Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops.
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.
SourceAvailable from: Jonathan P Lynch
[Show abstract] [Hide abstract]
ABSTRACT: Chickpea is increasingly being grown in tropical areas, and terminal drought is becoming a major constraint to its increased productivity. A trait-based selection approach can achieve further gains in drought tolerance that has been achieved through direct selection for yield. Separation of yield into its components including the rate of partitioning and its duration could permit a better focus on the most relevant trait for yield enhancement under terminal drought. Current work is aimed at understanding the importance of rate of partitioning or the partitioning coefficient (p) as a major contributory trait associated with drought tolerance both in germplasm and breeding lines. A reference collection of chickpea germplasm (n = 280) was evaluated in the field under both terminal drought and optimally irrigated environments; and a set of desi (n = 60) and kabuli (n = 60) advanced breeding lines under terminal drought. Grain yield was associated with its analytical components - crop growth rate (C), reproductive duration (Dr) and p. The path analysis showed that C and p had a large direct positive contribution to yield while Dr had a marginal but negative contribution to yield under drought. The direct contribution of p was the highest but it was marginally reduced by the indirect negative contributions of Dr. However, the total contributions of p to grain yield remained large. The yield of germplasm accessions under drought across the seasons were closely associated (r2 = 0.70) and also the genotype × year interaction was minimum. The contribution of C, Dr and p to grain yield were similar in the advanced breeding lines. However, kabuli breeding lines had a larger variation for p than the desi lines. The results suggest that a conscious selection for greater p will confer greater tolerance to abiotic stresses, given that terminal drought tends to curtail the length of the reproductive period.Field Crops Research 08/2013; 149:354-365. DOI:10.1016/j.fcr.2013.05.022 · 2.61 Impact Factor
Field Crops Research 01/2015; 174:1-11. · 2.61 Impact Factor
Anton Paul Wasson