REDUCED RECOMBINATION AND DISTORTED SEGREGATION IN A SOLANUM-TUBEROSUM(2X) X S-SPEGAZZINII(2X) HYBRID

In this paper we describe the reduced recombination and distorted segr egation in an interspecific hybrid between Solanum tuberosum and Solan um spegazzinii. To study these phenomena, a cross was made between a ( di)haploid S. tuberosum, used as a female parent, and a diploid wild p otato species, S. spegazzinii, used as a male parent. Next, a backcros s (BC) population was made with F-1 genotype 38 that was backcrossed t o S. tuberosum. In the backcross, S. tuberosum was used as the male pa rent. RFLP linkage maps were made using the F-1 and the BC populations , yielding linkage maps of the interspecific hybrid, S. spegazzinii, a nd S. tuberosum from which male and female linkage maps could be const ructed. The computer program JOINMAP was used to construct and combine the separate linkage maps. Subsequently, the separate linkage maps we re compared with each other, and reduced recombination was observed in the linkage maps of the male S. tuberosum and the interspecific hybri d. The reason for this reduced recombination is discussed. Another com mon feature in linkage maps is the observation of distorted segregatio n. The distorted segregation of alleles from the interspecific hybrid was studied in more detail in the BC population. Most of the distortio n was probably caused by gamete selection, but for 3 loci, on chromoso mes 2, 3, and 4, we found evidence for the presence of a strong select ion force acting at the zygote level against homozygous genotypes.