A visit to Suva’s only Japanese restaurant prompted some googling. First, there was the name of the place: Daikoku. Daiwhat? Turns out this is the name of the Japanese Buddhist god of wealth, farmers, agriculture, rice and the kitchen. 
Which would have been cool enough. But then I asked myself, what is this wasabi anyway? Sure, the Japanese version of horseradish. But the same as “normal” horseradish, or what? I’m ashamed to have to report that I simply didn’t know.
So, to summarize. The horseradish is Armoracia rusticana, in the Brassicaceae. It probably originated in western Asia. Cultivation for its pungent root goes back to antiquity. But the “Horseradish Capital of the World” is apparently Collinsville, Illinois, from a small region around which comes over one third of the United States’ production and/or 60% of the world’s supply depending on who you read. Which actually brings me to the serious point that I wasn’t able to get hold of global production statistics, and not for want of trying. FAOSTAT doesn’t have anything on horseradish, for example. Anyway, you can go to an International Horseradish Festival in Collinsville every May to find out more. Wasabi, on the other hand, is Wasabia japonica (there’s a couple of other species as well, though). Also in the Brassicaceae, but again I wasn’t able to find out if Wasabia and Armoracia are much related, though I doubt it. The pungent flavour in both cases — as generally in crucifers — is due to glucosinolates. Wasabia is native to Japan, where it has been cultivated for its rhizome since the 10th century. Traditionally, it is prepared using a sharkskin grater. The plant requires flowing water and a small number of districts in Japan specialize in its cultivation (e.g. the Izu peninsula), although it is also grown in other parts of the world. But there is imitation wasabi on the market which is apparently made of Western (let’s call it) horseradish, mustard and green colouring. Pass the sushi. And make mine the shark-grated stuff.