Rootstocks influence fruit oleocellosis in 'Hamlin' sweet orange (Citrus sinensis L. Osbeck)

Oil spotting or oleocellosis, is a major problem in citrus crops. As the rootstock and fertilization play important roles in citrus growth and fruit development, we investigated the influence of different rootstocks on the growth, mineral nutrition metabolism, water relations, and fruit oleocellosis of eight-year-old field 'Hamlin' sweet orange trees. Trees grafted onto Lichi16-6 trifoliata (Poncircus trifoliate) had the greatest rate of oleocellosis (RO), and trees grafted onto Goutou orange (Citrus aurantium) had the greatest degree of oleocellosis (DO). In contrast, trees grafted onto Rangpur lime (Citrus limonia Osbeck) had the lowest RO and DO. Trees were the most vigorous on Rangpur lime rootstocks, followed by Lichi16-6 trifoliata, and then Gouto u orange. In addition, because the scion/stock girth ratio showed significant correlations with the RO and DO, oleocellosis parameters can be a good indicator of scion/stock affinity. The total N. total P. Ca2+, and Mg2+ in leaves from trees on Rangpur lime were significantly lower than in leaves from trees on Goutou orange or Lichi16-6 trifoliata. In addition, the RO showed a significant correlation with the leaf Ca2+ and S concentrations and with the peel Mg2+ concentration. The DO was significantly correlated with the total peel N and S concentrations. In addition, the RO showed a significant correlation with the net assimilation of CO2 (ACO(2)), stomatal conductance (GS), transpiration rate (ET), and water-use efficiency (WUE). However, the DO showed a significant correlation with the GS, ACO(2), and WUE. Taken together, these results indicate that rootstocks affect the development of oleocellosis in 'Hamlin' sweet orange due to their effects on the mineral nutrition balance and water relations. (C) 2011 Elsevier B.V. All rights reserved.