Effects of Fungal Endophyte Treatment and Herbivory on Extra Floral Nectar Carbohydrate Composition in Cotton

Fungal endophytes are microorganisms, living in plant tissue, that cause no symptoms of disease. Plants can be inoculated with endophytic fungi in order to measure phenotypic responses. In this study, cotton seeds were inoculated with different fungal endophytes (Beauveria bassiana, Chaetomium globosum, and Phialemonium inflatum) and the effect on the carbohydrate composition of the extrafloral nectar (EFN), was assessed using high performance liquid chromatography (HPLC) with a refractive index detector. Extrafloral nectaries were sampled from the base of the blooming flower of the cotton plant. Extrafloral nectar secretions play a role in plant defense by attracting predatory insects to consume plant damaging insects. The carbohydrate compositions were compared with a constitutive profile, which is the normal EFN secretions, and an induced profile, which is the EFNs produced as a result of damage to the plant. The induced profile was achieved by subjecting the plant to herbivory by Spodoptera exigua. To collect the EFN constitutive samples, cotton plants were grown in a greenhouse and 5µl of EFN was collected from the base of the first or second flower. Then, the leaf from the next fruiting branch was infested with third instar Spodoptera exigua. Upon flowering, another 5µl of EFN was collected to make up the induced sample. The samples are to be filtered before using HPLC and later analyzed to compare the carbohydrate composition.