Somaclonal variation induction and in vitro testing for phalaenopsis resistance improvement againts soft rot disease

Abstract

Penyakit busuk lunak yang disebabkan oleh bakteri Erwinia carotovora subsp. carotovora merupakan penyakit yang dapat menyebabkan kerugian bagi para petani anggrek Phalaenopsis. Salah satu metode untuk mengendalikan penyakit ini yaitu menggunakan kultivar tahan. Kultivar tahan penyakit busuk lunak dapat dirakit melalui berbagai cara di antaranya melalui hibridisasi dan seleksi. Sejatinya perakitan kultivar tahan Erwinia carotovora subsp. carotovora melalui hibridisasi tidak mudah dilakukan karena ketersediaan sumber genetik yang membawa sifat tahan sangat terbatas. Pendekatan untuk memperluas keragaman genetik dengan menggunakan kombinasi perlakuan mutagenesis radiasi sinar gamma dan EMS secara in vitro yang diikuti dengan pengujian in vitro merupakan metode yang efisien untuk memperolah kultivar Phalaenopsis tahan terhadap penyakit busuk lunak. Penelitian ini bertujuan untuk mendapatkan materi genetik anggrek Phalaenopsis yang tahan terhadap penyakit busuk lunak yang disebabkan oleh Erwinia carotovora subsp. carotovora. Induksi ketahanan terhadap penyakit busuk lunak telah dilakukan melalui iradiasi sinar gamma dan EMS dalam beberapa tahap percobaan. Pertama, penyiapan kalus embriogenik klon SGN-PV2.11 , 642 dan klon 377. Kedua, kalus yang diperoleh, diradiasi dengan sinar gamma dan sebagian lainnya direndam dalam larutan EMS. Ketiga, kalus diregenerasikan pada media yang diberi zat pengatur tumbuh. Keempat, plantlet yang terbentuk (berukuran 5 cm atau memiliki 4 daun sejati) diuji ketahanannya terhadap Erwinia carotovora subsp. carotovora. Hasil pengujian tersebut diperoleh varian yang potensial tahan terhadap patogen busuk lunak. Kelima, varian potensial tahan hasil uji in vitro yang diperoleh, diaklimatisasi hingga tanaman berukuran 7-10 cm dan selanjutnya diuji kembali di lapangan menggunakan Erwinia carotovora subsp. carotovora. Hasil pengujian tersebut diperoleh mutan tahan terhadap penyakit busuk lunak.

Soft rot disease caused by Erwinia carotovora subsp. carotovora is an important disease of Phalaenopsis sp. Efforts have been made to control the disease, but the results are not sufficiently promising. The use of resistant varieties is commontly recommended to control the disease because of its save impact to the environment and human life. Therefore, development of new superior varieties that are highly resistant to the disease is very urgent at the moment. Somaclonal variation using mutagenic agents is proven to be one of feasible technique to provide promising resistant varieties. In this study, development new resistant varieties to soft rot disease was conducted by using physical mutagenesis gamma ray irradiation and chemical mutagenesis EMS that were induced somaclonal variation and combined with in vitro testing technique. Gamma ray and EMS were applied separately to the calli. The treated calli were regenerated on selected in vitro medium enriched with plant growth regulator. The results showed that somaclone variation occured on the three clones treated. Frequency of occurance of somaclone variation using gamma ray variation was 0.4- 6.85 while using EMS was 0.9 – 20.8%. The all variants were in vitro tested for their resistance to soft rot disease by using pathogen suspension agent Erwinia carotovora subsp. carotovora and it was obtained 162 potential mutant resistant to soft rot. After all potential mutant resistant being tested using the same agent in the field, it was proven that of the total available genetic materials, 14 mutants of SGN-PV2.11, 6 mutants of clone No. 642 and 4 mutants of clone No. 377 were resistant to Erwinia carotovora subsp. carotovora, the cause agent of soft rot disease.