Effects of stress and genomic plasticity on the reproductive mode of facultative apomictic plants of weeping lovegrass (Eragrostis curvula Schrad. Nees)

RODRIGO JM; OCHOGAVIA A; MEIER M; ZAPPACOSTA D; PESSINO SC; ECHENIQUE V

Buenos Aires

Simposio; The 6th International Symposium of the Molecular Breeding of Forage and Turf (MBFT 2010); 2010

Molecular Breeding of Forage and Turf International Committee

To overcome an environmental stress, plants mostly develop physiological responses triggered y genetic or epigenetic changes, some of them involving DNA methylation and transposon activation. It has been proposed that apomixis control occurs by temporal or spatial deregulation of a sexual process.In this sense, apomixis will be expressed depending on genetic and epigenetic factors affected by the environment. The aim of this study was to analyze the genetic and epigenetic changes that took place in a weeping lovegrass tetraploid plant (UNST1131) obtained by chromosome doubling which showed a high level of sexual reproduction when it was generated (2003) and 15-20% four years later (2007). The genetic (AFLPs) and epigenetic (MSAPs) profiles of this plant obtained by colchicine treatment from a sexual diploid plant obtained by tissue culture was analysed. These profiles were compared with the corresponding patterns of the apomictic tetraploid plant (cv Tanganyika), the origin of this euploid series. Gene libraries (cDNA, 2003) from both plants were screened for retrotransposon activity. On the other hand, a progeny test of somaclones from cvTanganyika was performed using isozymes (1998) and RAPD (2007). AFLP patterns (UNST1131 and cv Tanganyica) showed variation between 2003-2007, indicating genetic changes over time and certain genome plasticity. Also, MSAP results showed that plants were epigenetically more similar to each other  in 2007 that at the begginning of the tetraploidization, with a tendency to methylation over demethylation. Retrotransposon activity was higher in UNST1131, which could be explained as a response to tissue culture and/or polyploidization stress. Progeny test of somaclones using isozymes and RAPDs indicated a high level of sexual reproduction (variable progeny) immediately after the tissue culture procedure (1998) and a high level of uniform progeny (apomixis) ten years later. Taken together these results would indicate that epigenetic mechanisms affected by genomic stress could be regulating the expression of apomixis in this grass.