Improve Crops in Arid Regions and future climates

Experimental setups – Mapping of radiation in the two glasshouses where the load cell platform at IRD-Montpellier is installed is on-going and will be completed in 2024.   

In WP2-a, following the progress from 2022, we confirmed that: (i) plants with a smaller leaf to root area ratio restricted transpiration more; (ii) the leaf to root area ratio was somewhat larger in sorghum than in pearl millet, although not in all experiments, suggesting interactions with the environment; (iii) Soil had no influence on the leaf to root area ratios in sorghum but appeared to be larger in the sandy than in the clay soil for pearl millet. In addition, experiments on the transpiration response following ablation of about 50% of the root system, confirmed wide variations for both sorghum and pearl millet in the root’s capacity to channel water to support transpiration.

In WP2-b, testing the response to an increase sowing density in sorghum has been expanded to locally bred varieties and the paper reporting earlier density response results has been submitted. We have progressed with the formalization and measurement of 16 new traits characterizing the 3D architecture of the canopy (and which could explain light distribution differences hence possibly transpiration efficiency differences reported earlier). Using these traits, a multi-factor model using deep learning method has been identified with the capacity to distinguish genotypes more efficiently than usual single-factor phenotyping analyses. This model will be now applied to genotypes contrasting for their response to sowing density. A paper reporting this work is currently under review.

On the applied side of the response to an increased density, a first campaign has been carried out in farmer’s fields with exciting results in pearl millet: higher sowing density increased grain and straw yield by about 30-40%, on average across two communities representing contrasting rainfall conditions. These results were obtained both with locally adapted and improved varieties. Repeat of this work will be done in 2024 and shows the huge potential of crop intensification for Senegal’s food security, both for human and cattle populations. This practice can indeed enhance production of adapted crops like sorghum and pearl millet and reduce dependence on imported crops like wheat or rice.

In WP3, the analysis of pearl millet transpiration efficiency (TE) data is completed and a paper has been submitted, reporting genetic variations, differences among hybrids bred for wet and dry zones, and genotype-by-environmental effect justifying the need to re-focus on traits underlying TE rather than TE itself. To support this claim, a full GWAS analysis is under way to report the near absence of major SNP peaks for TE in both sorghum and pearl millet, in contrast to recent results in rice. These results, and the comparison to other species, suggests a multigenic determinism of TE in two drought-adapted species.

A lot of phenotyping efforts have also been made for traits underlying TE, like the transpiration response to an increased VPD, with several datasets generated and ready for GWAS, a refined protocol that has been tested and validated, and a pipeline of analysis of high throughput phenotyping platforms fully revisited and corrected.