In vitro efficiency of embryo rescue of intra- and interspecific hybrid crosses of sweet cherry and Chinese cherry cultivars

Abstract Hybrid cherry seedlings are very hard to obtain as the embryos easily abort during development and loose germination ability, especially some interspecific hybrids. An in vitro technique of embryo rescue has been developed for intra- and interspecific hybrids with the embryos by crossing 4 sweet cherry genotypes as maternal, and these have been planted in South China where the climate is not ideal for planting sweet cherry due to its hot and humid climate in summer and warm climate in winter. The success of embryo rescue approach is affected by several factors, in which the genotypes are one of the main factors for embryo germination and significant differences were found with the same genotypes that were used differently either as maternal or paternal in cross breeding. ‘Chaoyang-1’ (‘CY-1’) as mother performed the best, and ‘Zijing’ (‘ZJ-1’) and ‘CY-1’ were the best parents as fathers in cross breeding. The embryo development stage, breaking dormancy method and in vitro culture condition significantly affected the efficiency of seedlings production. When the development of their embryos reached to 0.5 to 0.7, then the young fruit was harvested and stored at 4 °C for 35 days were found to be the best initiating materials for culturing, and the embryo germination rates after removal of the embryo coat reached up to 69.84 ± 2.75 %, and their shoots were robustly and fastly grown. The medium when combined with different concentrations of plant growth regulators (PGRs) were tested, the optimal medium for immature embryo culturing was found to be 1/2 MS supplemented with 2 mg L−1 BA and 1.8 mg L−1 IAA, the multiplication of shoots culture media was MS +0.3 mg L−1 BA +0.4 mg L−1 IAA or MS +0.7 mg L−1 BA +0.1 mg L−1 IAA, the 1/2 MS medium supplemented with 0.3 mg L−1 IBA and 1.1 mg L−1 IAA showed the best for the rooting of shoots. Taken together, this system by integrating the genotypes, embryo development and in vitro culture condition with pre-treatments together significantly improved the rates of production of hybrid cherry seedlings. This is the first study to systematically explore all these factors on cherry embryo rescue in order to produce hybrid seedlings to breed new cultivars for the subtropical monsoon climatic areas like South China and provide new insights to keep the micropropagation of hybrid shoots with different PGRs.