Ploidy stability in embryogenic cultures and regenerated plantlets of tamarillo

Abstract

Ploidy levels of short-term (1 and 2 years) and long-term (7 and 10 years) embryogenic cultures as well as of regenerated plantlets of tamarillo were analyzed by flow cytometry and chromosome counts. Embryogenic cultures were induced from expanding leaves cultured in the presence of Picloram or 2,4-dichlorophenoxyacetic acid (2,4-D) and monthly subcultured on the same media. Embryo development and plantlets were obtained following subculture of the embryogenic tissue in auxin free medium containing gibberellic acid (GA 3). Seedlings and rooted shoots from axillary shoot proliferation were used as controls. The results showed that in long-term embryogenic cultures the ability to develop somatic embryos and plantlets was reduced. Embryogenic tissues maintained for 10 years were mostly aneuploids of the tetraploid (2n = 4x = 48) level whereas those kept in culture for 7 years or less were also mostly aneuploids but of the diploid (2n = 2x = 24) level. The results obtained by flow cytometry were, in general, consistent with those obtained by chromosome counts. The chromosome alteration observed in the embryogenic tissues was already present after 1 year of culture and increased with culture age, hence impairing the maintenance of these tissues for long periods without affecting chromosome stability of the regenerated plantlets. However, the occurrence of triploids and tetraploids as well as aneuploids can be useful for breeding purposes. A value around 23 pg/2C was found for the genome size of tamarillo largely exceeding the value previously published (15.50 pg/2C).

Somaclonal variations and their applications in horticultural crops improvement

“…This is so, because DNA in the initial stages of development in somatic embryogenesis contains lower levels of methylation than in the later stages (Sahijram et al 2003). Variation in in vitro cultures raised through somatic embryogenesis has been reported in several horticultural crops like hazel nut (Diaz-Sala et al 1995), Citrus paradisi (Hao et al 2004), oil palm (Jaligot et al 2004), rose (Xu et al 2004), potato (Sharma et al 2007), grapevine (Schellenbaum et al 2008), coffee (Menéndez-Yuffá et al 2010), olive (Leva et al 2012), tamarillo (Currais et al 2013) and brinjal (Naseer and Mahmood 2014). …”

“…A wide variety of tools are available for the detection and characterization of somaclonal variants which are primarily based on the differences in morphological traits (Pérez et al 2009, 2011; Nhut et al 2013), cytogenetical analysis for the determination of numerical and structural variation in the chromosomes (Clarindo et al 2012; Currais et al 2013; Abreu et al 2014), biochemical (Vujovic et al 2010; Kar et al 2014), molecular DNA markers (Krishna and Singh 2007; Pathak and Dhawan 2012; Hossain et al 2013; Bello-Bello et al 2014) or their combinations (Horáček et al 2013; Dey et al 2015; Stanišić et al 2015). The best test for assessing somaclonal variation is to fruit out the plants and conduct an extensive horticultural evaluation, which is unfortunately a long-term endeavor with woody fruit crops, particularly (Grosser et al 1996).…”

“…The uniformity of individual plants within a clone population is a major advantage of clonal cultivars in commercial production (Krishna and Singh 2013). However, genetic variations do occur in undifferentiated cells, isolated protoplasts, calli, tissues and morphological traits of in vitro raised plants (Bairu et al 2011; Currais et al 2013). In 1981, Larkin and Scowkraft coined a general term “somaclonal variation” for plant variants derived from any form of cell or tissue cultures.…”

Genome Status of Lippia alba Polyploid Complex Long-term in vitro Cultivated

“…Therefore, it is clear that the species retained its growth capacity even after culturing for a long period. Usually, ploidal changes reduce the regeneration capacity of in vitro culture explants [53,54], which apparently was not observed in natural polyploid complex L. alba. All ploidal levels (diploid, aneuploid, triploid, tetraploid, and hexaploid) showed the same behavior regarding their regeneration capacity.…”

Genetic Diversity of Chrysanthemum Plants Derived via Somatic Embryogenesis Using Rapd Markers

“…As a consequence, the resulting plants can be unstable [Miler and Zalewska 2014]. Until now it is the flow cytometry (FCM) which has been a widely used method to study the genetic stability of plants produced by micropropagation [Pinto et al 2010, Naing et al 2013b, Prado et al 2010, Konieczny et al 2012, Currais et al 2013, Lema-Rumińska and Śliwińska 2015. However, changes in the genetic material may be not only quantitative but also qualitative.…”