Peach rootstock tolerance to excess zinc in sandy acidic soil
De Conti L
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In some areas dedicated to the cultivation of peach plants, soils are characterized by high levels of zinc (Zn) as a consequence of successive applications of Zn-containing fungicides and/or use of animal manure as fertilizer. In these cases, choosing an appropriate Zn-tolerant rootstock is essential to optimize orchard production. The current study evaluated the behavior of three peach rootstocks grown in a soil containing variable levels of Zn availability. Samples of a Typic Hapludalf soil were collected from a natural grassland in southern Brazil. The soil was dried and sieved. Subsamples of the soil were amended with increasing rates of Zn added as ZnSO4, incubated for 60 days, transferred to rhizoboxes, and planted with three types of peach rootstocks (Tsukuba-1, Rigitano and Flordaguard). The treatments were arranged in a completely randomized experimental design with three replications per rootstock X Zn dosage treatment. The rootstocks were grown for 65 days, at which time dry matter production of leaves, shoots and stem, as well as increase in height and stem diameter at ground level, were measured. Total concentrations of Zn, Fe, N, P, Ca and Mg were analyzed in each organ. The photosynthetic pigments and catalase (CAT) activity were analyzed in the leaves. Concentrations of Zn increased linearly in all the organs of all the rootstocks; however, the Tsukuba-1 rootstock presented greater sensitivity to high levels of Zn availability in soil, with a reduction in leaf dry matter production, chlorophyll a and carotenoid concentrations, and CAT activity. The Flordaguard rootstock showed an increase in height with increasing Zn concentration applied to the soil. Development of the Rigitano rootstock plants was unaffected by Zn amendment.