variasi somaklonal
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Variasi somaklonal
• Fenomena umum dalam regenerasi tanaman in vitro• Keragaman somaklonal adalah keragaman genetik
yang dihasilkan melalui kultur jaringan
• Keragaman genetik eksplanmutasi
• Keragaman genetik yang terjadi di dalam kultur jaringan
Fase tak berdiferensiasi yang relatif panjang
Pembentukan kalus
Massa sel parenkim yang terjadi karena proliferasi jaringan awal
•Somaklonal variation•Material utk mempelajari perkembangan•Dieksploitasi utk produksi bahan alamKumpulan sel amorphous dari sel-sel yang
membelah diri terus menerus
Keuntungan utama
Plant improvement
Somaclonal variation dapat menciptakan tambahan variabilitas genetik
Variasi Somaklonal Tujuan Khusus
1.Perubahan harus stabil
2. Perubahan harus merupakan sifat-sifat penting seperti vigor, hasil, kemasakan, tipe tanaman, fertilitas, dan lain-lain
3. Variasi somaklonal yang menarik pada umumnya meliputi sifat-sifat positif yang belum ada pada nomor-nomor galur yang dihasilkan oleh para pemulia tanaman
Komersial/Crop Improvement
Program
Terjadinya Variasi Somaklonal1. Genetic (Heritable Variations)
• Pre-existing variations in the somatic cells of explant (sudah ada variasi pada sel somatik sebelumnya)
• Caused by mutations and other DNA changes• Occur at high frequency
2. Epigenetic (Non-heritable Variations)• Variations generated during tissue culture
(variasi yang diinduksi oleh kondisi kuljar)• Caused by temporary phenotypic changes• Occur at low frequency
Somaclonal VariationPossible causes
the dedifferentiation – redifferentiation processaxillary shoot proliferation vs. organogenesis
& embryogenesishypothesis 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 VariationPossible causes
the "culture environment"the hypothesis – that tissue culture is
inherently stressful to cultured plant cellsenvironmental 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 VariationPossible causes
the "culture environment"environmental stress is known to cause:
transpositional changesinadequate control of the cell cycle
(errors in microtubule synthesis, spindle formation)
importance of PGRsscant evidence of direct mutagenic
actionmore evidence for transient
modifications of phenotype (e.g., dwarfing)