Hydrogel polymer in emergency and early growth of citrus rootstocks

Abstract

The development of techniques for rapid and uniform emergence of seeds is the alternative to the diversification of citrus rootstocks that were little used due to low vigor compared to 'Rangpur' lime, the main rootstock used in Brazil, but it has shown susceptible to serious disease problems, such as the citrus sudden death (CSD). The addition of the hydrogel polymer to the substrate can increase the uniformity of seed emergence and reduce the time for the production of rootstocks due to the increase in water availability. Thus, the study was done to evaluate the formulation of the substrate with the hydrogel polymer on the uniformity of emergence and early growth of citrus rootstocks. The factorial scheme 3 × 2 × 2 was used, with the factors: Three rootstocks ['Rangpur' lime (Citrus limonia Osbeck), Poncirus trifoliata (L.) and 'Sunki' mandarin (Citrus sunki Hort. ex Tanaka); two formulations of substrate (with and without 0.4 g per container of Hidroplan-EB/HyB-M ® polymer and two environments (greenhouse with an average maximum temperature of 36.6°C and minimum of 17.2°C and growth chamber programmed with temperature to 25°C and a photoperiod of 12 h, distributed in a completely randomized design with four replications and 35 seeds per plot. The emergency velocity index (EVI), the percentage of emergence and early growth of rootstocks were evaluated. Data were subjected to analysis of variance and the means were compared by Tukey test at 5% of probability. The addition of the polymer to the substrate favored the percentage of emergence and EVI of 'Rangpur' lime and of mandarin 'Sunki' seeds in the growth chamber. The 'Rangpur' lime was the rootstock which presented the highest percentage of emergence and uniformity in both environments. The addition of the hydrogel polymer to substrate favored initial growth of citrus rootstocks.