Agronomic characters of early maturity soybean mutant lines

The high demand for soybean in Indonesia needs to be balanced with increasing of domestic soybean production. One effective way to increase soybean production is by using superior varieties seeds, which not only have high yield but also have special favorable character, such as early maturity. Early maturity soybeans can be applied in agricultural systems that apply rice-rice-soybean cropping system. The research objective was to study agronomic characters of early maturity soybean mutant lines grown in different agroecologies. The genetic material used were six homogeneous mutant lines derived from gamma-ray irradiation of Cobalt-60 of cv. Argomulyo with a dose of 250 Gray which was carried out in 2012. The six mutant lines were developed based on early maturity selection since M2 generation. In addition, the control varieties of Argomulyo, Grobogan and Burangrang were also used in the experiment. The research was carried out in seven different locations. Observation were made on agronomic characters, such as plant height, flowering time, harvesting time, number of filled pods, 100 seeds weight and seed yield. The results showed that the average of harvesting time of mutant lines were below 70 days, in contrast to the control varieties that had an average harvesting time of more than 80 days. The GEE-5 mutant line showed the shortest harvesting time of 66.79 days. Harvesting time under 70 days is classified as super early maturity in soybean. Considering the flowering time, the mutant lines showed flowering time range of 31-32 days, while the control varieties were about 35 days. Usually longer flowering time will improve seed filling in soybean which can increase seed yield. However, the GBB-2 and GEE-5 lines had higher average seed yield compared to the control varieties and other mutant lines. This was also in line with the higher number of filled pods of the two mutant lines compared to other genotypes. In addition, the seed size of the mutant lines was smaller than the control varieties, which could be seen from the 100 seed weight of the mutant lines ranged from 10-11 grams, while the control varieties ranged from 13-16 grams.