Advances in the Molecular Cytogenetics of Bananas, Family Musaceae.

Denisa Šimoníková,Pavla Christelová,Eva Hřibová,Veronika Zoulová,Jana Čížková

doi:10.3390/plants11040482

Abstract

The banana is a staple food crop and represents an important trade commodity for millions of people living in tropical and subtropical countries. The most important edible banana clones originated from natural crosses between diploid Musa balbisiana and various subspecies of M. acuminata. It is worth mentioning that evolution and speciation in the Musaceae family were accompanied by large-scale chromosome structural changes, indicating possible reasons for lower fertility or complete sterility of these vegetatively propagated clones. Chromosomal changes, often accompanied by changes in genome size, are one of the driving forces underlying speciation in plants. They can clarify the genomic constitution of edible bananas and shed light on their origin and on diversification processes in members of the Musaceae family. This article reviews the development of molecular cytogenetic approaches, ranging from classical fluorescence in situ hybridization (FISH) using common cytogenetic markers to oligo painting FISH. We discuss differences in genome size and chromosome number across the Musaceae family in addition to the development of new chromosome-specific cytogenetic probes and their use in genome structure and comparative karyotype analysis. The impact of these methodological advances on our knowledge of Musa genome evolution at the chromosomal level is demonstrated. In addition to citing published results, we include our own new unpublished results and outline future applications of molecular cytogenetics in banana research.

Highlights

Bananas (Musa ssp.) are large herbaceous plants grown in tropical and subtropical regions of Southeast Asia, Africa, and South America [1,2]
It was impossible to detect recombination events between interspecific chromosomes [97,98,99]. These findings demonstrate the limits of the genomic in situ hybridization (GISH) technique for analyzing the genomic constitution of A × B banana hybrid clones
Radka DNA sequences were initially isolated from M. acuminata and cytogenetically localized to all mitotic chromosomes in M. acuminata and M. balbisiana [27]. These two short parts (742, resp. 193 nt long) of banana retroelements were determined to be specific to Eumusa species, and fluorescence in situ hybridization (FISH) analysis with probes derived from Radka5 and Radka6 in the genome of A × T banana hybrids resulted in signals specific to chromosomes originating from the A subgenome progenitor (Figure 8A,B, unpublished)

Summary

Introduction

Bananas (Musa ssp.) are large herbaceous plants grown in tropical and subtropical regions of Southeast Asia, Africa, and South America [1,2]. Wild Musa species have traditionally been subdivided into four sections based on the basic chromosome number (x) and a set of morphological descriptors [4,5]. Modern cultivated bananas originated from natural inter- and intraspecific crosses between two wild diploid species of the Eumusa section: M. acuminata (A genome) and M. balbisiana (B genome). Information about chromosome structural changes could help banana breeders select appropriate parents during banana breeding processes Traditional cytogenetic methods, such as for estimating genome size, ploidy, and chromosome counting, provide important information about the genome. Additional information on genomic constitution and large-scale chromosome structural changes that are associated with the evolution and speciation of bananas and their closely related genera can be obtained using molecular cytogenetics methods such as fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH)

Nuclear Genome of Bananas

Identification of Chromosomes by FISH

Analysis of Genome Constitution in Banana Hybrid Clones

Conclusions and Future Perspectives