Raman spectroscopy for early detection of fusarium oxysporum f. sp. vasinfectum race 4 in pima cotton seeds

Overview

This research proposes using Raman spectroscopy (RS) as a rapid, non-destructive tool for the early detection of the seed-borne fungus Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) in pima cotton seeds. FOV4 is a serious pathogen that threatens cotton production, and current detection methods rely on time-intensive laboratory assays performed after planting. By applying RS to seeds prior to planting, the project aims to establish a scalable seed certification program that helps growers avoid introducing infected seed into fields. The approach builds on prior success using RS to detect Huanglongbing (HLB) in oranges, demonstrating the feasibility of spectroscopic pathogen detection in plant tissue.

Technical specifications

Core approach:

• Raman spectroscopy scanning of cotton seeds to identify spectral signatures associated with FOV4 infection
• Confirmation of RS results using quantitative polymerase chain reaction (qPCR) to quantify fungal presence
• Correlation analysis between RS spectral data and qPCR results to validate detection accuracy

Experimental design:

• Twenty cotton varieties representing resistant, tolerant, and susceptible FOV4 response categories
• Field plots planted in El Paso, Texas, with four replications per variety, including both commercial and breeding lines
• Stand counts, soil sampling, and variety gene identification conducted during the growing season
• Plots harvested and ginned for seed collection
• Seeds evaluated first by RS, then confirmed by qPCR for fungal density

Key features:

• Non-destructive, pre-planting screening capability
• Potential to scale into a routine seed certification workflow
• Integration of spectroscopic and molecular diagnostic methods for higher confidence results

Technology readiness level

The project is at an early-to-mid validation stage. Prior laboratory work has established qPCR protocols for quantifying FOV4 in soil, evaluated cotton variety responses to fungal inoculum, and assessed the impact of inoculum density on yield. The current effort extends this foundation by testing whether RS can reliably detect FOV4 in seeds and how well RS results correlate with qPCR confirmation. The validation timeline runs from December 2020 seed harvest through December 2021 data analysis, with results to be presented at the Beltwide Cotton Conference in January 2022. Additional field seasons and larger sample sets will be needed before a commercial seed certification protocol can be deployed.