TY - BOOK
T1 - Genetic Variation in Deep Root Growth of North-European Winter Wheat
AU - Ytting, Nanna Karkov
PY - 2015
Y1 - 2015
N2 - Increased rooting depth in crops is known to enhance nitrogen use from deep soil layers and increase drought tolerance. Both parameters are known to increase productivity when natural occurring topsoil resources are scarce and input to the agricultural system is limited. Problems with nitrogen leaching from agricultural soils in Northern Europe has caused a strict legal limitation on
nitrogen fertilization in the region. Leached nitrogen is therefore a highly valuable resource but, if left unexploited, a potential cause of environmental problems for the aquatic environment. Plant breeders and scientists wish to develop screening methods that allow breeding for genotypes with
increased deep root growth for effective N uptake.
The study revealed that tube rhizotrons allows for screening of root traits in close-to-field conditions. It is important to perform the screening in relevant seasons and environments, as the interaction between genotypes and environment is substantial for most root traits. Root quantification with the line intersect method can be optimized by choosing the right strategy when
scoring the root traits. For example, by adapting counting grids to match specific root densities, data variability can be decreased at low root intensities and man hours can be minimised at high root intensities. In rooting depth measurements data variability can be decreased by recording the depth
below which 5, 10 and 25 roots are observed compared to root depth measurements of the deepest root.
Deep root traits were found to vary between modern North-European winter wheat cultivars including variation in depth penetration rate and root density in the deepest part of the root system. Wheat was shown to be capable of using deep N resources. After three to six weeks of root proliferation in the N rich subsoil, 21 to 39 % of the deep N was utilized for shoot growth. Furthermore, the tested cultivars indicated variation in root response to deep N and in N uptake. Increased root density at depth improved N content in the shoot at moderate to high subsoil N levels (3.2 to 12.5 mg N mg-1 soil). However no correlation between root length density in the subsoil and shoot N content was found at higher subsoil N levels (> 12.5 mg N kg-1 soil). Shoot size and
especially average tiller size was highly correlated to subsoil root density (R2 = 0.26 – 0.37, p ≤ 0.001). Low N levels (< 3 mg N kg-1 soil) in the subsoil can be a limiting factor for effective deep water utilization. Root length density was reduced by 42 % at low subsoil N levels and especially the length of large and medium sized roots (diameter > 0.25 mm) was reduced. At these low subsoil N
levels, it appeared that increased root density reduced the total N content of the shoots.
Overall the results show, that variation exists for deeper root traits in existing elite germplasm adapted to North Europe. This opens the way for wider screening to assess the value in breeding for deeper roots in winter wheat. Deeper rooting, but not necessarily higher subsoil root density, has the potential to increase deep N utilization by winter wheat.
AB - Increased rooting depth in crops is known to enhance nitrogen use from deep soil layers and increase drought tolerance. Both parameters are known to increase productivity when natural occurring topsoil resources are scarce and input to the agricultural system is limited. Problems with nitrogen leaching from agricultural soils in Northern Europe has caused a strict legal limitation on
nitrogen fertilization in the region. Leached nitrogen is therefore a highly valuable resource but, if left unexploited, a potential cause of environmental problems for the aquatic environment. Plant breeders and scientists wish to develop screening methods that allow breeding for genotypes with
increased deep root growth for effective N uptake.
The study revealed that tube rhizotrons allows for screening of root traits in close-to-field conditions. It is important to perform the screening in relevant seasons and environments, as the interaction between genotypes and environment is substantial for most root traits. Root quantification with the line intersect method can be optimized by choosing the right strategy when
scoring the root traits. For example, by adapting counting grids to match specific root densities, data variability can be decreased at low root intensities and man hours can be minimised at high root intensities. In rooting depth measurements data variability can be decreased by recording the depth
below which 5, 10 and 25 roots are observed compared to root depth measurements of the deepest root.
Deep root traits were found to vary between modern North-European winter wheat cultivars including variation in depth penetration rate and root density in the deepest part of the root system. Wheat was shown to be capable of using deep N resources. After three to six weeks of root proliferation in the N rich subsoil, 21 to 39 % of the deep N was utilized for shoot growth. Furthermore, the tested cultivars indicated variation in root response to deep N and in N uptake. Increased root density at depth improved N content in the shoot at moderate to high subsoil N levels (3.2 to 12.5 mg N mg-1 soil). However no correlation between root length density in the subsoil and shoot N content was found at higher subsoil N levels (> 12.5 mg N kg-1 soil). Shoot size and
especially average tiller size was highly correlated to subsoil root density (R2 = 0.26 – 0.37, p ≤ 0.001). Low N levels (< 3 mg N kg-1 soil) in the subsoil can be a limiting factor for effective deep water utilization. Root length density was reduced by 42 % at low subsoil N levels and especially the length of large and medium sized roots (diameter > 0.25 mm) was reduced. At these low subsoil N
levels, it appeared that increased root density reduced the total N content of the shoots.
Overall the results show, that variation exists for deeper root traits in existing elite germplasm adapted to North Europe. This opens the way for wider screening to assess the value in breeding for deeper roots in winter wheat. Deeper rooting, but not necessarily higher subsoil root density, has the potential to increase deep N utilization by winter wheat.
UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01009153733&context=L&vid=NUI&search_scope=KGL&tab=default_tab&lang=da_DK
M3 - Ph.D. thesis
BT - Genetic Variation in Deep Root Growth of North-European Winter Wheat
PB - Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
ER -