Seleksi dan Identifikasi Bakteri Antagonis sebagai Agens Pengendali Hayati Penyakit Hawar Pelepah Padi

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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Leaf endophytic fungi of chili (Capsicum annuum) and their role in the protection against Aphis gossypii (Homoptera: Aphididae)

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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Pewarisan Sifat Beberapa Karakter Kualitatif pada Tiga Kelompok Cabai

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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ADAPTABILITY OF MUTANT GENOTYPES OF ARTEMISIA (Artemisia annua L.) AS RESULT OF GAMMA IRRADIATION IN THREE LOCATIONS WITH DIFFERENT ALTITUDE

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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Evaluasi Daya Gabung dan Heterosis Lima Galur Jagung Manis (Zea mays var. saccharata) Hasil Persilangan Dialel

Abstrak. Penelitian ini bertujuan mengestimasi nilai daya gabung umum (DGU), daya gabung khusus (DGK), dan heterosis lima galur jagung manis untuk mendukung perakitan varietas hibrida. Lima galur jagung manis yang dijadikan tetua adalah Mr12/SC/BC4-6-1B-1, Mr14/SC/BC4-6-1B-1, Mr4/SC/BC4-2-1B-1, Mr11/SC/BC4-2-1B-1, dan Mr12/SC/BC3-3-1B-1. Penelitian dilaksanakan pada bulan April sampai Juni 2010 menggunakan Rancangan Kelompok Lengkap Teracak dengan dua ulangan, yang dilaksanakan di Kebun Percobaan Maros, Balai Penelitian Tanaman Serealia (Balitsereal) Sulawesi Selatan. Nilai DGU dan DGK dianalisis berdasarkan metode I model tetap Griffi ng. Nilai heterosis dihitung berdasarkan nilai rata-rata kedua tetua dan heterobeltiosis dihitung berdasarkan nilai rata-rata tetua tertinggi. Persilangan B x D (Mr14/SC/BC4-6-1B-1 x Mr11/SC/BC4-2-1B-1) mempunyai nilai DGK tertinggi untuk hasil yaitu 990.67. Persilangan A x B (Mr12/SC/BC4-6-1B-1 x Mr14/SC/BC4-6-1B-1)mempunyai nilai DGK tertinggi untuk diameter tongkol yaitu 0.36. PersilanganA x D (Mr12/SC/BC4-6-1B-1 x Mr11/SC/BC4-2-1B-1) mempunyai nilai heterosis and heterobeltiosis tertinggi untuk hasil;Persilangan A x D (Mr12/SC/BC4-6-1B-1 x Mr11/SC/BC4-2-1B-1) mempunyai nilai heterosis and heterobeltiosis tertinggi untuk panjang tongkol. Persilangan A x B (Mr12/SC/BC4-6-1B-1 x Mr14/SC/BC4-6-1B-1) dan E x A (Mr12/SC/BC3-3-1B-1xMr12/SC/BC4-6-1B-1) mempunyai nilai heterosis and heterobeltiosis tertinggi untuk diameter tongkol.

Kata kunci: daya gabung, heterosis, jagung manis, persilangan dialel

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Evaluation and Selection of Mutative Artemisia (Artemisia annua L.) According to the Altitude Variants

Abstract. Induction of genetic variant of Artemisia annua L. was conducted through the application of gamma ray irradiation in 2007-2008. The aim was to obtain a plant with high artemisine content > 0.5% and late flowering period of about > 7 month after planting. Tweleve selected genotypes were subsequently examined to gain genetic stability on altitude of 1500, 950, and 540 m asl. The results showed that the plants had shorter flowering age in Cicurug (540 m asl) than that of in Pacet (950 m asl) and Gunung Putri (1540 m asl). Genotype 8 had the latest age of flowering in the three locations than the other genotypes, however, the growth and biomass were the lowest. Vegetative growth of Artemisia in Pacet and Gunung Putri was better than those in Cicurug. Genotype of 15 in Cicurug and 5A genotype in Gunung Putri and Pacet had higher wet and dry weight than that of two other associates. Based on plant biomass, 5 genotypes from Gunung Putri and Pacet i.e. 1D, 3, 5A, 14, and 15 genotypes were selected, as well as 5 genotypes i.e. 1D, 3, 4, 5A, and 15 genotypes from Cicurug. Analisys on artemisin content successfully obtained 5 selected somaclone lines i.e. 1B, 2, 4, 14, and 3 somaclones.

Key words: Artemisia annua, mutation, genetic improvement, malaria, artemisinin

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