Understanding the impacts of climate change on crop yield is important for improving crop growth and yield formation in northwestern China. In this study, we evaluated the relationship between meteorological dryness/wetness conditions and spring wheat yield in the Ili river basin (IRB). The climate and yield data from 1961 to 2013 were collected to analyze characteristics and correlations between these two variables using the standardized precipitation evapotranspiration index (SPEI), yield detrending method, modified Mann-Kendall test and Spearman correlation analysis. Main results were as follows: (1) correlations between monthly SPEI values (MSV) and climatic yield of spring wheat indicated that the dryness/wetness condition in May was a key factor affecting yield in the whole region; (2) although the MSV in May and yield fluctuated from negative to positive values in time, the severely and extremely dryness events were in good agreement with the higher yield losses; (3) each increase of 0.5 MSV in May promoted over 3% increase of yield in most part of IRB; however, the larger variability of MSV in May resulted in larger yield fluctuations; and (4) the Tibetan Plateau index in April showed significant correlations with the MSV in May and yield, which provided a precursory signal for decision-makers to better understand potential yield fluctuations.
For estimation of grain yield in wheat, Normalized Difference Vegetation Index (NDVI) is considered as a potential screening tool. Field experiments were conducted to scrutinize the response of NDVI to yield behavior of different wheat cultivars and nitrogen fertilization at agronomic research area, University of Agriculture Faisalabad (UAF) during the two years 2008-09 and 2009-10. For recording the value of NDVI, Green seeker (Handheld-505) was used. Split plot design was used as experimental model in, keeping four nitrogen rates (N1 = 0 kg ha(-1), N2 = 55 kg ha(-1), N3 = 110 kg ha(-1), and N4 = 220 kg ha(-1)) in main plots and ten wheat cultivars (Bakkhar-2001, Chakwal-50, Chakwal-97, Faisalabad-2008, GA-2002, Inqlab-91, Lasani-2008, Miraj-2008, Sahar-2006, and Shafaq-2006) in subplots with four replications. Impact of nitrogen and difference between cultivars were forecasted through NDVI. The results suggested that nitrogen treatment N4 (220 kg ha(-1)) and cultivar Faisalabad-2008 gave maximum NDVI value (0.85) at grain filling stage among all treatments. The correlation among NDVI at booting, grain filling, and maturity stages with grain yield was positive (R(2) = 0.90; R(2) = 0.90; R(2) = 0.95), respectively. So, booting, grain filling, and maturity can be good depictive stages during mid and later growth stages of wheat crop under agroclimatic conditions of Faisalabad and under similar other wheat growing environments in the country.
Aluminum (Al) sensitive wheat cultivar kalyansona was grown for 14 d in a range of Ca solution (125, 625, and 2500 μM) plus other nutrients without Al. At 14 d after Ca treatment, half of these plants were harvested (H1), and the rest of the plants were exposed to 100 μM Al for additional 6 d and harvested (H2). Severe Al injury was found only in the plants with the lowest supply of Ca before Al treatment. Aluminum concentration in the apoplastic fluid was very high at 125 μM Ca probably because the plasma membrane of some of the cells was destroyed due to the attack of 100 μM Al. Aluminum content in roots decreased with increasing supply of Ca before Al treatment. Calcium content decreased drastically at harvest (H2) in the plants with 100 μM Al. Under Al stress conditions, the plant responded to Al in different ways due to not only the different Ca supply but also the variation of Ca content in the plant tissues. Actually, the plants having the largest Ca content in the roots before Al treatment can receive less Al injury during Al treatment. To substantiate this idea, a companion study was conducted to investigate the effects of 2500 μM Ca supply during, before, and after 100 μM Al treatment on root growth. The results indicated clearly that exogenous Ca supply before Al treatment is able to alleviate Al injury but less effective than Ca supply during Al treatment.
Emmer wheat (Triticum dicoccon Schrank) is a potential source of new genetic diversity for the improvement of hexaploid bread wheat. Emmer wheat was crossed and backcrossed to bread wheat and 480 doubled haploids (DHs) were produced from BC1F1 plants with hexaploid appearance derived from 19 crossses. These DHs were screened under well-watered conditions (E1) in 2013 to identify high-yielding materials with similar phenology. One-hundred and eighty seven DH lines selected on this basis, 4 commercial bread wheat cultivars and 9 bread wheat parents were then evaluated in extensive field experiments under two contrasting moisture regimes in north-western NSW in 2014 and 2015. A significant range in the water-use-efficiency of grain production (WUEGrain) was observed among the emmer derivatives. Of these, 8 hexaploid lines developed from 8 different emmer wheat parents had significantly improved intrinsic water-use-efficiency (WUEintr) and instantaneous water-use-efficiency (WUEi) compared to their bread wheat recurrent parents. Accurate and large scale field-based phenotyping was effective in identifying emmer wheat derived lines with superior performance to their hexaploid bread wheat recurrent parents under moisture stress.
Mitochondrial respiration and tricarboxylic acid (TCA) cycle activity are required during salt stress in plants to provide ATP and reductants for adaptive processes such as ion exclusion, compatible solute synthesis and reactive oxygen species (ROS) detoxification. However, there is a poor mechanistic understanding of how salinity affects mitochondrial metabolism, particularly respiratory substrate source. To determine the mechanism of respiratory changes under salt stress in wheat leaves, we conducted an integrated analysis of metabolite content, respiratory rate and targeted protein abundance measurements. Also, we investigated the direct effect of salt on mitochondrial enzyme activities. Salt-treated wheat leaves exhibit higher respiration rate and extensive metabolite changes. The activity of the TCA cycle enzymes pyruvate dehydrogenase complex and the 2-oxoglutarate dehydrogenase complex were shown to be directly salt-sensitive. Multiple lines of evidence showed that the γ-aminobutyric acid (GABA) shunt was activated under salt treatment. During salt exposure, key metabolic enzymes required for the cyclic operation of the TCA cycle are physiochemically inhibited by salt. This inhibition is overcome by increased GABA shunt activity, which provides an alternative carbon source for mitochondria that bypasses salt-sensitive enzymes, to facilitate the increased respiration of wheat leaves.