HORTICULTURAL AND ANATOMICAL ASPECTS OF GRAPE IN VITRO MICRO- GRAFTING

Abstract

This study aimed to determine the limit of micro- grafting success of some important grape rootstocks and cultivars in vitro. Simultaneously, this study supported by an anatomical study through cross sectors application in grafting union of the studied micro-grafts. Stem node explants of nematode resistant rootstocks: 'Freedom', 'Harmony' and 'Ramsey' were employed as rootstocks and another stem node explants of grape cultivars: 'Flame seedless', 'Thompson seedless' and 'Superior' were employed as scions. After washing and sterilizing the explants; the cleft micro-grafting was applied then the micro-grafts were inoculated into glass culture tubes (15×150 mm) filled with 20 ml of full strength B5 medium supplemented with adding 1 mgl-1 IBA in order to stimulate rooting of the micro-grafts. Contamination, scion survival, bud burst, union graft formation, micro-grafts rooting percentages, quality characteristics of shoots proliferated from the successful scions and micrografts adventitious roots characteristics were recorded four weeks from culture. Cross sectors in grafting union of all studied micro-grafts were taken five weeks from culture then prepared, stained and microscopically examined by the proper methods. The results proved that Superior scions achieved the highest percentages of union graft formation (100.00, 71.53 and 78.18) when grafted on Freedom, Harmony and Ramsey grape rootstocks respectively. Also, Freedom rootstock achieved the highest bud burst percentage for all scions grafted on it whereas Harmony rootstock gave the lowest bud burst values. These findings were supported by the anatomical results so Harmony micro-grafts were the poorest in producing callus in the grafting union whereas Freedom ones were the richest so its cells showed high dividing activity. Also, new cambium between scion and rootstock was formed although the anatomical layers in both of them sometimes were not matched.