Download In vitro tunas Pengakaran Tanam di pot Variasi Somaklonal Tujuan

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
• 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 alam
Kumpulan sel amorphous dari sel-sel yang membelah
diri terus menerus
Keuntungan utama
Plant improvement
Somaclonal variation dapat
menciptakan tambahan
variabilitas genetik
gamma
mahkota bunga
500 dan 1000 rad
In vitro
tunas
Pengakaran
Tanam di pot
Variasi Somaklonal Tujuan Khusus
Komersial/
Crop Improvement Program
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
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)