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 eksplan mutasi

• 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

•Somaclonal variation •Material utk mempelajari perkembangan •Dieksploitasi utk produksi bahan alam

Kumpulan 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 Somaklonal

1. 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 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)