Water Stress Alters Morphophysiological, Grain Quality and Vegetation Indices of Soybean Cultivars

Abstract

Rainfall is among the climatic factors that most affect production, as in the Brazilian Cerrado. Non-destructive and automated phenotyping methods are fast and efficient for genotype selection. The objective of this work was to evaluate, under field conditions, the morphophysiological changes, yield, and grain quality of soybean (Glycine max L. Merrill) under water stress in the Brazilian Cerrado. The plots comprised six soybean cultivars and the subplots of four water regimes, corresponding to 31, 44, 64 and 100% of crop evapotranspiration replacement. The experiments were conducted from May to September 2018 and 2019. An irrigation system with a bar of sprinklers with different flow rates was used. Gas exchange, vegetation indices (measured using a hyperspectral sensor embedded in a drone), yield and grain quality were evaluated. Water stress had different effects on gas exchange, vegetation indices, grain yield and chemical composition among the cultivars. Embrapa cultivar BRS 7280 Roundup ready (RR) and Nidera cultivar NA 5909 RG (glyphosate resistant) are yield stable and have a greater tolerance to drought. BRS 7280RR showed a higher tolerance to drought and higher water use efficiency (WUE) than all other tested cultivars. Vegetation indices, such as the NDVI (Normalized Difference Vegetation Index), correlated with the morphophysiological traits, such as plant height, were the most responsive variables to water stress. The NDVI can be used to predict soybean yield as a tool in a selection program under drought.

Water Stress and Seed Color Interacting to Impact Seed and Oil Yield, Protein, Mucilage, and Secoisolariciresinol Diglucoside Content in Cultivated Flax (Linum usitatissimum L.)

“…Seed oil content decreased under water stress in brown-seeded families. Previous studies found a negative correlation between oil and protein content in soybean seeds under water stress conditions that can also be explained by the competition of synthesis pathways by carbon skeletons, changes in accumulation, and the distribution of nutrients [21]. Similarly, in this study, the amount of fiber and fiber components such as ADF, NDF, CEL, HCEL, and lignin in seeds increased due to water stress, but it was more in brown-seeded genotypes.…”

“…In the present study, in most families with brown seeds, water stress increased the amount of protein and amino acids more than the yellowseeded ones. Foroud et al [25] and Tavares et al [21] also observed an increasing amount and quality of protein under water deficit conditions in other oil seed crops such as soybean. When plants are stressed, they usually accumulate protein and amino acids.…”

“…The initial objective of this study was to investigate the effect of water stress conditions and seed coat color on seed yield and quality traits. In general, water stress causes a decrease in seed yield, associated with reduced assimilate synthesis required for seed filling [21]. Flax families and parents with brown seed coats had higher seed yield stability than yellow seed ones under water stress conditions, probably due to a higher amount of secondary metabolites such as lignans and tannins [22].…”

The Impact of Foliar Fertilization on the Physiological Parameters, Yield, and Quality Indices of the Soybean Crop

“…Soybean culture is sensitive to water deficit, especially during the period of vegetative growth and development [37][38][39]; thus, it is possible to have a significant reduction in the leaf surface and even the abortion of flowers [40][41][42], a lower assimilation of nutrients [43], a smaller number of pods [7,40], as well as a 14-32% reduction in grain size (as observed by Souza et al in 1997) [44], all of which led to a decrease in yield, as also revealed by the data obtained by Van Heerden and Krüger in 2002 [45]. Excess soil water is equally harmful, limiting the yield potential, as observed by Santos and Carlesso in 1998 [46] and Lobato et al in 2008 [47], who carried out various experiments.…”

Optimal-Band Analysis for Chlorophyll Quantification in Rice Leaves Using a Custom Hyperspectral Imaging System

“…Most VIs are ratios or linear combinations of spectral reflectance in two or more wavelength bands [ 39 ] that can be obtained from HSI [ 37 , 40 ]. Consisting of a straightforward transformation of spectral bands, VIs are estimated without bias or presumptions about land cover class, soil type, or climate conditions—enabling the observations of seasonal and long-term changes in a vegetation’s structural, phenological, and biophysical characteristics [ 41 , 42 , 43 ]. VIs have proven to be a valuable tool for monitoring plant health and productivity, and they are widely applied in fields such as agriculture, forestry, and ecology.…”