DNA methylation patterns and karyotype analysis of off-type and normal phenotype somatic embryos of feijoa

Abstract

Acca sellowiana is a native species to the southern region of Brazil, with secondary dispersion in Uruguay northeast. The potentially economic interest of this species motivated many fundamental and applied researches, such as micropropagation protocols development, including somatic embryogenesis (SE). Previous studies have reported the high frequency of off-type somatic embryos in A. sellowiana SE and low conversion efficiency, possibly due to this high off-type somatic embryos formation. In this sense, this study was aimed to evaluate the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) in the induction and development of somatic embryos in direct and indirect SE through cytogenetic and DNA methylation analysis. The results of the present work reinforces the previous findings that 2,4-D plays a key role in the SE induction in A. sellowiana. However, the continuous presence of this auxin in the culture medium enhances the rate of off-type somatic embryos. This auxin also apparently affects the cells and chromosomes size in normal and off-type somatic embryos and DNA methylation patterns of the analyzed samples. These findings may indicate that the off-type somatic embryos formation may be related to genetic and/or epigenetic changes caused by long-term cultivation in A. sellowiana. The intermediate phase of callus also indicated increased formation of off-types, corroborating other studies that showed that indirect SE could cause increased formation of anomalies in regenerated plantlets