Genome size and repetitive sequences are driven by artificial selection on the length of the vegetative cycle in maize landraces from Northeastern Argentina

María Florencia Realini,Lidia Poggio,Julián Cámara-Hernández,Graciela Esther González

doi:10.1590/2175-7860202172004

María Florencia Realini, Lidia Poggio + Show 2 more

Open Access

https://doi.org/10.1590/2175-7860202172004

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Abstract

Abstract Variation in genome size and knob heterochromatin content was explored in relationship to altitudinal cline and length of the vegetative cycle in northern Argentina, USA and Mexico landraces. It was considering that the decrease in DNA and heterochromatin content could be an adaptation to a shorter growing season and the result of artificial selection by man. Guaraní landraces from Northeastern Argentina (NEA) show similar variation in genome size (3.81pg to 7.56pg) and knob heterochromatin content than maize growing across an altitudinal cline. The present analysis offers an overview of the genetic variability of NEA maize to explain why Guaraní landraces and those along an altitudinal cline share this similar variation. Karyotype and flow cytometry data were employed. The DNA content of Guaraní landraces which lacking B chromosomes, showed no significant relationship with knob heterochromatin, suggesting differences in the amount of interspersed DNA. A significant positive relationship was found between the length of the vegetative cycle and both number and percentage of knob heterochromatin. No significant correlation was found between genome size and vegetative cycle. All these results allow us to conclude that the variation in heterochromatin content among Guaraní maize is driven by the selection of farmers for flowering time.

Highlights

Resumo La variación observada en el tamaño del genoma y el contenido de heterocromatina knob en relación con el cline altitudinal y la duración del ciclo vegetativo en razas de maíz nativas del norte de Argentina, Estados Unidos y México, permitió considerar que la disminución del contenido de ADN y heterocromatina se debería a una adaptación a temporadas cortas de crecimiento y al resultado de selección artificial por parte del hombre
51 morphological maize landraces have been described in northern Argentina (NA): 28 Northwestern (NWA) landraces distributed along an altitudinal cline, and 23 Northeastern (NEA) landraces cultivated without differences in altitude
B chromosomes (Bs) are common in NWA landraces, showing large intraand inter-population differences in number and frequency (Fourastié et al 2017; Poggio et al 1998; Rosato et al 1998), they have not been previously detected in Guaraní landraces from Northeastern Argentina (NEA) (Realini et al 2018)

Summary

Introduction

Resumo La variación observada en el tamaño del genoma y el contenido de heterocromatina knob en relación con el cline altitudinal y la duración del ciclo vegetativo en razas de maíz nativas del norte de Argentina, Estados Unidos y México, permitió considerar que la disminución del contenido de ADN y heterocromatina se debería a una adaptación a temporadas cortas de crecimiento y al resultado de selección artificial por parte del hombre. In Argentinian landraces, variation in genome size and knob heterochromatin content was explored in relationship to altitudinal cline and length of the vegetative cycle (Fourastié et al 2017; Realini et al 2016; Realini 2017).

Results

Conclusion