The role of polyploidy in the adaptive significance of polymorphism at the GOT 1 locus in the Dactylis glomerata complex

Abstract

SUMMARYClinal variation along both altitudinal and latitudinal gradients was clearly observed in glutamate oxaloacetate transaminase gene frequencies (GOT 1 locus) from 21 diploid and 90 tetraploid populations of Dactylis glomerata L. collected over the entire area of the primary and secondary geographic distribution of the species. This was the starting point for experiments designed to detect selective effects and determine the significance of polymorphism at this locus. Progressive investigations were made combining different approaches to determine correlations between allelic frequencies and environmental variables. Consistency of these correlations was tested by small scale studies in sites that exhibited gradients in particular environmental variables and comparisons of the in vitro activiti of the allozymes were also made.The results show that alleles, specifically three among the eight investigated, are not randomly distributed. Two of the alleles are correlated with humidity and the other allele with temperature.From these experimental results and the data from natural populations, there appears to be an advantage to those individuals of this perennial species that possess maximal allelic diversity at this locus, especially in transitional climatic areas where variations in temperature and water availability are particularly high and unpredictable.As only tetraploid plants with the highest allelic diversity are found in such fluctuating conditions, it is suggested that tetraploid genetic structure may be directly responsible for the wider niches of tetraploids than of diploids. Consequently, tetraploids may occupy a wider range of habitats and possess a stronger colonisation potential and wider spatial distribution than diploids.

Allozyme polymorphism in diploid and polyploid populations of Galium

“…There is evidence for somewhat reduced activities of multiple copies of enzyme loci in polyploids, but no suggestion of their complete "silencing". These data are in line with theoretical and factual evidence from several polyploid complexes (both auto-as well as allopolyploid) studied in a comparable way (Barber, 1970;Bingham, 1980;Lumaret, 1984).…”

Diversity comparison and phylogenetic relationships of cocksfoot (Dactylis glomerata L.) germplasm as revealed by SSR markers

“…A strong genetic similarity between the Galician diploids and the tetraploids was revealed by means of isozyme profile and cpDNA restriction patterns (Lumaret 1984;Lumaret et al 1989). These results were also in good agreement with reports by Lumaret and Borrientos (1990), who assessed phylogenetic relationships between sympatric diploid and tetraploid plants of cocksfoot.…”

Relationships between agronomic characters and ecogeographical factors in a collection of French perennial ryegrass populations

“…However, as suggested by Peeters et al (1990), it would be interesting to gather populations with identical agronomic characteristics and from the same ecological area, and mate them in order to constitute new genetic resources for plant breeding programs. In the same way, as suggested by Lumaret (1984), the search for isoenzymatic systems as a means of revealing specific adaptation must be investigated. These different points will be presented in further papers.…”

“…Finally, in herbage grasses, most work relating to the relationships between ecological and agronomic traits has been aimed at perennial ryegrass in Europe (studies undertaken by the Welsh Plant Breeding Station: Breese, 1966, 1968;Lorenzetti et al, 1971;Tyler andChorlton, 1976, 1978;Tyler et al, 1984;Humphreys and Eagles, 1988) and also in New Zealand (Forde and Suckling, 1980). But some studies have also been performed on cocksfoot (Tyler, 1979;Lumaret, 1984) and tall fescue (Veronesi and Falcinelli, 1988 Charmet et al, 1990).…”