ANALISIS KERAGAMAN GENETIK Phytophthora capsici Leonian ASAL LADA (Piper nigrum L.) MENGGUNAKAN PENANDA MOLEKULER - CHAERANI, CHAERANI; KOERNIATI, SRI; MANOHARA, DYAH (Pusat Penelitian dan Pengembangan Perkebunan)
ABSTRAKPhytophthora capsici adalah penyebab penyakit busuk pangkalbatang yang paling merugikan pada lada di Indonesia dan sulitdikendalikan karena dapat bertahan lama dalam tanah serta memilikikeragaman agresivitas isolat luas. Pengetahuan mengenai keragamangenetik strain-strain P. capsici dapat membantu perancangan strategiefektif pengelolaan patogen. Penelitian ini bertujuan mengevaluasikeragaman dan struktur genetik isolat-isolat P. capsici asal ladamenggunakan penanda RAPD. Penelitian dilaksanakan pada bulanOktober 2009 sampai April 2010 di Laboratorium Biokimia BB Biogendan Laboratorium Hama dan Penyakit Balittro. Keragaman genetik 59isolat P. capsici yang berasal dari koleksi kultur tahun 1982-2009 dari 37lokasi di Sumatera, Bangka, Jawa, dan Kalimantan, dikarakterisasimenggunakan enam primer RAPD. Pengelompokan menggunakanunweighted pair-group method with arithmatic averaging (UPGMA)berdasarkan profil RAPD membagi ke-59 isolat ke dalam lima gerombolutama; yang menunjukkan adanya keragaman genetik tinggi antar isolat.Pengelompokan RAPD tidak berkaitan dengan asal lokasi isolat. Analysisof molecular variance (AMOVA) juga menunjukkan adanya keragamangenetik yang tinggi di antara isolat-isolat P. capsici, dengan ragam genetiktotal sebesar 96% terletak di dalam masing-masing pulau (withinpopulations). Namun demikian, terdapat ragam genetik antar isolat daripulau berbeda (among populations) yang signifikan (4% ; P=0,001), yaituantar populasi di Sumatera dan Bangka dengan jarak genetik sebesar 0,081(P=0,002). Ketidakterkaitan antara pengelompokan RAPD dengan asallokasi geografik isolat dan ragam genetik yang tinggi dalam satu pulaudapat diakibatkan oleh terjadinya penyebaran isolat antar daerah, terutamamelalui bibit tanaman yang terinfestasi P. capsici. Pencegahan penyebaranisolat antar pulau perlu dilakukan melalui sertifikasi bibit bebas penyakitBPB dan pengembangan sistem perbenihan lokal.Kata kunci: lada, penyakit busuk pangkal batang, Phytophthora capsici,RAPD, keragaman genetik, struktur populasiABSTRACTPhytophthora capsici is the causal agent of foot rot, the mostdestructive disease of pepper in Indonesia and difficult to control .Knowledge in the genetic structure of P. capsici strains can enrichdesigning effective disease management strategies. This study was aimedat analyzing the genetic variability and structure of P. capsici isolates frompepper using RAPD. The study was done from October 2009 until April2010 at the Biochemical Laboratory of Indonesian Center for AgriculutralBiotechnology and Genetic Resources Research and Development, and thePlant Pest and Disease Laboratory of the Indonesian Research Institute ofSpice and Medicinal Crops. Fifty-nine isolates collected from 1982 to2009 from Sumatera, Bangka, Java, and Kalimantan were characterizedbased on six RAPD markers. Unweighted pair-group method witharithmatic averaging (UPGMA) clustering based on RAPD profilesdivided the isolates into five major cluster, which indicated high geneticvariability among isolates. No apparent relationship between RAPDclustering and geographic origin of isolate was observed. Hierarchicalpartitioning of genetic variation using analysis of molecular variance(AMOVA) confirmed the overall high variability among isolates, with96% of total genetic variance was resided among isolates within islands(within populations). Nevertheless, a small (4%) but significant (P=0.001)genetic variance among isolates between different islands (amongpopulations) were observed, which was detected between populations inSumatera and Bangka with genetic distance (Ð¤ PT ) as high as 0,081(P=0,002). The lack of association between RAPD clustering andgeographic origin as well as high genetic variance within populations mayhave been the result of movement of isolates between locations, mostlikely through infested plant cuttings. Use of certified and development ofblackpepper clones locally are required to prevent disease spread amongislands.Keywords: black pepper, foot rot disease, Phytophthora capsici, geneticdiversity, RAPD, population structure