Soybean breeding for earliness and seed quality by induced mutations

Mutant soybean germplasm lines were developed by the pedigree method from two local varieties, Karpatalja (KA) and VL40, by 100-300 Gy doses of chronic gamma irradiation. The objective was to produce early mutant lines with an increased oil content and/or protein content and acceptable agronomic performance. Selection for earliness commenced in M2 generation, for oil content and agronomic characteristics in the M3 generation and for protein content in M4 generation. Due to the limited genetic variation for earliness no mutant genotypes earlier than the control could be identified. Chronic gamma irradiation increased the genetic variability for oil content in both local varieties, and the genetic variability for protein content in VL40. Progenies with 23.9% oil content were detected among the KA 100 Gy progenies and among the VL40 250 Gy progenies. Furthermore, a VL40 250 Gy offspring with 43.6% protein content was selected. The applied chronic doses (100, 150, 200 and 300 Gy) significantly lowered the first pod height and the 1000-seed weight as compared to the check cultivar. The significant increase in the number of pods and in the number of seeds per plant led to an increase in yield per plant in KA 150 Gy lines despite the fact that the 1000-seed weight was decreased significantly. The applied doses did not change the colors of the seed, hylum and flowers. Correlation studies in M6 generation between oil content and agronomic characteristics revealed that only the oil content and the number of seeds per plant were significantly (p < 0.05) associated (r -0.24*). (author)