Disappointment the world's largest potato... may not be one at all.  

Waikato couple Colin and Donna Craig-Brown last year unearthed a massive tuber in their garden. 

Weighing 7.9 kilograms, Doug the Spud hit headlines worldwide.  

But Guinness World Records has now told them a DNA test shows Doug isn't a potato but a "tuber of a type of gourd”. 

Colin told Andrew Dickens they've had the run-around. 

“It was a lot of secret squirrel stuff, you ring up and ask a question or send an email you wouldn’t get a reply for like 2 weeks and when you did it was an incomplete, non-committal kind of, well, let’s fob him off.” 

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