This study characterized physiological traits associated with wheat yield under heat stress. 161 recombinant inbred wheat lines and checks were evaluated. Several lines yielded higher than parents Cham-6 and Cham-8. Yield correlated positively with ground cover, heads/m2, biomass and harvest index. Emergence and flag leaf traits did not correlate significantly with yield. Ground cover and photosynthate supply during grain filling may influence yield stability under heat stress. Further work is characterizing traits in multiple environments.

1. Physiological Characterization of Heat Adaptive
Traits in Bread Wheat (Triticum aestivum L.)
A. Farag Alla*, 1,2
FC Ogbonnaya, M. Ahmed and O. Abdalla
2 3 2
1
University of Juba, Khartoum Center, Sudan. E-mail awatif9@gmail.com CGIAR
2
ICARDA, PO Box 5466, Aleppo, Syria
3
University of Khartoum, Sudan
Introduction • 49 RILs gave higher yield than Cham-6, Table 2. Correlation coefficient between
3.35-2.93 t ha-1. grain yield (t ha-1) and investigated traits.
In Sudan, wheat is grown at low latitudes under irrigation. Heat stress is the main • RILs were superior to Cham-6 with regard
Trait r2
constraint, affecting the crop at all stages of growth and development – with even to E1, E3, E4, E5, GC4, GC5, and GC6,
Early Vigor 0.002ns
greater impacts in the future, as a result of global warming. It is important to identify FLL (cm), DTPM, Duration of GL, GFP,
peduncle length (cm) and TKW (g). Flag Leaf Length (cm) (-)ve 0.08ns
genotypes that give adequate yields under heat stress and high yield under normal
conditions. This study sought to characterize physiological traits that are associated • RILs were superior to Cham-8 with Flag Leaf Width (cm) 0.1ns
with yield performance under heat stress. regard to E6, E7, GC3, FLW (cm), DTH, Days to Heading (Days) (-)ve 0.15ns
glaucousness, plant height (cm), biomass Glaucuones 0.07ns
(g), head length (cm), threshing %, HI and Number of heads m-2 0.65***
Materials and Methods grain yield (t ha-1).
Plant height (cm) 0.32ns
161 F8 recombinant inbred lines (RILs) derived from the cross between Cham-6 (drought • Cham-6 was superior to the RILs in E1
Days to Physiological Maturity (Days) 0.06ns
and number of heads per m2, Cham-8 was
tolerant) and Cham-8 (heat tolerant), along Duration of Green Leaf (Days) 0.04ns
Manual weeding before irrigation superior to the RILs for GC1 and GC2.
with 13 check cultivars, were grown under Extended Grain Filling (Days) 0.01ns
There were significant differences amongst
field conditions at the ARC experimental farm Dry Wt. (g) 0.32***
the traits (pr<0.001) except for EV, number
at Wad Medani, Sudan (14°N, 33°E, 414 m of heads per m2, threshing % and harvest Peduncle length (cm) 0.005ns
asl), with surface irrigation. index (Table 1). Grain yield was positively Head Length (cm) (-)ve 0.05ns
• Conditions during growing season: mean and highly significantly correlated with Threshing % 0.08ns
max. and min. temperatures 36.1˚C and ground cover (GC1 to GC5) (Fig. 2), number Harvest Index 0.28***
17.6˚C, mean relative humidity 25.8% of heads per m2, biomass and harvest index.
1000 Kernel Wt. (g) (-)ve 0.005ns
Yield was non-significantly (p<0.001) and
• Experimental design: Alpha lattice with
three replicates. The Crop two weeks before maturity Crop at Maturity
• Measurements: Emergence % (E), early
vigor (EV), ground cover (GC), flag leaf
characteristics, days to heading (DTH),
days to physiological maturity (DTPM),
4
grain filling period (GFP), glaucousness,
3.5
plant height, biomass, yield and its
3
components.
Yield (Ton ha-1)
2.5
2
Results and Discussion 1.5
1
Tables 1 and 2 summarizes the results. The
RILs displayed transgressive segregation 0.5
for all investigated traits. Only 3 RILs gave 0
RILmax C_8 C_6 Population RILmin
negatively correlated with flag leaf length 0.7
higher yield than the adaptive heat tolerant Average
(cm), days to heading and kernel weight (g).
parent Cham-8: predicted mean yield 3.64- Figure 1. Yields of RILs compared to parents, There was no correlation between yield
0.6
3.39 t ha-1, increase of 7.4% (Fig. 1). showing trangressive segregation. and the other traits investigated. The linear 0.5
regression of yield and harvest index was the
most positive and highly significant amongst 0.4
Table 1. Phenotypic traits measured in RILs and two parents, 2009/10 season, Wad the traits under study (Fig. 3).
r2
Medani, Sudan. 0.3
These results suggest that ground cover,
Parents RILs Fpr LSD number of heads per m2, biomass and 0.2
Trait CV SE
Cham 6 Cham 8 Max Min (<0.001) (0.05) harvest index could play an important role in
E1 26.86 16.87 31.77 4.03 1.71*** 0.16 24.20 0.09 yield stability of bread wheat in heat stress 0.1
E2 37.21 23.94 36.69 9.45 1.76*** 0.17 19.53 0.09 environments. Ground cover is important at
0
E3 46.00 42.32 52.89 13.86 1.33 ns
4.66 20.05 1.51 all stages of crop growth; it shades the soil
GC1 GC2 GC3 GC4 GC5 GC6
E4 65.48 54.20 74.69 23.87 1.66*** 23.06 26.23 13.07 surface, reducing evaporation. This ensures Ground Cover (GC)
E5 72.56 67.04 82.39 33.33 1.84*** 20.44 19.97 11.58 that the developing grains are provided with Figure 2. Correlation coefficient of grain yield
E6 77.93 78.94 87.98 43.66 1.97*** 17.51 14.82 9.92 assimilates from current photosynthesis (t ha-1) and ground cover.
E7 86.96 87.90 92.66 62.94 1.78*** 13.02 9.44 7.38 which translates into increased biomass.
Early vigor 2.77 1.90 3.47 0.90 1.06ns 0.51 13.02 0.29 Emergence, early vigor and flag leaf
characteristics were non-significantly
GC1 11.73 13.72 13.09 3.33 1.56*** 0.09 18.72 0.05
correlated with yield. It is likely these traits
GC2 39.18 46.42 45.99 13.90 1.69*** 13.80 25.19 7.77
have limited physiological role in heat
GC3 76.83 83.50 92.61 50.63 2.08*** 16.48 13.08 9.27
tolerance in the environment studied.
GC4 86.13 84.79 96.71 53.51 2.47*** 13.82 9.81 7.83
GC5 83.82 81.31 95.41 56.62 3.29*** 12.04 8.52 6.78 Further physiological characterizations in
GC6 74.94 73.46 89.97 47.07 3.20*** 11.39 9.37 6.40 multi-environmental trials are ongoing.
Flag leaf length (cm) 18.46 16.33 26.17 15.67 2.54*** 3.34 9.09 1.88
Flag leaf width (cm) 1.26 1.32 1.62 1.19 2.99*** 0.15 6.28 0.09 References
Days to heading 57.12 59.14 68.40 41.50 8.28*** 4.33 4.21 2.45 Blake, N. K., Lanning, J. M., Martin, J. M., Sherman,
J. D. and Talbert, L. E. 2007. Relationship of flag leaf
Glaucousness 2.62 3.85 4.16 1.58 4.26*** 0.75 10.58 0.42 characteristics to economically important traits in two
No. of heads m2 559.00 384.10 533.50 303.00 1.40ns 120.30 17.11 67.65 spring wheat crosses. Crop Sci., 47:492-496.
Margreet W. ter Steege, Franka M. den Ouden,
Plant height (cm) 61.70 64.36 83.71 53.05 7.24*** 5.08 4.60 2.86 Hans Lambers, Piet Stam , and Anton J.M. Peeters. Figure 3. Regression analysis of harvest index
Days to physiological maturity 91.29 89.62 104.31 82.06 4.68*** 4.99 3.10 2.81 2005. Genetic and Physiological Architecture of Early with grain yield (t ha-1)
Vigor in Aegilops tauschii, the D-Genome Donor of
Duration of green leaf (days) 36.09 31.83 48.15 24.79 1.85*** 6.09 9.83 3.43
Hexaploid Wheat. A Quantitative Trait Loci Analysis.
Extended grain filling (days) 34.31 30.54 41.91 26.53 1.59*** 6.21 10.67 3.50 Plant Physiology. 139(2):1078-1094.
Biomass (g) 1.52 1.57 1.88 1.11 1.75*** 0.31 11.98 0.18 Steege, M. W., Ouden, F. M., Lambers, H., Stam, P., Peeters, A. J. M. 2005. Genetic and physiological Architecture
of Early Vigor in Aegilops tauschii, the D-Genome Donor of Hexpaploid Wheat. A Quantitative Trait Loci Analysis.
Peduncle length (cm) 30.35 20.33 32.78 17.49 2.32*** 4.03 8.97 2.27 Plant Physiology. 139(2): 1078-1094.
Head length (cm) 6.82 7.81 15.83 5.22 1.52*** 2.35 17.39 1.32
Poster Design Abdurrahman Hawa
Xun-Li Lu, Ao-Lei Niu, Hai-Ya Cai, Yong Zhao, Jun-Wei Liu, Ying-Gau Zhu, Zhi-Hong Zhang. 2007. Genetic
Threshing % 0.63 0.77 0.80 0.44 1.32ns 0.19 17.06 0.11 dissection of seedling and early vigor in the recombinant inbred line population of rice. Plant Sci., 172:212-220.
Harvest Index 0.31 0.35 0.38 0.23 1.39ns 0.07 12.13 0.04
1000-kernel wt. (g) 29.42 26.23 37.55 22.94 2.99*** 4.33 8.03 2.43 Acknowledgments
Yield (t ha-1) 2.93 3.39 3.64 1.59 1.79*** 0.73 14.96 0.42 Ministry of Higher Education, University of Juba and ARC, Sudan.