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Mutation breeding using gamma irradiation is one of the alternative ways to increase the variability and productivity of Guinea grass (Panicum maximum cv Purple guinea). The aimed of the study was to determine the dosage of gamma irradiation and morphological characters for highyielding of the putative mutant of guinea grass. The Guinea grass seeds was irradiated by gammaray. The treatment was 8 doses of gamma irradiation and control (non-irradiated). The treatment was arranged in a randomized complete block design (RCBD) with 3 replications. The study was conducted for 3 generations, which were mutants 1 (M1), mutant 1 vegetative 1 (M1V1), and mutant 1 vegetative 2 (M1V2). The results showed that the gamma irradiation dose affected variables observed. The variables affected in M1 were fresh and dry weights of shoot, the number of tillers, and the length of the leaves. Whereas in the populations of M1V1 and M1V2, almost all characters were influenced by gamma irradiation, except stem diameter, length of internode, and leaf length. Gamma irradiation doses of 175 x 2 Gy, 250 Gy and 350 Gy in M1V1 and 100 x 2 Gy, 150x2 Gy and 175 x 2 Gy in M1V2 produced the high number of tillers, fresh and dry shoot weights. Heritability value and GCV of number of tillers, fresh and dry weight of shoot were high for M1V1 and M1V2 populations. These results indicated that gamma-ray irradiation can be applied to increase productivity and genetic variability of Guinea grass. The highest forage production was obtained at a dose of 100 x 2 Gy, which was 625 g/plant.

The aim of this study was to evaluate the performance of several Sorghum bicolor cultivars as forage on a dry land with pH of 5.4, N of 0.08%;  C/N of 9%, P of 0.06% and K of 0.01%. Nine cultivars of S. bicolor (Super 1, Super 2, Numbu, Kawali, G2, G5, PAC 537, PAC 593 and PAC 501) were evaluated. Plot size was 16 m2 with space planting of 15 x 75 cm. The experimental design used was randomized block design with three replications.  Parameters observed were plant height, time of flowering, forage production and quality. The result showed that the primary plant growth was not different in all cultivars. In the 65 days old primary plant,  the Super 2, PAC 537 and Kawali had no flower yet. Biomass production varied in primary plant between cultivars of 11.35 - 26.17 kg/16 m2. The highest biomass production was obtained in PAC 537 of 26.17 kg/16 m2 (16.34 t/ha) which were significantly higher than G2 of 11.35 kg/16 m2 (7.09 ton/ha) and was not significantly different with other cultivars. In the 45 days ratoon I, Super 2, G5 and Super 1 showed faster growth. Biomass production increased in the ratoon I around 19.88 kg/16 m2 (12.42 ton/ha). PAC 537 produced the highest biomass of 30.14 kg/16 m2 (18.84 ton/ha) and was not significantly different with other cultivars, except with the G2. Biomass production of ratoon II decreased around 1.83 kg/16 m2 (1.14 t/ha)–4.77 kg/16 m2 (2.98 t/ha) and increased in the ratoon III of 15.72 kg/16 m2 (9.82 t/ha)–26.05 kg/16 m2 (16.28 t/ha). The quality of forage ratoon I was better compared to the primary plant with the lowest one was in ratoon II. It could be concluded that Super 1, Super 2 and PAC 537 cultivars might be recommended as potential forage.

<em></em><p class="abstrak2">The induction mutation using gamma rays is one way to increase the diversity of Bengggala grass (<em>Panicum maximum</em>). Diversity is the main base in selecting to produce varieties of Benggala grass on acid land. The aim of this study is to know the morphological character and genetic diversity of grass that received gamma rays. The research was conducted in the Tenjo district, Bogor which has pH 4.9-5.5 and the content of Al-dd 2.26 c mol/kg with Al saturation of 10.68%. The study started by looking for Benggala grass radio sensitivity, then from radio sensitivity determined radiation treatment dose of 200 Gy, 250 Gy, 300 Gy and 350 Gy. Treatment of radiation dose is acute and fractionated, so there are 8 treatment doses plus control (plants without radiation). The variables measured were plant height, stem height, stem diameter, length of segment, leaf length, leaf width, fresh weight, dry weight, and number of tillers. The results showed that the radio sensitivity of Benggala grass produced in the form of lethal doses (LD) LD 20 and LD50 is 176.83 Gy and 358.23 Gy. By the mathematical equation: Y = 44.22 + 45.91 X Cos (0.0042x -0.07). The morphological character of M1 shows that the radiation dose affects the measured variable. 300 Gy fractionated radiation dose (150 Gy x 2) results in higher fresh weight of the plant. While in the generation of M1V1 radiation dose of 250 Gy produces high fresh forage weight. Medium to high heritability with GVC value (criteria of coefficient of genetic variability) is high enough until high is obtained on the character of the number of tillers, fresh weight and dry weight. So it is possible to do next selection on these three characters.</p><strong>Key Words</strong>: <em>Panicum maximum</em>, Irradiation, Mutation, Morfology, Genetic Variability<em><br /></em>