Indonesian Journal of Agricultural Science Vol. 22 No. 2 December 2021: 77–84 DOI: http//dx.doi.org/10.21082/ijas.v.22.n2.2021.p.77–84 SSR MARKERS REVEALED GENETIC DIVERGENCE OF RICE BROWN PLANTHOPPER POPULATIONS MAINTAINED ON TWO SETS OF DIFFERENTIAL HOST VARIETIES Penanda SSR Mengungkap Perbedaan Genetik Populasi Wereng Batang Cokelat Padi yang Dipelihara pada Dua Set Varietas Inang Diferensial Chaerani*, Siti Yuriyah, Ahmad Dadang, Kusumawaty Kusumanegara, Diani Damayanti, Bahagiawati Amir Husin, Sutrisno, and Muhamad Yunus Indonesian Center for Agricultural Biotechnology and Genetic Resources Research and Development Jalan Tentara Pelajar 3A, Bogor 16111, West Java, Indonesia * Correspondence author: chaeran1@yahoo.com Submitted 3 April 2021; Revised 10 May 2021; Accepted 18 May 2021 ABSTRACT Resistance screening of promising rice lines in Indonesia requires the use of brown planthopper (BPH) biotypes 1, 2, and 3. Three BPH populations have been raised as biotypes 1, 2, and 3 on diferential rice host of improved varieties Pelita I-1 (no Bph gene), IR26 (Bph1), and IR42 (bph2), respectively. Three alternative populations have also been developed on the respective traditional varieties TN1 (no Bph gene), Mudgo (Bph1), and ASD7 (bph2). Although these populations displayed two virulence patterns other than biotype 1 to 3 phenotypes, they were expected to be discriminated into two virulence groups by SSR analysis. The study aimed to investigate the level of genetic variation among the six BPH populations using SSR markers and to relate it with the observed virulence patterns. Genotyping of 30 females with 29 polymorphic SSR markers revealed higher genetic parameter values in populations reared on improved varieties than those on traditional varieties. This diference was marked as two population clusters in PCoA plots corresponding to the host variety type, in contrast to the previous assumption that clustering would be based on virulence patterns. The presence of individuals with unwanted virulence allele, either resulting from contamination during the long period of rearing or lack of host adaptation period, is suspected. The result of this study indicates that the six populations are not suitable for resistance screening. Virulence selection must be performed until they attain biotype 1 to 3 phenotypes which can be genetically separated by DNA markers. [Keywords: brown planthopper, rice, virulence adaptation, DNA marker, genetic diferentiation] ABSTRAK Penapisan ketahanan padi calon galur unggul harapan di Indonesia terhadap wereng batang cokelat (WBC) mensyaratkan penggunaan biotipe 1, 2, dan 3. Tiga populasi WBC telah dipelihara sebagai biotipe 1, 2, dan 3 pada inang varietas padi diferensial hasil perbaikan, yaitu berturut-turut Pelita I-1 (tanpa gen ketahanan Bph), IR26 (Bph1), dan IR42 (bph2). Tiga populasi alternatif juga telah diadaptasikan berturut-turut pada varietas tradisional TN1 (tanpa gen ketahanan Bph), Mudgo (Bph1), dan ASD7 (bph2). Keenam populasi masih memperlihatkan dua pola virulensi selain fenotipe biotipe 1 sampai 3, tetapi diharapkan dapat dipisahkan menjadi dua kelompok virulensi berdasarkan genotipe penanda SSR. Penelitian ini bertujuan menganalisis keragaman genetik enam populasi WBC menggunakan penanda SSR dan menghubungkannya dengan pola virulensi yang teramati. Analisis genotipe 30 ekor betina menggunakan 29 penanda SSR polimorfk mengungkap nilai parameter genetik yang lebih tinggi pada populasi asal varietas hasil perbaikan dibandingkan dengan populasi asal varietas tradisional. Perbedaan ini ditandai oleh terbentuknya dua kelompok populasi pada plot PCoA sesuai tipe varietas inangnya, sehingga berbeda dari anggapan semula bahwa pengelompokan genotipe SSR akan sesuai dengan fenotipe virulensi. Diduga keenam populasi masih mengandung individu pembawa alel virulensi yang tidak diinginkan, akibat terkontaminasi selama jangka waktu pemeliharaan yang lama atau kurangnya periode adaptasi pada inang. Hasil penelitian menunjukkan bahwa keenam populasi belum memenuhi syarat untuk digunakan dalam penapisan ketahanan padi. Seleksi individu harus dilakukan hingga keenamnya memperlihatkan pola virulensi biotipe 1 hingga 3 yang dapat dipisahkan secara genetik antarbiotipe menggunakan penanda DNA. [Kata Kunci: wereng batang cokelat, padi, adaptasi virulensi, penanda DNA, perbedaan genetik] INTRODUCTION Brown planthopper (Nilaparvata lugens Stål; Hemiptera: Delphacidae) exhibits phenotypic plasticity, or fexible change of phenotype over time, in response to environmental changes (Ferrater 2016; Saxena and Barrion 1983). When exposed to a monoculture of resistant rice varieties having a single major resistance (R) Bph gene, feld brown planthopper (BPH) populations are capable of evolving new virulence characters or biotypes (Cheng et al. 2013). Various alleles of virulence genes contained in a feld population facilitated the population to adapt to any