Systems and methods for detecting a pathogenic organism

A method of detecting a presence and/or amount of a soybean rust fungus in and/or on an agricultural substrate suspected as being infected by the soybean rust fungus or in an environment surrounding said substrate, the method comprising:

• contacting an air sample of an environment surrounding a plant suspected as being infected by said soybean rust fungus with a gas-permeable carbon electrode, to thereby absorb said soybean rust fungus or a portion thereof, if present in said sample, to at least a portion of a surface of said electrode, to thereby obtain said gas-permeable carbon electrode having at least a portion of said soybean rust fungus absorbed to a surface thereof;
• subsequent to contacting said sample, contacting said electrode with an aptamer that selectively binds to said soybean rust fungus or said portion thereof, said aptamer has a nucleobase sequence selected from the group consisting of SEQ ID NO:8-18 and 32-36 and having biotin conjugated thereto;
• subsequent to contacting said aptamer, contacting said electrode with a phosphatase having avidin or streptavidin conjugated thereto;
• and
• subsequent to contacting said electrode with said phosphatase, contacting the electrode with an electrolyte solution containing a substrate of said phosphatase and performing said electrochemical reaction in the presence of said electrode, wherein an electric signal produced by said reaction is indicative of a presence and/or amount of said phosphatase, and is thereby indicative of a presence and/or amount of said soybean rust fungus or said portion thereof in the sample.