Degree of Callus Formation in Grafted Walnut Plants under Different Stratification Treatments

Abstract

The effect of different stratification treatments on the degree of callus formation in one cultivar (control 'Seinovo') and four selections of walnut ('Ovcar', 'G-286', 'Elit' and 'G-139') were evaluated in this study. Three stratification treatments were employed, including: Treatment I - stratification of walnut grafts without the use of paraffin by completely covering with conifer sawdust, Treatment II - dipping of scions and graft unions into paraffin (paraffin temperature being 60-70 degrees C) and their stratification in sawdust up to the top of the scion, and Treatment III - dipping of scions and graft unions into paraffin, their stratification in sawdust up to the graft union and covering with polyethylene foil. Degree of callus formation was highest in treatment III (excellent callus formation in 53.4% of grafted plants, very good in 24.8%, good in 12.9%, and no callus formation in 8.9%), and lowest in treatment I (excellent, very good, good and no callusing in 36.3%, 22.0%, 19.4%, and 22.3% of grafted plants, respectively). As for cultivars, callus formation was highest in 'Seinovo' (excellent in 54.5%, very good in 23.6%, good in 14.9%, and no callusing in 7.0%), and lowest in 'G-139' (32.8% excellent, 27.5% very good, 18.2% good, and 21.5% no callus formation).