Estratégias de manejo químico da ferrugem asiática e do míldio na soja e seu efeito no desempenho da cultura e na indução de resistência

Abstract

Soybean cultivation is recognized for its importance in the supply of grains and derivatives for human consumption, animal, biofuel production, pharmaceuticals, among others. Positive results from studies of isolated resistance inducers in some cultures have led to further study. The work was conducted during two harvests (2015/2016, 2016/2017) at the Experimental Station of the Federal Technological University of Paraná (UTFPR), Campus Dois Vizinhos. For both experiments, C2 soybean seeds of NIDERA NA 5909 RG were used. For the 2015/2016 harvest, the evaluations regarding seed quality were carried out, as well as the effect of the association of phosphites and acibenzolar-s-methyl with fungicides on induction of resistance and control of Asian rust and mildew. The experimental design was a randomized block design, consisting of twelve treatments and three replicates. The treatments corresponding to combinations of two commercial fungicides (Fungicide 1: Azoxystrobin + Benzovindiflupir, and Fungicide 2: Azoxystrobin + Cyproconazole) three phosphite (phosphite 1: Phosphite Manganese Phosphite 2: Phosphite potassium, and phosphite 3: Phosphite Copper and Boron) and a plant activator (acibenzolar-S-methyl-ASM), in addition to a control. For the 2016/2017 harvest, the evaluations were carried out regarding seed quality and control of Asian rust and mildew in soybean plants. The experimental design was a randomized block design (DBA), composed of ten treatments with four replicates. The treatments corresponding to combinations of two commercial fungicides (Fungicide 1: Azoxystrobin + Benzovindiflupir, and Fungicide 3: Picoxystrobin + Cyproconazole) three phosphite (phosphite 1: Phosphite Manganese Phosphite 2: Phosphite potassium, and phosphite 3: Phosphite Copper) and a plant activator (acibenzolar-Smethyl), in addition to a control. After harvesting in both experiments, analyzes were performed to characterize the crop and its yield components and analyzed the physiological seed quality (time of insertion of the first and last pod, number of pods per plant and seeds per pod, weight of seed, yield, germination, normal and abnormal seedlings, emergence, emergence speed index, seedling length and dry matter mass). Also, in both experiments the evaluation of disease severity was carried out, and four plants of the useful area of each plot were chosen at random. In each plant were evaluated 09 leaflets chosen at random and marked, being three in the lower, middle and upper third of the plant. To estimate this parameter, specific diagrammatic scales were used for each disease. The mean severity values of each plot were used to calculate the area below the disease progress curve. In the first experiment, the activity of the pathogenicity-related enzymes (PRPs) was evaluated, being: phenylalanine ammonia-lyase (FAL), chitinase and β-1,3 glucanase. For this, the plant materials were collected at intervals of 48, 96 and 168 hours after the application of the treatments, marking two plants per plot, from which three leaves of the middle third of each plant were collected, obtaining samples for analysis. After tabulation and compilation, the data set were subjected to the normality data test, by Lilliefors, and the homogeneity of variance by Bartlet. The data related to Area Below the Progress Curve of Mildew and Rust were transformed by chi- quare (X2 + K) for8 later analysis of variance. When significant were compared by the Scott Knott averages test at the 5% level of error probability. The use of phosphites and ASM does not promote superior results when compared to the application of fungicides alone, which also does not improve crop productivity due to Asian rust and mildew. The application of the fungicides alone is sufficient to mitigate the effects of severity of Asian rust and mildew. Overall, the results showed that Mn base phosphites, K, Cu, and when ASM associated with fungicides have specificity activation of metabolic pathway enzymes of resistance induction in soybean cultivation, not differing from the use of fungicides, only, with occasional exceptions.