<![CDATA[Sengon is commonly developed by community forest farmers because it is a fast-growing species and the demand for wood is quite high. The development of sengon is constrained by the attack of gall rust disease caused by the fungus Uromycladium falcatarium. Efforts to obtain disease-resistant plants can be done through mutation breeding, one of which is using gamma rays. This study aims to assess the resistance of M1 generation sengon to gall rust disease. Sengon seeds were irradiated using gamma rays at doses of 0, 25, 75, 125, and 175 Gy. Sengon seeds that had been irradiated were germinated and sown for up to 2 months of age. Inoculation of U. falcatarium fungus was carried out on sengon seedlings M1 (1st generation mutant) and M0 (control) generations, at 2 months old. The number of seeds used in each dose was five seeds with four replications. This study used a randomized block design (RBD). Observation on seedlings were disease severity, mortality rate, and resistance of seedlings to gall rust disease. Data were analyzed using analysis of variance (ANOVA) and then analysis of the least significant difference (LSD) was carried out at a level of 5%. The results showed that the dose of gamma irradiation had a significant effect on the severity of gall rust disease at 17, 27, and 37 days after isolation (DAI). The resistance levels of the M0 and M1 generations of sengon seedlings (doses of 25, 75, and 125 Gy) from 7 – 37 DAI were in the very resistant-moderately susceptible category, while the M1 seedlings with a dose of 175 Gy tended to be very resistant-resistant.Keywords: gall rust, gamma irradiation, mutation breeding. AbstrakSengon umum dikembangkan petani hutan rakyat karena termasuk jenis cepat tumbuh dan permintaan kayunya cukup tinggi. Pengembangan sengon terkendala dengan adanya serangan penyakit karat tumor yang disebabkan oleh jamur Uromycladium falcatarium. Upaya untuk memperoleh tanaman yang tahan penyakit dapat dilakukan melalui pemuliaan mutasi, salah satunya dengan sinar gamma. Penelitian ini bertujuan untuk mengaji ketahanan sengon generasi M1 terhadap penyakit karat tumor. Benih sengon diiradiasi menggunakan sinar gamma dengan dosis 0, 25, 75, 125, dan 175 Gy. Benih sengon yang telah diiradiasi dikecambahkan dan dipelihara hingga umur 2 bulan. Inokulasi jamur U. falcatarium dilakukan pada bibit sengon generasi M1 (mutan generasi ke-1) dan M0 (kontrol) berumur 2 bulan. Jumlah bibit yang digunakan pada masing-masing dosis sebanyak 5 bibit dengan empat kali ulangan. Penelitian ini disusun dengan rancangan acak kelompok (RAK). Pengamatan bibit meliputi keparahan penyakit, tingkat kematian, dan resistensi bibit terhadap penyakit karat tumor. Data dianalisis menggunakan sidik ragam dan kemudian dilakukan analisis beda nyata terkecil (BNT) dengan taraf 5%. Hasil penelitian menunjukkaan bahwa dosisi iradiasi sinar gamma berpengaruh nyata terhadap keparahan penyakit karat tumor pada 17, 27, dan 37 HSI. Tingkat resistensi bibit sengon generasi M0 dan M1 (dosis 25, 75, dan 125 Gy) dari 7 – 37 HSI masuk dalam kategori sangat resisten-cukup rentan, sedangkan bibit sengon M1 dengan dosis 175 Gy cenderung sangat resisten-resisten.Kata kunci: karat tumor, iradiasi sinar gamma, pemuliaan mutasi.]]>
