Nickel and glyphosate on the potentiation of the soybean resistance against infection by Phakopsora pachyrhizi

• Ano de defesa: 2020
• Autor(a) principal: Einhardt, Andersom Milech
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Soja - Resistência a doenças e pragas; Plantas - Nutrição; Herbicidas; Fotossíntese; Ferrugem-da-soja; Fisiologia de Plantas Cultivadas
• Link de acesso: https://locus.ufv.br//handle/123456789/29065

In this study, the effects of nickel (Ni) (60 g ha -1 Ni) and glyphosate (Gl) (960 g ha -1 e.a. Gl) spray on the antioxidative, defense, and ethylene metabolisms of soybean plants inoculated with P. pachyrhizi were evaluated. In the first experiment, the severity of Asian soybean rust (ASR) decreased by 35% in plants of cv. TMG 135 treated with Ni (+Ni). The malondialdehyde (MDA) concentration was higher in plants not treated with Ni (-Ni) than in +Ni plants and was linked to ASR severity and extensive colonization of the palisade and spongy parenchyma cells by fungal hyphae. The lignin concentration, β-1,3-glucanase (GLU) activity, and expression of the URE gene and the defense-related genes PAL1.1, PAL2.1, CHI1B1, and PR-1A were up- regulated in +Ni infected plants. Taken together, the information provided in this study showed the great potential of Ni to increase the basal level of soybean resistance to ASR and to complement other control methods within the context of sustainable agriculture. In the second experiment, ASR severity in plants of cv. TMG 135 decreased by 34% due to Ni supply. In inoculated plants, the MDA concentration and superoxide (O2-) and hydrogen peroxide (H2O2) accumulation were lower for +Ni plants in comparison to -Ni plants. The antioxidant enzymes activities were inefficient to avoid the high reactive species of oxygen (ROS) accumulation on -Ni inoculated plants. The photosynthetic pigments, maximum photochemical efficiency of photosystem II (PSII), effective yield of PSII, electron transport rate, rate of net carbon assimilation, stomatal conductance to water vapor, and transpiration rate values were higher and the yield for other non-regulated losses and internal CO2 concentration values were lower for +Ni inoculated plants in comparison to -Ni inoculated plants. High ROS production and the great damage to the photosynthetic apparatus damage caused by P. pachyrhizi infection on -Ni plants affected the synthesis of the sugars and increased the energetic consumption limiting therefore, the plant energetic reserves faster in contrast to +Ni plants. In conclusion, the cellular oxidative damage and the impairment on the photosynthetic apparatus of soybean plants caused by P. pachyrhizi infection were alleviated by supplying Ni foliarly. In the thirst experiment, ASR severity was lower by 37, 68, and 77% in plants of cv. TMG 132 supplied with Ni, Gl, and Ni and Gl (Ni+Gl) in comparison to plants supplied with water (control). The inoculation caused largest and fastest increase in the concentration of ROS and MDA in control plants in comparison to Ni and Gl plants. In inoculated plants, the Ni and Gl increased phenylalanine ammonia lyase and GLU activities and phenolics concentration. Additionally, Ni-treated plants showed a fasted cell wall lignification than control plants. Polyphenoloxidase activity was increased by Gl at 5 days after inoculation, regardless of P. pachyrhizi infection. In conclusion, this study demonstrated that Ni and Gl regulate differently the activity of defense enzymes and did not affect the antioxidant enzymes in soybean plants infected by P. pachyrhizi. In the fourth experiment, the ASR severity was reduced on plants of cv. TMG 132 sprayed with Ni and Gl. Carotenoids and chlorophylls concentrations were preserved for Ni, Gl, and Ni+Gl inoculated plants in comparison to that in control plants. Parameters of chlorophyll a fluorescence revealed photosynthetic apparatus damage and lowest destination of energy to photochemistry process on inoculated plants from the control treatment. Limitations on the photosynthetic machinery capacity of inoculated plants to capture light and use the absorbed energy by PSII reflected on their capacity to reduce the CO2 as indicated by the high values for internal CO2 concentration and low values for rate of net carbon assimilation. Low sugars concentration on inoculated plants from the control treatment was linked to their reduced photosynthetic capacity due to the high ASR severity. For non-inoculated plants, ethylene concentration was not affected by Ni and Gl, but its concentration decreased for inoculated plants being more pronounced for plants from the control treatment. In conclusion, this study sheds light into the role played by both Ni and Gl on ASR control from a physiological point of view. Soybean plants exposed to Ni and Gl were able to maintain their photosynthetic capacity and the great ethylene concentration during the infection process of P. pachyrhizi. Keywords: Plant nutrition. Herbicide. Host defense. Photosynthesis. Asian Soybean Rust.