This study aims to investigate the effect of these stay-green mechanisms on grain nutrition profile (specifically amino acid profile) and its variation in different environmental conditions. Understanding the link between plant functions and the grain nutrient profile in different environments can accelerate breeding for nutrition improvement.

1. Physiological processes influencing grain amino acid profile
and its interactions with environment in stay-green sorghum
[Sorghum bicolor (L.) Moench]
Keerthi Chadalavada1
, Vincent Vadez1
, Michael Blümmel2
, KVSV Prasad3
, Srikanth Mallayee1
, Saikat Datta Mazumdar1
, Jana Kholová1
*
1
International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Telangana-502 324, India.
2
International Livestock Research Institute, Addis Ababa, Ethiopia
3
International Livestock Research Institute, Patancheru, Telangana-502 324, India.
* E-mail: Corresponding author: j.kholova@cgiar.org
Introduction
The sorghum stay-green (stg) phenotype (i.e. retention of greenness) has proved to
enhance sorghum adaptation to water-limited cropping systems (Vadez et al. 2011,
Kholová et al. 2014, Borrell et al. 2013, 2014a, b). Some of the plant physiological
mechanisms underlying stay-green phenotype were shown to improve the stover
quality parameters that are important for enhancement of livestock production
(Blummel et al. 2015). Therefore this study aims to investigate the effect of these
stay-green mechanisms on grain nutrition profile (specifically amino acid profile)
and its variation in different environmental conditions. Understanding the link
between plant functions and the grain nutrient profile in different environments
can accelerate breeding for nutrition improvement.
Materials and methods
Materials: Sorghum stay-green QTL introgression lines (ILs); R16 senescent parent
and R16 originated: K359W (stg B) and K648 (stg 4), S35 senescent parent and
S35 originated: 6040 (stg1), 6008 (stg A), 6026 (stg 2) and 7001 (stg B) along with
postrainy check (Maldandi – M35-1).
Methods: Crop was raised under well-watered (WW) and terminal water stressed
(WS) conditions in the field. Plant physiological characteristics [biomass (g/plant),
tillering propensity, grain yield (g/plant) and grain size (100 seed weight)] were
assessed. Matured grains were oven-dried to 10% moisture and ground to uniform
particle size using precision mill (Cemotech; Foss). Flour samples were profiled for
near-infrared reflectance (NIR) spectra signature. Amino acid (AA) contents were
predicted using World Aquafeed amino acid calibration model baseline.
Key results
▪▪ Negative production trade-off was found in several stay-green ILs compared
to senescent parents in WW but some of the ILs maintained the yield or out-
yielded the parental under WS treatments.
▪▪ Total AA content was on an average 8.97% (w/w) in WW and 8.55% (w/w)
under WS.
▪▪ Across treatments – S35 (6040, 6008, 6026 and 7001) introgression lines
attained higher total AA content compared to R16 lines (K359W and K648)
(average of 9.53% versus 7.75% respectively).
▪▪ Most of the ILs originated from S35 attained higher grain AA content compared
to senescent parent S35 across water treatments.
▪▪ Total AA content was significantly influenced by grain size in the case of S35
originated lines, but not in R16 background lines.
▪▪ Tryptophan, a physiological precursor of auxins (essential amino acid;
(range: 0.01-2.14%)), was negatively correlated with plant tillering propensity
under WS.
▪▪ Strong positive correlation of total AA (specifically proline and histidine) with
stem/stover ratio was observed across all the genotypes, indicating that
processes influencing this ratio (possibly linked to photosynthetic efficiency)
may influence the grain amino acid composition.
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Mean grain yield [g/plant] of senescent parents (R16 and S35) and R16 originated stay-green QTL introgression
lines: K359W (stg B), K648 (stg 4) and S35 originated stay-green QTL introgression lines: 6040 (stg 1), 6008 (stg A),
6026 (stg 2) and 7001 (stg B) along with the postrainy check M35-1 under well-watered (WW) and water stress (WS)
conditions. Mean is shown along with the standard error bar.
Mean total AA (%; w/w) of senescent parents (R16 and S35) and R16 originated stay-green QTL introgression lines:
K359W (stg B), K648 (stg 4) and S35 originated stay-green QTL introgression lines: 6040 (stg 1), 6008 (stg A), 6026
(stg 2) and 7001 (stg B) along with the postrainy check M35-1 under well-watered (WW) and water stress (WS)
conditions. Mean is shown along with the standard error bar.
Relation between grain size and total AA content in R16:
K359W (stg B), K648 (stg 4) and S35: 6040 (stg 1), 6008
(stg A), 6026 (stg 2) and 7001 (stg B) genetic backgrounds
across water treatments (well-watered and water
stressed).
Conclusions
▪▪ Total AA content was genetic background-line-specific and differentially
influenced by environmental factors.
▪▪ Most of stay-green ILs of S35 origin had enhanced grain AA content compared
to senescent parent S35.
▪▪ Plant biological processes that are likely influencing the amino acid profile of
the grain were observed.
▪▪ The results emphasized the need to understand the plant mechanisms
underlying the grain nutritional profile and its interaction with environment to
accelerate the crop grain nutrition improvement.
▪▪ The possible negative production trade-off associated with stay-green
technology in WW might be compensated by enhanced nutritional profile of
the grain and stover (Blummel et al. 2015).
Acknowledgement
The authors are thankful for the funding from Australian Centre for International
Agriculture Research (ACIAR) to support the present study.
Positive correlation of total AA (41%) and proline content
(53%) with stem/stover ratio across genotypes: senescent
parents (R-16 and S35) and stay-green QTL introgression
lines originated from R16: K359W (stg B), K648 (stg 4)
and S35: 6040 (stg1), 6008 (stg A), 6026 (stg 2) and 7001
(stg B) and M35-1 across water treatments.
Relationship between tiller count and
tryptophan (physiological precursor of
auxins) under water stress condition across
two genetic backgrounds; (R16: K359W
(stg B), K648 (stg 4) and S35: 6040 (stg1),
6008 (stg A), 6026 (stg 2) and 7001(stg B)).
Totalaminoacids(%w/w)
Genotype
WW WS
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
Grainyield(g/plant)
Genotype
y = 1.6134x + 4.4771
R² = 0.5819
y = -0.145x + 8.2069
R² = 0.0027
4.00
6.00
8.00
10.00
12.00
2.00 2.50 3.00 3.50 4.00 4.50
S35 background
R16 background
grain size(g)
TotalAAcontent(%w/w)
Stem/stoverratio
Transformed total AA content (%)
Total AA
y = 0.1883x + 0.5242
R² = 0.4126
0.60
0.62
0.64
0.66
0.68
0.70
0.72
0.74
0.76
0.78
0.80
0.5 0.7 0.9 1.1 1.3 1.5
Proline
y = 0.2142x + 0.4982
R² = 0.5331
Tryptophan(ug/g)
Tiller number
Oct 2016
WSWW