Plant growth, yield and quality of tubers of potato crop (Solanum tuberosum L.) in response to application of plant growth regulators

Abstract

The potato yield depends on the plant's capacity to synthesize carbohydrates in the leaves and mobilize them for growing tubers. Thus, excessive leaf growth in the later stages of the crop cycle can negatively affect tuber yield. In favorable conditions of the plant shoot growth the use of plant growth retardants or regulators may be an alternative for improving crop yield through reduction in size of plants and the increase in the allocation of dry matter (DM) to growth of tubers. Thus, the aim of this study is to evaluate the effect of the plant growth regulators mepiquat chloride, chlormequat chloride, placobutrazol, and prohexadione-calcium (prohexadione-Ca) on plant growth and tuber yield of Agata and Mondial potato cultivars. Two independent experiments will be conducted, one with the cultivar Agata and another with the cultivar Mondial. Both experiments will be installed in the experimental design of randomized blocks in a 4x5+1 factorial scheme, with four replications. The treatments are represented by four plant growth regulators (mepiquat chloride, chlormequat chloride, paclobutrazol, and prohexadione-Ca) applied at rates of 25, 50, 100, 200, and 400 g ha-1 of a.i., plus the control treatment (no application plant growth regulator). The plots will be composed of five plant rows of five meters long. The following variables will be evaluated in the tuber bulking stage (70 DAP): a) number of stems per plant and length of stems; b) number of leaves per plant; c) leaf area and leaf area index; d) number of tubers per plant; e) DM accumulation in shoots, tubers and in the whole plant; and e) DM partitioning to the tubers. Before the crop desiccation is determined the DM accumulation in the shoot, tubers and in the whole plant. In the final harvest will be evaluated: a) number of tubers per plant, incidence of misshapen tubers and tuber mean weight; b) yield and classification of tubers produced; c) tubers shape index; d) percentage of DM in tubers; e) dormancy of tubers and incidence of sprouted tubers; f) firmness and post-harvest tuber greening. Data from each experiment will be submitted to ANOVA separately. The means related to the plant growth regulators are compared by LSD test (pd0.05), while the effects of rates of the plant growth regulators will be assessed by regression analysis (pd0.05).