Embryo rescue in stone fruit breeding: specifics and application success

Abstract

The development of stone fruit varieties that meet modern production requirements is a labor-intensive process involving low yields of progeny obtained through controlled intraspecific and interspecific hybridization, which can take up to 25 years. The non-viability of hybrid seeds is caused by the abortion of the embryo that does not have time to complete its morphophysiological development and endosperm abortion in interspecific hybrids. It is possible to preserve hybrids having a unique combination of traits by removing embryos derived from interspecific and intergeneric crossing that are unable to survive in vivo or when using conventional methods for breeding embryos at early developmental stages and placing them under in vitro conditions for further development. On the basis of literary sources, the study aims to analyze growth media, conditions of their application, and time of embryo placement under in vitro conditions designed to preserve immature embryos and create hybrids of stone fruit crops, as well as to identify the most effective in vitro embryo isolation schemes for further use in the breeding process. The analytical review used open sources containing information on the composition of the most commonly used growth media, their compositions, modifications, application conditions, time of embryo placement under in vitro conditions for common peach (Prunus persica (L.) Batsch.), common apricot (P. armeniaca L.), common plum (P. domestica L.), Chinese plum (P. salicina Lindl.), cherry plum (P. cerasifera Ehrh.), sloe (P. spinosa L.), sour cherry (P. cerasus L.), sweet cherry (P. avium (L.) L.), as well as electronic scientific libraries (eLibrary, Scopus, and Google Scholar). The performed analysis of works revealed the following media as optimal for sustaining the development of embryos: common peach – modified growth medium Woody Plant (up to 100 % of preserved embryos); common apricot – modified Monnier (up to 92.4 % of preserved embryos); sour cherry, sweet cherry, plum, and interspecific hybrids – different variants of Murashige and Skoog (over 70 % of preserved embryos). The used modifiers include 6-benzylaminopurine (6-BAP), gibberellic acid (GA), kinetin, peracetic acid, carbohydrates, L-glutamine, iron chelate, ascorbic acid, thiamine, glutamic acid, tryptophan, casein hydrolysate, etc. The time of placement under in vitro conditions varies from 28 days (sour cherry) to 99 days (common peach) depending on the crop. Stratification in the dark at +4…+5 ℃ prior to development increases the yield of viable embryos. The optimal photoperiod for in vitro embryo cultivation ranges from 12 (common peach) to 16 (cherry plum, sour cherry, sweet cherry, and interspecific hybrids) hours. As a result of selection from the fund of hybrids obtained through embryo preservation, one common peach variety (Krymskii Shedevr) and three sweet cherry varieties (Vesnyany Naspivy, Prizerka, and Uslada), recommended for the North Caucasus region, were included in the State Register of Breeding Achievements approved for use; two common plum varieties (Tulitsa and Velichavaya) were included into the Register of Protected Breeding Achievements for the Central Region.