Genome size, cytogenetic data and transferability of EST-SSRs markers in wild and cultivated species of the genus Theobroma L. (Byttnerioideae, Malvaceae)

Abstract

The genus Theobroma comprises several trees species native to the Amazon. Theobroma cacao L. plays a key economic role mainly in the chocolate industry. Both cultivated and wild forms are described within the genus. Variations in genome size and chromosome number have been used for prediction purposes including the frequency of interspecific hybridization or inference about evolutionary relationships. In this study, the nuclear DNA content, karyotype and genetic diversity using functional microsatellites (EST-SSR) of seven Theobroma species were characterized. The nuclear content of DNA for all analyzed Theobroma species was 1C = ~ 0.46 pg. These species presented 2n = 20 with small chromosomes and only one pair of terminal heterochromatic bands positively stained (CMA+/DAPI− bands). The small size of Theobroma ssp. genomes was equivalent to other Byttnerioideae species, suggesting that the basal lineage of Malvaceae have smaller genomes and that there was an expansion of 2C values in the more specialized family clades. A set of 20 EST-SSR primers were characterized for related species of Theobroma, in which 12 loci were polymorphic. The polymorphism information content (PIC) ranged from 0.23 to 0.65, indicating a high level of information per locus. Combined results of flow cytometry, cytogenetic data and EST-SSRs markers will contribute to better describe the species and infer about the evolutionary relationships among Theobroma species. In addition, the importance of a core collection for conservation purposes is highlighted.

Identification, analysis and development of salt responsive candidate gene based SSR markers in wheat

“…Our study demonstrated a reasonably good level of transferability of cg-SSRs to other Triticum species, suggesting loci containing these markers were conserved during evolution/domestication of wheat species. High levels of transferability of unigene derived-SSRs have been also reported in other crops [ 50 , 51 ]. The findings showing localization of many wheat salt responsive genes on rice and Brachypodium genomes indicate that the genomic fragment carrying the salinity tolerance associated genes are broadly conserved in these species to enable them to survive extreme salinity stress conditions.…”

Poliploidia e variações reprodutivas em Bombacoideae (Malvaceae): distribuição geográfica, filogeografia e tamanho do genoma

“…In general, it was possible to observe a weak correlation between the chromosome number and genome size (2C) as found in other studies (Collevatti and Dornellas 2016;Costa et al 2017) and in agreement with Soltis et al (2003) which emphasizes that the genome size may vary regardless of chromosome Silva et al 2017;Soltis et al 2003), as can also be visualized inside of each subfamily here.…”

Efficient anchoring of alien chromosome segments introgressed into bread wheat by new Leymus racemosus genome-based markers

“…Sequencing of all the potential gene sources for wheat breeding in the near future is not expected. Hence, transferability of markers between useful species of this gene pool, as a compensational approach of analysis, is highly desired [ 44 – 47 ]. Our analysis has proven clearly that markers from L. racemosus can be successfully transferred to L. mollis, P. huashanica and E. ciliaris , three other important species in the tribe Triticeae (Table 6 ).…”