The utility of two pollen genetic markers for estimating the extent of meiotic recombination between the centromere and a marker gene was tested in 2n pollen of diploid potato clones. One of these markers was the distal locus amylosefree (amf) on chromosome 8 and the other was the isozyme locus alcohol dehydrogenase (Adh-1) on chromosome 4. In the case of the amf locus, the gene-centromere distance was estimated in a normal synaptic and a desynaptic genotype. In both cases the genetic analysis was confined to: (1) a direct estimation of the phenotypic (blue vs red) segregation ratios in FDR (first- division restitution) 2n pollen and (2) a classification of the 4x progeny from 4x (nulliplex amf) x 2x (Amf/amf) crosses into duplex, simplex and nulliplex classes. The recombination frequency between the centromere and the amf locus in the normal synaptic genotype B92-7015-4 corresponded to a gene- centromere distance of 48.8 cM, whereas this distance amounted to 13.3 cM in the desynaptic genotype RS93-8025-1. Hence desynapsis reduced crossing-over by 73%. The observed genetic distance of 48.8 cM in the normal synaptic clone, B92-7015-4, is the highest gene-centromere distance reported so far in potato and this could be explained on the assumption of absolute chiasma interference. For the Adh-1 locus, it was found that heterozygous 2n pollen grains could be detected in pollen samples of the diploid clones, because of the occurrence of a heterodimeric band of the isozyme. Unlike the amf locus, the gene centromere distance for the Adh-1 locus was estimated only on the basis of the duplex, simplex and nulliplex classes in the progenies from 4x (nulliplex Adh-I2) x B92-7015-4 (Adh-I1/Adh-12) crosses and was found o be 19.4 cM. Because the accurate positions of centromeres in relation to other loci are not available in the existing genetic maps of potato, which are saturated with molecular markers, half-tetrad analysis is a promising additional approach to the basic genetics of this crop.
Pollen markers for gene-centromere mapping in diploid potato / Bastiaanssen, Hjm; Ramanna, Ms; Sawor, Z; Mincione, Antonio; Steen, A VON-DER; Jacobsen, E. - In: THEORETICAL AND APPLIED GENETICS. - ISSN 0040-5752. - 93:7(1996), pp. 1040-1047. [10.1007/s001220050332]
Pollen markers for gene-centromere mapping in diploid potato
MINCIONE, Antonio;
1996-01-01
Abstract
The utility of two pollen genetic markers for estimating the extent of meiotic recombination between the centromere and a marker gene was tested in 2n pollen of diploid potato clones. One of these markers was the distal locus amylosefree (amf) on chromosome 8 and the other was the isozyme locus alcohol dehydrogenase (Adh-1) on chromosome 4. In the case of the amf locus, the gene-centromere distance was estimated in a normal synaptic and a desynaptic genotype. In both cases the genetic analysis was confined to: (1) a direct estimation of the phenotypic (blue vs red) segregation ratios in FDR (first- division restitution) 2n pollen and (2) a classification of the 4x progeny from 4x (nulliplex amf) x 2x (Amf/amf) crosses into duplex, simplex and nulliplex classes. The recombination frequency between the centromere and the amf locus in the normal synaptic genotype B92-7015-4 corresponded to a gene- centromere distance of 48.8 cM, whereas this distance amounted to 13.3 cM in the desynaptic genotype RS93-8025-1. Hence desynapsis reduced crossing-over by 73%. The observed genetic distance of 48.8 cM in the normal synaptic clone, B92-7015-4, is the highest gene-centromere distance reported so far in potato and this could be explained on the assumption of absolute chiasma interference. For the Adh-1 locus, it was found that heterozygous 2n pollen grains could be detected in pollen samples of the diploid clones, because of the occurrence of a heterodimeric band of the isozyme. Unlike the amf locus, the gene centromere distance for the Adh-1 locus was estimated only on the basis of the duplex, simplex and nulliplex classes in the progenies from 4x (nulliplex Adh-I2) x B92-7015-4 (Adh-I1/Adh-12) crosses and was found o be 19.4 cM. Because the accurate positions of centromeres in relation to other loci are not available in the existing genetic maps of potato, which are saturated with molecular markers, half-tetrad analysis is a promising additional approach to the basic genetics of this crop.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
