Abstract. Biological control of bacterial wilt pathogen (Ralstonia solanacearum) of tomato using endophytic bacteria is one of the alternative control methods to support sustainable agriculture. This study was conducted to select and characterize endophytic bacteria isolated from healthy tomato stems and to test their ability to promote plant growth and suppress bacterial wilt disease. Among 49 isolates successfully isolated, 41 were non-plant pathogenic. Green house test on six selected isolates based on antagonistic effect on R. solanacearum or ability to suppress R. solanacearum population in dual culture assays obtained BC4 and BL10 isolates as promising biocontrol agents. At six weeks after transplanting, plants treated with BC4 isolate showed significantly lower disease incidence (33%) than that of control (83%). Plants height was not significantly affected by endophytic bacterial treatments. Based on 16S rRNA sequence, BC4 isolate had 97% similarity with Staphylococcus epidermidis (accession number EU834240.1), while isolate BL10 had 98% similarity with Bacillus amyloliquefaciens strain JK-SD002 (accession number AB547229.1).

Key words: biological control, endophytic bacteria, Ralstonia solanacearum, Staphylococcus epidermidis, tomato

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Abstrak. Seleksi dan identifikasi merupakan langkah penting dalam mendapatkan agens hayati untuk pengendalian penyakit tanaman. Penelitian ini bertujuan mendapatkan isolat bakteri antagonis yang potensial mengendalikan penyakit hawar pelepah padi. Penelitian dilaksanakan di laboratorium bakteriologi tanaman dan rumah kaca, Departemen Proteksi Tanaman IPB, Bogor, sejak bulan Mei 2010 sampai Pebruari 2011. Penelitian menggunakan rancangan acak lengkap dengan perlakuan isolat bakteri hasil isolasi dari beberapa lokasi ekosistem. Sebanyak 30 isolat dari 144 isolat bakteri yang diproleh bersifat antagonis terhadap penyebab penyakit hawar pelepah padi (R. solani) di tingkat in vitro. Hasil pengujian di tingkat in vivo, ternyata tiga isolat dari 30 isolat bakteri antagonis tersebut menunjukkan penekanan signifikan terhadap perkembangan penyakit hawar pelepah, yaitu isolat TT47, SS19, dan BR2. Penekanan penyakit pada perlakuan isolat bakteri TT47, SS19, dan BR2 berturut-turut sebesar 79,6%, 56,4%, and 49,4%, indeks penyakit sebesar 1,7, 3,7, dan 4,3 serta kejadian penyakit 33,3%, 73,3%, dan 80%. Berdasarkan hasil identifikasi sekuens 16S rRNA ternyata isolat SS19, TT47, dan BR2 secara berturut-turut diidentifikasi sebagai Serratia marcescens, Ralstonia pickettii, dan Bacillus subtilis.

Kata kunci: bakteri antagonis, agens pengendali hayati, Rhizoctonia solani, hawar pelepah padi.

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Abstract. The objectives of the research were to study the diversity of leaf endophytic fungi of chili, and investigate its potency in protecting host plants against Aphis gossypii Glov. Endophytic fungi were isolated from chili leaves with two categories: aphid infested plants and aphid-free plants, collected from farmer’s field in Bogor, West Java. Abundance of each fungal species from leave samples was determined by calculating frequency of isolation. The isolated fungi
were tested on population growth of A. gossypii. The fungal isolates showed suppressing effect in population growth test, was further tested on biology attributes i.e. life cycle, fecundity and body length. Five species of leaf endophytic fungi of chili were found i.e. Aspergillus flavus, Nigrospora sp., Coniothyrium sp., and SH1 (sterile hypha 1), SH2 (sterile hypha 2). Eventhough the number of endophytic fungi species in aphid-free and aphid-infested plant was same, the abundance of each species was different. Nigrospora sp., sterile hyphae 1 and sterile hyphae 2 was more abundant in aphid-free plants, but there was no difference in dominance of Aspergillus flavus and Coniothyrium sp. Nigrospora sp., SH1 and SH2 treatment reduced significantly fecundity of A. gossypii. Only SH2 treatment significantly prolonged life cycle and suppress body length, therefore the fungus had the strongest suppressing effect on population growth among fungi tested. The abundance and dominance of endophytic fungal species has relation with the infestation of A. gossypii in the field.

Key words: leaf endophytic fungi, chili, biological control, resistance, Aphis gossypii

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Abstrak. Metode seleksi adalah salah satu faktor penting yang menentukan keberhasilan pemuliaan cabai. Metode seleksi akan lebih efektif jika didukung oleh pengetahuan yang lengkap tentang pola pewarisan karakter genetik. Penelitian ini bertujuan untuk mengetahui pola pewarisan yang sesuai untuk karakter-karakter kualitatif. Penelitian ini berlangsung dua tahap, yaitu pembentukan materi genetik dan studi pewarisan karakter kualitatif di lapang. Hasil penelitian menunjukkan semua karakter kualitatif dikendalikan oleh satu gen. Ada beberapa karakter kualitatif yang dipengaruhi oleh gen dominan penuh (warna batang muda dan tekstur permukaan buah) dan karakter lainnya dipengaruhi oleh gen dominan sebagian (warna buah muda dan posisi bunga).

Kata kunci: Capsicum annuum L., Pewarisan, karakter
kualitatif, aksi gen

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Abstract. The objective of this study was to identify the adaptability of twelve artemisia mutant genotypes, which were planted in three locations with different altitude, as a result of gamma irradiation. Randomized Complete Block Design (RCBD) was applied in this research with three replications as blocks. The genotypes 1B, 1C, 1D, 2, 3, 4, 5A, 6B, 7A, 8, 14, 15 and two control genotypes as parent genotype from seed and from in vitro were used. The genotypes were planted in three different locations such as Mount Putri, Cianjur (1450 m above sea level), Pacet, Cianjur (950 m above sea level) and Cicurug, Sukabumi (540 m above sea level). Based on the method of postdictive and predictive success, the model used was AMMI2 which was able to explain up to 100% of interaction-influenced variation. The genotypes which were found stabile and adaptive in these three locations were 1B, 1C, 1D, 6B and 15. Genotypes 3 and 7A were adaptive specifically in Pacet area, 5A was adaptive for Gunung Putri while genotype 4 was for Cicurug only.

Keywords: AMMI, Artemisia annua, mutant genotype, adaptability

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