Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops

Title 
Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops 
Publication Type 
Journal Article 
Authors 
Wasson AP, Richards RA, Chatrath R, Misra SC, Prasad SVS, Rebetzke GJ, Kirkegaard JA, Christopher J, Watt M 
Year of Publication 
2012 
Volume 
63 
Journal 
Journal of Experimental Botany 
Issue 
Pagination 
3485 - 3498 
Date Published 
05/2012 
ISSN 
1460-2431 
Keywords 
Architecture, branch root density, Disease resistance, drought, Flowering time, genetics, grain-filling period, gravitropism, molecular markers, Phenotyping, radial hydraulic conductivity, root-based constraints, toxicity resistance, vigour, water use efficiency, Wheat 
URL 
http://www.ncbi.nlm.nih.gov/pubmed/?term=Traits+and+selection+strategies+to+improve+root+systems+and+water+uptake+in+water-limited+wheat+crops. 
DOI 
10.1093/jxb/ers111 
Abstract 

Wheat yields globally will depend increasingly on good management to conserve rainfall and new varieties that use water efficiently for grain production. Here we propose an approach for developing new varieties to make better use of deep stored water. We focus on water-limited wheat production in the summer-dominant rainfall regions of India and Australia, but the approach is generally applicable to other environments and root-based constraints. Use of stored deep water is valuable because it is more predictable than variable in-season rainfall and can be measured prior to sowing. Further, this moisture is converted into grain with twice the efficiently of in-season rainfall since it is taken up later in crop growth during the grain-filling period when the roots reach deeper layers. We propose that wheat varieties with a deeper root system, a redistribution of branch root density from the surface to depth, and with greater radial hydraulic conductivity at depth would have higher yields in rainfed systems where crops rely on deep water for grain fill. Developing selection systems for mature root system traits is challenging as there are limited high-throughput phenotyping methods for roots in the field, and there is a risk that traits selected in the lab on young plants will not translate into mature root system traits in the field. We give an example of a breeding programme that combines laboratory and field phenotyping with proof of concept evaluation of the trait at the beginning of the selection programme. This would greatly enhance confidence in a high-throughput laboratory or field screen, and avoid investment in screens without yield value. This approach requires careful selection of field sites and years that allow expression of deep roots and increased yield. It also requires careful selection and crossing of germplasm to allow comparison of root expression among genotypes that are similar for other traits, especially flowering time and disease and toxicity resistances. Such a programme with field and laboratory evaluation at the outset will speed up delivery of varieties with improved root systems for higher yield.

 
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