Citrus hope: the navel variety M7 at the Chisletts' orchard.
http://www.weeklytimesnow.com.au/article/2009/05/01/73691_horticulture.html
Chisletts show off M7 orange
Sandra Godwin
May 1, 2009
THERE is renewed excitement in the Australian citrus industry, thanks to a new variety of early-maturing navel orange.
Known as M7, it is being developed by growers Greg and Susan Chislett at their orchard at Kenley, northwest of Swan Hill in Victoria.
The consensus at last week's open day for growers, packers and agronomists was that the Chisletts had found a winner.
Thought to be the earliest-maturing navel orange anywhere in the world, M7 is round, sweeter and superior in every way to the elongated navelina 7.5 clone that inadvertently created it.
Mr Chislett said the variety's other advantages were its even early colouring, the ability to be harvested over an extended period, firmer skin, less albedo breakdown, less oleo (oil glands in the skin) and that it was less prone to blemishing.
"It eats better at any stage because the brix (sugar to water ratio) is usually 1.5 degrees higher, and acid has always been higher too," he said.
"In the four years since 2005, the acid has always been higher, which is good for flavour and also shelf life.
"We have harvested it over a four-month period and it holds up very well. At the end of the day, hopefully growers are going to make more money." Mr Chislett said the perfectly round shape would give the M7 an advantage over navelinas, which were often rejected in Asian export markets because of their uneven elongated shape.
NSW Department of Primary Industries research horticulturalist Graeme Sanderson said the variety was one of the best naturally-occurring mutations he had seen in 20 years of citrus breeding.
"What stands out in the three years of data we have is the high sugar content, sweet taste and the fruit is round," he said.
"It shows you don't have to be a plant breeder to get something worthwhile. You just have to keep your eyes open. Some of the better things come up through natural mutations and this is one of those cases. I think this is probably a good proposition for this area and could well become a major variety down the track."
Mr Chislett discovered the M7 as he was walking through a block of navelina trees in May 2004 and spotted a sport limb - a naturally occurring mutation - with fruit that had matured three weeks earlier than the rest of the tree.
He marked it so it would not be pruned by accident and budwood was grafted on to two different rootstocks five months later.
Trials have included a comparison with five other varieties top worked onto what were originally valencia orange trees.
The M7 has already attracted interest from Spain and South Africa, even though it is only in its sixth season of testing and evaluation.
It is the second new variety Mr Chislett has found at Kenley - in 1986 he identified a late-maturing summer navel which hit the market in 2003 under the brand name Chis-Elite.
As well as the 64ha citrus and avocado orchard, the Chisletts operate a container-grown citrus nursery which produces more than 60,000 trees a year.
On show: Greg Chislett shows a group of growers and packers the new early navel variety, M7. 
