers near the two QTLs for resistance against P. infestans that we detected on chromosomes 3 and 5. Distorted segregation of molecular markers was found in other populations near these loci on chromosome 3 (Leonards-Schippers et al 1994) andchromosome 5 (Collins et al 1999).…”

Pairing analysis and in situ Hybridisation reveal autopolyploid-like behaviour in Solanum commersonii × S. tuberosum (potato) interspecific hybrids

“…Although we have not analysed the female meiosis in these hybrids, its recombination rate is generally higher than in the male meiosis in hermaphroditic plants (reviewed by Lenormand and Dutheil 2005;Wijnker and de Jong 2008). The recombination ratio between male and female meiosis ranged between 0.84 in hybrids between tomato and a wild relative (de Vicente and Tanksley 1991) and 0.73 between potato and a wild relative (Kreike and Stiekema 1997), and was 0.72 in a close wild relative, S. chacoense, (Rivard et al 1996). Therefore, it can be inferred that the ratio might be similar in the hybrids studied here, and thus that homoeologous pairing could be as frequent or even more frequent in the female meiosis.…”

Linkage group correction using epistatic distorted markers in F2 and backcross populations

“…If the new linkage group is seriously different from the old one, the recombination fraction between distorted markers should be re-estimated. However, the traditional approach does not work well because a new variable, selection coefficient, is involved (Kärkkäinen et al, 1996;Kreike and Stiekema, 1997;Faris et al, 1998). To overcome this issue, Lorieux et al (1995a,b) regarded the selection coefficient as a parameter and adopted the maximum likelihood method to estimate the recombination fraction and selection coefficient simultaneously under a fitness model.…”