Histopathological aspects of mango resistance to the infection process of Ceratocystis fimbriata

Abstract

Mango wilt, caused by Ceratocystis fimbriata, is one of the most important diseases affecting mango yields in Brazil. Information regarding the infection process of C. fimbriata in the stem tissues of mango from different cultivars and the basis of host resistance to the pathogen is rare in the literature. Thus, the objective of the study was to investigate how infection by two isolates of C. fimbriata can be affected by mango cultivar-specific mechanisms of resistance. Disease progress on the inoculated stem tissues of the mango cultivars was evaluated and stem sections were obtained from the site of inoculation and prepared for histopathological observations using light microscopy. The factors mango cultivars and C. fimbriata isolates and their interaction were significant for all measures of disease development. Plants from the cultivars Espada, Haden and Palmer inoculated with isolates of C. fimbriata were more susceptible, whereas plants from the cultivars Tommy and Ub a were moderately resistant and resistant, respectively. Histopathologically, fungal isolates apparently massively colonized the stem tissues of plants from the susceptible cultivars Espada, Haden and Palmer, starting from the collenchyma and moving in the direction of the cortical parenchyma, xylem vessels and pith parenchyma. By contrast, on stem tissues of plants from the resistant cultivars Tommy Atkins and Ub a, most of the cells reacted to C. fimbriata infection by accumulating amorphous material. The results from the present study strongly indicated the importance of phenolic compounds for mango cultivar resistance against infection by Brazilian C. fimbriata isolates.

Development of mango wilt in mango cultivars submitted to salt stress

“…Data from Na concentration was best fitted to the quadratic model (Figure 2). Plants from cultivars Ubá and Tommy Atkins showed a great Na concentration at the doses of 30 and 60 mmol NaCl·L The results from the present study confirm the findings from Araujo et al (2014) that plants from cultivar Ubá are more resistant to mango wilt than plants from cultivar Tommy Atkins. However, when plants from cultivars Tommy Atkins and Ubá were exposed to the highest doses of NaCl, the TRLL was dramatically reduced, especially for the former cultivar.…”

“…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).…”

“…Some host induced defense mechanisms, such as the synthesis of pathogenesis-related proteins and the production of phenolic-like compounds, are intrinsically related to the plant genotype (Steiner and Schönbeck 1995). According to Araujo et al (2014), the rapid and high accumulation of phenolic-like compounds contributed to reduce the colonization of C. fimbriata on the stem tissue of mango plants from cultivar Ubá compared to plants from cultivar Tommy Atkins. Bispo et al (2015) reported that plants from cultivar Tommy Atkins exhibited an increase in the activities of enzymes and in the concentration of metabolites related to the oxidative stress responses in comparison with plants from cultivar Ubá.…”

“…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 TRLL was determined as the ratio between the length from the graft scar to the top of the stem (LGST) and the lesion length (LL) at the same interval (upward and downward) from the inoculation point according to the following formula: TRLL = LL × 100/LGST. The plants were standardized to a length of 50 cm (distance from the graft scar to the top of the stem) (Araujo et al 2014).…”