Indirect somatic embryogenesis in Coffea with different ploidy levels: a revisiting and updating study

Abstract

Indirect somatic embryogenesis (ISE) is required for plant propagation and a prerequisite for applications that may provide new germplasms. Genetic, epigenetic and physiological features of the explant donor are barriers for ISE establishment, hindering its wide use. Despite the identification and/or expression analysis of genes during ISE, no approach to establish the karyotype aspects has been performed so far. So, this study aims to establish the ISE and compare the in vitro responses between diploid (Coffea canephora and Coffea eugenioides), allotriploid (“Híbrido de Timor”—HT) and true allotetraploid (Coffea arabica) Coffea in a taxonomic and evolutive scenario. Under the same in vitro conditions, the four Coffea differed from each other during ISE. Leaf explants of the true allopolyploids yielded the highest mean number of friable calli (FC) in relative short time and visually exhibiting more pronounced length. FC of the allotetraploid C. arabica presented the highest mean number of mature cotyledonary somatic embryos (MCSE), which were also recovered faster in this species. However, MCSE mean number in HT was the same or lower than diploid Coffea. Besides, intraspecific variation related to the ISE responses was observed in each Coffea, mainly the mean number of FC obtained from ex vitro and in vitro C. arabica and C. eugenioides explants. So, epigenetic and physiologic features may also have influenced the ISE responses. The findings provide the basis for performing other approaches considering the ploidy level, epigenetic and physiological backgrounds. Besides, the data also contributed for understanding about the consequences of polyploidy.