The Native Dryland PGPR ‘Pseudomonas 42P4’ Promotes Adventitious Rooting in Woody Cuttings of Vitis spp.

This study evaluated the effect of two native PGPR strains from an arid region (Mendoza, Argentina) on the rooting of woody cuttings of Vitis spp. These strains are known for their growth-promoting capacity, including auxin production. Dormant V. vinifera cv. Malbec cuttings were grafted onto four rootstocks - 1103 Paulsen, 110 Richter, 101-14 MGt and SO4. Then, basal ends of these grafted cuttings and own rooted controls were incubated for 12 h in solutions of (1) Pseudomonas 42P4 at 107 CFU mL-1, (2) Enterobacter 64S1 at 107 CFU mL-1, (3) autoclaved LB medium, (4) water, and (5) a quick-dip immersion of Indole-3-butyric acid (IBA). After treatment, the cuttings were placed in a forcing chamber at 28°C and relative humidity ~100% for 21 days. Rooting parameters and scion-rootstock union percentages were recorded. Pseudomonas 42P4 significantly promoted rooting in Malbec own-rooted cuttings. However, Enterobacter 64S1 had negative or null effects. Furthermore, Pseudomonas 42P4 enhanced rooting in Malbec grafted onto 1103 Paulsen, but not on 101-14 MGt, 110 Richter or SO4. This strain also improved graft union success on SO4, but did not affect the other rootstocks. These results suggest that a dryland native strain such as Pseudomonas 42P4 could sustainably enhance the quality of both own-rooted and grafted grapevine plants in commercial nurseries. Highlights: • Pseudomonas 42P4, a native PGPR strain from arid soils, has genotype-specific effects during grapevine propagation. • Pseudomonas 42P4 promotes rooting in own-rooted Malbec woody cuttings and in Malbec grafted onto 1103 Paulsen. • Pseudomonas 42P4 might be a sustainable alternative to synthetic auxins in commercial nurseries.