Exploring wild genetic resources of Musa acuminata Colla distributed in the humid forests of southern Western Ghats of peninsular India using ISSR markers

Narrow genetic diversity in germplasm from the Guinean and Sudano-Guinean zones in Benin indicates the need to broaden the genetic base of sweet fig banana (Musa acuminata cv Sotoumon)

Sweet fig (M. acuminata cv. Sotoumon) is an economically important dessert banana in Benin, with high nutritional, medicinal, and cultural values. Nevertheless, its productivity and yield are threatened by biotic and abiotic stresses. Relevant knowledge of the genetic diversity of this economically important crop is essential for germplasm conservation and the development of breeding programs. However, very little is known about the genetic makeup of this cultivar in Benin. To advance the understanding of genetic diversity in sweet fig banana germplasm, a Genotype-By-Sequencing (GBS) was performed on a panel of 273 accessions collected in different phytogeographical zones of Benin. GBS generated 8,457 quality SNPs, of which 1992 were used for analysis after filtering. The results revealed a low diversity in the studied germplasm (He = 0.0162). Genetic differentiation was overall very low in the collection as suggested by the negative differentiation index (Fstg = -0.003). The Analysis of Molecular Variance (AMOVA) indicated that the variation between accessions within populations accounted for 83.8% of the total variation observed (P < 0.001). The analysis of population structure and neighbor-joining tree partitioned the germplasm into three clusters out of which a predominant major one contained 98.1% of all accessions. These findings demonstrate that current sweet fig banana genotypes shared a common genetic background, which made them vulnerable to biotic and abiotic stress. Therefore, broadening the genetic base of the crop while maintaining its quality attributes and improving yield performance is of paramount importance. Moreover, the large genetic group constitutes an asset for future genomic selection studies in the crop and can guide the profiling of its conservation strategies.

Metabolite profiling characterises chemotypes of Musa diploids and triploids at juvenile and pre-flowering growth stages

Bananas (Musa spp.) are consumed worldwide as dessert and cooking types. Edible banana varieties are for the most part seedless and sterile and therefore vegetatively propagated. This confers difficulties for breeding approaches against pressing biotic and abiotic threats and for the nutritional enhancement of banana pulp. A panel of banana accessions, representative of the diversity of wild and cultivated bananas, was analysed to assess the range of chemotypes available globally. The focus of this assessment was banana leaves at two growth stages (juvenile and pre-flowering), to see when during the plant growth metabolic differences can be established. The metabolic data corresponded to genomic trends reported in previous studies and demonstrated a link between metabolites/pathways and the genomes of M. acuminata and M. balbisiana. Furthermore, the vigour and resistance traits of M. balbisiana was connected to the phenolic composition and showed differences with the number of B genes in the hybrid accessions. Differences in the juvenile and pre-flowering data led to low correlation between the growth stages for prediction purposes.

Efficacy of RAPD, ISSR and DAMD markers in assessment of genetic variability and population structure of wild Musa acuminata colla

North east India is considered as one of the major biodiversity hotspots worldwide and centre of origin of several plant species including Musa. Musa acuminata Colla is known to be one of the wild progenitors of cultivated bananas and plantains. Three single primer based DNA marker techniques viz., random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR) and directed amplification of minisatellites DNA (DAMD) were used for diversity diagnostics among 25 genotypes of wild M. acuminata collected from Meghalaya province of north east India. A total of 58 primers (26-RAPD, 21-ISSR, and11-DAMD) yielded 451 DNA fragments, of which 395 (87.58 %) were found to be polymorphic in nature. The polymorphic information content (PIC) values were almost identical for each marker system. The resolving power of the marker system was found to be highest in RAPD (3.96) whereas ISSR resolved highest marker index (16.39) in the study. Selected amplicon data obtained through single primer amplification reactions were utilized for determination of diversity within and among the populations of M. acuminata. Nei's genetic differentiation (Gst) value (0.451) indicated higher proportion of the genetic variation within the populations which is supported by the AMOVA analysis (88 %). The study provides insight into the efficacy of RAPD, ISSR and DAMD to analyse the genetic variation existing in the wild Musa germplasm, which can further be exploited for quality trait improvement and domestication of such important horticultural crops. The genetic diversity based population structure may shed light on the genetic basis of speciation and evolution of various species within the genus Musa.