Defence‐Related Enzymes in Soybean Resistance to Target Spot

Abstract

Target spot, caused by the fungus Corynespora cassiicola, has become a serious foliar disease in soybean production in the Brazilian Cerrado. Information in the literature regarding the biochemical defence responses of soybean to C. cassiicola infection is rare. Therefore, the objective of this study was to determine the biochemical features associated with soybean resistance to target spot. The activities of chitinases (CHI), b-1-3-glucanases (GLU), phenylalanine ammonia-lyases (PAL), peroxidases (POX), polyphenol oxidases (PPO) and lipoxygenases (LOX), as well as the concentrations of total soluble phenolics (TSP) and lignin-thioglycolic acid (LTGA) derivatives, were determined in soybean leaves from both a resistant (FUNDACEP 59) and a susceptible (TMG 132) cultivar. The target spot severity, number of lesions per cm 2 of leaflet and area under the disease progress curve were significantly lower for plants from cv. FUNDA-CEP 59 compared to plants from cv. TMG 132. The GLU, CHI, PAL, POX and PPO activities and the concentration of LTGA derivatives increased significantly, whereas LOX activity decreased significantly on the leaves infected by C. cassiicola. Inoculated plants from cv. FUNDACEP 59 showed a higher PPO activity and concentrations of TSP and LTGA derivatives at 4 and 6 days after inoculation compared to plants from cv. TMG 132. In conclusion, the results of this study demonstrated that the defence-related enzyme activities increased upon C. cassiicola infection, regardless of the basal level of resistance of the cultivar studied. The increases in PPO activity and concentrations of TSP and LTGA derivatives, but lower LOX activity, at early stages of C. cassiicola infection were highly associated with soybean resistance to target spot.

Association of the Production of Phenylpropanoid Compounds at the Infection Sites of Corynespora cassiicola with Soybean Resistance against Target Spot

“…A total of ten soybean seeds from cultivars TMG 132 and Fundacep 59, considered as susceptible and resistant to target spot, respectively (Fortunato et al. ,b), were sown into two‐L plastic pots (Ecovaso, Jaguariuna, SP, Brazil) containing 2 kg of Tropstrato ® (Vida Verde, Mogi Mirim, SP, Brazil) substrate composed of a 1 : 1 : 1 mixture of pine bark, peat and expanded vermiculite. Five days after seedlings emergence, each pot was thinned to two seedlings.…”

“…; Fortunato et al. ,b). The necrotic lesions occasionally are large and coalesce, which can cause premature defoliation of the infected plants grown under favourable climatic conditions such as intense rainfall and high temperatures (Sinclair ; Godoy et al.…”

“…; Fortunato et al. ,b). The fungus is also able to cause rot of the roots and pods and lesions on stems and seeds (Sinclair ; Godoy et al.…”

“…At the biochemical level, Fortunato et al. () demonstrated that inoculated plants from cultivar Fundacep 59 showed a higher polyphenol oxidase activity, as well as the concentrations of total soluble phenolics and lignin thioglycolic acid at four and 6 days after inoculation with C. cassiicola compared to plants from cultivar TMG 132. Thus, this study investigated, at the microscopic level, whether resistance of soybean cultivars could be associated with an increase in the production of phenolics, flavonoids and lignin at the infection sites of C. cassiicola .…”

The role of silicon (Si) in increasing plant resistance against fungal diseases

“…Enhanced production of fl avonoids in wheat leaves reduced incidence of blast caused by Pyricularia oryzae . Fortunato et al (2015) found that higher activity of total soluble phenolics and ligninthioglycolic acid derivatives in leaves of soybean plants supplied with silicon led to reduced incidence of target spot (Corynespora cassiicola). Regarding the perennial ryegrass-Magnaporthe oryzae interaction, Rahman et al (2015) found that several phenolic acids, including chlorogenic acid and fl avonoids, and relative levels of genes encoding phenylalanine ammonia lyase and lipoxygenase were signifi cantly increased in silicon-amended plants compared with non-amended control plants.…”