Biomass Production,Nutritional and Mineral Content of Desiccation‐Sensitive and Desiccation‐Tolerant Species of Sporobolus under Multiple Irrigation Regimes

The development of low‐water‐input forages would be useful for improving the water‐use efficiency of livestock production in semi‐arid and arid regions. The desiccation‐tolerant (DT) species Sporobolus stapfianus Gandoger and two desiccation‐sensitive (DS) species, Sporobolus pyramidalis and Sporobolus fimbriatus (Trin.) Nees. (Poaceae), were evaluated for aerial biomass production and seed productivity under three different irrigation regimes. Sporobolus stapfianus displayed the least biomass production, whereas S. pyramidalis and S. fimbriatus produced up to 3.8‐ and 11.2‐fold greater dry biomass, respectively, at the highest irrigation rate of 12 334 l (0.01 acre‐feet). Sporobolus fimbriatus and to a lesser extent S. pyramidalis showed significant increases in biomass production in response to increased irrigation rates, whereas S. stapfianus did not. Sporobolus pyramidalis and S. fimbriatus exhibited 3.2‐ and 6.0‐fold greater seed production, respectively, in response to increased irrigation rates, whereas S. stapfianus showed only a 1.4‐fold increase. All Sporobolus species possessed forage quality traits (e.g. crude protein, fibre content) comparable to those of timothy, a forage grass grown widely in the Great Basin in the western United States. Micronutrient content exceeded the minimum requirements of beef cattle, without surpassing tolerable limits, with the exception of zinc, which appeared low in all three Sporobolus species. The low water requirements displayed by these species, combined with their acceptable forage qualities, indicate that these grasses have the potential to serve farmers and ranchers in semi‐arid and arid regions of the western United States where irrigation resources are limited.     

Leaf,canopy and agronomic water‐use efficiency of field‐grown sugar beet in response to potassium fertilization

Potassium (K) fertilization is important to maintain adequate concentrations of plant available K in agricultural soils to achieve best yields and improve crop stress tolerance and water‐use efficiency (WUE). Water‐use efficiency (WUE) can be expressed on various spatiotemporal scales, and it is known that responses of WUE to external stress are not uniform across scales. Multiscale evaluations of the impact of varying K fertilization on the WUE of C₃ crops under field conditions are missing so far. In the present field study, we evaluated effects of K fertilization on WUE of sugar beet (Beta vulgaris L.) on short‐termed leaf‐ (WUE_Leaf) and canopy‐scales (WUE_Canopy) and as the agronomic ratio of white sugar yield (WSY) to in‐season water use (i.e. WUE_WSY). In K‐fertilized plots, WUE_WSY was enhanced by 15.9%. This effect is attributed to increased beet yield and WSY, as no differences in total in‐season water use between fertilized and unfertilized plots were observed. Potassium (K) fertilization significantly enhanced the leaf area index, resulting in a more efficient depletion of soil moisture by roots in K‐fertilized plots. As a consequence, WUE_Leaf was increased due to stomatal adjustment. Potassium (K) improved WUE_Canopy only by tendency. It is concluded that K fertilization improves the WUE of field‐grown sugar beet across scales, but processes that regulate WUE are highly scale dependent.     

Characterization of Drought‐Tolerance Traits in Nodulated Soya Beans: The Importance of Maintaining Photosynthesis and Shoot Biomass Under Drought‐Induced Limitations on Nitrogen Metabolism

Drought is the single most important factor limiting soya bean (Glycine max L. Merr.) yields in the field. The following study was therefore undertaken to identify phenotypic markers for enhanced drought tolerance in nodulated soya beans. Leaf and nodule parameters were compared in three genotypes: Prima 2000, glyphosate‐resistant A5409RG and Jackson, which had similar shoot biomass and photosynthesis rates at the third trifoliate leaf stage under water‐replete conditions. When water was withheld at the third trifoliate leaf stage, photosynthesis, nodule numbers, nodule biomass and symbiotic nitrogen fixation (SNF) were greatly decreased. Significant cultivar–drought interactions were observed with respect to photosynthesis, which also showed a strong positive correlation with nodule SNF, particularly under drought conditions. Prima leaves had high water‐use efficiencies, and they also maintained high photosynthetic electron transport efficiencies under long‐term drought. Moreover, Prima had the highest shoot biomass under both water‐replete and drought conditions. A‐5409RG was the most drought‐sensitive genotype showing early closure of stomata and rapid inhibition of photosynthesis in response to drought. In addition to classifying the genotypes in relation to drought tolerance, the results demonstrate that the ability to sustain shoot biomass under nitrogen limitation is an important parameter, which can be easily applied in germplasm screening for drought tolerance in soya bean.     

Comparison of Drought Tolerance of Maize,Sweet Sorghum and Sorghum‐Sudangrass Hybrids

In drought‐prone environments, sweet sorghum and sorghum‐sudangrass hybrids are considered worthy alternatives to maize for biogas production. The biomass productivity of the three crops was compared by growing them side‐by‐side in a rain‐out shelter under different levels of plant available soil water (PASW) during the growing periods of 2008 to 2010 at Braunschweig, Germany. All crops were established under high levels of soil water. Thereafter, the crops either remained at the wet level (60–80 % PASW) or were subjected to moderate (40–50 % PASW) and severe drought stress (15–25 % PASW). While the above‐ground dry weight (ADW) of sweet sorghum and maize was insignificantly different under well‐watered conditions, sweet sorghum under severe drought stress produced 27 % more ADW than maize. The ADW of sorghum‐sudangrass hybrids significantly lagged behind sweet sorghum at all levels of water supply. The three crops differed markedly in their susceptibility to water shortage. Severe drought stress reduced the ADW of maize by 51 %, but only by 37 % for sweet sorghum and 35 % for sorghum‐sudangrass hybrids. The post‐harvest root dry weight (RDW) in the 0–100 cm soil layer for maize, sweet sorghum and sorghum‐sudangrass hybrids averaged 4.4, 6.1 and 2.9 t ha^?1 under wet and 1.9, 5.7 and 2.4 t ha^?1 under severe drought stress. Under these most dry conditions, the sorghum crops had relatively higher RDW and root length density (RLD) in the deeper soil layers than maize. The subsoil RDW proportion (20–100 vs. 0–20 cm) for maize, sweet sorghum and sorghum‐sudangrass hybrids amounted to 6 %, 10 % and 20 %. The higher ADM of sweet sorghum compared with maize under dry conditions is most likely attributable to the deep root penetration and high proportion of roots in the subsoil, which confers the sorghum crop a high water uptake capacity.     

Phosphorus Fertilization and Fungal Inoculations Affected the Physiology,Phosphorus Uptake and Growth of Spring Wheat Under Rainfed Conditions on the Canadian Prairies

Some fungal species have been shown to improve plant growth under drought conditions and to increase plant phosphorus (P) uptake from the soil. How moisture limitation, P availability and fungal inoculation interact to affect plant physiology and growth is, however, poorly understood. Here, we studied the combined effects of fungal (arbuscular mycorrhizal fungi (AMF) or Penicillium spp.) inoculations and phosphorus (P) fertilization (0, 45 and 90 kg ha^?1) on the net rate of photosynthesis, water‐use efficiency, P uptake and growth of spring wheat (Triticum aestivum var. Superb) under field conditions at two locations (Castor and Vegreville) in Alberta, Canada. Both fungal inoculation and P application increased the rate of photosynthesis. Under the same P level, AMF inoculation had a greater positive effect on the rate of photosynthesis than Penicillium inoculation. The AMF inoculation increased the instantaneous water‐use efficiency (WUEi) of plants at Castor, but not at Vegreville. Leaf carbon isotope discrimination (CID, Δ¹³C) increased with the rate of P application but was not affected by fungal inoculations. Phosphorus concentrations of stem and seed increased with both fungal inoculation and P application irrespective of location, with AMF inoculation showing the largest effects. The interaction between P addition and fungal inoculation was significant for stem P concentration in Vegreville. Both fungal inoculation and P application increased the leaf area index (LAI), biomass production and grain yield at both locations. Under the same P level, AMF inoculation had a greater positive effect on LAI, biomass production and grain yields than Penicillium inoculation. Morphological characters such as spike length and kernels/spike were also improved by fungal inoculation and P application at both locations. We conclude that the studied sites were deficient in P availability, and both fungal inoculation and P application improved P uptake and crop productivity, while the effect of fungal inoculation on water‐use efficiency was site specific.     

Drought Tolerance and Water Use of Cereal Crops: A Focus on Sorghum as a Food Security Crop in Sub‐Saharan Africa

Sub‐Saharan Africa (SSA) faces twin challenges of water stress and food insecurity – challenges that are already pressing and are projected to grow. Sub‐Saharan Africa comprises 43 % arid and semi‐arid area, which is projected to increase due to climate change. Small‐scale, rainfed agriculture is the main livelihood source in arid and semi‐arid areas of SSA. Because rainfed agriculture constitutes more than 95 % of agricultural land use, water scarcity is a major limitation to production. Crop production, specifically staple cereal crop production, will have to adapt to water scarcity and improved water productivity (output per water input) to meet food requirements. We propose inclusion and promotion of drought‐tolerant cereal crops in arid and semi‐arid agro‐ecological zones of SSA where water scarcity is a major limitation to cereal production. Sorghum uniquely fits production in such regions, due to high and stable water‐use efficiency, drought and heat tolerance, high germplasm variability, comparative nutritional value and existing food value chain in SSA. However, sorghum is socio‐economically and geographically underutilized in parts of SSA. Sorghum inclusion and/or promotion in arid and semi‐arid areas of SSA, especially among subsistence farmers, will improve water productivity and food security.     

Vitamin C,B5, and B6 contents of segregating potato populations detected by GC‐MS: a method facilitating breeding potatoes with improved vitamin content

Vitamin C, B5, and B6 contents of potato tubers were measured by gas chromatography‐mass spectrometry (GC‐MS). Two diploid potato populations derived from two different crosses were analyzed. Plants were grown at two locations under different environmental conditions. Measurements of vitamin content of tubers showed high variation in both populations. A weak correlation was found between the vitamin concentrations of tubers harvested at the two locations. Correlations between the mean values of vitamins in field‐grown tubers and in different tissues derived from in vitro or greenhouse‐grown potato plants were also determined. A very high correlation between the vitamin content of field‐ and greenhouse‐grown tubers, and between field‐grown tubers and sink leaves of greenhouse‐grown plants was detected. This finding can facilitate breeding by preselection of individuals with improved vitamin content under greenhouse conditions at their early developmental stage.     

Marker‐assisted introgression of rare allele of β‐carotene hydroxylase (crtRB1) gene into elite quality protein maize inbred for combining high lysine,tryptophan and provitamin A in maize

Vitamin A deficiency in humans is a widespread health problem. Quality protein maize (QPM) is a popular food rich in lysine and tryptophan, but poor in provitamin A (proA). Here, we report the improvement of an elite QPM inbred, HKI1128Q for proA using marker‐assisted introgression of crtRB1‐favourable allele. HKI1128 was one of the parental lines of three popular hybrids in India and was converted to QPM in our earlier programme. Severe segregation distortion for crtRB1 was observed in BC₁F₁, BC₂F₁ and BC₂F₂. Background selection by 100 SSRs revealed mean recovery of 91.07% recurrent parent genome varying from 88.78% to 93.88%. Across years, introgressed progenies possessed higher mean β‐carotene (BC: 9.22 µg/g), β‐cryptoxanthin (BCX: 3.05 µg/g) and provitamin A (proA: 10.75 µg/g) compared to HKI1128Q (BC: 2.26 µg/g, BCX: 2.26 µg/g and proA: 3.38 µg/g). High concentration of essential amino acids, viz. lysine (mean: 0.303%) and tryptophan (0.080%) in endosperm, was also retained. Multi‐year evaluation showed that introgressed progenies possessed similar grain yield (1,759–1,879 kg/ha) with HKI1128Q (1,778 kg/ha). Introgressed progenies with higher lysine, tryptophan and proA hold immense potential as donors and parents in developing biofortified hybrids.