Development of mango wilt in mango cultivars submitted to salt stress

DOI: http://dx.doi.org/10.1590/1678-4499.224 J.C. Vieccelli et al. BASIC AREAS - Note Development of mango wilt in mango cultivars submitted to salt stress Juliana Cristina Vieccelli1, Leonardo Araujo2, Ueder Pedro Lopes3, Dalmo Lopes de Siqueira1, Fabrício de Ávila Rodrigues4* 1. Universidade Federal de Viçosa - Departamento de Fitotecnia - Viçosa (MG), Brazil. 2. Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina - Fitopatologia - São Joaquim (SC), Brazil. 3. Universidade Federal Rural de Pernambuco - Departamento de Fitopatologia - Unidade Acadêmica de Garanhuns Garanhuns (PE), Brazil. 4. Universidade Federal de Viçosa - Departamento de Fitopatologia - Viçosa (MG), Brazil. ABSTRACT: Mango wilt, caused by Ceratocystis fimbriata, is one of the development was evaluated at 42 days after inoculation. During this most important diseases affecting mango yield worldwide. Salt stress period, the plants were also submitted to salinization. After disease can affect host defense responses against pathogens infection. The aim evaluation, the stems of plants from each treatment were collected to of this study was to evaluate the development of mango wilt in 2 mango determine the concentrations of chlorine (Cl) and sodium (Na). Plants cultivars submitted to salt stress. Mango plants from cultivars Tommy from the 2 cultivars showed reduced mango wilt symptoms as the Atkins and Ubá, considered to be moderately resistant and resistant to NaCl doses increased from 0 to 90 mmol·L–1. Plants submitted to mango wilt, respectively, were grown in plastic pots which contained the highest NaCl doses showed greater Cl and Na concentrations on the 20 kg of washed sand and daily irrigated with 3 L of a modified Hoagland stem. In conclusion, the resistance of plants against C. fimbriata solution during 40 days before being submitted to salinization. For this infection can be potentiated when submitted to salt stress regardless process of salinization, the plants received nutrient solution containing of their basal level of resistance to mango wilt. 0, 30, 60, and 90 mmol·L–1 of sodium chloride (NaCl) during 50 days. At Key words: Ceratocystis fimbriata, Mangifera indica, resistance, the 50 day, the plants were inoculated with C. fimbriata, and disease salinity, vascular pathogen. th *Corresponding author: Received: May 30, 2016 – Accepted: Oct. 3, 2016 372 Bragantia, Campinas, v. 76, n. 3, p.372-377, 2017 Development of mango wilt submitted to salt stress Mango wilt, caused by the fungus Ceratocystis fimbriata Ellis & Halst., is one of the most important diseases affecting mango production worldwide, especially in Brazil (Ribeiro 2005; Viégas 1960). Mango wilt has caused significant decrease in yield in several mango growing areas because C. fimbriata can lead to the death of the entire tree in a few months upon roots infection or more slowly if the penetration occurs in wounded branches on the plant canopy caused mainly by beetles (Ribeiro 2005; Viégas 1960). The use of certified seedlings free of C. fimbriata and the eradication of mango trees exhibiting disease symptoms are some of the major control strategies used by the growers to reduce the yield losses caused by mango wilt (Ribeiro 2005; Rossetto et al. 1996; Viégas 1960). In Brazil, the use of mango cultivars showing high level of basal resistance against C. fimbriata infection has been the most effective control strategy mainly because of a failure in the use of pesticides (Ribeiro 2005; Rossetto et al. 1996; Viégas 1960). Some mango cultivars showing greater resistance to mango wilt are at the same time very sensitive to salt stress (Lucena et al. 2012). For example, Tommy Atkins and Ubá cultivars, considered to be resistant to mango wilt (Araujo et al. 2014; Rossetto et al. 1996), are tolerant and sensitive, respectively, to salt stress (Lucena et al. 2012). The number of cultivated areas suffering from salinity around the world has dramatically increased nowadays (Lucena et al. 2012; Zuazo et al. 2003; Zuazo et al. 2004; Zuazo et al. 2006) and it affects many important physiological processes on plants such as photosynthesis, synthesis of protein, and lipid metabolism (Carillo et al. 2011). According to Zuazo et al. (2003), Zuazo et al. (2004), and Zuazo et al. (2006), many mango cultivars sensitive to salinity when grown in saline soils show the apex or the edges of the leaves burned, reduction in growth, leaf abscission, and further plant death, and, for some pathosystems, the host defense responses against pathogens infection are negatively impaired (Bartels and Sunkar 2005; Dileo et al. 2010; Maurya and Gothandam 2014). Considering the importance of mango wilt to decrease mango yield and the effect of salinity on plant performance, this study aimed to evaluate the development of mango wilt in 2 mango cultivars differing in their basal level of resistance to mango wilt when exposed to salt stress. One-year-old plants were transferred into plastic pots filled with 20 kg of washed sand each. Plant in each pot was daily irrigated with 3 L of a modified nutrient solution (Hoagland and Arnon 1950) that consisted of: 4 mmol·L–1 KNO3, 1 mmol·L–1 NH4H2PO4, 13 mmol·L–1 NH4Cl; 2 mmol·L–1 MgSO4∙7H2O; 5 mmol·L–1 Ca(NO3)2; 2 mmol·L–1 S-SO42–; 0.50 μmol·L–1 CuSO4∙5H2O; 2 μmol·L–1 ZnSO4∙7H2O, 25 μmol·L–1 H3BO3; 2 μmol·L–1 MnCl2∙4H2O; 0.5 μmol·L –1 (NH 4 )6Mo 7 O 24 ∙4H 2 O and 80 μmol·L –1 FeSO4∙7H2O. Plants were grown in this nutrient solution for 40 days before being submitted to salt stress. For salinization, plants received nutrient solution containing 0, 30, 60, and 90 mmol·L–1 of sodium chloride (NaCl) during 50 days. In order to maintain the nutrient solution stable and to make sure that plants were under salt stress, an initial reading of the electrical conductivity (EC) was performed with the aid of a portable conductivity meter. This first reading served as a reference for the subsequent ones. The EC was checked weekly and, when the depletion was equal to or greater than 20% of the initial EC reading, the pH of the NaCl solutions was adjusted to 5.5 by using solutions of nitric acid or potassium hydroxide, both at 0.1 mol·L–1. At the 50 th day, the plants were inoculated with C. fimbriata according to Araujo et al. (2014). The isolate CEBS15 of C. fimbriata, used to inoculate the plants, was obtained from symptomatic mango plants collected in Brejo Santo, Ceará State, Brazil. The isolate was preserved using Castellani’s method. Plugs of a malt extract agar medium containing fungal mycelia were transferred to Petri dishes containing potato dextrose agar (PDA). After 3 days, the PDA plugs containing fungal mycelia were transferred to Petri dishes containing the same culture medium and maintained in an incubator (temperature of 25 °C and 12-h photoperiod) for 14 days. Bark disks (10 mm diameter and 2 mm height) were removed from the stems of plants from both cultivars using a punch. The (...truncated)