Effect of the timing of embryo isolation on the output of seedlings of sour cherry varieties when cultivated <i>in vitro</i>

Abstract

The breeders are faced with the task of the fastest breeding of sour cherry (Prunus cerasus L) varieties, which will be able to fill a niche among the insurance stone fruit crops, complementing the existing assortment. It is practically impossible to speed up this process without the use of in vitro culture. In this regard, the purpose of the present study was to identify the most favorable timing for isolating embryos of sour cherry varieties and hybrids with sweet cherry for embryos active development and growth in vitro. Analysis of the literature data and the results obtained in this study allows a conclusion that the timing of embryos isolation for their introduction into in vitro culture plays a very important role for the entire breeding process. Due to the discrepancy in defining the timing, a certain starting point is proposed, which is the date of fertilization (artificial pollination), or mass flowering in the case of free pollination. The parameters (height and width) of sour cherry seeds, which depend on the period of pollination, are given. Together with the cotyledons, the embryos of sour cherry varieties on the 14th day of their development correspond to sizes from 1.2 × 0.4 mm to 1.6 × 1.0 mm and, in the case of normal fertilization, increase in size from 6 .5 × 5.1 mm to 7.2 × 6.3 mm by day 28-30, on an average. At the same time, the seed with the embryo of hybrid sour cherry varieties (dukes) reaches higher values, e.g., 11.3 × 8.1 mm. When introducing cherry embryos into culture, one should focus on their size, as well as on the period that has passed from pollination. It was found that the periods of isolation, both early on day 14-19 and late on day 44-52, negatively affect the development of embryos: they stop their development, and the number of the obtained seedlings decreases. It has been experimentally proven that the most optimal timing of fruit picking for growing cherry hybrids in vitro is the period from day 28 to 32 after pollination of flowers: active development was observed in them on days 10-15 in test tubes, and most of them (83-85%) began to germinate 40 days later (on day 39-47 after the introduction into in vitro culture). In general, this leads to the efficient hybridization and accelerated obtaining of seedlings in the same year.