Screening of Florida sugarcane varieties against Thielaviopsis spp., the causal agent of pineapple disease

The Florida sugarcane industry is transitioning from manual to mechanical planting systems, which use comparatively smaller seed cane pieces (billets) as planting material. A major limitation of mechanical planting is the increased seed cane requirement due to mechanical damage and the increased vulnerability of seed cane pieces to soil-borne pathogens that cause sett rots, particularly pineapple disease caused by Thielaviopsis spp. Current sugarcane breeding programs in Florida screen for major diseases such as rusts, smut, ratoon stunting, and viruses early in the breeding process, but not for pineapple disease. This study aimed to isolate and identify Thielaviopsis spp. in the Everglades Agricultural Area (EAA), develop a single-bud inoculation protocol for greenhouse-based disease screening, and phenotype the current widely grown sugarcane varieties in Florida against Thielaviopsis spp. The pathogen was confirmed as T. ethacetica, consistent with previous reports from the EAA. A reproducible inoculation method was established and validated through symptom assessment, pathogen re-isolation, and molecular confirmation. Using this protocol, six widely grown Florida sugarcane varieties showed significantly reduced germination (by more than 50%), as well as reduced above- and below-ground morphological characteristics under infection, indicating susceptibility. Varietal differences were observed, with CP 03-1912 showing the highest mortality percentage and reduced growth under T. ethacetica infection. These findings highlight the vulnerability of current varieties to pineapple disease, especially under mechanical planting systems where smaller seed cane pieces are used. Furthermore, the developed inoculation protocol provides a scalable tool for early-stage evaluation of resistance in breeding programs, offering potential to accelerate the development of varieties better adapted to mechanical planting.