KORELASI ANTARA AGRESIVITAS INOKULUM SPORANGIA DENGAN TOKSISITAS FILTRAT Phytophthora capsici ASAL TANAMAN LADA (Piper nigrum L.)
Authors: CHAERANI CHAERANI , MANOHARA DYAH 
Published: June 2020

<p>ABSTRAK<br />Penggunaan varietas lada tahan penyakit paling praktis dan efektif<br />untuk menekan serangan Phytophthora capsici, penyebab penyakit busuk<br />pangkal batang (BPB) lada, tetapi varietas lada tersebut belum tersedia.<br />Seleksi dini ketahanan lada dapat dilakukan di laboratorium menggunakan<br />inokulum sporangia atau filtrat biakan P. capsici. Tujuan penelitian ini<br />ialah membandingkan agresivitas inokulum sporangia dengan toksisitas<br />filtrat biakan (FB) P. capsici. Penelitian dilakukan dari bulan Juni sampai<br />September 2009 di laboratorium Biokimia BB Biogen dan Hama dan<br />Penyakit Balittro. Penelitian menggunakan 50 isolat P. capsici dari<br />berbagai daerah pertanaman lada yang diisolasi tahun 1982 sampai 2009.<br />Daun-daun lada yang diambil dari varietas Natar-1 (agak tahan terhadap P.<br />capsici) dan Petaling-1 (rentan terhadap P. capsici) diinokulasi dengan<br />potongan agar mengandung sporangia atau 20 µl FB P. capsici. Percobaan<br />dilakukan secara faktorial (2 varietas × 50 isolat) dengan rancangan acak<br />kelompok dan tiga ulangan. Derajat agresivitas isolat dan toksisitas FB<br />diukur berdasarkan luas bercak nekrotik. Hasil penelitian menunjukkan<br />bahwa agresivitas inokulum sporangia dan toksisitas FB bervariasi antar<br />isolat P. capsici. Bercak nekrotik yang disebabkan oleh inokulum<br />sporangia lebih luas (0,0–2.535,2 mm 2 ) dibandingkan dengan FB (0,7–<br />233,0 mm 2 ). Derajat agresivitas isolat dan toksisitas FB sangat dipengaruhi<br />oleh asal isolat (P&lt;0,0001), tetapi tidak dipengaruhi oleh varietas dan<br />interaksi isolat×varietas (P&gt;0,05). Derajat ketahanan pada varietas tahan<br />Natar-1 diduga tidak berbasis genetik dan tidak berbeda nyata dari varietas<br />rentan Petaling-1 sehingga kedua metode seleksi ketahanan tidak dapat<br />dibedakan keefektifannya. Luas bercak nekrotik yang diinduksi oleh FB<br />tidak berkorelasi nyata dengan yang ditimbulkan oleh inokulum sporangia<br />(R 2 =0,002; P&gt;0,05), sehingga secara umum FB P. capsici tidak dapat<br />digunakan sebagai standar pengujian ketahanan lada. Oleh karena itu<br />masih perlu dikembangkan metode inokulasi yang konsisten untuk seleksi<br />dini ketahanan lada.<br />Kata kunci: lada, penyakit busuk pangkal batang, Phytophthora capsici,<br />agresivitas, filtrat biakan, seleksi dini</p><p>ABSTRACT<br />Resistant varieties are the most practical and effective means to<br />control Phytophthora capsici, the pathogen of foot rot disease of black<br />pepper. However, no resistant cultivars are available. Early selection of<br />black pepper resistance can be performed in laboratory using P. capsici<br />inocula or culture filtrate. The objective of this study was to compare P.<br />capsici isolate aggressiveness with culture filtrate (CF) toxicity. The study<br />was conducted from June until September 2009 at the Biochemistry<br />Laboratory of the Indonesian Center for Agriculutral Biotechnology and<br />Genetic Resources Research and Development and the Plant Pest and<br />Disease Laboratory of the Indonesian Research Institute of Spice and<br />Medicinal Crops. The study used 50 P. capsici isolates collected from<br />various black pepper plantations during 1982 until 2009. Detached leaves<br />of two black pepper cultivars, i.e. moderately resistant cv. Natar-1 and<br />susceptible cv. Petaling-1, were inoculated with agar blocks containing<br />sporangia or 20 µl CF of P. capsici. The experiments were designed as<br />factorial experiments (2 cultivars × 50 isolates) under a randomized<br />completely block design. Isolate aggressiveness and CF toxicity were<br />measured based on the necrotic area of the inoculated leaves. The results<br />from the two inoculation methods showed varying levels of aggressiveness<br />and CF toxicity among isolates. Necrotic lesions incited by sporangial<br />inoculum were more extensive (0.0-2,535.2 mm 2 ) than those induced by<br />CF (0.7-233.0 mm 2 ). Degree of isolate aggressiveness and CF toxicity<br />were significantly affected by origins of isolate (P&lt;0.0001), but not by<br />cultivar and isolate×cultivar interaction (P&gt;0.05). Resistance degree in the<br />moderately resistant cv. Natar-1 was presumably not genetically based and<br />was not different to that in the susceptible cv. Petaling-1, and hence both<br />selecting agents were unable to discriminate resistance level between the<br />two cultivars. Necrotic sizes induced by CF did not well correlate with<br />those incited by sporangial inocula (R 2 =0.002; P&gt;0.05), indicating that CF<br />is generally not suitable to be used as early selection agent of resistant<br />plants. Therefore, further study is justified to find more reliable inoculation<br />method for early detection of resistant black pepper.<br />Key words: black pepper, foot rot disease, Phytophthora capsici,<br />aggressiveness, culture filtrate, early selection in laboratory</p>