A tomato line hyposensitive to simulated proximity shade shows altered auxin-related gene expression and improved fruit yield under high-density field conditions

Plants detect the presence of nearby vegetation as a reduction in the ratio of red to far-red light (low R/FR). This proximity shade signal can be simulated in the lab by supplementing white light (W) with FR (W+FR). While shade avoidance strategies are considered undesirable in agricultural crops, FR supplementation enhances plant growth and fruit quality in tomato ( Solanum lycopersicum ).

Here we compared the response of different tomato genotypes to W+FR in the lab and identified one S. pennellii introgression line (IL2-2) with a shade-tolerant phenotype at the seedling stage.

Compared to the shade-avoider parental genotype M82, IL2-2 plants showed reduced elongation upon W+FR exposure and a disrupted expression of auxin-related genes both under W and W+FR. At harvest, W+FR treatment improved M82 fruit quality by increasing °Brix, ascorbic acid and carotenoids, and these quality traits remained virtually unchanged in IL2-2. Under high density (HD) conditions, fruit quality traits were hardly impacted by planting density or genotype, but IL2-2 showed improved fruit yield.

Our findings suggest that IL2-2 could serve as a valuable genotype for high-density or intercropping agrosystems.