IN VITRO PROPAGATION OF PEAR (PYRUS L.)

Abstract

Background. The micropropagation methods are used for the conservation of Pyrus L. phytodiversity, as well as for the creation of collections of the threatened species and pear cultivars including genotypes necessary for breeding and genetic studies.
Materials and Methods. The two Pyrus species, P. communis, and P. salicifolia Pall. as well as four pear P. communis cultivars, ’Bere Desiatova’, ’Umans’ka Juvileina’, ’Kniahynia Olga’, and ’Sofia Umans’ka’, were chosen as the experimental plants. Young shoots of Pyrus species and cultivars with apical meristem from three-year-old plants were used as primary explants. The effectiveness of sterilization was determined by the rate of sterile and viable explants. Rooted in vitro test tube shoots with 3–4 roots 2–5 cm long were transplanted to adapt into nutrient disks Jiffy-7 and Ellepress. The statistical analysis of the results was performed according to Ronald Fisher (2017) and Peter Bruce with co-workers (Bruce et al., 2020) using Statistica ver.10 (StatSoft, Inc. STATISTICA version 10.0).
Results and Discussion. According to our results, mercury dichloride (HgCl₂) was the most effective of all tested sterilizers of P. communis. The P. communis explants steri­lization technique was extremely difficult or unsuccessful for P. salicifolia, probably due to the dense pubescence on shoots and buds of this species. Therefore, we used the seeds as explants for micropropagation of P. salicifolia according to the standard protocol. In the best variant of Murashige–Skoog (MS) medium modification for P. communis, where MS-276 was modified by 2.0 mg/L 6-benzylaminopurine (6-BAP) and 0.01 mg/L indole-3-butyric acid (IBA), a value of 9.50 microclones per passage was obtained. However, the most active shoot formation of P. salicifolia in vitro was observed in the variant where the Driver and Kuniyuki (DKW) medium was modified by adding 2.5 mg/L 6-BAP. To induce rhizogenesis, the best medium for P. communis and P. salicifolia rhizogenesis was MS-302, modified by the addition of 0.5 mg/L α-naphthaleneacetic acid (NAA). In this variant, the first root in microclones developed in 8–10 days, and after a month, rooting reached 87.50% of P. communis and 98.54 % of P. salicifolia. The efficiencies of both Pyrus species adaptation were better with Ellepress peat plugs, than with Jiffy-7 peat pellets.
Conclusion. It is recommended to cultivate explants of P. communis on MS medium with the addition of 2.0 mg/L 6-BAP and 0.01 mg/L IBA, and P. salicifolia on DKW medium with the addition of 2.5 mg/L 6-BAP and 0.1 mg/L IBA. It is also recommended that MS medium with the addition of 0.5 mg/L NAA be used for rooting of the microclones of both Pyrus species, and Ellepress peat plugs for the adaptation of regenerated plants.