Molecular and Cytogenetic Study of East African Highland Banana.

Alžběta Němečková,Rony Swennen,Jaroslav Doležel,Brigitte Uwimana,Radim Svačina,Moses Nyine,Jana Čížková,Eva Hřibová,Ines Van Den Houwe,Pavla Christelová

doi:10.3389/fpls.2018.01371

Abstract

East African highland bananas (EAHBs) are staple food crop in Uganda, Tanzania, Burundi, and other countries in the African Great Lakes region. Even though several morphologically different types exist, all EAHBs are triploid and display minimal genetic variation. To provide more insights into the genetic variation within EAHBs, genotyping using simple sequence repeat (SSR) markers, molecular analysis of ITS1-5.8S-ITS2 region of ribosomal DNA locus, and the analysis of chromosomal distribution of ribosomal DNA sequences were done. A total of 38 triploid EAHB accessions available in the Musa germplasm collection (International Transit Centre, Leuven, Belgium) were characterized. Six diploid accessions of Musa acuminata ssp. zebrina, ssp. banksii, and ssp. malaccensis representing putative parents of EAHBs were included in the study. Flow cytometric estimation of 2C nuclear DNA content revealed small differences (max ~6.5%) in genome size among the EAHB clones. While no differences in the number of 45S and 5S rDNA loci were found, genotyping using 19 SSR markers resulted in grouping the EAHB accessions into four clusters. The DNA sequence analysis of the internal transcribed spacer region indicated a relation of EAHB clones with M. acuminata and, surprisingly, also with M. schizocarpa. The results suggest that EAHB cultivars originated from a single hybrid clone with M. acuminata ssp. zebrina and ssp. banksii being its most probable parents. However, M. schizocarpa seems to have contributed to the formation of this group of banana.

Highlights

Bananas and plantains are giant monocotyledonous plants of major importance in tropical and subtropical areas
The final dendrogram (Figure 1), which contains all East African highland bananas (EAHBs) representatives analyzed in this work, six diploid M. acuminata subspecies representing putative parents of EAHB, and the core subset of Musa accessions (Christelová et al, 2017) were adjusted as described in section Materials and Methods
Subspecies of M. acuminata ssp. burmannicoides and ssp. siamea were clustered within two small subclusters: subcluster II superimposed to the rest of the A-genome representatives (Figure 1, yellow cluster II) and subcluster IV

Summary

Introduction

Bananas and plantains are giant monocotyledonous plants of major importance in tropical and subtropical areas. Their domestication is not well-understood, but it is considered to have begun some 7000 years ago in Southeast Asia, which is considered the primary center of diversity from where bananas expanded to other parts of the world (D’Hont et al, 2012). Most of the edible banana cultivars are parthenocarpic triploid clones that originated from intra- and interspecific hybridization between subspecies of Musa acuminata with the A genome and EAHB Cytogenetic and Genetic Diversity. Minor groups of cultivated bananas are derived from interspecific hybridization of diploid M. schizocarpa (S genome) and M. textilis (T genome) in combination with M. acuminata and M. balbisiana (Carreel et al, 1994)

Methods

Results

Conclusion