Spectral Reflectance Indices as a High Throughput Selection Tool in a Sesame Breeding Scheme

Abstract

On-farm genotype screening is at the core of every breeding scheme, but it comes with a high cost and often high degree of uncertainty. Phenomics is a new approach by plant breeders, who use optical sensors for accurate germplasm phenotyping, selection and enhancement of the genetic gain. The objectives of this study were to: (1) develop a high-throughput phenotyping workflow to estimate the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Red Edge index (NDRE) at the plot-level through an active crop canopy sensor; (2) test the ability of spectral reflectance indices (SRIs) to distinguish between sesame genotypes throughout the crop growth period; and (3) identify specific stages in the sesame growth cycle that contribute to phenotyping accuracy and functionality and evaluate the efficiency of SRIs as a selection tool. A diversity panel of 24 sesame genotypes was grown at normal and late planting dates in 2020 and 2021. To determine the SRIs the Crop Circle ACS-430 active crop canopy sensor was used from the beginning of the sesame reproductive stage to the end of the ripening stage. NDVI and NDRE reached about the same high accuracy in genotype phenotyping, even under dense biomass conditions where “saturation” problems were expected. NDVI produced higher broad-sense heritability (max 0.928) and NDRE higher phenotypic and genotypic correlation with the yield (max 0.593 and 0.748, respectively). NDRE had the highest relative efficiency (61%) as an indirect selection index to yield direct selection. Both SRIs had optimal results when the monitoring took place at the end of the reproductive stage and the beginning of the ripening stage. Thus, an active canopy sensor as this study demonstrated can assist breeders to differentiate and classify sesame genotypes.

Leveraging genomics and temporal high-throughput phenotyping to enhance association mapping and yield prediction in sesame

“…SVI can assist by tracking the plant's physiological status (Sarić et al, 2022). The use of NDVI and NDRE has been studied in other sesame populations (Dong et al, 2021;Petsoulas et al, 2022), and they reported similar results when these two indices reached the highest values at the peak of the reproductive stage (57 to 70 DAS) and then decreased as the plants started senescence. This suggests that our HTP platform is reliable for monitoring longitudinal traits in sesame, although additional analysis is required to dissect these traits in the vegetative phase.…”

“…Furthermore, this type of information can be used as a secondary trait for indirect selection and prediction of the target trait by exploiting the correlation between the traits (Rutkoski et al, 2016; Sun et al, 2017). In addition, spectral vegetation indices (SVI) can provide information about plant status and development (Tayade et al, 2022) and previous studies suggested that SVI calculated from HTP could increase the efficiency of indirect selection for seed yield and can be integrated into sesame breeding programs (Petsoulas et al, 2022).…”