Hi, Julio, what is the fina aim of your invetsigatiion? Do you plan to study process of somatic embryogensis itself, or you aim is different? I thuink that immature cotyleodon is much better starting materail.  But you can use also mature in the case in the case if mature cotyledion still remain competence for both stages of cell re-programming. Please, remeber that somatic embryogensis is strictly genotype depemding!

may be this paper will help you:

Verma, K., Saini, R., & Rani, A. (2014). Recent advances in the regeneration and genetic transformation of soybean. Journal of Innovative Biology March, 1(1), 015-026.

Best wishes!

Dear Taras Pasternak, thanks for your reply! My goal is to regenerate transformed soybean cotyledons and, in my view, somatic Embryos can provide a more homogeneous material. I will check the reference you sent. All the best! Julio

Dear Julio, Yes somatic Embryos could provide the homogeneous material for genetic transformation. For further information you could go through the below recently published books.

1) Somatic embryogenesis and genetic transformation in plants

2) Somatic embryogenesis and gene expression 

Junaid

Hi, Julio, yes,. with direct somatic embryos you can avoid somaclonal variation. But better if you use immature explants and choose genotype with high regeneration capacity.

Dear Dr. Maia:

I have successfully transformed Indonesian soybean, mediated by Agrobacterium, using explant of cotyledonary node.  Based on review by Verma et al. (2014), Agrobacterium-mediated transformation through organogenesis is relatively efficient.  The improvement of the protocol was reported by Paz et al.  (2006):

Plant Cell Reports  March 2006, Volume 25, Issue 3, pp 206-213.

Improved cotyledonary node method using an alternative explant derived from mature seed for efficient Agrobacterium-mediated soybean transformation

Best regards,

Setyo Dwi Utomo