ROME, Nov 27 (Reuters) - A 1.5-kg white truffle found in the Italian countryside will be sold at a charity auction in Macau where it is expected to fetch 150,000 euros (S$321,645).

Truffle hunter Cristiano Savini displayed his precious find at a five-star hotel in Rome on Tuesday before it was flown to the Chinese enclave for Saturday's auction.

Savini's dog, Rocco, sniffed out the truffle, one of the biggest unearthed in the past 50 years, by an oak tree near Pisa last weekend, in an area of Tuscany where Cristiano and his father scout for truffles every year.

Ten years ago, they found a half-kilo white truffle by the same tree.

The truffle was 75 centimetres underground. As two men dug deeper, the dog went "wild", jumping from one side to the other as if to indicate they had to enlarge the hole.

"This is very unusual in truffle hunting - rather than digging down and narrowing towards the spot where the truffle was, we had to dig wider and wider, like in a reverse cone," Savini said.

It took Savini and his father more than an hour to get the truffle out.

Savini decided to donate his truffle to organisers of the Macau auction. "Even if the truffle is very much linked to trade and money, we took this one as a gift, a gift to us - me and my family," he said.

A truffle of the same size, found in Italy's truffle town of Alba, was bought for 125,000 euros by a Hong Kong bidder last year.

According to media reports, the 1.5-kg truffles were the biggest since a 2.5-kg truffle was found in 1954 and presented to former U.S. President Dwight Eisenhower.