Keanekaragaman Genetik Mangga (Mangifera indica L.) dan Kerabatnya di Pulau Seliu, Kabupaten Belitung

Abstract

Information on mango germplasm in small islands, including Seliu Island, known as ‘Mango Island’, is limited. Data on the identity, taxonomic status, and number of mangoes are not yet available. Research on mango diversity in Seliu Island needs to be conducted to identify the genetic diversity of mangoes in Seliu Island based on fruit morphology and molecular with inter simple sequences repeat (ISSR) markers. As many as 49 mango accessions were collected from Seliu Island, and 13 were collected from Majalengka and Bogor for comparison; a herbarium was made and identified based on the local name of each species. Thirty-five mango accession fruits were collected and characterized using 34 fruit morphological characters, and matrices were created for Pearson correlation analysis. All mango leaf samples were isolated and tested for quantity and quality. A total of 22 ISSR primers were selected, and 15 primers that produced polymorphic banding patterns were used to amplify all samples. The amplification results were electrophoresed, documented, matrixed, and genetically analysed, including the number of alleles observed, number of effective alleles, Shannon information index, expected heterozygosity, and polymorphic information content. Cluster analysis was performed by calculating the similarity coefficient of simple matching and constructing a dendrogram using the unweighted pair group method with arithmetic mean. Fruit morphological data matrix and polymorphic bands were used for Pearson correlation analysis. A total of 49 mango accessions from Seliu Island were successfully determined into 24 local cultivars and can be classified into eight species, namely Mangifera indica, M. laurina, M. zeylanica, M. magnifica, M. quadrifida, M. caesia, M. odorata, and M. foetida. Fruit characterization of 35 accessions comprising M. indica, M. laurina, and M. zeylanica showed variation. There were three separate subgroups based on fruit flesh thickness characters. However, the grouping did not separate all accessions according to the species. The genetic diversity profile of 49 mango accessions on Seliu Island showed 193 polymorphic bands out of 222 bands (86.17%). Mangifera has a high level of polymorphism and genetic diversity (PPP=86.17%; I=0.334; He=0.210), while M. indica has a relatively high level of genetic polymorphism (PPP=62.61%) and low genetic diversity (He=0.172). Cluster analysis based on ISSR data visualized two main groups based on subgenus, namely Limus and Mangifera. Mango accessions from Seliu Island and West Java tended to cluster based on geographical origin. Primary band UBC-825 (1500 bp) correlated with fruit flesh thickness (r=0.72), while primary band UBC-808 (1000 bp) was associated with fruit blush colour (r=-0.77). Studying mango genetic diversity provides essential information on the genetic relationships and variability of local mango cultivars on Seliu Island.

Informasi plasma nutfah mangga di pulau kecil masih terbatas, termasuk di Pulau Seliu yang dikenal sebagai “Pulau Mangga”. Data mengenai identitas, status taksonomi, dan jumlah mangga di pulau tersebut belum tersedia. Penelitian keanekaragaman mangga di Pulau Seliu perlu dilakukan dengan tujuan mengidentifikasi keanekaragaman genetik mangga di Pulau Seliu berdasarkan morfologi buah dan molekuler dengan marker inter simple sequence repeat (ISSR). Sebanyak 49 aksesi mangga dikoleksi dari Pulau Seliu dan 13 aksesi mangga dikoleksi dari Majalengka dan Bogor sebagai pembanding, dibuat herbarium, dan diidentifikasi berdasarkan nama lokal dari setiap spesies. Sejumlah 35 buah aksesi mangga dikoleksi, dikarakterisasi menggunakan 34 karakter morfologi buah, dan dibuat matriks untuk analisis korelasi Pearson. Seluruh sampel daun mangga diisolasi, lalu diuji kuantitas dan kualitasnya. Sejumlah 22 primer ISSR diseleksi, lalu 15 primer yang menghasilkan pola pita polimorfik digunakan untuk mengamplifikasi seluruh sampel. Hasil amplifikasi dielektroforesis, didokumentasi, dibuat matriks, lalu dianalisis parameter genetiknya meliputi jumlah alel yang diamati, jumlah alel efektif, indeks informasi Shannon, heterozigositas yang diharapkan, dan polymorphic information content. Analisis gugus dilakukan dengan menghitung koefisien simple matching dan mengonstruksi dendrogram dengan unweighted pair group method with arithmetic mean. Matriks morfologi buah dan pita polimorfik digunakan untuk analisis korelasi Pearson. Sebanyak 49 aksesi mangga dari Pulau Seliu berhasil dideterminasi ke dalam 24 kultivar lokal dan dapat diklasifikasikan menjadi delapan spesies yaitu Mangifera indica, M. laurina, M. zeylanica, M. magnifica, M. quadrifida, M. caesia, M. odorata, dan M. foetida. Karakterisasi buah pada 35 aksesi yang terdiri atas M. indica, M. laurina, dan M. zeylanica menunjukkan variasi. Tiga subkelompok terbentuk berdasarkan karakter ketebalan daging buah. Namun, pengelompokan yang dilakukan belum berhasil memisahkan seluruh aksesi sesuai dengan spesiesnya. Profil keanekaragaman genetik 49 aksesi mangga di Pulau Seliu menunjukkan 193 pita polimorfik dari total 222 pita (86,17%). Mangifera memiliki tingkat polimorfisme dan keanekaragaman genetik tinggi (PPP=86,17%; I=0,334; He=0,210), sedangkan M. indica memiliki tingkat polimorfisme genetik yang cukup tinggi (PPP=62,61%) dan keanekaragaman genetik rendah (He=0,172). Analisis gugus berdasarkan data ISSR memvisualisasikan dua kelompok utama berdasarkan subgenus, yaitu Limus dan Mangifera. Aksesi mangga dari Pulau Seliu dan Jawa Barat cenderung mengelompok berdasarkan asal geografis. Pita primer UBC-825 (1500 bp) berkorelasi dengan ketebalan daging buah (r=0,72), sedangkan pita primer UBC-808 (1000 bp) berkorelasi dengan warna perona buah (r=-0,77). Studi keanekaragaman genetik mangga memberikan informasi penting mengenai hubungan genetik dan variabilitas kultivar mangga lokal di Pulau Seliu.