RESUMEN
Bidirectional selective genotyping carried out independently for five quantitative traits within a biparental population of recombinant inbred lines of rye has revealed dramatic changes in alleles distribution in the population tails. A given allele, predominant in the lower tail, is often neutral for reversely directed selection or associates with the upper tail following divergent selection for a related trait. Such radical changes in the alleles distribution cannot be explained by differences in genotypic values within a single locus. This paper presents the theoretical model of a genetic mechanism underlying observed responses of individual loci to divergent selection. The presented model refers to the specific interactions between alleles at two loci. Its wider application in genetic analysis will open up new possibilities for testing positions of genes in the hierarchical structure of interacting loci revealed under selection pressure.
Asunto(s)
Genética de Población , Sitios de Carácter Cuantitativo , Secale/genética , Selección Genética , Alelos , Mapeo Cromosómico , ADN de Plantas/genética , Marcadores Genéticos , Genotipo , Modelos Genéticos , Fenotipo , Análisis de Secuencia de ADNRESUMEN
A fragment of the ScHd1 gene derived from eight inbred lines was sequenced and showed homology to other Hd1 genes from different cereals. Sequences were analysed with respect to the presence of a single-nucleotide polymorphism (SNP) difference. A C-T transition at position 312 of the consensus sequence was found, which distinguished two lines from the remaining six. The deduced amino acid sequence revealed a high identity (93%) to a Hd1-like protein from wheat. The identified mutation allowed the localisation of ScHd1 on a genetic map of rye (6RS). A small, statistically significant linkage between ScHd1 and earliness per se (eps) and some morphological traits was also established. The chromosomal region, including the S76 allele for the ScHd1 gene was linked to earlier heading, elongated spikes, a greater number of spikelets per spike and an increased weight of 1000 kernels.
Asunto(s)
Mapeo Cromosómico , Genes de Plantas/genética , Secale/anatomía & histología , Secale/genética , Cromosomas de las Plantas/genética , Ligamiento Genético , Polimorfismo de Nucleótido Simple/genética , Sitios de Carácter Cuantitativo , Secale/crecimiento & desarrolloRESUMEN
Bi-directional selective genotyping (BSG) carried out on two opposite groups of F(9)(541 × Ot1-3) recombinant inbred lines (RILs) with extremely low and extremely high alpha-amylase activities in mature (dry) grain of rye, followed by molecular mapping, revealed a complex system of selection-responsive loci. Three classes of loci controlling alpha-amylase activity were discerned, including four major AAD loci on chromosomes 3R (three loci) and 6RL (one locus) responding to both directions of the disruptive selection, 20 AAR loci on chromosomes 2RL (three loci), 3R (three loci), 4RS (two loci), 5RL (three loci), 6R (two loci) and 7R (seven loci) responding to selection for low alpha-amylase activity and 17 AAE loci on chromosomes 1RL (seven loci), 2RS (two loci), 3R (two loci), 5R (two loci) and 6RL (four loci) affected by selection for high alpha-amylase activity. The majority of the discerned AA loci also showed responsiveness to selection for preharvest sprouting (PHS). Two AAD loci on chromosome arm 3RL coincided with PHSD loci. The AAD locus on chromosome arm 3RS was independent from PHS, whereas that on chromosome 6RL belonged to the PHSR class. AAR-PHSR loci were found on chromosomes 4RS (one locus) and 5R (two loci) and AAE-PHSE loci were identified on chromosomes 1RL (one locus) and 5RL (one locus). Some PHSD loci represented the AAE (chromosomes 1RL, 3RS and 3RL) or AAR classes (chromosome 5RL). AAR and AAE loci not related to PHS were found on chromosomes 1RL, 2R, 3RS, 4R, 6RL and 7RL. On the other hand, several PHS loci (1RL, 3RS, 5RL, 6RS and 7RS) had no effect on alpha-amylase activity. Allele originating from the parental line 541 mapped in six AA loci on chromosomes 2R (two loci), 5R (three loci) and 7R (one locus) exerted opposite effects on PHS and alpha-amylase activity. Differences between the AA and PHS systems of loci may explain the weak correlation between these two traits observed among recombinant inbred lines. Strategies for the breeding of sprouting-resistant varieties with low alpha-amylase and high PHS resistance are discussed.