AVOCADO SELECTIONS WITH POTENTIAL USE AS ROOTSTOCKS. II. ROOTING RESPONSE TO AIR LAYERING

Abstract

In Mexico there are avocado selections with tolerance to drought, salinity or root rot (Phytophthora cinnamomi Rands) that could be
propagated for use as clonal rootstocks; however, there is no information on their rooting capability. This research was conducted to determine the rooting time and success rate of 38 avocado (Persea americana Mill.) and two chinini (P. schiedeana Nees) selections using
stem bark ringing and basal air layering. The evaluation was carried out in a 50 % shade nursery in Xalisco, Nayarit. Selections were veneer grafted onto seven-month-old seedling rootstocks. When scions were 15 to 20 cm in length a 2-cm wide bark ring was made at the base of the stem and a solution of indole-3-butyric acid (2000 mg L^-1) plus α-naphthalene acetic acid (1000 mg L^-1) was applied above the ringed area. Root production varied among selections with 10 to 100 % of the selections successfully rooted, although overall rooting averaged 66 %. The rooting response of drought and salinity tolerant selections was similar (69 %), whereas for P. cinnamomi-tolerant selections it was 57 %. According to the elapsed time from bark ringing to presence of roots ≥ 10 cm in length, nine out of 13 salinity tolerant and six out of 18 drought tolerant selections produced roots in 60 to 90 days. For P. cinnamomi tolerant selections, seven out of nine selections required 120 to 180 days for successful rooting.