Screening of highly efficient genotypes for in vitro regeneration in Litchi chinensis Sonn

Abstract

The difficulty of in vitro regeneration greatly limits its application in the genetic transformation and improvement of litchi (Litchi chinensis Sonn.). To identify genotypes exhibiting efficient in vitro regeneration capacity, 102 litchi germplasm resources were selected, and their anthers were used as explants for in vitro regeneration. The in vitro regeneration ability varied significantly among the litchi genotypes. The proportion of anthers that could be induced to form calli varied from 0 to 88 %, and the proliferation rate of callus tissue ranged from 2.0 to 8.2 times, depending on the genotype. The embryonic calli were tiny, light-yellow particles. The induction, maturation, and regeneration efficiencies of somatic embryos varied widely among the genotypes. The somatic embryos exhibited five distinct morphological types, and the ranking of these types in terms of the amount of induced somatic embryogenesis per gram of calli was as follows: other somatic embryos, semitransparent, multicotyledonous, dicotyledonous, and monocotyledonous. After maturation, multicotyledonous embryos had the highest plantlet regeneration rate, followed by dicotyledonous embryos. Semitransparent embryos were usually converted into one of the other four types, or else they gradually browned and died. Whole plantlets with roots, stems, and leaves were successfully regenerated in vitro from 16 genotypes, and ‘Shangshuhuai’ had the highest regeneration efficiency. This study lays the foundation for the in vitro regeneration and genetic breeding of litchi.