Effect of Several Factors on Rooting and Cultivar Differences in Rooting Abilities of Air-layered Mango

Abstract

For the purpose of producing own-rooted nursery trees of mango (Mangifera indica L.), several factors affecting rooting of air-layered mango using to 13- to 21-year-old ‘Irwin’ and 8- to 11-year-old ‘Aikou’, and cultivar differences in rooting abilities using fifteen 8-year-old cultivars and 5-year-old ‘Irwin’ and ‘Aikou’ were investigated. Auxin solution (50% ethanol) was sprayed on the girdle (2–3 cm width) of the air-layered branch. In both cultivars (‘Irwin’ and ‘Aikou’), the rooting percentage (after two months of air layering) of air layers treated with NAA tended to be superior to those of air layers treated with IBA. However, there was no significant difference between two auxins in the root number or total root length per rooted air layer. In both cultivars, there was no rootings in controls not treated with auxin. The rooting percentage of air layers treated with NAA 1,000 ppm tended to be low in both cultivars. The total root length of air layers treated with NAA 2,000 ppm was longer than that of air layers treated with NAA 1,000 ppm. It was considered that the optimal concentration of NAA for rooting was 2,000 ppm in both cultivars. In both cultivars, the rooting percentage of air layers tended to decrease when additional treatment of NAA was performed. In ‘Irwin’, the root number and the total root length was significantly decreased by additional treatment with NAA. Combination of NAA 2,000 ppm and ABA 20 or 100 ppm did not affect rooting of air-layered ‘Irwin’. In both cultivars, branch age did not affect rooting. Removal of cambium did not affect rooting of air-layered ‘Aikou’. In both cultivars, air-layered shoots with many leaves tended to be higher in the rooting percentage, and were significantly high in the root number and total root length than those of air-layered shoots with few leaves. Water content (20–40%) in the rooting medium did not affect rooting of air-layered ‘Aikou’. In both cultivars, a suitable time for air layering to obtain rooting seemed to be July to August. In seventeen cultivars, ‘Spirit of 76’ showed the highest rooting ability, followed by ‘Aikou’, ‘Irwin’, ‘Khom’ and ‘Glenn’; The rooting ability of ‘Sensation’, ‘Golden Lippens’ and ‘Dot’ was slightly low, and that of ‘Lippens’, ‘Tommy Atkins’, ‘Florigen’ and ‘Valencia Pride’ was low. Air-layered ‘Alphonso’, ‘Edward’, ‘Florigon’, ‘Khieo Sawoei’ and ‘Nam Doc Mai’ did not root at all.