Abstract
BackgroundInflorescence dichotomy in Musa species is a rare developmental event which leads to the production of multiple bunches on a single pseudostem at fruiting. In spite of its fascinating attraction and seductive appeal, little is known about the cytogenetic basis and molecular mechanisms that could be ascribed to this phenomenon. To bridge this gap in information, an integrative approach using cytological fingerprinting and DNA ploidy level profiling (based on chromosome counting and flow cytometry) were assayed on five inflorescence dichotomous plantain varieties and a single-bunching cultivar that served as control. This was done to assess the number and behaviour of chromosomes on the one hand and single nucleotide polymorphisms identified during analysis of nucleotide variations on the other.ResultsChromosomes stained with aceto-orcein were very tiny, compact, metacentric and acrocentric, and differed both in number and ploidy level between the inflorescence dichotomous and single-bunching cultivars. The dichotomous plantains were mainly diploid (2n = 2x = 22) while the single-bunching ‘Agbagba’ cultivar was consistently a triploid (2n = 3x = 33), as revealed by histological chromosome counting and flow cytometry, implying that there was a high incidence of genomic divergence on account of ploidy variations among the different Musa cultivars. Molecular genotyping using single nucleotide polymorphisms detected on the GTPase-protein binding gene of the leaf tissue gene complex provided further evidence indicating that differences in the number of bunches among the inflorescence dichotomous cultivars could be ascribed to nucleotide diversity that was elicited by changes in amino acid sequences in the genome of the crops. Non-synonymous nucleotide substitutions resulted mainly from transversion (from purine to pyramidine and vice versa), tacitly implying that these changes were crucial and promoted a cascade of reactions in the genome that were, probably, responsible for the non-persistence of the dichotomization event(s) or the reversals in the bunch phenotype detected among the inflorescence dichotomous cultivars.ConclusionsThis is the first report of cytogenetic fingerprints and nucleotide diversity detection among single- and multiple-bunching Musa cultivars. A clear distinction between the two groups was found that is indicative of variations both in ploidy level and nucleotide sequences. The pattern of single nucleotide polymorphisms provided profound clues suggesting that there was a high incidence of genomic divergence, due to random and unstable genetic events that were triggered by frequent spontaneous somatic mutations.
Highlights
Inflorescence dichotomy in Musa species is a rare developmental event which leads to the production of multiple bunches on a single pseudostem at fruiting
The present study represents the first attempt at using an integrative approach involving cytological and nuclear DNA ploidy profiling and molecular fingerprinting data to address the underlying genetics of inflorescence polymorphism in plantain, a phenomenon that has lately become noticeable in False Horn plantain cultivars
The results presented here show that while the five inflorescence dichotomous cultivars consisted mainly of diploids with several polymorphic variants that were genetically unstable, the single bunch-bearing ‘Agbagba’ cultivar was triploid and genetically stable
Summary
Inflorescence dichotomy in Musa species is a rare developmental event which leads to the production of multiple bunches on a single pseudostem at fruiting. In spite of its fascinating attraction and seductive appeal, little is known about the cytogenetic basis and molecular mechanisms that could be ascribed to this phenomenon To bridge this gap in information, an integrative approach using cytological fingerprinting and DNA ploidy level profiling (based on chromosome counting and flow cytometry) were assayed on five inflorescence dichotomous plantain varieties and a single-bunching cultivar that served as control. Aside from these, plantain is converted into high quality flour when the green, unripe fruit is peeled and the pulp dried and powdered Such flour is known to be a very good source of energy and is usually preferred by diabetics as it has been demonstrated to be more digestible than that derived from any of the common cereals
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