Magnesium in Citrus nutrition: integrating processes associated with abiotic stresses, productivity and fruit quality

• Grant number: 17/10345-6
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2018
• End date: December 31, 2020
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Rodrigo Marcelli Boaretto
• Grantee: Rodrigo Marcelli Boaretto
• Host Institution: Instituto Agronômico (IAC). Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil

Abstract

Well balanced nutrient management is essential to ensure high productivity and quality of citrus fruits. Magnesium (Mg) is directly related to the fruit quality, especially to the one destined to the Citrus industry, due to the importance of the nutrient in the metabolism and transport of sugar in the tree. And it is also related to greater tolerance of the plant to abiotic stresses caused by the recent increase in excessive radiation and temperature in the main producing region of the country. Liming is the main form of Mg supply to citrus, however, the new citrus scenarios that seek increasingly productive orchards in the first years after planting, the nutrient supply from limestone alone is not sufficient to meet plant demand, and further fertilization is required. Thus, the project aims to evaluate the effects of Mg supply on the nutritional status of citrus plants and to correlate these responses with the resistance of the plant to the stress caused by the binomial light and thermal radiation on yield and fruit quality. Experiments will be conducted; three in greenhouse conditions and two in field. In greenhouse experiments will be evaluated: (i) the absorption of Mg in orange trees cultivated under two conditions of heat and light radiation in low, adequate and high nutrient availability; (ii) the redistribution of Mg depending on the nutritional status of the plant in two citrus species with distinct characteristics in nutrient use efficiency; and (iii) assessing the efficiency of Mg foliar uptake in two fertilizer sources with different water solubility. While the experiments in field conditions will be evaluated Mg supply efficiency in nutritional status of the plant, yield and fruit quality in two varieties of oranges with different fruit maturation periods. In the greenhouse trials besides biomass accumulation, nutrient contents in the plant and in the substrate, determinations related to biochemical and photosynthetic parameters, such as chlorophyll content, SPAD, carbohydrate balance, biochemical markers (antioxidant enzyme activities, hydrogen peroxide and lipid peroxidation) and rates of photosynthesis and transpiration will be performed. In the experiments in field conditions will be evaluated attributes related to soil, nutritional status of the plant, yield and fruit quality. The information obtained in the work will allow a better understanding of the Mg role in the nutrition of the citrus trees in order to maximize the productive efficiency of the orchards and will contribute to the update the current guidelines of Mg fertilization for citrus. (AU)