BackgroundRetrotransposons-RTNs, are main source of variations in plant genomes that copying and pasting themselves into different transposon and work by changing RNA back into DNA via reverse transcription. For that reason, they are largely utilized in plants as optimum molecular markers to determine DNA fingerprinting, genetic mapping, and genetic variability. ResultsInter-retrotransposon amplified polymorphisms (IRAPs) were used to measure genetic variability and structure in a collection of 118 sweet wormwood (A. annua) accessions identifying and amplifying 849 loci using 32 IRAP primers, derived from Rosaceae, Gramineae, and Solanaceae retroelements. Single IRAP primer Tnt1.OL16 based on RTN produced the maximum count of markers. Percentage of polymorphic loci (PPL), mean expected heterozygosity (He), number of effective alleles (Ne) and information index (I) of Shannon, in the studied collection were 95.80%, 0.30, 1.48 and 0.46, in the same order. AMOVA analysis showed nonexistence of significant genetic structures during structure analysis, however, the 4 populations had three clusters based on the NJ dendrogram that depicted a relatively higher level of genetic variation within each population. These clusters were approximately congruent with corresponding geographical distributions. ConclusionsIn conclusion, low genetic diversity of Iranian Sweet wormwood was detected that could be reduced through introduction of appropriate exotic or improved germplasm to reduce the effects of inbreeding depression.
The identification of polymorphic markers associated with various quantitative traits allows us to test their performance for the exploitation of the extensive quantitative variation maintained in gene banks. In the current study, a set of 97 wheat germplasm accessions including 48 cultivars and 49 breeding lines were evaluated for 18 agronomic traits. The accessions were also genotyped with 23 ISSR, nine IRAP and 20 REMAP markers, generating a total of 658 clear and scorable bands, 86% of which were polymorphic. Both neighbor-joining dendrogram and Bayesian analysis of clustering of individuals revealed that the accessions could be divided into four genetically distinct groups, indicating the presence of a population structure in current wheat germplasm. Associations between molecular markers and 18 agronomic traits were analyzed using the mixed linear model (MLM) approach. A total of 94 loci were found to be significantly associated with agronomic traits (P≤0.01). The highest number of bands significantly associated with the 18 traits varied from 11 for number of spikelets spike (NSS) to two for grain yield in row (GRY). Loci ISSR16-9 and REMAP13-10 were associated with three different traits. The results of the current study provide useful information about the performance of retrotransposon-based and ISSR molecular markers that could be helpful in selecting potentially elite gene bank samples for wheat-breeding programs.
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