Resistance of cotton varieties and new lines against primary pathogens

anglais. Tests for the resistance of 30 varieties/lines against three major pathogens, i.e. Rhizoctonia solani, Sclerotium rolfsii, and Xanthomonas campestris pv. malvacearum were conducted at the laboratory and glass house of Research Institute for Tobacco and Fibre Crops from July 1996 to March 1997. The test were conducted separately. The experiment was designed as a completely randomized with three replications. Parameters observed for R. solani and S. rolfsii were the percentage of healthy seedlings from 50 seeds sown per tray and for X. c. pv. malvacearum was the disease intensity of 50 days old plants. Inoculum of S. rolfsii was cultured in hull of rice. The inoculum was covered over planting holes at the dosage of 50 g/50 planting holes then double covered with a thin layer of sterilized sand. Inoculum of R. solani was prepared in autoclaved maize meals and mixture (20 g maize meal: 980 g sand) + 250 ml distilled water, incubated for 3 weeks. The inoculum was diluted with sterilized sand at 2 of the power of- 7 level before using. The inoculum was covered on the planting holes at the dosage of 0.5 kg/50 holes. The inoculation method of X.c.pv.malvacearum was seed inoculation. The seeds were soaked in the suspension of two days old culture for 2-3 hours and then coated with tapioca flour before planting. Results showed that 7 varieties and 4 lines were resistant to S. rolfsii. There were 9 lines and 13 germplasms were resistant to R. solani and not significantly different to TAMCOT SP-37 (control variety). There were 8 lines and 15 germplasms were not significantly different to Quebracho which was resistant to X. c. pv. malvacearum

indonésien. Penelitian bertujuan untuk mengetahui ketahanan 30 varietas dan galur kapas terhadap tiga patogen utama, yaitu Rhizoctonia solani, Sclerotium rolfsii, dan Xanthomonas campestris pv. malvacearum, dilaksanakan di laboratorium dan rumah kaca Balittas Malang, menggunakan bak pertanaman dengan 50 tanaman/bak dari bulan Juli 1996-Maret 1997. Pengujian ketahanan terhadap ketiga patogen dilakukan secara terpisah. Rancangan percobaan yang digunakan adalah rancangan acak lengkap dengan ulangan tiga kali. Parameter pengamatan adalah persentase tanaman sehat untuk R. solani, S. rolfsii, dan intensitas serangan bakteri pada umur 50 hari untuk X. c. pv. malvacearum. Inokulum S. rolfsii berupa biakan pada medium sekam, diinokulasikan sebagai penutup lubang tanaman, sebanyak 50 g biakan tiap bak tanaman. Inokulum R. solani berupa biakan pada medium pasir + beras jagung + air dengan perbandingan (98:2:25), yang sudah diencerkan 2 pangkat -7, diinokulasikan sebagai penutup lubang tanam sebanyak 500 g biakan tiap bak tanaman. Inokulum X.c.pv malvacearum berupa suspensi bakteri (konsentrasi 10 pangkat 9), diinokulasikan dengan cara merendam biji selama 2-3 jam (5 ml tiap 150 butir benih), lalu digulirkan dalam tepung kanji, kemudian ditanam. Hasil pengujian menunjukkan bahwa 7 varietas dan 4 galur tahan terhadap S. rolfsii, 13 varietas dan 9 galur tahan terhadap R. solani dan tidak berbeda nyata dengan pembanding TAMCOT SP-37; serta 15 varietas dan 8 galur yang ketahanannya terhadap X. c. pv. malvacearum tidak berbeda dengan pembanding Quebracho