Genetic diversity and population structure of Musa accessions in ex situ conservation

Abstract

BackgroundBanana cultivars are mostly derived from hybridization between wild diploid subspecies of Musa acuminata (A genome) and M. balbisiana (B genome), and they exhibit various levels of ploidy and genomic constitution. The Embrapa ex situ Musa collection contains over 220 accessions, of which only a few have been genetically characterized. Knowledge regarding the genetic relationships and diversity between modern cultivars and wild relatives would assist in conservation and breeding strategies. Our objectives were to determine the genomic constitution based on Internal Transcribed Spacer (ITS) regions polymorphism and the ploidy of all accessions by flow cytometry and to investigate the population structure of the collection using Simple Sequence Repeat (SSR) loci as co-dominant markers based on Structure software, not previously performed in Musa.ResultsFrom the 221 accessions analyzed by flow cytometry, the correct ploidy was confirmed or established for 212 (95.9%), whereas digestion of the ITS region confirmed the genomic constitution of 209 (94.6%). Neighbor-joining clustering analysis derived from SSR binary data allowed the detection of two major groups, essentially distinguished by the presence or absence of the B genome, while subgroups were formed according to the genomic composition and commercial classification. The co-dominant nature of SSR was explored to analyze the structure of the population based on a Bayesian approach, detecting 21 subpopulations. Most of the subpopulations were in agreement with the clustering analysis.ConclusionsThe data generated by flow cytometry, ITS and SSR supported the hypothesis about the occurrence of homeologue recombination between A and B genomes, leading to discrepancies in the number of sets or portions from each parental genome. These phenomenons have been largely disregarded in the evolution of banana, as the “single-step domestication” hypothesis had long predominated. These findings will have an impact in future breeding approaches. Structure analysis enabled the efficient detection of ancestry of recently developed tetraploid hybrids by breeding programs, and for some triploids. However, for the main commercial subgroups, Structure appeared to be less efficient to detect the ancestry in diploid groups, possibly due to sampling restrictions. The possibility of inferring the membership among accessions to correct the effects of genetic structure opens possibilities for its use in marker-assisted selection by association mapping.

Molecular and cytological characterization of the global Musa germplasm collection provides insights into the treasure of banana diversity

“…Hippolyte et al 2012;de Jesus et al 2013), the intraspecific diversity of M. balbisiana is low compared to M. acuminata. This is reflected in our work by clustering all balbisiana accessions in a single coherent block (Fig.…”

FRUIT CHARACTERISTIC AND NUTRIENT VALUES OF FOUR INDONESIAN BANANA CULTIVARS (Musa spp.) AT DIFFERENT GENOMIC GROUPS

“…Edible bananas have 22, 33 or 44 chromosomes with the basic number is n=11, so that ploidy levels of banana cultivars are diploid, triploid and tetraploid respectively with 7 genome configurations including M. acuminata cultivars consists of AA, AAA and AAAA and the hybrid forms (M. acuminata x M. balbisiana) consists of AB, AAB, ABB and ABBB (Frison & Sharrock, 1998;Simmonds, 1959). Furthermore, various techniques of molecular analysis to identify the genomic group of bananas has already been employed (Jesus et al, 2013).…”

Physico-chemical characterization of banana varieties resistant to black leaf streak disease for industrial purposes

“…All bananas were grown at the Banana Germplasm Bank at Embrapa's Cassava and Fruits in Cruz das Almas, Bahia, Brazil. Some of these varieties were recommended by Embrapa (JESUS et al, 2013 Samples were prepared with ten banana fingers (each were replicated). The pH was evaluated by a direct reading using a pHmeter method 017/IV (INSTITUTE ADOLFO LUTZ, 2005).…”