**8. Genetic aspects of mineral nutrition of soybean**

Plant varieties of the same species differ in absorption and utilization of nutrients from the environment. Varietal differences in the uptake of individual nutrients can be used as basis for the testing of both commercial varieties and selection materials under unfavorable soil conditions. An adequate distribution of soybean varieties based on their tolerance or susceptibility to less favorable conditions could contribute to better utilization of their yield potential (Saric, 1981; Saric & Loughman, 1983). According to Epstein (1976) agricultural intervention in the process of nature has two corresponding strategies: selection and genetic manipulation of the organism and modification of the environment. Many crops in Brazil have their yield improved thanks to the selection and breeding, especially in the large savanna (cerrado) region of Central Brazil. Soybean cultivation in the low-latitude acidic soils of Brazilian Savanach has become a reality since 1970's. Great contribution for this success has been achievements in soil science and plant breeding. There are however, constraints for sustainable production like high-Al and low-Ca in the deep layers of the soil. Measures can be taken to reduce the negative effects of acidity on plant growth are liming and selection of more tolerant genotypes.

Kastori (1978) found that Ca uptake was higher in *Corsoy* than in *Stella* and *Wilkin*. Later research showed that K uptake was the highest at the variety *Corsoy* (Kastori et al., 1979). Keoght et al., (1977) found lower N uptake in the varieties *Hill*, *Lee* and *Bragg* than in *Hood*. Queiroz et al. (1980) tested residual effects of P fertilizers on the yield of three soybean varieties over four years. The variety *Bossier* increased grain yield by 320 kg/ha, *Parana* by 640 kg/ha, whereas variety *Vicoja* did not show any response to P fertilization. Saric and Krstic (1982) tested ten soybean varieties 30 days in N-deficient nutrient solution. The variety *Yoslie Kataya 2* showed the lowest and the variety *Traverse* the highest N contents.

Kovacevic and Krizmanic (1987) tested 12 soybean genotypes of maturity group I (*Corsoy* and *Hodgson* as standard varieties and remaining ten are experimental lines from the F8 generation) under calcareous soil conditions. Grain yield of soybean genotypes ranged from 2.1 4 to 3.11 t/ha. The highest yield of *Vuka* and the lowest yield of *Os 155/82* on this soil may be due to the lowest Ca status by the former and the highest Ca status by the latter genotype (Table 14).

Spehar (1995a, b; 1999) studied genetic differences in the accumulation of nutrients in leaves and seeds of tropical soybean cultivars from diallel crosses with the cultivars *IAC-9, IAC-2, UFV-1, IAC-5, IAC-8, Vx5-281, IAC-7, Biloxi* and *Cristalina* under high and low Al-stress. The diallel analysis indicated that an additive-dominance model could explain the genetic differences among those genotypes for nutrient accumulation in leaves and seeds. The diallel analysis, although not conclusive, indicated that the mechanisms of mineral element accumulation in the leaves are not fully associated to those of accumulation in the seeds of soybeans. The expression of these characters is, however, dependent on mineral plant-stress.

interferes with Fe metabolism and the formation of haem. The total Pb concentrations of agricultural soils lie between 2 to 200 mg/kg soil. Pb contamination very clearly follows the motorway areas. Vegetation at the side of the road may have levels of 50 mg/kg dry matter but in distance of only 150 m away from the motorway the level is normally about 2 to 3 mg/kg. Contamination occurs only on the outer part of plant seed or leaves and stem, and

Plant varieties of the same species differ in absorption and utilization of nutrients from the environment. Varietal differences in the uptake of individual nutrients can be used as basis for the testing of both commercial varieties and selection materials under unfavorable soil conditions. An adequate distribution of soybean varieties based on their tolerance or susceptibility to less favorable conditions could contribute to better utilization of their yield potential (Saric, 1981; Saric & Loughman, 1983). According to Epstein (1976) agricultural intervention in the process of nature has two corresponding strategies: selection and genetic manipulation of the organism and modification of the environment. Many crops in Brazil have their yield improved thanks to the selection and breeding, especially in the large savanna (cerrado) region of Central Brazil. Soybean cultivation in the low-latitude acidic soils of Brazilian Savanach has become a reality since 1970's. Great contribution for this success has been achievements in soil science and plant breeding. There are however, constraints for sustainable production like high-Al and low-Ca in the deep layers of the soil. Measures can be taken to reduce the negative effects of acidity on plant growth are liming

Kastori (1978) found that Ca uptake was higher in *Corsoy* than in *Stella* and *Wilkin*. Later research showed that K uptake was the highest at the variety *Corsoy* (Kastori et al., 1979). Keoght et al., (1977) found lower N uptake in the varieties *Hill*, *Lee* and *Bragg* than in *Hood*. Queiroz et al. (1980) tested residual effects of P fertilizers on the yield of three soybean varieties over four years. The variety *Bossier* increased grain yield by 320 kg/ha, *Parana* by 640 kg/ha, whereas variety *Vicoja* did not show any response to P fertilization. Saric and Krstic (1982) tested ten soybean varieties 30 days in N-deficient nutrient solution. The variety *Yoslie Kataya 2* showed the lowest and the variety *Traverse* the highest N contents. Kovacevic and Krizmanic (1987) tested 12 soybean genotypes of maturity group I (*Corsoy* and *Hodgson* as standard varieties and remaining ten are experimental lines from the F8 generation) under calcareous soil conditions. Grain yield of soybean genotypes ranged from 2.1 4 to 3.11 t/ha. The highest yield of *Vuka* and the lowest yield of *Os 155/82* on this soil may be due to the lowest Ca status by the former and the highest Ca status by the latter

Spehar (1995a, b; 1999) studied genetic differences in the accumulation of nutrients in leaves and seeds of tropical soybean cultivars from diallel crosses with the cultivars *IAC-9, IAC-2, UFV-1, IAC-5, IAC-8, Vx5-281, IAC-7, Biloxi* and *Cristalina* under high and low Al-stress. The diallel analysis indicated that an additive-dominance model could explain the genetic differences among those genotypes for nutrient accumulation in leaves and seeds. The diallel analysis, although not conclusive, indicated that the mechanisms of mineral element accumulation in the leaves are not fully associated to those of accumulation in the seeds of soybeans. The expression of these characters is, however,

high proportion can be removed by washing (Mengel and Kirkby, 2001).

**8. Genetic aspects of mineral nutrition of soybean** 

and selection of more tolerant genotypes.

genotype (Table 14).

dependent on mineral plant-stress.


Table 14. Yield and nutritional status of 12 soybean genotypes on Osijek calcareous soil (Kovacevic & Krizmanic, 1987)

Sudaric et al. (2008) reported about the effectiveness of biological nitrogen fixation in soybean linked to genotype for four growing season in eastern Croatia. Fields study involved eight cultivars in two treatments (control - without ionoculation and inoculation by *Bradyrhizobium japonicum*). The obtain results suggested on significant positive effect of rhizobial inoculation on both nitrogen fixation indicators and grain yield at all tested soybean cultivars (Table 15). Significant differences among tested cultivars in each measured trait indicate genetic diversity of tested material in both potential of biological nitrogen fixation and compatibility cultivar by *B. japonicum* strain, as well. Tested cultivars with the best potential for nitrogen fixation (OS-1-00, OS-3-0, OS-3-I) had the highest grain yield increasing (14.4%, 14.3% and 14.0%, respectively). These results indicate that the cultivars with the favorable performances of biological nitrogen fixation could be used as the parents for development new cultivars that are able to accomplish high grain yield with lower nitrogen level in soil.

Phosphorus is a major limiting factor for crop production of many tropical and subtropical soils. In Brazilian soils, high productivities of soybean are achieved by soil amendment techniques, using lime and fertilizers, supplying the nutrients required for best crop performance. The yield potential is an intrinsic factor and depends on plant germplasm characters that can be modified by selection and breeding (Furlani et al., 2002). Differences in grain yield among soybean cultivars under field conditions for P-, K- and N-efficiencies , were also reported by Raper and Barber (1970), De Mooy et al. (1973), Sabbe & Delong (1998), Sarawgi & Tripathi (1998), Hanumanthappa et al. (1998; 1999) and Ogburia et al. (1999).

Plant efficiency for phosphorus uptake and utilization may contribute to improve crop yield potential in situations of low P availability. Furlani et al., (2002) evaluated and classified twenty nine soybean cultivars in relation to the response to phosphorus (P) levels in nutrient solution. P uptake and use efficiency were estimated by the variables: shoot and root dry matter (DM) yield, P-concentrations and contents in plant parts and P-efficiency index (EI). The experiment was conducted in a greenhouse, during 1999, at Campinas, State of São Paulo, Brazil. The experimental design consisted of randomized complete blocks, arranged in split-plots, with three replications. The main plots were the P levels in the nutrient solution (64.5; 129; 258 and 516 mmol L-1), and the subplots were the twenty-nine soybean cultivars, grouped according days to maturity. Multivariate analysis showed high correlation among the variables shoot-DM, total-DM and shoot P-concentration and Pefficiency index (EI). Cultivars were classified in efficient-responsive (ER)¾ *IAC-1, IAC-2, IAC-4, IAC-5, IAC-6, IAC-9*, *Sta. Rosa* and *UFV-1*; efficient-non-responsive (ENR) ¾ *IAC-7*, *IAC-11, IAC-15, S. Carlos* and *Cristalina*; inefficient-responsive (IR) ¾ *IAC-8, IAC-10, IAC-14, Bossier* and *Foscarin*; and inefficient-non-responsive (INR) ¾ *IAC-12, IAC-13, IAC-16, IAC-17, IAC-18, IAC-19, IAC-20, IAC-22, Paraná*, *IAS-5* and *BR-4.* The efficient-responsive soybean cultivars showed the highest values for shoot and total DM and EI, and the lowest shoot Pconcentrations.


Table 15. Mean values of nitrogen fixation indicators and grain yield of 8 soybean cultivars (2004-2007; Osijek, Croatia) (Sudaric et al., 2008)

Ojo et al. (2010) tested 55 soybean genotypes under acid soil conditions in area of Umudike, Nigeria for two growing seasons. Highly significant differences in genotypic effects were observed for all the traits (days to 50% flowering, plant height at maturity, number of pods/plant, 100-seed weight and grain yield). Eight acid tolerant varieties were found (*Conqvista, TGX 1896-3F, TGX 1897-17F, TGX 1866-7F, TGX 1805-31F, Milena, Doko* and *TGX 1844-18E*) with a higher grain yield of >1.80tons/ha compared to <1.45tons/ha in the previously recommended varieties (*TGX 1485- 1D* and *TGX 1440-1E*). The result also showed the potential of the EMBRAPA genotypes in upgrading the TGX varieties for higher productivity. The eight identified acid tolerant varieties could therefore be explored in the development of improved high yielding soybean genotypes for production on acid soils of Nigeria.
