Factor Controlling Micropropagation of Fruit Trees: A Review

Abstract

There were several factors controlling micropropagation of fruit trees such as explant type and size, surface sterilization , phenol exudation and its control, different culture medium, different media (strength, type and state), carbon source and additives, light and temperature, plant growth regulators, pH and agriculture media. The data indicated that smaller explants 0.5 mm such as shoot tip culture lead to establishment stage of in vitro culture which will be free from viruses free of the most plant species. The best surface sterilization was obtained when the explants were sterilized by using (10-30%) clorox solution with two drops of tween 20 for 15-20 min. According to explant type (shoot tip, axillary bud, one node cutting, leaf disc, flower buds and seeds). The incorporations of antioxidant agent (150 mg LG1 citric acid+100 mg LG1 ascorbic acid) for 2-24 h prior culturing in the medium is the most treatments for controlling phenol exudation. The pH of the media was adjusted to 5.7 gave better response in growth and proliferation of explant and induction of roots in many explant species. The cultured explants were incubated under 16 h of artificial light and 8 h of darkness at average temperature of 25-28EC in several explant species. Sucrose is the most common carbon source and energy because sugar is reported as a source of energy and carbon in inducing growth and development during all different stages of micropropagation. Culture at full medium strength supported better growth and proliferation in most explant species. Also, liquid medium is the best medium state during in vitro establishment stage when the phenolic products released from culture explants such as (Date palm, Mango, apple and some explant types) and rooting stage. The plant growth regulators such as (auxins, cytokinins and gibberellins) are required in very minute quantities. Both BAP and 2ip have been preferred for used in vitro proliferation media for most fruit micropropagation. In addition, NAA and IAB are the least stable in vitro rooting media. Also, gibberellins are used less frequently compared to auxin and cytokinins. Using combination of agriculture media consists of vermiculite: sand: peatmoss (1:1:1) is the best suitable media during in vivo acclimatization stage in the most plantlets.