The results showed that there was a decrease in the percentage of germination of soybean (cv. Gepak Kuning) seeds due to the treatment of various EMS mutagen concentrations. The percentage of germination was seen decrease at a concentration of 0.5%, but at the highest concentration, namely 1% EMS, it did not show any growth at all. The average germination of soybean seeds of the soybean (cv. Gepak Kuning) due to various EMS concentrations can be seen in Table 1.
The reduction in germination of seeds due to EMS mutagen treatment has been widely reported by previous researchers, including pepper
(Arisha et al., 2015), peanut
(Chen et al., 2020), cowpea (
Opoku Gyamfi et al., 2022), rice
(Talebi et al., 2012) and soybean
(Sagel et al., 2017), (Kalpande et al., 2020). The reduction in germination may be due to the seeds absorbing the mutagen, which subsequently reaches the meristem region and affects the germ cell
(Serrat et al., 2014). Also, a reduction in germination may be because of the damage of cell constituents (
Kumar and Pandey, 2019), alteration of enzyme activity or delay or inhibition of physiological and biological processes
(Talebi et al., 2012). A reduced germination percentage could be attributed to disturbances of seed meristematic tissue at cellular level resulting in chromosome damage, disrupting growth promoters due to increased accumulation of growth inhibitors (
Jayakumar and Selvaraj, 2003).
EMS mutagen treatment on soybean (cv. Gepak Kuning) seeds also caused a decrease in seedling height. Fig 1 shows that at an EMS concentration of 0.05% there was stimulation of the seedling height, but starting at a concentration of 0.25% there was suppression of the seedling height of soybean (cv. Gepak Kuning). The response of soybean (cv. Gepak Kuning) to EMS concentrations of 0.01% to 1% showed a quadratic response. The graph between EMS concentration and the seedling height of soybean (cv. Gepak Kuning) can be seen in Fig 2.
In previous research,
(Hossain et al., 2021) also found that rice plant height was significantly increased at lower concentration of EMS (1 and 2%) with a 6-12 hours treatment duration compared to the control plant. But when this concentration was increased, plant height was decreased compared to control as well as low concentration treated plant.
Talebi et al., (2012) added, EMS-induced mutagenesis imposed significant impact on the seedling height of rice cv. MR219. The maximum reduction in seedling height was observed when rice MR219 was treated with a concentration of 0.25%.
For artificially induced mutations either with physical or chemical mutagens, LD
50 is considered to be an ideal level to achieving high frequency of mutations
(Anbarasan et al., 2013). The LD
50 of the mutagen is useful for determining an optimal dose for mutation induction. The LD
50 was calculated using seed germination percentage at different doses of EMS. The best curve for soybean (cv. Gepak Kuning) is describe through a quadratic curve based on the results of the analysis using Curve Expert 1.4 (Fig 3).
This study showed that the LD50 of soybean (cv. Gepak Kuning) treated with EMS mutagen was found at a concentration of 0.63%, the LD
20 value was at a concentration of 0.25% and the LD
30 value was at 0.41%. The regression equation obtained is
Y(x) = 86.87-80.22x-79.36x2
Y(x) = Logarithm of the overall germination growth rate.
x = Concentration of EMS.
a, b, c = Regression parameters.
The LD
50 differs for each type of plant depending on the stage of plant growth and development and the plant parts treated with EMS mutagen. The EMS concentration range below LD
50 was used to induce plant diversity and the desired character in future studies.
The LD
50 dose range is useful for estimating the appropriate dose or concentration to induce mutations. The EMS mutagen treatment was carried out at a dose range of 50% with the consideration that the physiological damage was balanced by the genetic changes obtained.
Selvaraj et al., (2014) stated, optimum dose is the dose that causes maximum mutation with minimum damage to the plant. Furthermore, Van Harten, (1998) added, the EMS concentration range used to induce variability was below the LD
50 dose, ranging between LD
20 and LD
30. In this study, we found that LD
20 dose was obtained at a concentration of 0.25% and LD
30 was found at a concentration of 0.41%.
Kavina et al., (2020) have reported the results of a study on the determination of the LD50 of the EMS mutagen in Fenugreek. Seeds without EMS treatment showed a germination percentage of 100%. Germination percentage decreased with increasing EMS concentration. EMS-treated Fenugreek showed reduced germination percentage at higher concentrations. The lowest germination percentage (2.1%) was found at a concentration of 1% at 7th days germination observation. Based on the germination data, the LD
50 value of Fenugreek was obtained at a concentration of 0.4% EMS.
The LD50 value in the results of this study is almost the same as the results of previous studies.
Arisha et al., (2015) studied LD50 some pepper cultivar and found that 0.6% (v/v) EMS was the concentration that produced about 50% lethality.
Sharamo et al., (2021) also found a decreasing trend due to increasing doses and soaking time with EMS on barley. The LD
50 value of 0.64% (v/v) EMS dosage was identified as an optimal dose for large-scale mutagenesis protocol to select barley mutants with high biomass yield.
The LD
50 in the present study is much lower than LD
50 of tepary bean.
(Thangwana et al., 2021) reported LD
50 tepary bean of 3.37%, 2.68% and 2. 26% v/v EMS for genotype 3, 4 and 6, respectively. In addition, there were high coefficients of determination for each of the linear functions (>75%) suggesting that there was a notable association between the reduction in seed germination and the concentration of the mutagen. These values are much higher than reported in the present study attributed to differences in genotypes and crop species used during mutagenesis.
The mutagenesis protocol will be useful to develop recessive and point mutations to aid selection of best individuals involving the M
2-M
5 mutant families with high yield production in soybean (cv. Gepak Kuning). The present study determined the optimum treatment condition for inducing genetic variation in soybean cv. Gepak Kuning. These results revealed that EMS dosage of 0.63% v/v of EMS can be used to increase genetic variability for key traits in soybean (cv. Gepak Kuning).