EFFECT OF SOME FACTORS ON THE MICROPROPAGATION AND MICROGRAFTING OF SOME GRAPE ROOTSTOCKS IN VITRO

This study aimed to investigate the attitude of three nematode and phylloxera resistant grape rootstocks (Freedom, Ramsey and SO4) through the micropropagation stages till be micrografted by Superior scions. During that the effect of paclobutrazol (PP333) on rootstocks stem diameter, transverse sections in graft union regions and acclimatization of resulted micrografts were studied. The results proved that the most effective sterilization durations using 1% NaOCl were 15 min for Freedom and SO4 explants as they achieved 0.00 and 0.00%of  contamination and 100% and 90% of survival percentages respectively, while 10 min duration was sufficient for Ramsey explants as it achieved 0.00 % contamination and 100% survival percentages. Significantly, Ramsey achieved the highest number of shoots (1.25), Freedom gave the tallest shoots (4.13 cm)and SO4 got the highest leaf number (7.33) all on MS medium. In multiplication stage; Freedom rootstock proved to be the most reacted rootstock as it significantly accomplished the highest shoot number (2.00) when planted on BA medium, the tallest shoots (3.54 cm) when planted on TDZ medium and the highest leaf number on Kin medium. Whereas, in order to get thicker shoots for easier grafting; using of PP333 at 5 mgl-1 significantly was the best for Freedom (3.55 mm) followed by SO4 (3.03 mm) and Ramsey (2.85 mm) rootstocks. In micrografting stage, Superior micrografts significantly achieved the best results on rooted Freedom rootstocksin scion survival (100.00%) and on un rooted rootstocks in scion bud burst (75.00 %), graft union formation (50.00%), rooting (75.00%). On the same trend, Freedom rootstock was more active in cell dividing activity when grafted by Superior cultivar compared to Ramsey and SO4 rootstocks which were very poor in producing callus cells in graft union. Finally, Freedom rootstock grafted with Superior gained the highest survival (100%) after acclimatization.