Website INRA - French National Institute for Agricultural Research

Reproduction is a key trait in forest trees population renewal (natural and/or artificial regeneration). Climate change (higher temperature, frequent drought) have a negative impact on the fructification of the trees, and then on seed production (Lebourgeois et al. 2010), which finally induces a limitation on seedling production. Vegetative multiplication could appear as an alternative to the lack of seedling. Among all the multiplication methods, somatic embryogenesis allows efficient multiplication of elite genotype obtained from the tree breeding programs (Lelu-Walter et al. 2013, 2016). However, somatic embryo at its final maturation stage is similar to a fresh zygotic embryo (seed embryo; Morel et al. 2014, Teyssier et al. 2014). Therefore, it does not reach the desiccated stage of a seed in the nature. This desiccation is characterized by many biochemical events come along with (accumulation of energy storage compounds) and a potential conservation of the seed. Seed quality is conditioned by its energy storage compounds (lipidic and proteic form), whereas its desiccation tolerance results from the presence of specific lipids and proteins.

The objective of this thesis is firstly to study physiological and molecular modifications involved in somatic embryo desiccation and the consequences on its quality through the germination ability. We propose biochemical and proteomic analysis in order to realize a qualitative and quantitative survey of the modifications occurring during somatic embryo desiccation. This study realized on somatic embryo, developed under controlled environmental conditions, will be then completed with a similar approach on seed in order to better understand its physiological and molecular developments during desiccation. Following this seed characterization using infrared spectroscopy, we should develop a calibration model that could allow predicting of seed quality.

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