Variasi Morfologi dan Virulensi Phytophthora capsici Asal Lada - Dono Wahyuno; Dyah Manohara; Dwi N. Susilowati (Balai Besar Penelitian dan Pengembangan Bioteknologi dan Sumberdaya Genetik Pertanian, 2007)
Phytophthora capsici is the most important plant parasitic fungus causes stem rot disease in black pepper cultivation in Indonesia. The objective of the present study was to observe morphological variation and virulence of Phytophthora isolated on black pepper from various areas in Indonesia. Fifty isolates of Phytophthora were observed under light microscope. The observed morphological characteristics of each isolate, i.e. sporangiophore branching type, colony type, mating type and shape of sporangium after they were grown in growth medium of V8 juice agar, while length and width of sporangium, length of sporangiophore, and papilla were measured by micrometer. The variation of their virulence was observed by inoculating the hypha of each isolate on detached leaves of black pepper that incubated in damped boxes in room conditions. The width of necrotics were measured with leaf area meter after incubated for four days. The results indicated, those morphological characteristics of the isolates were vary in size, shape, colony pattern, mating type and sporangiophore branching pattern, which those characteristics were belong to P. capsici. Those morphological characteristics were not related with the mating type, isolated plant parts and its geographic distribution. The virulence of the tested isolates were also vary from low to high, and their virulence were also not related with the mating type, isolated plant parts and its geographic distribution. AbstrakPhytophthora capsici merupakan cendawan penyebab penyakit busuk pangkal batang yang paling banyak menimbulkan kerusakan pada tanaman lada di Indonesia. Penelitian ini bertujuan untuk mengamati variasi morfologi dan virulensi Phytophthora yang diperoleh dari berbagai lokasi pertanaman lada di Indonesia. Setelah ditumbuhkan pada media V8 jus agar, sebanyak 50 isolat Phytophthora diamati karakteristik morfologinya di bawah mikroskop cahaya, yang meliputi tipe percabangan tangkai sporangium, tipe koloni, tipe kawin, dan bentuk sporangium. Pengukuran panjang dan lebar sporangium, tangkai sporangium, dan papilla dilakukan menggunakan micrometer. Variasi virulensi yang ada diamati dengan cara menginokulasikan potongan hifa dari setiap isolat pada helaian daun lada, kemudian diinkubasi di dalam kotak yang lembab dan diletakkan di suhu ruang. Setelah diinkubasi selama empat hari, luas nekrose yang terjadi diukur menggunakan leaf area meter. Hasil pengamatan menunjukkan adanya variasi karakterisitik morfologi dari setiap isolat pada tipe koloni, tipe kawin, percabangan sporangium, ukuran, dan bentuk sporangium. Semua isolat menunjukkan karakteristik P. capsici. Variasi morfologi yang ada tidak berkaitan dengan tipe kawin, asal bagian tanaman yang diisolasi, dan geografi asal isolat. Lima puluh isolat P. capsici juga bervariasi virulensinya, dari rendah sampai tinggi. Variasi virulensi tersebut juga tidak berkaitan dengan tipe kawin, asal bagian tanaman yang diisolasi maupun geografi asal isolat.