Effect of heat or chemical disinfection on the viability of ‘Fuji’ apple graft wood
Bundles of dormant wood were submerged in water (45°C for 45 min or 50°C for 15 min), or were wrapped in moist cloth, placed inside zip-locked bags and submerged for 3–6 h or treated with one of three GRAS chemicals or untreated (two bundles per treatment). Scion wood was grafted onto ‘M9’ rootstocks then planted in a randomised order, with growth assessed after 16 weeks. Two of the GRAS treatments and submersion at 45°C for either 45 min or 3 h in a bag did not significantly affect viability compared with the untreated control (83–95% viable). Submersion at 50°C for 15 min reduced viability significantly (70%). Scions did not survive exposure to 50°C for 3–5 h in bags (P<0.001). No significant differences in mean scion shoot length were observed between the untreated wood (107 cm) and that submerged in 45°C water for 45 min, 3 h in a bag, or GRAS-treated. Wood treated at 45°C for 5–6 h in a bag or at 50°C for 15 min had significantly shorter shoots (54–75 cm, P<0.001). Dormant ‘Fuji’ wood remained viable after treatments known to eliminate pathogens from wood.