Physical attributes and yield of wheat seeds originated from plants under temporary flooding of the soil

ABSTRACT: The aim of this work was to evaluate whether there is any influence of temporary soil flooding on the agronomic performance and yield of wheat varieties. The experimental design was completely random blocks, in an 11x2 factorial scheme (eleven varieties and two soil water conditions), with four replications. Stress was imposed in the stage prior to plant anthesis. The assessments were made in two seasons (2016/2017) in relation to the number of spikelets in the main ear, number of seeds in the main ear, mass of seeds in the main ear, number of seeds in the tiller ear, mass of seeds in the tiller ear and yield in the useful area. The physical attributes number of seeds, seed mass and wheat seed yield, according to variety and agricultural year, are negatively affected by the temporary flooding (12 days) of the soil. There is influence of temporary soil flooding on the agronomic performance and yield of wheat varieties. The varieties TBio Toruk, TBio Sinuelo, TBio Sintonia, and CD151 are superior in soil flooding condition for the number of spikelets, number of seeds end for the seed mass attribute. In the soil at field capacity, the seeds produced have higher yield compared to those produced under flooding period, reaching about 309.2 Kg more for the variety TBio Sinuelo, 262 Kg for TBio Toruk and 114 Kg in CD1303.


INTRODUCTION
Wheat (Triticum aestivum L.) belongs to the Poaceae family and is one of the most cultivated cereals in the world.Both the diversity in the use of grains and its nutritional characteristics and the ease of storage make this species a staple food for approximately one third of the world population (SLEPER & POEHLMAN, 2006).Wheat production in Brazil is concentrated in the South Region, although it has expanded to the Midwest where it is cultivated under center-pivot irrigation.The total volume of grains produced in Brazil reached a value greater than 5 million tons in the 2018 season, however, does not meeting the consumer demand that is greater than 10 million tons, generating the need to import 6.4 million tons (CONAB, 2019).

Monteiro et al.
In lowland areas, monoculture production is considered a global problem (GARRITY & PERNITO, 1996), so the cultivation of wheat emerges as a highly relevant alternative to be used in the succession or rotation of other species, such as rice, in addition, successful cultivation contributes to the reestablishment of extensive areas that are affected by the infestation of invasive plants, such as red rice and rice grass (CALHEIROS et al., 2000).
In this context, lowland areas in Brazil have alluvial or hydromorphic soils, being able temporarily be flooded by the excess of rain that is associated with the deficiency of drainage, the elevation of the water table level and the presence of a textural horizon in the soil (LOPES et al., 1988).In Rio Grande do Sul, the cultivation of wheat in hydromorphic soils comes as an alternative to extensive livestock farming, which is generally practiced in these areas during the period of paousio to rice cultivation.In addition to the south of the country, cereal is also cultivated in central Brazil during the winter with the use of irrigation, due to the region offering good climate and soil conditions, in addition to its strategic market position, industrialization conditions and because it can be harvested in off-season production in the southern region (ALBRECHT et al., 2006).
In floodplain soils, flooding is one of the main abiotic stresses on the plant, being a limiting factor to crop yields (WANG et al., 2012).In those environments, unlike non-flooded soils, there is a limitation in the diffusion of gases and thus the cellular amount of oxygen can be reduced to levels that negatively affect aerobic respiration (FUKAO & BAILEY-SERRES, 2004), reflecting in low energy (WANG et al., 2012) with lactate and ethanol production (ZABALZA et al., 2009).The reduction of available energy affects the growth and productivity of plants (BAILEYSERRES & VOESENEK, 2008).
The effect of stress is dependent on the period imposed and the growth stage of the plant (REYNA et al., 2003).The flooding of the soil can reduce the quality of the seeds due to the reduction of the production and transport of carbohydrates, as well as, due to the lesser absorption of nutrients (KOZLOWSKI, 1997).According to PESKE et al. (2019), stress during in the seed filling phase and the vegetative phase results in reduced productivity and smaller seeds.VERNETTI JUNIOR (2009) reported that the greatest sensitivity to flooding occurs at the beginning of the seed filling phase.However, it must be considered that the effect of stress depends on the variety, intensity, and duration of the stress (AUMONDE et al., 2017).
Having this context, the objective of this work was to evaluate whether there is influence of the temporary flooding of the soil on the agronomic performance and the yield of different wheat varieties.

MATERIALS AND METHODS
The experiment was carried out in the Experimental Field of the Federal University of Pelotas, located at the Capão do Leão Campus, in the geographical location of 31 o 52' S and 52 o 21' W, being the performance attributes analyzed in the Seeds Analysis Laboratory of the Post-Graduation Program in Seed Science and Technology at the Department of Phytotechnics.
Eleven wheat varieties (Triticum aestivum L.) were used to obtain the seeds used to determine the response to the periods of flooding of the soil, being: TBio Sinuelo, TBio Sintonia, TBio Mestre, TBio Noble, TBio Toruk, CD1303, CD1440, CD1550, CD1252, CD150 and CD151, which were cultivated in two different seasons (2016/2017) and in the same area with Hydromorphic Planosol soil type and a sandy-loam texture (EMBRAPA, 1999).The nutritional and acidity soil correction was carried out according to soil analysis and the recommendation of the Fertilization and Liming Manual for the States of RS and SC (2004).
The spacing between rows was 17 centimeters, resulting in a population density of 330 seeds per m 2 .After the end of the development cycle, at 123 days after sowing, 10 plants were removed from each repetition for the evaluation of yield attributes and the rest of the useful plot area was manually harvested for yield evaluation.The ears were taken for drying in an oven up to 12% humidity, after the seeds were threshed manually and stored in a cold, dry chamber (10 ± 2 ºC and 33% RH), in order to maintain their physiological potential.
For the establishment of the soil flooding, bunds were built around each plot in order to hold the water inside.The period of flooding was imposed in the stage prior to plant anthesis, by the maintenance of the water depth at 20 millimeters above the ground and inside each plot.After the period of 12 days, the bunds were opened and the water layer was removed for soil drainage.
In order to evaluate the effect of the flooding period on the wheat seed yield attributes, the following analyzes were done: a) Number of spikelets: manually counted at the main ear.b) Number of seeds in the main ear: after counting the spikelets, the number of seeds was counted by manual threshing.c) Mass of seeds in the main ear: after the counting, the seeds mass was measured on a precision balance and the result expressed in grams (g).d) Number of seeds in the tiller ear: threshing was carried out manually, and the number of seeds was counted.e) Mass of seeds in the tiller ear: after the counting, the seeds mass was measured on a precision balance and the result expressed in grams (g).f) Yield in the useful plot area: performed after harvest, where ears were dried, threshed and having the mass of each plot measured by a precision balance, the result being expressed in kilograms (Kg).
The experimental design adopted was completely randomized blocks with eleven varieties, two water conditions (field capacity/no flooding and temporary flooding) and four replicates.The data obtained were submitted to the assumptions of homogeneity of variances using the Bartlett test and normality using the ShapiroWilk test.After meeting the assumptions of homogeneity and normality, the data were subjected to analysis of variance and, if significant at 5% probability by the F test, subjected to mean analysis by the Scott Knott test at 5% probability, using the SISVAR statistical software.

RESULTS AND DISCUSSION
In the first season (2016), for the number of spikelets from the main ear, when the plants were kept in field capacity condition, showed superior behavior the varieties TBio Sinuelo, Tbio Sintonia, Tbio Noble, Tbio Toruk and CD1252 while, in the condition of soil flooding, the varieties TBio Toruk and Tbio Sinuelo obtained superiority in relation to others (Table 1).
The number of seeds in the main ear of the varieties TBio Sinuelo and TBio Toruk got was higher values on field capacity condition.Similarly, to the soil flooding condition, TBio Sinuelo and TBio Toruk was superior were superior compared to the other cultivars tested (Table 1).
Regarding the seed mass of the main ear, for a field capacity condition, the varieties TBio Sinuelo, TBio Noble, TBio Toruk, CD1252 and CD150 obtained higher values.In the soil flooding condition, only one cultivar Tbio Toruk presented a greater increase in seed mass compared to the other varieties (Table 1).For the number of seeds per tiller, in field capacity the varieties TBio Sinuelo and TBio Toruk were superior to the others.(Table 1).When submitted to soil flooding, TBio Sinuelo, Tbio Toruk and Tbio Mestre demonstrated superiority, while TBio Noble, CD1252, CD150 and CD151 obtained the lowest values for an analyzed variable (Table 1).
For the variable of seed mass produced by tillers maintained under field capacity condition, the varieties TBio Sinuelo and TBio Toruk demonstrated increase in seed mass.In the flooding condition, TBio Sinuelo, Tbio Mestre e TBio Toruk a greater increase in seed mass compared to other varieties (Table 1).
For the yield of seeds, harvested in the useful area of the plots, it was observed a superiority of the variety TBio Sinuelo when maintained in field capacity.And for flooding, the highest seed yield was processed by variety CD1440.On the other hand, varieties TBio Noble and CD150 obtained the lowest values for seed yield per useful area, when in field capacity and under flooding, respectively (Table 1).
The production of carbohydrates and energy that is intended for the structural maintenance of the plant, growth and productivity, are directly related to the execution of adequate nutrition, management and cultural treatments, strategic choice of cultivars, population as well as the plant architecture and vitality of the sheets (AUMONDE et al., 2017).In this sense, appropriate conditions of soil, climate, management and cultural treatments, as well as the choice of cultivars suitable for each environment, favor the attainment of greater productive ceilings.
Soil flooding can change plant physiology by affecting the rate of oxygen diffusion in the soil and reducing its availability to plant roots (BALAKHNINA et al., 2010).The response to production and accumulation of toxic compounds is closely related to the species, cultivar and detoxification capacity of each plant.
In the second wheat season (2017), for the assessment of number of spikelets in the main ear, in plants maintained at field capacity, the superior varieties were TBio Sinuelo, TBio Mestre, TBio Noble, TBio Toruk, CD1303, CD1252 and CD150, while the variety CD1440 was inferior, obtaining the lowest value for the analyzed variable.To flooding condition, the varieties that achieved superiority were TBio Sintonia, CD1252, CD150 and CD151, while the varieties TBio Meste, TBio Noble, TBio Toruk and CD1550 obtained lower values (Table 2).
For the number of seeds in the main ear, the varieties TBio Sinuelo, TBio Mestre, TBio Noble, TBio Toruk, CD1303 e CD150 maintained in soil at field capacity showed a greater number of seeds, whereas CD1252 and CD151 showed the lowest results.In the flooding condition, the varieties that showed higher values were TBio Sinuelo, TBio Sintonia, CD1440 e CD151 in relation to TBio Mestre, TBio Noble, TBio Toruk, CD1303, CD1550, CD1252 e CD150 (Table 2).
The seed mass in the main ear for a field capacity condition was higher in varieties TBio Ciência Rural, v.53, n.3, 2023.

Monteiro et al.
Sinuelo, Tbio Mestre, TBio Noble and Tbio Toruk and lower in varieties CD1252 and CD151.When comparing the varieties in the condition of flooding, it is noted that TBio Sinuelo, TBio Sintonia, CD1440, CD150 and CD151 produced higher mass compared to the other varieties (Table 2).Regarding the number of seeds in the tiller, TBio Sinuelo, TBio Toruk and CD1303 showed a higher number when kept in field capacity, while under flooding the variety with the highest value was CD151 (Table 2).
For the variable seed mass in tiller at field capacity, the varieties TBio Toruk and CD1303 showed higher values.However, in the flooding condition, CD151 stood out compared to the other varieties (Table 2).
The maintenance of crop productivity is associated with the ability to defend and overcome the stress faced.In this context, to tolerate the stress imposed, plants can present morphological, anatomical or metabolic strategies, which guarantee the use of energy in order to prolong their survival under waterlogged soil (PERATA et al., 2011;SHINGAKI-WELLS et al., 2011).
On the other hand, regarding the yield in the useful area harvested, it was observed that the variety CD151 at field capacity was superior the others.Under soil flooding, CD1303, CD1440, CD151 and CD1252 showed higher yield value (Table 2).
In the condition of field capacity, the seeds produced have higher yield compared to those produced under flooding period, reaching 309.2 Kg more for the variety TBio Sinuelo, 262 Kg for TBio Toruk and 114 Kg in CD1303.
Productivity can be negatively affected by soil flooding stress depending on the species and Table 1 -Number of spikelets in the main ear (SPMEc), number of seeds in the main ear (SEMEc), seed mass in the main ear (SMMEc), number of seeds in the tiller ear (SETE), seeds mass in the tiller ear (SMTE), yield in the useful plot area, of wheat varieties submitted to temporary soil flooding, in the 1 st season of evaluation.
cultivar used.This reduction can be related, among other factors, to the limitation in the absorption of water and minerals, which compromises the development of plants (LIU et al., 2011).In addition, stress can decrease carbon assimilation by the plant, as well as altering the partition and allocation of carbon (CHAVES et al., 2002).With flooding, the plant can modify the relationship between source and drain, investing a smaller input of assimilates in the "filling" of seeds, which justifies the results obtained, in which the physical attributes and yield were negatively affected by stress.In general, in cereals, water stress conditions can negatively affect grain quality and yield, due to reduced photosynthetic rates and dry matter accumulation, determined by the drain force (RAJJOU et al., 2012).

CONCLUSION
The physical attributes of number of seeds, seed mass and wheat seed yield, according to variety and season, are negatively affected by the temporary flooding of the soil.The varieties TBio Toruk, TBio Sinuelo, TBio Sintonia and CD151 are superior in condition of flooding of the soil, for number of spikelets, number of seeds and for the seed mass attribute.In the condition of field capacity, the seeds produced have higher yield compared to those produced under flooding period.
Table 2 -Number of spikelets in the main ear (SPMEc), number of seeds in the main ear (SEMEc), seed mass in the main ear (SMMEc), number of seeds in the tiller ear (SETEf), seeds mass in the tiller ear (SMTEf), yield in useful plot area, of wheat varieties submitted to temporary soil flooding, in the 2 nd season of evaluation.