Pemilihan Tetua Persilangan pada Kubis (Brassica oleracea var. capitata) melalui Analisis Keragaman Genetik [Parental Line Selection in Cabbage (Brassica oleracea var. capitata) through Genetic Diversity Analysis]

Kubis (Brassica oleracea var. capitata) merupakan salah satu jenis sayuran yang mempunyai nilai ekonomis tinggi. Untuk meningkatkan hasil panen kubis tiap tahunnya perlu didukung oleh tersedianya varietas unggul yang tahan penyakit, terutama penyakit busuk hitam dan akar gada yang dapat menggagalkan panen. Metode yang dapat diaplikasikan untuk merakit varietas unggul adalah melalui persilangan. Penelitian ini bertujuan untuk memilih kombinasi tetua persilangan yang ideal pada tanaman kubis melalui analisis keragaman genetik menggunakan marka SSR (Simple Sequence Repeats). Penelitian dilakukan pada bulan Februari sampai Mei 2013 di laboratorium Functional Crop Genomics and Biotechnology, Seoul National University, Korea Selatan menggunakan 16 genotipe kubis yang diperoleh dari perusahaan benih Joeun, Korea Selatan. Keragaman genetik 16 genotipe kubis dianalisis menggunakan 35 marka SSR polimorfik, dan selanjutnya digunakan untuk menentukan keragaman genetik berdasarkan metode UPGMA. Nilai jarak genetik antar genotipe diperoleh berdasarkan rumus 1-nilai kesamaan genetik. Hasil analisis keragaman genetik membagi 16 genotipe kubis menjadi dua kelompok heterotik utama pada nilai kesamaan genetik 65,2%. Berdasarkan hasil analisis keragaman genetik dan nilai jarak genetik diperoleh empat kombinasi tetua persilangan ideal, yaitu genotipe IMO-03 vs IMO-08 (nilai jarak genetik 43%) dan IMO-03 vs IMO-10 (nilai jarak genetik 39%) untuk karakter ketahanan terhadap penyakit busuk hitam, serta genotipe IMO-18 vs IMO-10 dan IMO-17 vs IMO-10 dengan nilai jarak genetik masing-masing 45% dan 44% untuk karakter ketahanan terhadap penyakit akar gada. Keempat kombinasi tetua tersebut dipilih karena terletak pada kelompok heterotik berbeda serta mempunyai nilai jarak genetik yang jauh sehingga diharapkan dapat meningkatkan peluang heterosis pada progeni yang dihasilkan.KeywordsBrassica oleracea var. capitata; Genotipe; Keragaman genetik; Kubis; Pemilihan tetuaAbstractCabbage (Brassica oleracea var. capitata) is one of vegetable that has high economic value. The availability of high-yielding varieties that are resistant to some diseases, particularly black rot and clubroot disease is needed in order to increase cabbage yield per year. The method which can be applied to assemble new varieties is through crossbreeding program. The objective of this research was to select the ideal combination of parental lines in cabbage through analysis of genetic diversity by using SSR markers (Simple Sequence Repeats). The research was conducted from February to May 2013 in the laboratory of Crop Functional Genomics and Biotechnology, Seoul National University, South Korea using 16 cabbage genotypes obtained from Joeun seed company, South Korea. The genetic diversity of 16 cabbage genotypes were analyzed using 35 polymorphic SSR markers, and then used to determine the genetic diversity based on UPGMA method. Meanwhile, genetic distance value among cabbage genotypes obtained by the formula of 1-value genetic similarity. The results of genetic diversity analysis divided 16 cabbage genotypes into two main heterotic groups at genetic similarity value of 65.2%. Based on the results of genetic diversity analysis and genetic distance value, we selected four combinations of ideal parental lines, namely genotype IMO-03 vs IMO-08 (genetic distance value of 43%) and IMO-03 vs IMO-10 (genetic distance value of 39%) for black rot disease resistance character, as well as genotype IMO-18 vs IMO-10 and IMO-17 vs IMO-10 with genetic distance value of 45% and 44%, respectively for club root disease resistance character. These four parental lines combination were selected as ideal parental combinations due to they were located on a different heterotic groups and has high genetic distance value, which is expected to increase the chances of heterosis in their progeny.