Clonal micropropagation of rhododendrons as affected by varietal characteristics and nutrient media

Abstract

Purpose. To develop clonal micropropagation for representatives of the genus Rhododendron L. for different varietal characteristics and nutrient media.
 Methods. Rhododendron seeds of various cultivars were used for sterilization and in vitro culture: 'Summetglut', 'Cunningham's White', 'Grandiflorum', 'Libretto', 'Yakushymanskyi', 'Shamrock' and 'Balalaika'. Sterile shoots were planted on different types of nutrient media, such as Murashige and Skoog (MS), Hamborg and Evelegh (B5) and Anderson (An), modified with different compositions and concentrations of hormones BAP and zeatin.
 Results. Regardless of varietal characteristics, the largest number (12) and height (7 cm) of rhododendron shoots was formed on the Anderson medium. The smallest number and height of shoots were noted in cultivars 'Yakushymanskyi' and 'Balalaika' on all nutrient media. On the Anderson nutrient medium, variety 'Cunningham's White' formed 10 shoots and 'Grandiflorum' 12 shoots. These varieties also had the highest height of 7 cm. On the MS medium, these varieties formed 2 and 4 shoots of 2.5 and 3 cm high, respectively. The best shoot-forming ability was recorded on the Anderson nutrient medium, with 8 to 22 shoots. The largest number (20 and 22) of newly formed shoots was noted in variety 'Grandiflorum', 20 and 22 shoots, respectively. This number of shoots was somewhat lower in varieties 'Shamrock' (17 and 21), 'Cunningham's White' (18), 'Libretto' (15 and 17), 'Yakushymanskyi' (8 and 10) and 'Balalaika' (9).
 Conclusions. With the use of zeatin, the number of shoots in all studied cultivars was almost the same as with the BAP concentration of 1.0 mg/l. The lowest number and the lowest height of shoots were formed on the Hamborg and Eveleg nutrient medium, besides, the shoots of all varieties were in suppressed condition. This medium and its modifications do not provide a sufficient number of shoots and cannot be recommended for clonal micropropagation of rhododendrons. MS nutrient medium with the addition of BAP (1.0 mg/l) makes it possible to obtain cultivars from 0.8 to 7 cm in height and with the use of zeatin (0.5 mg/l) from 1.8 to 9 cm, respectively. Regardless of varietal characteristics and nutrient media, vitrification of shoots was observed with an increase in the concentration of zeatin to 1.0 mg/l.