P-176 - Beyond detection: Can qPCR be used to better understand Fusarium wilt in cotton?

Fusarium oxysporum f. sp. vasinfectum (FOV) causes Fusarium wilt in cotton (Gossypium hirsutum). FOV is divided into several races, with races 1, 2, 3, and 4 present in Texas. This research aimed to assess the significance of quantifying FOV in roots using quantitative PCR (qPCR). A survey of 75 Texas cotton fields in 2023 revealed that FOV was more prevalent in necrotic root samples (52%) than healthy samples (8%); however, there was no significant difference in pathogen densities on roots. FOV was quantified in roots in four variety trials: one trial with race 4 and one with race 3 in 2023, and two trials with race 1 in 2024. Despite low disease severity across trials, pathogen density and visual severity ratings were correlated, with significant differences in FOV density among varieties within trials, even when severity ratings were similar between varieties. The site with the highly virulent race 4 had the highest pathogen density, and an inverse correlation between pathogen density and yield. FOV density on roots with races 1 and 3 were not correlated with yield.  These are the first studies where root FOV quantification has been utilized to evaluate Fusarium wilt in cotton.