VARIASI SOMAKLONAL

VARIASI SOMAKLONAL

Dr.Ir. Sukendah, MSc

Dasar Bioteknologi Tanaman

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

mahkota bunga

500 dan 1000 rad

gamma

In vitro

tunas

Pengakaran

Tanam di pot

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)