This Is AuburnElectronic Theses and Dissertations

Fungal endophyte presence in relation to various nutrient regimes applied to Gossypium hirsutum




Middleton, Elizabeth

Type of Degree

Master's Thesis


Entomology and Plant Pathology


Proper nutrient conditions are necessary for optimal growth and yield of Gossypium hirsutum. This can be achieved through fertilizer application, but plants may also be assisted by fungal endophytes, potentially beneficial microorganisms in the tissue of plants. In the Southeastern United States, Cotton leafroll dwarf virus (CLRDV) is a concern for cotton producers; however, a potential management strategy is the use of fungal endophytes. Experiments in 2022 and 2023 evaluated culturable fungal endophytes from the foliage of G. hirsutum growing in various nutrient regimes at the Cullars Rotation (Auburn, AL), where the soil fertility treatments have been in place for over 100 years. The isolated genera included Alternaria, Cladosporium, Colletotrichum, Diaporthe, Fusarium, Phoma, and Stemphylium. In 2022, the relative abundance of Colletotrichum truncatum was around 50% in the no potassium regime, Diaporthe sp. abundance was over 50%, in the no phosphorous regime, and Alternaria abundance was around 25% in all sampled regimes except the no potassium regime. The only endophytic species isolated from the no potassium regime in 2023 were Stemphylium vesicarium and S. solani. Relative to endophyte diversity, a significant difference (P ≤ 0.05) was observed in 2023 between the no potassium regime and all other sampled regimes. Incidence of CLRDV was determined in the Fall of 2023 to observe whether infection differs among G. hirsutum treated with various nutrient regimes or if it relates to endophytic presence. The results were insufficient to further explore a relationship between CLRDV, endophytes, and nutrients. The fungal endophyte microbiome in G. hirsutum leaf tissue was analyzed in 2023. In relation to fungal endophyte diversity, the no potassium regime was significantly different (P ≤ 0.05) from all other sampled regimes. The relative abundance of Stemphylium was over 50% of the population in the no potassium regime. Diaporthe abundance was high, greater than 50% of the community composition in the no phosphorous regime. Stemphylium spp. and Colletotrichum truncatum were identified as indicator species, signifying differences in the community based on the applied nutrient regime. The findings of this research indicate that fungal endophyte presence may be impacted by nutrient regimes applied to G. hirsutum.