Grain and Flour Wheat Quality Modified by Genotype, Availability of Nitrogen, and Growing Season

,e objective of the present study was to determine physical and chemical parameters that determine grain and flour quality of wheat grown in Mexico’s highlands (Toluca, Estado de Mexico) as a response of nitrogen fertilization and growing season. Experiments were carried out in winter-spring 2010 (irrigation) and summer-autumn 2011 (rainfed) season cycles. Nine wheat cultivars were tested under four levels of nitrogen fertilization (N00, N100, N200, and N300 kgN·ha) with a population density of 336 seeds m. For each growing season and N rate, three replications were performed for each experiment under a randomized complete block design. Best quality indexes were obtained in the winter-spring cycle as a result of genetic variability. Nitrogen availability modified significantly some quality parameters (grain and flour protein, test weight, and hardness) obtaining the highest values at a rate of 100 kgN·ha. On the other hand, volume of sedimentation showed positive effects only at a rate of 300 kgN·ha. ,is rate showed positive effects on grain and flour protein, sedimentation volume, and hardness during the summer-autumn cycle. Eneida F94, Tollocan F2005, and Urbina S2007 cultivars presented the highest grain and flour protein content of tested varieties. Finally, Eneida F94 and Tollocan F2005 presented the highest test weight and flour percentage.


Introduction
Bread wheat is one of the most important cereal crops in the world and is grown in a wide range of environmental conditions. Wheat grain quality characteristics depend greatly on genotype, environment and genotype × environment interactions. In fact, many quality attributes such as grain protein content are modified by climatic parameters, genotype, nitrogen fertilizer rate, time of nitrogen application, and available water during grain filling [1][2][3]. Mexican highlands' wheat (>2000 masl) often produces grain with insufficient quality for industrial purposes (flour and bakery products) [4]. In this sense, knowing the effect of the environment and management practices (mainly the use of N) on wheat quality characteristics, it would be useful to increase its industrial potential. Sowing of this crop is usually performed under rainfed conditions (summer-autumn season), but grains present marketing problems due to their low milling quality [4]. Conversely, sowing under irrigation (winter-spring season) increases industrial grain quality. ere is evidence of neither environmental variables responsible for such quality differences nor the cultivars better adapted to them. us, to evaluate different cultivars exposed to both environments could be useful to select genotypes for specific purposes (bakery and/ or biscuit industry).
Physical characteristics such as color, test weight, and hardness determine the quality of wheat grain, so soft, hard, or very hard grains are related to kernel hardness which defines the milling and baking process [5][6][7]. Grain hardness can be affected by environmental factors such as soil type, irrigation, fertilizer, management practices, precipitation, and temperature during maturation and postripening [8].
is attribute is influenced by many factors such as kernel shape and density, agronomic practice (included nitrogen management), and climatic and weather conditions [9]. Nitrogen fertilization has a significant effect on test weight [10] as increase in nitrogen availability decreases significantly test weight in wheat but increases the amount and composition of gluten proteins (gliadins:glutenins) [11][12][13].
Espitia et al. [4] found that protein performance between the two seasons was different with the same N application, and N availability in soil affects quantity and quality of grain protein content [14]. Maximum temperatures during grain filling [11,15] and water input during this phase [16] are also associated to grain protein content. e sedimentation test using sodium dodecyl sulphate (SDS) is a simple test to measure wheat bread-making quality on small samples and in a short period of time [17] and is modified by nitrogen availability. Saint Pierre at al. [18] found that the increase in N availability increased SDS value. e aim of the present document is to determine how GxE interaction affects grain quality in wheat genotypes with different yield potentials. erefore, it is important to find out whether nitrogen fertilization and growing season have a direct effect on wheat grain quality.

General Conditions.
Two experiments were carried out during winter-spring (W-S) 2010 (irrigation) and summerautumn (S-A) 2011 (rainfed) seasons in the experimental field of the Agricultural Sciences Faculty of the Mexico State University (UAEMex) located 18 km north of the Toluca city (19°15′33″°N, 99°39′38″°W, altitude 2640). e climate of this region corresponds to type C (w2) (w) b (i), according to the Köppen climatic classification, modified by García [19], and is defined as subhumid temperate, with rains concentrated during summer and low rainfall in winter (5%), slight thermal oscillation, annual average temperature 12.8°C, and annual precipitation above 900 mm. e soil is pelvic vertizol with 36% clay, apparent density 1.26 g·cm −3 , pH 5.5, the nitrogen content before sowing 0.11%, phosphorus 20 ppm, and potassium 60 ppm.

Treatments and Experimental Design.
Experiments consisted on a factorial combination of nine cultivars of wheat released from 1975 to 2007 and four levels of nitrogen availability. Cultivars (Salamanca S75, Saturno S86, Eneida F94, Cortazar S94, Rebeca F00, Barcenas S02, Tollocan F05, Maya S07, and Urbina S07) were selected according to their greater representation in every era, based on the acreage of each cultivar. Nitrogen availability treatments consisted of an unfertilized control (N 00 kg N·ha −1 ) and fertilizer treatments N 100 , N 200 , and N 300 kg N·ha −1 with N applied as urea. Urea application was split into 2 or 3 identical quantities according to the treatment, for example, 50 kg N·ha −1 for all rates at sowing, 50 kg N·ha −1 (N 100 ), 75 kg N·ha −1 (N 200 ), and 125 kg N·ha −1 (N 300 ) broadcasted at terminal spikelet, and subsequently 75 kg N·ha −1 (N200) and 125 kg N·ha −1 (N 300 ) at flag leaf appearance. Application of P and K was 60 and 30 kg·ha −1 , respectively, for all levels including the control which was applied at sowing. Within each N rate, the nine cultivars were distributed under a randomized complete block design with 3 replications, where each N rate corresponds to a particular environment.
Experiments were hand-sown at 336 seeds m −2 in plots of 6 rows, 0.20 m apart and 3.0 m long, with a separation between plots of 0.40 m. Plots were managed to minimize interferences from biotic stress. Weeds were removed by hand to avoid any negative effect of hormonal herbicides that may have differentially affected the cultivars. Fungicides and insecticides were sprayed throughout the crop cycle to prevent or control fungal diseases and insect damages. Onwards nets were installed from the onset of stem elongation to prevent lodging.

Measurements.
All experiments were conducted in the Quality Lab of National Institute of Forest, Agriculture and Livestock Research (INIFAP).

Physical
Analysis. Physical analysis consisted in evaluating test weight (TW), grain texture (% hardness), and flour yield (FY). Test weight (kg hL −1 ) was determined on a sample at 500 ml with a volumetric balance (Seedburo Equipment Co., Chicago IL.), and grain texture was determined with a near infrared spectrum reflectance analyzer (NIR) INFRATEC 1255 calibrated (method 39-70 A) [20]. Refined flour was obtained from grain samples conditioned at 14% moisture, with 24 hours rest prior to milling which was performed with a Brabender Quadrumat Senior mill (Brabender, Germany).

Chemical Analysis.
Chemical analyses consisted in the determination of protein content in grain (GP) and flour (FP), sedimentation volume (SDS), and ash content of grain (ACG). Protein content in grain and flour (%) was measured in the NIR INFRATEC 1255 (method 39-10) [20]). Sedimentation volume (mL) was determined in a sample of 1 g of flour to which sodium dodecyl sulphate was added (SDS) according to the procedure written by Peña et al. [21]. Ash content (%) was determined by calcination in a muffle furnace at 550°C (method 923.03) [22].

Statistical Analysis.
In order to study the means effects (cycle, N, and varieties) and their interactions, a combined analysis of variance was conducted with a Minimum Honest Significant Difference (MHSD) mean test when the F test was significant (Tukey test to a significance level of 5%) [23,24].

Climatic Characterization and Statistical Analysis.
During growing season of both planting dates, weather conditions were characterized by moderate precipitation during the winter-spring (W-S) cycle which was between December and June (145 mm). However, for the summerautumn (S-A) cycle, high precipitation (383 mm), cloudy days, and low temperature during grain ripening occurred. Grain filling for the W-S cycle occurred between April and May and for S-A, between August and October ( Figure 1). Possibly, environmental conditions described above affected significantly the filling and quality parameters of grain.
With the exception of flour yield (FY), all quality variables showed significant responses attributed to cycle effect. Nitrogen affected significantly GP and FP (Table 1). Nonsignificant interaction cycle x nitrogen was evident. Varieties affected significantly all physical and chemical quality parameters. In the case of factor varieties, significant effects were observed for all varieties considered in this study (Table 1). e interaction cycle x variety was present significantly in all variables with the exception of ash percentage, while nitrogen x variety interaction affected only hardness. GP variables were significant as well as cycle x nitrogen x variety interaction. Coefficients of variation ranged between 2.8 and 13.2% for TW and SDS, respectively (Table 1).

Mean Values for the Studied Factors.
Growing season was the most important factor because weather conditions that occurred during each cycle affected the physical and chemical properties of wheat, with a strong influence of the environment being observed on the variables that determined grain quality. With the exception of flour yield, all    International Journal of Agronomy   For the W-S cycle, all varieties showed the highest values of TW and hardness; Eneida F94, Rebeca F00, and Tollocan F05 showed the highest FY in both cycles from the remaining 6 varieties. e highest percentages of GP were achieved in S-A, standing out again the varieties Eneida F94, Rebeca F00, and Tollocan F05. Higher percentages of FP were observed in S-A in 6 of the 9 varieties; likewise, highest values of SDS were obtained for all varieties evaluated ( Figure 2).
Grain hardness was significantly larger in five out of nine cultivars (Barcenas S02, Cortazar S94, Maya S07, Saturno S86, and Urbina S07) without significant changes between N doses. Tollocan F05 and F94 Eneida cultivars showed less grain hardness but higher protein content than the other cultivars. It is important to point out that the response saturation grain protein appears to have been set at 100 kg N·ha −1 . Interestingly, for the same dose of N, grain protein was different in each cultivar (Figure 3). e relationship between sedimentation volume and grain protein was positive and statistically significant with an increase due to N fertilization rate (Figure 4).

Discussion
Environmental conditions, primarily those prevailing during the grain filling (rainfall and low temperatures in the S-A cycle), in both crop cycles affected some quality parameters (test weight) and composition of grain protein which could cause problems in the marketing of grain to the milling industry [16,25]. Growing season caused changes in the physical quality attributes of the grain (TW, hardness, FY, and ACG) being higher in the WS cycle compared to the SA cycle. e difference could be attributed to drier conditions in the WS cycle, such as a higher average temperature, lower cloud cover, and good radiation incidence during grain filling [26,27]. Conversely, GP, FP, and SDS were negatively affected under conditions of the W-S cycle, possibly    attributed to cooler temperatures during grain filling, thus enabling a higher accumulation of protein.
In terms of bread quality, accumulation of protein occurs during grain filling, with gliadins being the first to be deposited at about 5-10 days and glutenins which are detectable around 20 days. If any alteration process takes place during grain development in this stage, grain will exhibit a different composition (gliadins:glutenins) [28]. Our results showed that the commercial quality of wheat was affected by growing season (cycle) indicating that physical properties of wheat grain are characteristics highly influenced by the environment, irrigation or rainfed [29], growing season, and cultivar [30], while others found that year effect was the principal environment factor in defining wheat quality [16,29].
Grain's protein content is related to the amount of nutrients (N mainly) in the soil; lower amount of protein means lower N content in the plant at the stage of appearance of the first node and next stages [31]. In rainfed conditions, the strategy of application of N fertilizer depends basically on edaphic N interactions with rainfall and potential crops requirements [32]. e interaction of nitrogen x variety showed that Barcenas S2002, Cortazar S94, Maya S2007, Saturno S86, and Urbina S2007 varieties increased significantly grain hardness when N rate was increased, while Urbina S2007, Tollocan F2005, and Eneida F94 cultivars obtained higher values of GP with a dose of 100 and 200 kg N·ha− 1 . is is consistent with the work of Lerner et al. [33], who mentions that percentages of protein were significantly higher in treatments with N, finding a considerable difference between varieties and years. On the other hand, Souza et al. [34] showed that values of grain hardness were influenced by the variety, season, and N rate.
Wheat sowing in rainfall conditions showed lower values of TW, hardness, and ACG when compared to wheat under irrigation conditions; conversely, values of protein and sedimentation had a significant increase. Lowest values of TW could be due to the shortest period available for grain filling, so it is important to identify varieties to achieve short cycle crops with good grain quality, since a sucked grain is not acceptable for milling due to its low yield flour [12]. On the other hand, the high values of protein can be attributed to the low test weight, which is defined mainly by genotype; which could be affected positively or negatively by late showing dates, deficiency of N, availability of water, and high humidity in the stage of filling [12].
Grain ash content is very important because high ash values are related to grains of low-test weight promoting contamination of flour and semolina; therefore, the desirable levels must be less than 2% [35]. According to the results of the present study, all the varieties showed an acceptable ash content (1.8-1.9%) which is an acceptable value for baking [36].
e highest values of SDS obtained were shown in rainfall conditions compared with irrigation, indicating irrigation during grain filling reduces sedimentation volume [36].
All varieties showed significant effects when evaluating quality variables, and the highest values of TW and FY were obtained in the varieties Eneida F94 and Tollocan F2005 which make them suitable for baking [35]. e hardness of the grain showed variability between varieties, prevailing more varieties of grain of semihard texture (<56%) as Salamanca S75, Eneida F94, Saturno S86, Rebeca F2000, Urbina S2007, Maya S2007, and Tollocan F2005. Meanwhile, Cortazar S94 and Barcenas S2002 are texture catalogued as varieties of semisoft grain (56-62%); this parameter is important since it determines the potential use of wheat for the cookies production (soft to semisoft), bread (from semisoft until hard), or mixtures of flour for bread making (soft wheat to semisoft with semihard wheat to durum) [12]. In general, all varieties showed an acceptable protein content similar to that reported by Peña et al. [35] who evaluated the quality of wheat, finding that some wheat varieties showed low ash content in spite of their low test weight (71.1 kg·hL −1 ) but excellent protein content. e quality of the wheat grain depends on their genetic composition, agronomic management, and on the environment [4,12]. us, results of the present study indicated that the effect of the availability of the N increases the quantity of the wheat protein, obtaining good quality standards mainly under irrigation conditions, which suggests that sowing in winter-spring would allow obtaining good baking quality wheat. Given the acceptable values of protein, test weight, hardness, and SDS observed in this study, it would be interesting to analyze the rheological characteristics and baker's quality of the flour.

Conclusions
Genetic and environmental variability were observed to be determinant in assessing the quality attributes during the winter-spring cycle. N availability modified significantly the grain and flour protein. Winter-spring cycle with a rate of 100 kg N·ha −1 obtained the highest values of grain and flour protein, test weight, and grain hardness, whereas with a 300 kg N·ha −1 dose only sedimentation volume showed positive effects. e summer-autumn cycle was favorable in grain and flour protein, sedimentation volume, and hardness when using a 300 kg N·ha −1 dose. Eneida F94, Tollocan F2005, and Urbina S2007 varieties showed the highest grain and flour protein content. Likewise, Eneida F94 and Tollocan F2005 varieties showed high test weight and flour yield values suggesting its use for baking, while the rest of the varieties can be used for the biscuit industry.

Data Availability
e data used to support the findings of this study are included within the article.

Conflicts of Interest
e authors declare that there are no conflicts of interest regarding the publication of this article.