CHARACTERIZATION OF FATTY ACIDS FROM BLUEBERRY AND CRANBERRY FLOWERS AND THEIR EFFECTS ON THE FRUIT ROTTING PATHOGEN COLLETOTRICHUM FIORINIAE
Applied Research
Timothy Waller
Agriculture & Natural Resources County Agent III
Rutgers
Millville
Abstract
The bloom period is the critical disease control window in blueberry and cranberry, yet the biological factors underpinning this period are only now coming to light. Previously, aqueous and chloroform-based floral extractions were shown to stimulate secondary conidiation and appressorial formation in Colletotrichum fioriniae. Floral chemical signals also decrease wetness period requirements and temperature optima of C. fioriniae. Thus, it appears that plant signals produced or present during bloom play a critical role in the disease cycle of this latent fruit rotting pathogen. Initially floral nectar sugars were thought to be the main source of pathogen stimulation, however when compared directly to floral extracts, sugars were significantly less stimulatory. The next logical source of stimulation; the waxy cuticle covering the surfaces of plants, moreover the interface between host : pathogen. This surface composed primarily of cutin (hexadecanoic and octadecanoic fatty acid derivatives). In order to better understand the fatty acid composition within multiple blueberry and cranberry tissues, cultivars, and extraction types tissues were extracted with chloroform and subjected to a GC-FAME (GC-MS) procedure (characterization of C9:0 – C20:0 fatty acid derivatives). Identified and characterized fatty acid concentrations were estimated for each tissue by comparing to a standard curve. The samples clustered by crop, tissue, and extraction type. The aqueous extractions from both crops were found to have three compounds in common; hexadecanoic (C16:0), octadecanoic (C18:0) and decanoic acid (C10:0) fatty acids, meaning that cutin monomers were capable of being mobilized into water. Hexadecenoic acid was found to be most abundant during bloom. The bioactivity of fatty acids was assessed in a glass coverslip bioassay. Decanoic acid was found to stimulate secondary conidiation, hexadecenoic acid was found to stimulate appressorial formation and minimal conidiation, and octadecanoic acid was non-stimulatory. It appears likely that hexadecanoic fatty acid plays a crucial role in pathogen recognition of host surfaces.
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Authors: T. Waller, P. Oudemans, M. Haggblom, J. Gager
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Waller, T. Agriculture & Natural Resources County Agent III, Rutgers, New Jersey, 08332-9776
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Oudemans, P. Extension Specialist, Rutgers University, New Jersey, 08019
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Haggblom, M. Department of Biochemistry and Microbiology, Rutgers University, New Jersey, 08901
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Gager, J. Plant Biology, Rutgers University, New Jersey, 08019