MICROPROPAGATION OF FRUIT PLANTS

Cultivars and mature fruiting selections of 4 crops have been micropropagated successfully during the last 4 years. With apples, research emphasis was placed on factors affecting rooting of cuttings made from in vitro-produced shoots. Phloroglucinol had little if any effect, the auxin concentration required was relatively low, and little difference in effectiveness between IBA and NAA was noted. Trees of 16 cultivars have been established in a test orchard and 4 of these cultivars began to flower in 1981. Blueberries produced adventitious shoots directly from the leaves; these shoots as well as ones from axillary buds were easily rooted under non-aseptic conditions. Strawberries were micropropagated using a modified Boxus medium. The newly released cultivars 'Allstar', 'Tristar', and 'Tribute' were increased in vitro to permit rapid introduction. Phenotypic stability of micropropagated plants of 'Earliglow', 'Guardian', and 'Redchief' was satisfactory. Micropropagated plants of these 3 cultivars outperformed runner-propagated controls although fruit size was reduced somewhat. Thornless blackberries were easily proliferated in vitro but rooted most readily in the greenhouse. The resulting plants were vigorous, uniform, and capable of fruiting within 1 year from micropropagation.