Interactive effect of water and nitrogen regimes on plant growth, root traits and water status of old and modern durum wheat genotypes

Abstract

The selection of the ideal root drought adaptive traits should take into account the production and maintenance of root tissues alongside the capacity to capture soil resources. Ten old and modern Spanish durum wheat (Triticum turgidum L. var durum) genotypes were grown in lysimeters under two contrasting water and nitrogen regimes to study the effect of such growth conditions on: (1) the aerial biomass, (2) the growth and structure of the roots and (3) the relationships of the root structure with aerial biomass, photosynthetic and transpirative characteristics and water use efficiency. Both high water and nitrogen regimes significantly increased aerial biomass. Root dry biomass and root length increased and decreased in response to improved water supply and nitrogen regimes, respectively. No significant correlations were detected between aerial biomass and any root trait under well-watered conditions. Under water stress aerial biomass was negatively correlated with root dry biomass, root length and root weight density and positively correlated with the specific root length, particularly for the subset of old genotypes. The high nitrogen regime significantly enriched the carbon isotope composition of the flag leaf (δ (13)CFL) and hindered the effect of the high water regime on decreasing δ (13)CFL enrichment. Thus, positive correlations of aerial biomass with δ (13)CFL were detected regardless of the water regime. The study revealed: (1) the importance of root traits for higher aerial biomass under the low water regime; (2) that the interaction between nitrogen and the water regime may affect the predictive nature of the δ (13)C in drought breeding programs; and (3) the selection of the ideal root system structure should take into account the metabolic costs of the production and maintenance of root tissues alongside the capacity of capturing resources.

Modern wheat semi-dwarfs root deep on demand: response of rooting depth to drought in a set of Swiss era wheats covering 100 years of breeding

“…5). This is in agreement with results of Carvalho et al (2014) and Elazab et al (2016) who reported a stronger reduction of above-ground biomass compared to root biomass and an increased root-shoot ratio under drought. We observed an increase in root-shoot dry weight ratio from 0.14 under WW to 0.22 under EWS.…”

“…Yet, Rht genes are known to have an effect on rooting behavior. A negative effect of Rht genes was reported for root mass (Elazab et al 2016) and total root length (Wojciechowski et al 2009). Other studies did not find a negative effect of semi-dwarfism on root mass or root growth (e.g.…”

“…Root parameters are not directly selected by breeders and the indirect effect of their selection on root architecture is not well studied yet. Some authors found reduced root length and root biomass weights in modern wheat varieties compared to their tall ancestors (Wojciechowski et al 2009;Elazab et al 2016;Waines and Ehdaie 2007;Aziz et al 2017). In other studies, modern varieties had an increasing or similar amount of roots in deeper soil layers (Hurd 1974;Chloupek et al 2006) and while some studies observed no effect (Lupton et al 1974;Cholick et al 1977).…”

Root System Architecture and Its Association with Yield under Different Water Regimes in Durum Wheat

“…However, incorporating selection for root traits directly in a breeding program has been met with many challenges, foremost the difficulty of phenotyping large numbers of genotypes in a cost-and time-efficient manner (Mace et al, 2012). Several wheat studies have evaluated roots using different phenotyping methods including rhizotrons (Nagel et al, 2012;Lobet and Draye, 2013;Clarke et al, 2017), soil coring (Trachsel et al, 2011;Wasson et al, 2012;Wasson et al, 2014), lysimeters (Ehdaie et al, 2014;Elazab et al, 2016), hydroponics (Liu et al, 2015), paper roll culture and Petri dishes for seedling (Tomar et al, 2016), rhizoboxes (Fang et al, 2017, and X-ray-computed tomography (Gregory et al, 2003;Mairhofer et al, 2013;Colombi and Walter, 2017;Flavel et al, 2017). However, most of these techniques are either expensive or not precise enough and reproducible.…”

Leaf Gas Exchange and Fluorescence of Two Winter Wheat Varieties in Response to Drought Stress and Nitrogen Supply

“…Many researchers have investigated the responding mechanism of water regime and nitrogen supply on the yield of wheat plants [20, 21]. The effects of water status and nitrogen application on leaf gas exchange have also been measured [22–24]. However, the research results have not been consistent due to differences in the planting area, experimental design, varieties and fertilizer levels.…”