We meet a press photographer who gave up work and moved to Hawaii to immerse himself in tropical fruit; an actor trying to orchestrate a community orchard on a vacant lot in Hollywood; and an Italian who spends her days scrutinising Renaissance art to ascertain the exact fruit varieties depicted.

Canadian filmmaker Yung Chang spent two years shadowing people with such a profound penchant for fruit that one of them describes it as an obsession that has ''blossomed into a full-time case of insanity''.

But it's an obsession that is also blossoming into something of a rally cry for preserving fruits in all their diversity. The film is like an ode to the edible fruiting plant. Since it was made last year, The Fruit Hunters has been screening at environmental film festivals around the world, and a few months ago won the top prize at a festival in Paris.

''There are two different ways of looking at fruit,'' Chang says in the film's voiceover narration.

''One way is the search for the single perfect crop, tough enough to be shipped around the world. The other approach is to always search for something new, not just for your own personal pleasure, but to become a guardian of biodiversity.''

Chang's way of looking at fruit changed after he read a 2008 book, also called The Fruit Hunters, which dissects every aspect of people's relationships with these ''seed envelopes'' that have ''fuelled wars, dictatorships and the discovery of new worlds''.

Written by his friend, Adam Leith Gollner, who lives in the same area of Montreal as Chang, the book traverses matters of taste, science, erotica, commerce, history, discovery and mania. In his compelling and rollicking read, Gollner seems as irrepressibly obsessive as the fruit devotees he interviews.

His descriptions of fruits are so vivid you want to devour them yourself. The ice-cream bean snipped from a tree in Hawaii is ''a snowy, sweet, cotton-candy-like substance with hints of vanilla cream coursing through its veins''. ''It's like eating cloud,'' Gollner writes. ''It's the most delicious thing I've ever tasted. I can see how it might make someone dance with joy.''

Chang, who read the book while in Australia to promote his previous film, Up the Yangtze, says it prompted his consumption of fruit to escalate immediately. He asked all those he met to recommend fruits he could try.

But the idea for making a film from the book only dawned on him later - after he started to mull over whether the ''Rare Fruit Council International'' that Gollner described could actually exist.

''I went on a little research trip to Miami to verify it and I met all kinds of hobbyist horticulturalists and I got hooked by their energy and enthusiasm,'' he says. ''People only talked about fruit and how to grow it, they didn't talk about politics or anything else.''

Gradually, Chang says he was alerted to a whole network of people with a fetish for growing and eating fruit.

While some of the subjects of Chang's film appeared in Gollner's book, Chang also filmed other fruit hunters - actor Bill Pullman, for example, who for more than 20 years has been growing more than 100 different exotic fruits in his backyard in the Hollywood hills in California.

Australians Alan and Susan Carle, who have established a private botanical garden in north Queensland, were ''highly recommended by fruit hunters'', but ultimately were among those Chang didn't have the budget to visit.

Chang (and also Gollner) did, however, visit a garden in Miami - named after late botanist and plant explorer David Fairchild - where horticulturalists have spent 20 years attempting to graft the rare wani mango (Mangifera caesia). Also filmed is a Honduran scientist developing an alternative to the Cavendish banana.

In his book, Gollner visits plant breeders who consider ''the hubbub over ancient varieties'' nothing more than sentimentality. Gollner himself says the best raspberry he has tasted (the ''Tulameen'') was bred in Canada in the 1980s, while one of the finest strawberries (the ''Mara des Bois'') was developed in France in 1990. But there is no fruit either Gollner or Chang decries.

Since making the film, Chang has found himself bringing home cumquat seeds from a trip to Rome and making preserves from the fruits of a sour cherry tree growing near where he lives. He wants others to follow suit.

''I hope this film satiates the desires of individuals who can't get around to travel everywhere,'' he says. ''And that it encourages people to look at fruit in their own backyards.''

■ The Fruit Hunters screens at Kino Cinemas tonight at 8.10pm. The Environmental Film Festival Melbourne runs until September 13. effm.org.au