Agronomic performance of wheat genotypes and the use of nitrogen doses

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INTRODUCTION
The wheat crop (Triticum aestivum) is of great importance and is included in cropping systems, being one of the alternatives most used by farmers in the winter period, especially in the south of the country. In addition to the traditional areas for wheat cultivation, other areas are currently suitable for wheat cultivation in Brazil, including the Midwest, Southeast and South, in addition to the cerrado region in Bahia (Orso et al., 2014;Casagrande et al., 2022;Demari et al., 2022). In 2021, the wheat crop occupied a cultivation area of 2.73 million hectares, and a significant increase in production compared to 2020, this increase being 2.6%, resulting in 7.87 million tons and a productivity of 2.876 kg ha -1 (Companhia Nacional de Abastecimento [CONAB], 2022).
Just like other plants of the Poacea family, wheat comprises about 2.9% of nitrogen (N) in the plant and 2% in the grains (Orso et al., 2014). The wheat crop is demanding in terms of N, and it is essential for better development and higher productivity of the crop. This nutrient is of great importance for all its collaboration in the development of substances that will determine better quality and essential metabolic functions, such as protein synthesis.
Nitrogen is one of the nutrients most required by this crop and its yield is a direct function of the amount of nutrients accumulated by the plant (Megda, Buzetti, Andreotti, Teixeira Filho, & Vieira, 2009). In view of this, nitrogen has a great impact on the development of wheat, enhancing the development of the crop, some factors such as the dose, the time of application and the method of application have a direct effect on the productivity of the crop. Topdressing nitrogen fertilization provides greater accumulation of crude and soluble proteins in the seeds (Gomes Júnior & Sá, 2010). The amount of nitrogen application will depend and vary according to the area to be cultivated, mainly by the level of organic matter in the soil, predecessor crop and expected grain yield (ITTT, 2020). At sowing, the amount indicated varies between 15 kg ha -1 and 20 kg ha -1 , and the remainder in coverage between the tillering and stalk elongation phases (ITTT, 2020).
In order to reach a high production ceiling, enhancing productivity and thus being able to meet the demand in Brazil, there are some techniques to take place, such as management, choice of environment, adequate genotype and quality seeds (Abati, Brzezinski, Zucareli, Foloni, & Henning, 2018). However, the chosen sowing density is also of great importance, and therefore it is one of the key points for the highest grain yield, and along with it comes the fertilization management. Because it is a crop that allows for different management situations, presenting a relatively constant productive behavior (Fioreze & Rodrigues, 2012;Fioreze & Rodrigues, 2014). Thus, this work aimed to evaluate the agronomic performance of wheat cultivars and to evaluate the use of nitrogen doses.

MATERIAL AND METHODS
Two experiments took place at Centro de Pesquisas e Resultados Agronômicos das Missões (CEPRAM), in the municipality of Entre-Ijuís, Rio Grande do Sul, Brazil, latitude and longitude of 28º 23'17.82" S and 54º 19'13.74 " W, altitude of 215 meters. Soil classified as typical dystrophic Red Latosol (STRECK et al., 2008) and climate characterized by humid subtropical Cfa according to Koeppen.

Experiment II
The experiment took place in a randomized block experimental design, organized in a factorial scheme 7 nitrogen doses x 2 wheat genotypes. The doses were 0, 25, 50, 75, 100, 125, 150 kg ha -1 and two wheat cultivars ORS Senna and TBIO Audaz, with 4 replications.
In both experiments (Experiment I and II), sowing was carried out in the second half of May 2021, with base fertilization of 320 kg ha -1 of formula 11-30-20 (N-P2O5-K2O). The experimental units were 30 m² with row spacing of 0.17 m. For disease control, two fungicide applications were used, the first of Azoxystrobin + Flutriafol (0.25 L ha -1 ) in the elongation stages and the second of Tebuconazole (0.35 L ha -1 ) in full flowering. The insecticide management took place with two applications of Imidacloprid + Bifenthrin (0.20 L ha -1 ) along the fungicides.
At full physiological maturation, 10 plants per experimental unit, were randomly collected to measure the following characters: plant height (PH, cm), number of tillers. (TL, unit), ear length (EL, cm), ear weight (EW, g), number of grains per ear (NGE, unit), grain weight per ear (GWE, g) and grain yield (GY, kg ha -1 ).
The individual data, obtained in the two experiments, were submitted to the assumptions of the statistical model of normality of errors and homogeneity of residual variances. Analysis of variance performance was at 5% probability using the F test and Tukey's mean comparison test applied at the 5% probability level in both experiments for qualitative factors. In experiment 1, using Biplot principal component analysis in order to determine the associations between the analyzed traits and wheat genotypes. In order to develop the genetic dissimilarity dendrogram, the Euclidean distance matrix used the UPGMA algorithm for calculation and grouping. In experiment 2, the variables that showed a significant effect for interaction were broken down to simple effects through polynomial regression with adjustment of the degree of the polynomial based on the t test at 5% probability. All analyzes were performed using the R software version 4.1.3 (R Core Team, 2022).

Experiment I: Agronomic performance of wheat cultivars
There was a significant effect of cultivars for all evaluated variables. This indicates that the genotypes performed differently for these variables (Table 1). The CV ranged from 3.68 (PH) to 19.04% (GY), indicating that there is experimental precision.
The cultivar TBIO Noble expressed the highest average of ear grain weight ( Table  3). The ability to maintain productive tillers is associated with the supply of N to the plant, and this character contributes to an increase in the number of fertile ears, especially at low sowing densities (Fioreze & Rodrigues, 2012;Fioreze & Rodrigues, 2014;Ferrari et al., 2016). Therefore, the TBIO Ponteiro cultivar had the highest average number of tillers, while the lowest average was for the ORS 1403 cultivar. This indicates that the TBIO Ponteiro cultivar has a greater compensation capacity when subjected to low density conditions of plants. Grain weight per ear (GWE), number of tillers (TL), grain yield (GY) and thousand grain weight (TGW). 2 Means followed by the same lowercase letter in the column do not differ statistically at 5% probability by Tukey's test The highest grain yield average was by the cultivar TBIO Trunfo. The cultivar TBIO Noble potentiated the expression of thousand grain weight. The cultivar TBIO Noble did not differ statistically from the best averages of the evaluated traits. For example, characterized by a cultivar with low plant height, with a high expression of productive traits.
The first two principal components explained 42.56 and 31.33% of the total data variability (PC1 + PC2 = 73.89) (Figure 1). Cultivar TBIO Noble showed the highest magnitude of expression of thousand grain weight, ear length and ear weight. However, it had the lowest plant height and number of tillers. The cultivars TBIO Trunfo and TBIO Audaz showed the highest means of grain yield and grain weight per ear, respectively. Variables plotted close on the biplot show a positive correlation, while variables in opposite directions a negative one. Therefore, thousand grain weight, ear length and ear weight have positive correlation with each other. These correlate negatively with plant height and number of tillers. Grain yield and the number of grains per ear correlated positivily The genetic dissimilarity dendrogram formed two large groups (Group I: 9 cultivars and Group II: 13 cultivars) dissimilar to each other (Figure 2). Group I was formed by the genotypes TBIO Trunfo (22), TBIO Calibre (7), TBIO Astro (5), TBIO Capricho (8), TSZ Dominadore (11), TBIO Ello (13), TBIO Sinuelo (21), TBIO Noble (17) and ORS Senna (20). These cultivars stood out for the highest averages of plant height (PH), ear weighy, number of tillers, a thousand grain weight and grain yield.

Experiment II: Nitrogen doses
Analysis of variance revealed a significant effect of the cultivar x nitrogen dose interaction for the variables ear length and number of tillers (Table 4). For the effect of cultivars, a significant effect was observed for the variables plant height, ear weight, thousand grain weight, number of grains per ear and grain weight per ear. CV ranged from 3.75 to 34.70% for plant height and grain yield, respectively.
The cultivar TBIO Audaz had the highest ear length (7.07 cm) at the dose of 50 kg ha -1 of nitrogen, while the cultivar TBIO Senna had the highest average (7.45 cm) at the dose of 75 kg ha -1 of nitrogen (Table 5). In the other nitrogen doses, the average length of the ear of the cultivars did not differ statistically. The cultivar TBIO Senna showed the highest mean number of tillers (1.94 tillers) at the dose of 25 kg ha -1 of nitrogen. At the other doses, there was no significant difference between cultivars for the number of tillers.
The cultivar TBIO Audaz had the highest plant height (66.73 cm), number of grains per ear (28.97) and grain weight per ear (0.99 g) ( Table 6). The cultivar ORS Senna, on the other hand, stood out for having the highest average weight of the ear (1.22 g) and thousand grain weight (34.54 g).   Means followed by the same lowercase letter in the column do not differ statistically with a 5% probability of error using the Tukey test.
There was no significant effect of nitrogen doses on the variables ear length and number of tillers in the cultivar TBIO Audaz. In the regression analysis of the ORS Senna cultivar (Figure 3), a quadratic response of ear length was observed as a function of nitrogen doses. The maximum technical efficiency of ear length occurred at the dose of 44 kg of N ha -1 . Therefore, with the increase of 1 kg of N ha -1 above 44 kg of N ha -1 , there is a reduction of 0.0088 cm in ear length. The same behavior occurs with the variable number of tillers, in which it presented its maximum technical efficiency at the dose of 48 kg of N ha -1 , and there was a reduction of 0.0096 tillers for each kg of N above the dose of maximum technical efficiency.

CONCLUSIONS
The cultivar TBIO Noble showed productive and morphological characteristics that maximize the agronomic performance of wheat.
There is genetic divergence between wheat genotypes for productive and morphological traits.
Cultivar ORS Senna enhanced ear length and number of tillers at doses of 44 kg of N ha -1 and 48 kg of N ha -1 , respectively.