The influence of drought and breeding on root biomass and rooting depth of „Swiss Bread Wheat Genotypes“ (Affiliated)

Wheat breeding in the last century was mainly based on selecting for shorter varieties allowing increasing fertilizer inputs without the side-effect of lodging. This led to a strong increase of the harvest index from 35% to 50% harvested grain per unit total shoot biomass - the driving factor for yield increase during the green revolution. It may be anticipated, that breeding for shorter above ground biomass, may reduce below ground biomass in a similar manner. However, sufficient uptake of water from deep soil layers is crucial for high and stable yield in water limited cropping systems and might be increasingly important for Swiss agriculture. Accordingly, breeders may have indirectly counter selected for deep root systems. But deep rooting may have more benefits: deep carbon input into soil was proposed as one solution mitigates global atmospheric CO2 rise. It is expected that enhanced root biomass and rooting depth in deeper soil layers could have a positive effect on the amount of atmospheric carbon.

We therefore study the influence of drought and/or breeding on root architecture, rhizodeposition and decomposition of rhizodeposits under field and greenhouse conditions.

We tested the 14 most important Swiss Era Wheats (genotypes from the top and first class of the Swiss bread wheat breeding program) released between 1900 and 2011 on the interaction of root architecture and drought tolerance in the field and in the greenhouse. In the greenhouse, we developed the Deep Root Observation Platform (DROP) where above and below ground plant development can be monitored. The DROP enables to observe the plant development until maturity under simulated field conditions. In the field, natural abundance of ¹⁸O to determine water uptake depth of the plants and new methods such as core-break count method and shovelomics for determining root traits were used. Furthermore, a subset of 4 or 2 contrasting genotypes were studied for their rhizodeposition and decomposition of rhizodeposits using ¹³C stable isotope pulse/continuously (using the multi-isotope labelling in a controlled environment (MICE) facilities) labelling techniques and computed tomography (CT) under greenhouse conditions.  

Funding:
National Research Program NRP68 – Soil as a resource (SNSF)