Direct somatic embryogenesis of drought resistance pistachio (Pistacia vera L.) and expression analysis of somatic embryogenesis-related genes

Abstract

Pistachio (Pistacia vera) is one of the most important commercial nut crops worldwide. There is wild pistachio forest in Iran and is believed that all commercial genotypes originated from this forest. Climate change and its consequences like drought and salinity decreased the forests and orchards area. Vegetative propagation like somatic embryogenesis is necessary for the mass propagation of wild and elite genotypes to use in reforestation and revival orchards. Therefore, the focus of this study was to establish somatic embryogenesis protocol for wild, salt, and drought tolerant pistachio cultivars. Since molecular mechanisms involved in pistachio somatic embryogenesis pathway is largely unknown, expression of four notably embryogenesis-related genes (LEC, AGL15, BBM, and PKL) in embryonic explants were investigated. Explants were exposed to various combination and concentrations of plant growth regulators (PGRs) under light and dark conditions. In light condition, somatic embryos were directly established on explants in half strength MS medium supplemented with casein hydrolysate, and L-glutamine. Application of low concentration of auxins was increased the induction frequency of somatic embryos. Somatic embryos were matured and germinated on medium supplemented with 0.01 mg L−1 abscisic acid. The LEC, AGL15, and BBM genes exhibited high levels of expression in embryonic explants, which inferred that these genes played key roles during embryogenesis in pistachio. Successful establishment of a somatic embryo regeneration system for pistachio will produce a significant foundation for production and conservation of pistachio genotypes. This system is also provided an ideal model for investigating the role of embryogenesis-related genes.