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RESEARCH PRODUCT

Correlating stress and somatic embryogenesis for NBT: myth or reality?

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description

Global warming and growing demography have increased demand for agronomic resources, leading to increasing lack of land suitable for agriculture and provoking several abiotic stresses which, added to biotic ones, result in physiological and metabolic disorders that impact on crop yield when most needed. Reducing this impact is a major scientific and agronomic challenge and biotechnology would be an efficient alternative. However, to reduce risks of somaclonal variation among regenerants it is better to produce them by somatic embryogenesis directly from explants or gametes, or indirectly from callus or cell suspensions. Thus, globular embryos regenerate and develop through to the heart, torpedo and cotyledonary stages, finally reach maturity and develop into viable plantlets provided they have accumulated enough storage products. However, blockages may occur: i) during early development embryo may be arrested at the globular stage, ii) during transition from torpedo to cotyledonary, embryos display fused cotyledons and/or become pale due to lack of accumulation of storage compounds, and iii) at latest stages leading to rooting, when only the aerial part develops and embryos must transferred for rooting, when callus may proliferate instead and plantlets lack vascular connection between the roots and shoots and die upon in vivo transfer. Somatic embryogenesis is often triggered by growth regulators, but more and more frequently stress agents were shown to favor induction and development of somatic embryos in many species by activation of several genetic and metabolic paths. These relationships between embryogenesis and stress and their impact on generation of new genotypes more apt for a sustainable agriculture will be discussed.