460 likes | 2.44k Views
Dasar Bioteknologi Tanaman. VARIASI SOMAKLONAL. Dr.Ir . Sukendah , MSc. Variasi somaklonal. Fenomena umum dalam regenerasi tanaman in vitro. Keragaman somaklonal adalah keragaman genetik yang dihasilkan melalui kultur jaringan. Keragaman genetik eksplan. mutasi.
E N D
DasarBioteknologiTanaman • VARIASISOMAKLONAL Dr.Ir. Sukendah, MSc
Variasisomaklonal • Fenomenaumumdalamregenerasitanaman in vitro • Keragamansomaklonaladalahkeragamangenetik • yang dihasilkanmelaluikulturjaringan • Keragamangenetikeksplan mutasi • Keragamangenetik yang terjadididalam • kulturjaringan Fasetakberdiferensiasiyang relatifpanjang
Pembentukan kalus Massa selparenkim yang terjadikarenaproliferasijaringanawal • Somaklonal variation • Material utkmempelajariperkembangan • Dieksploitasiutkproduksibahanalam Kumpulan sel amorphous darisel-sel yang membelahdiriterusmenerus
Keuntungan utama Somaclonal variation dapat menciptakan tambahan variabilitas genetik Plant improvement
gamma mahkotabunga 500 dan 1000 rad In vitro tunas Pengakaran Tanamdi pot
VariasiSomaklonalTujuanKhusus Komersial/ Crop Improvement Program • Perubahanharusstabil • 2. Perubahanharusmerupakansifat-sifatpentingseperti vigor, hasil, kemasakan, tipetanaman, fertilitas, dan lain-lain • 3. Variasisomaklonal yang menarikpadaumumnyameliputisifat-sifatpositif yang belumadapadanomor-nomorgalur yang dihasilkanolehparapemuliatanaman
TerjadinyaVariasiSomaklonal • Genetic (Heritable Variations) • Pre-existing variations in the somatic cells of explant (sudahadavariasipadaselsomatiksebelumnya) • Caused by mutations and other DNA changes • Occur at high frequency • Epigenetic (Non-heritable Variations) • Variations generated during tissue culture (variasi yang diinduksiolehkondisikuljar) • Caused by temporary phenotypic changes • Occur at low frequency
Somaclonal Variation • Possible causes • the dedifferentiation – redifferentiation process • axillary shoot proliferation vs. organogenesis & embryogenesis • hypothesis of D'Amato • somaclonal variants are rare in micropropagated plants (when multiplication is by axillary branching of shoot tips/buds) • more common during shoot organogenesis & somatic embryogenesis (esp. w/a callus phase)
Somaclonal Variation • Possible causes • the "culture environment" • the hypothesis – that tissue culture is inherently stressful to cultured plant cells • environmental stress is known to cause: • DNA methylation – the methylation of cytosine is known to cause gene inactivation; this may occur during the redifferentiation process • gene amplification – can result in incr. gene expression
Somaclonal Variation • Possible causes • the "culture environment" • environmental stress is known to cause: • transpositional changes • inadequate control of the cell cycle (errors in microtubule synthesis, spindle formation) • importance of PGRs • scant evidence of direct mutagenic action • more evidence for transient modifications of phenotype (e.g., dwarfing)