Correlation between molecular markers and adaptively significant genetic variation in Bromus tectorum (Poaceae), an inbreedingannual grass

Abstract

Single sequence repeat (SSR) and amplified fragment length polymorphic (AFLP) molecular marker genotypes in cheatgrass (Bromus tectorum) were compared to published data on phenotypic variation in seed dormancy, vernalization requirement, and resistance to the pathogen Ustilago bullata. Several features of cheatgrass facilitated this study: it is a recent invader in the western United States, has considerable phenotypic polymorphism, and is an obligate self-pollinator. Forty self-pollinating lines from four populations common to the three phenotypic data sets were analyzed for molecular genetic variation using seven SSR loci and 31 AFLP loci. We examined correlations between distance matrices using the Mantel test for each pair of studies. The two molecular data sets were significantly correlated (r = 0.636). The AFLP markers often distinguished among several lines with identical SSR genotypes. The AFLP data were also significantly correlated with the phenotypic data (r values from 0.4640 to 0.5658), but the SSR data were much more highly correlated (r values from 0.677 to 0.844). The difference between molecular marker systems was especially notable when an outlier population from Potosi Pass, Nevada, was excluded from the analysis. These results suggest that SSR markers may be good surrogates for phenotypic traits in population genetic studies of strongly inbreeding species such as cheatgrass.

Genetic and morphological differentiation between Melica ciliata L. and M. transsilvanica Schur (Poaceae) in Europe reveals the non-presence of M. ciliata in the Polish flora

“…Moreover, our findings are congruent with those of previous allozyme study [7] showing that the proportion of the genetic diversity that resides between populations (G ST = 0.53) was far higher than reported for most diploid plants and were only comparable with the mean G ST reported for obligatory selfing species [78]. For example, a large reduction of genetic variability within populations and increased differentiation between populations have been observed in obligatory selfing grass Bromus tectorum [80] or in predominantly selfing grass Nassella pulchra [81] and in wetland species Typha latifolia [82].…”

Low level of genetic variation within Melica transsilvanica populations from the Kraków-Częstochowa Upland and the Pieniny Mts revealed by AFLPs analysis

“…Elymus caninus (Díaz et al 1999) or Elymus alaskanus (Sun et al 2002), but comparable with the level of genetic variation found in obligate self-pollinators, e.g. Bromus tectorum (Bartlett et al 2002;Ramakrishnan et al 2004) or in the self-compatible Calamagrostis porteri subsp. insperata (Esselman et al 1999).…”

Local population differentiation in Bromus tectorum L. in relation to habitat-specific selection regimes

“…Because the visualization in the current study was carried out on a different machine than the one used in our original studies (a Perkin-Elmer ABI 377 automated DNA analyzer), we included DNA from a set of B. tectorum reference lines from the earlier study (Ramakrishnan et al 2004) along with the 200 unknowns, to verify that the two DNA analyzers gave identical allele lengths for each of the SSR markers. We encountered small but consistent differences in allele lengths at each locus for reference lines from the two analyzers.…”

“…Because of its highly selfing breeding system, it is possible to associate B. tectorum SSR genotypes with particular suites of adaptive traits (Ramakrishnan et al 2004). There is also some support for the hypothesis that pre-adapted inbreeding lines with characteristic SSR marker fingerprints are favored by selection in similar environments over a wide geographic range (Ramakrishnan et al 2006).…”