High-throughput phenotyping tool for heat stress impact on biological nitrogen fixation in soybeans

Overview

Biological nitrogen fixation (BNF) is a critical driver of soybean sustainability, yet heat stress threatens rhizobia viability and the physiological processes that support BNF, ultimately limiting yield. This solution offers a high-throughput phenotyping tool that uses canopy reflectance spectra and thermal imaging to capture the complex interactions between heat stress, nitrogen availability, rhizobia strain, genotype, and growth stage. By linking canopy temperature and spectral indices to BNF activity, the tool enables breeders and agronomists to rapidly screen for heat-tolerant soybean genotypes that maintain BNF and yield under elevated temperatures, with potential extension to other legume crops.

Technical specifications

Core approach:

• Combines thermal and hyperspectral cameras with IR thermometers to track temporal canopy responses during flowering and pod fill
• Leverages spectral indices derived from reflectance spectra to detect heat stress impacts on BNF across controlled environments and field settings
• Quantifies BNF, seasonal fixed nitrogen, and plant nitrogen uptake using the ureide method and natural 15N isotope balance
• Tests the effects of nitrogen fertilizer and rhizobium strains under contrasting genotypes
• Associates yield and quality parameters with BNF based on canopy temperature and/or reflectance-based indices
• Designed for both controlled growth chamber conditions and field deployment

Key differentiators:

• First tool to address the heat stress–BNF interaction in soybeans
• First high-throughput phenotyping approach across abiotic stresses including drought for rapid, accurate BNF assessment
• Scalable temporal and spatial resolution suitable for breeding program integration

Technology readiness level

This is an early-stage research initiative co-led by the Crop Physiology lab (Dr. Jagadish) and the Farming Systems lab (Dr. Ciampitti) at Kansas State University. Validation will involve phenotyping genotypes with contrasting responses under control and heat stress conditions in both growth chambers and field settings. Current readiness is at the concept and initial experimental validation stage, with future work focused on refining the spectral and thermal indices into a reliable phenotyping tool deployable in breeding pipelines and extensible to other legume crops.