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 Somaclonal variation dapat menciptakan tambahan variabilitas genetik Plant improvement

gamma mahkota bunga 500 dan 1000 rad In vitro tunas Pengakaran Tanam di pot

Crop Improvement Program Variasi Somaklonal Tujuan Khusus Komersial/ Crop Improvement Program 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 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 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)

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