In vitro callus co-cultivation strategy for prospecting growth regulators to induce in vivo grapevine graft union

Abstract

The use of growth regulators (GRs) in a mechanized bench grafting system is essential for the final quality of grafted grapevine plants. In Brazil, the GRs used (commercial waxes) are imported, increasing the production cost for nurseries. This work aimed to test the in vitro callus co-cultivation technique as a strategy for prospecting effective doses and mixtures of GRs for in vivo graft union on grapevines. Two genotypes were used as scions (‘Bordo’ and ‘Riesling Italico’) and two as rootstocks (‘SO4’ and ‘P1103’). Callus from different scion/rootstock combinations were co-cultivated, varying the doses (0.25 to 20 mg l-1) of auxins (DBA, IAA and IBA) and cytokinin (BAP), following the Doehlert design. The best in vitro treatments were validated in vivo, in plants grafted with an ‘omega’ cutter machine. Multivariate and non-parametric methods were applied to integrate the results. In vitro prospecting combined with the in vivo validation strategy allowed us to select effectively the IAA(2.50 mg l-1) plus BAP(1.00 mg l-1) formulation with the potential to induce graft callus union similar to commercial waxes. The induction intensity varied among the genetic combinations but was similar in the in vitro and in vivo conditions.