Relationship of rootstock xylem anatomy with the initial growth of 'Tahiti' lime (Citrus x latifolia Tanaka ex Q. Jimenez)

Introduction: Rootstock diversification arises as a consequence of the appearance of diseases and the need to improve the yields and productive efficiency of orchards. Objective: To establish the relationship between the anatomical characteristics of the stem of four citrus rootstocks and the initial growth of 'Tahiti' lime (Citrus x latifolia Tanaka ex Q. Jimenez). Materials and methods: The rootstocks 'Volkamer' lemon (C. volkameriana Tenn. & Pasq.), sour orange (Citrus aurantium L.), 'Flying Dragon' trifoliate orange (Poncirus trifoliata var. monstrosa [T. Ito] Swingle) and 'Rubidoux' trifoliate orange (P. trifoliata [L.] Raf.) were evaluated. The degree of correlation between seven characteristics of the initial growth of the graft and eight characteristics of the secondary xylem of the stem of the rootstocks was established. Results and discussion: Sour orange and 'Volkamer' lemon showed more vigorous growth; the variables evaluated were 23 to 70 % higher than with 'Rubidoux' and 'Flying Dragon'. The sour and 'Volkamer' rootstocks had xylem vessels of greater area and lower density, as well as greater fiber length and xylem radiuses; these characteristics were correlated with higher shoot length and diameter values, growth rate, number of leaves and leaf area of the graft shoot. Smaller vessel size but higher density caused the opposite effect on graft growth. Conclusion: Vessel density, diameter and length, and fiber length showed higher correlations with the growth variables, so they can be used as prediction characteristics for graft growth.