Struktur genetik manggis (Garcinia mangostana L.) berbasis marka morfologi dan molekuler

Abstract

Knowledge of genetic variability is important for mangosteen breeding to increase fruit quality. The objectives of this study were: 1) to reveal genetic variation of mangosteen individuals from Sumatra region based on morphology and molecular markers, 2). to study the relationships between morphology and genetic of mangosteen, 3). to access genetic structure of mangosteen populations. Eleven random ISSR primers were chosen to differenciate 22 mangosteen accessions from Sumatera regions. Combination of fruit morphology and DNA analysis using 8 RAPD and 5 ISSR primers were used to study relationships between morphology and molecular. The total of 106 samples from four mangosteen populations were analyzed on the study population genetic structure. Morphological and molecular data were analyzed by using NTSYS 2.1 program, and population genetic structure by program GenAlex 6.2. The results showed that mangosteen has wide diversity of morphology and narrow molecular diversity with similarity coefficient 0.08 to 1.0 and 0.83 to 0.99 respectively. It is mean that the morphological characters strongly influenced by environmental factors. There is a close correlation between the grouping based on morphological and molecular (.r = 0.95). Genetic analysis based on morphology at individual and population level separate the accessions into two groups: 1). The group with elliptical stigma lobe, small and thin petals, and number of fruit segments 5 to 11, and 2). groups of accessions with round stigma lobe, thick and large petals and the number of fruit segments 4-8. Molecular-based analysis at the individual level divides accession into two groups while at the population level into three groups. These results suggest that population-based analysis by using molecular markers showed more accurate results. Study population genetic structure separating mangosteen individuals into three groups: (A), Tembilahan (B), and mixed groups Tembilahan, Purwakarta Kerinci and Bulukumba, (C) that are grouped based on geography. In addition, the study population structure able to detect difference genetic groups within one population. AMOVA describe that genetic differences within populations equal to among populations, i.e., 50%. Although genetic variation within and among mangosteen population is nil, sufficient DNA polymorphism is found among some accessions to allow differentiation. Population genetic parameters show that the highest genetic variation present at Purwakarta population (Na = 1320, Ne = 1322, I = 0276, and PPL 62%), and the lowest at Kerinci population (Na = 1.00, Ne = 1171, I = 0154, and PPL=30%). Relationships between populations suggests that pair of population Tembilahan and Bulukumba have the greatest genetic differences (PhiPT = 0.491, the furthest genetic distance (D = 0169) and the lowest genetic identity (Nei I =. 0849). In contrast, pair of Kerinci and Bulukumba populations show the smallest genetic difference ( PhiPT = 0.320), the closest genetic distance (D = 0079) and the highest genetic identity (0924). Each of Tembilahan and Purwakarta population divides into two distinct genetic groups where both regions have local specific clones.

Pengetahuan tentang variabilitas genetik manggis penting untuk program pemuliaan dan sebagai dasar bagi perbaikan tanaman serta peningkatan daya saing. Manggis dikenal sebagai tanaman buah tropika yang mempunyai mekasisme reproduksi secara apomiksis dengan variasi genetik yang sempit. Penelitian tentang variasi genetik pada manggis sudah cukup banyak dilakukan namun belum terverifikasi dengan baik. Informasi tentang struktur genetik serta hubungan antara keragaman morfologi dan genetik belum tersedia. Untuk itu perlu dilakukan serangkaian kegiatan penelitian yang bertujuan untuk: 1). Mempelajari variasi genetik manggis pada tingkat individu berdasarkan karakter morfologi dan molekuler, 2). Mempelajari hubungan antara variasi morfologi dan genetik, dan 3). Mengungkap struktur genetik empat populasi manggis Indonesia berbasis marka molekuler. Kombinasi antara pendekatan morfologi dengan teknik analisis DNA memegang peranan penting dalam studi keragaman dan identifikasi varietas manggis. Pendekatan ini dapat meningkatkan akurasi dan mempersingkat waktu penelitian. Sebelas marka Inter-simple sequence repeat (ISSR) digunakan untuk mengetahui variasi genetik 22 individu manggis dari berbagai wilayah Sumatera. Hubungan antara karakter morfologi dan molekuler dipelajari menggunakan 33 aksesi manggis yang berasal dari Leuwiliang (Bogor-Jawa Barat), Kiara Pedes (Purwakarta-Jawa Barat), dan Pulau Palas (Tembilahan-Riau). Pengamatan morfologi difokuskan pada 10 karakter buah, dan analisis molekuler dilakukan dengan menggunakan 8 primer RAPD dan 5 primer ISSR. Struktur genetik populasi dipelajari dengan menggunakan 106 sampel tanaman manggis dari empat populasi manggis di Indonesia yaitu Purwakarta (Jawa Barat), Kerinci (Jambi), Tembilahan (Riau) dan Bulukumba (Sulawesi Selatan). Data morfologi dianalisis dengan metode Kruskal Wallis. Pengelompokan berdasarkan morfologi, molekuler dan gabungan morfologi dan mplekuler dianalisis dengan program NTSYSpc 2.1. Struktur genetik populasi dianalisis menggunakan program GenAlex 6.2.