Induction of somatic embryogenesis in soybean: physicochemical factors influencing the development of somatic embryos

The embryogenic capability of five soybean cultivars (Renascença, IAS-5, IAC-17, BR-16 and FT-Cometa) was studied at different auxin concentrations (8, 10 and 12 mg/l naphthalene acetic acid, NAA), at different pHs (5.8 and 7.0) and at low (8-12 muEm-2 s-1) and high (27-33 mEm-2 s-1) light intensities. The experimental design was completely randomized with four replications. Immature cotyledons 4-6 mm in length were placed in the six induction mediums evaluated and submitted to two light intensities. Twenty immature cotyledons per cultivar were placed on each Petri dish, which was considered to be one replication. The number of somatic embryos per treatment per replication was counted. The results showed genotype influence on somatic embryogenic capability of each cultivar, with the most embryogenic cultivars being BR-16, FT-Cometa and IAS-5. Auxin concentration and pH value also influenced somatic embryo production, with 10 mg/l NAA being the best auxin concentration and 7.0 the best pH value. The interactions cultivar x auxin, auxin x pH and pH x light were significant, while other double interactions were not. All triple and quadruple interactions were significant, except cultivar x pH x light. No significant differences in somatic embryo production were observed in medium with different pHs or when the Petri dishes containing immature cotyledons were exposed to the two light intensities evaluated. However, a higher number of somatic embryos was produced when the medium pH was adjusted to 7.0. A capacidade embriogênica de cinco cultivares de soja (Renascença, IAS-5, IAC-17, BR-16 e FT-Cometa) foi estudada em diferentes concentrações de auxina (8, 10 e 12 mg/l de NAA), em diferentes valores de pHs (5,8 e 7,0) e em baixa (8-12 miEm-2 s-1) e em alta (27-33 miEm-2 s-1) intensidade luminosa. O delineamento experimental foi o inteiramente casualizado com quatro repetições. Cotilédones imaturos com 4-6 mm de tamanho foram depositados nos seis meios indutivos e submetidos às duas intensidades luminosas. Vinte cotilédones imaturos de cada cultivar foram depositados em cada placa de Petri, que foi considerada como uma repetição. O número de embriões somáticos por tratamento, por repetição foi contado e os resultados evidenciaram a influência do genótipo na capacidade embriogênica de cada cultivar, revelando-se mais embriogênicos os cultivares FT-Cometa, IAS-5 e BR-16. A concentração de auxina e o valor do pH tiveram influência no número de embriões somáticos prod