The effect of certain exogenous growth regulators on quality of grafted grapevine rootlings

Paclobutrazol (PB), chlormequat (CM), fenarimol (FM), and gibberellin A3 (GA3) were applied as exogenous growth regulators once (1 × PB, 1 × CM, 1 × FM, 1 × GA3), twice (2 × PB, 2 × CM, 2 × FM, 2 × GA3) or three times (3 × PB, 3 × CM, 3 × FM, 3 × GA3) onto grafted grapevine rootlings of cv. Cardinal on Kober 5BB grown in nursery and in vegetative pots. Water was also applied at each application, at every 15 days, as the control (C). Application treatments 2 × PB and 3 × PB, as well as 2 × CM retarded shoot elongation and increased dry matter content in shoots. Treatments 3 × PB, 2 × CM and 3 × CM also significantly increased dry weight of roots in comparison to C. Repeated application of growth inhibitors (PB and CM) significantly increased starch content in shoots when compared to C as well as to GA3-treated plants. A very strong correlation existed between the shoot sugar: starch ratio (that was increased by 3 × CM and 2 × PB) and the percentage of first-grade graftlings. PB and CM significantly enhanced lsquomaturityrsquo (defined here as giving a high rate of survival and reduced post damage) of grapevine graftlings. This is a very important quality attribute for their use as planting material.