Objective The resistance of Liaomian cotton to verticillium wilt was studied to aid disease control.

Methods In 2022-2023, 29 varieties of Liaomian cotton in Liaoning Province were evaluated for their resistance to verticillium wilt using multiple means including field disease nursery evaluation, in vitro Verticillium dahliae Vd991 inoculation on seedlings, and staining assay on burst of reactive oxygen species (ROS) in seedling stems and Morks as control. Euclidean distance-optimized data transformation with sum of squared deviations was applied to cluster the selected resistant species for classification.

Results The Liaomian series of cotton cultivars displayed significant resistance to the wilt at the nurseries in Liaoyang, Liaoning and Shijiazhuang, Hebei. Among them, 13 varieties were rated resistant (R) or highly resistant (HR). Although the indices of the in vitro inoculation test on the seedlings were relatively high, 12 of them were shown to be tolerant of the disease, as similarly indicated in the field test. In addition, the NBT and DAB staining on the seedling stems after ROS burst suggested that 11 varieties to be wilt resistant. Overall, LM19, LM23, LM25, LM27, LM33, LM40, and LM42 displayed stable and considerate resistance to verticillium wilt. The cluster analysis using the Euclidean distances of 3.25 and 4.0 classified the 29 cotton varieties into 5 categories. A comparative analysis on the cluster distribution revealed that the disease resistance of the plants tended to be higher on the more recent bred varieties.

Conclusion The varieties of Liaomian cotton carried verticillium wilt resistance in the genetic pool. Through enhancing the existing and/or incorporating new resources, they could be applied in breeding disease-resistant cotton for farming.