Systems responses to progressive water stress in durum wheat

Durum wheat is susceptible to terminal drought which can greatly decrease grain yield. Breeding to improve crop yield is hampered by inadequate knowledge of how the physiological and metabolic changes caused by drought are related to gene expression. To gain better insight into mechanisms defining resistance to water stress we studied the physiological and transcriptome responses of three durum breeding lines varying for yield stability under drought. Parents of a mapping population (Lahn x Cham1) and a recombinant inbred line (RIL2219) showed lowered flag leaf relative water content, water potential and photosynthesis when subjected to controlled water stress time transient experiments over a six-day period. RIL2219 lost less water and showed constitutively higher stomatal conductance, photosynthesis, transpiration, abscisic acid content and enhanced osmotic adjustment at equivalent leaf water compared to parents, thus defining a physiological strategy for high yield stability under water stress. Parallel analysis of the flag leaf transcriptome under stress uncovered global trends of early changes in regulatory pathways, reconfiguration of primary and secondary metabolism and lowered expression of transcripts in photosynthesis in all three lines. Differences in the number of genes, magnitude and profile of their expression response were also established amongst the lines with a high number belonging to regulatory pathways. In addition, we documented a large number of genes showing constitutive differences in leaf transcript expression between the genotypes at control non-stress conditions. Principal Coordinates Analysis uncovered a high level of structure in the transcriptome response to water stress in each wheat line suggesting genome-wide co-ordination of transcription. Utilising a systems-based approach of analysing the integrated wheat's response to water stress, in terms of biological robustness theory, the findings suggest that each durum line transcriptome responded to water stress in a genome-specific manner which contributes to an overall different strategy of resistance to water stress

Historical and current perspectives of agricultural knowledge, science and technology in Central and West Asia and North Africa

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Wheat production in Tunisia: progress, inter-annual variability and relation to rainfall

Corresponding author. Fax: +216 7123 1545; E-mail address: [email protected] audienceDuring the second half of the last century, average wheat yields have increased in most parts of the world, including in areas subject to drought. As a case study of factors affecting yield in drought-prone areas, we have studied durum wheat yields and their relation to rainfall in Tunisia, where from north to south there is a gradient in severity and frequency of drought. The mid 1960s delimited two periods: from the early 1900s to the 60s the rate of increase was rather low; after the 60s yields increased at a higher rate. However, yields were quite variable and extremely low in dry years. Recently the rate of yield increase has been slowing clown. In northern Tunisia, yield was highly correlated with autumn rainfall, indicating the importance of the early growth stages, whereas variation in the extent of terminal drought was poorly correlated with yield. In the centre and south, where drought occurs frequently, the area sown was highly variable, because farmers often cancel sowing if the first significant autumn rainfalls do not occur. Wheat production was also diminished through a reduction of harvested areas with respect to sown areas, a consequence of severe drought and crop failure. Water use efficiency (yield/growing season rainfall) was stable for durum wheat in northern Tunisia until the late 60s and since then has significantly increased. Given the identified sensitivities to drought, the main factors limiting wheat yield are discussed and analysed in order to give way to more genetic and crop management progres

Intercropping, a system allowing to increase durum wheat production and to maintain soil fertility in Northern Tunisia?

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Agriculture à la croisée des chemins

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PCo plots for the expression of all 19062 probe dataset.

<p>The first three PCos account for 72.8% of the variation represented in the (reduced) similarity matrix for the 18 wheat line by RWC combinations. Visualisation of the combinations in the three dimensions was achieved by plotting PCo1 <i>vs.</i> PCo2 (A), PCo1 <i>vs.</i> PCo3 (B) and PCo2 <i>vs.</i> PCo3 (C). Letters L, C and R represent the lines Lahn, Cham1 and RIL 2219 respectively at 90-50 leaf %RWC values. Arrows on plot A show the direction of the stress transient of decreasing leaf RWC and the free-drawn circles around the points highlight potential functional states for each line, inferred from distance between points.</p

Overview of cell function transcript expression during the water stress transient.

<p>Transcript profile changes, at decreasing leaf %RWC (82,74,66,58), were similar across the stress transient for the three wheat lines in probes taken from MapMan bins 15,17,20,21,26,27,28,29,30,31,33,34 in the <i>Line</i>+<i>Stress</i> ANOVA group dataset (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108431#pone.0108431.s005" target="_blank">File S4</a>). Results were visualised in MapMan and the colour scale for transcripts that were increased or decreased in abundance were denoted as red and green, respectively.</p

Top two probes showing largest changes in expression during the early phase in the stress for each wheat line. Data represents the ratio of change in expression (over and under-expression values) at 82% relative to that at 90 leaf %RWC taken from the ANOVA group dataset <i>line x stress</i> (File S5).

<p>Top two probes showing largest changes in expression during the early phase in the stress for each wheat line. Data represents the ratio of change in expression (over and under-expression values) at 82% relative to that at 90 leaf %RWC taken from the ANOVA group dataset <i>line x stress</i> (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108431#pone.0108431.s006" target="_blank">File S5</a>).</p

Physiological and biochemical parameters of leaves during water deficit.

<p>Plant water status was measured by flag leaf %RWC as a function of days of stress (A), leaf water potential (B) and total plant water loss (F) during a stress transient of 0–6 days for three wheat lines Lahn (▪), Cham1 (•) and RIL2219 (▴). Leaf photosynthetic and biochemical parameters were CO₂ assimilation (C), transpiration (D), stomatal conductance (E), osmotic adjustment (G) and ABA content (H). Linear regression analysis gave a single line relationship for leaf water potential, parallel lines (p<0.05, F-test) for water loss, and separate lines (p<0.05, F-test) for osmotic adjustment. Using the Gompertz curve, separate <i>C</i> and <i>k</i> parameters (p<0.05, F-tests) were required for CO₂ assimilation, whereas for transpiration and stomatal conductance only separate <i>C</i> parameters (p<0.05, F-test) were required; (C–H) red line, black dashed line and black solid line are for RIL2219, Lahn and Cham1 respectively. For ABA, separate c parameters were significant (p<0.05, F-test) in the rational functions model.</p