Rootstock advances underpin citrus future

An official ceremony was held at Russel and Lisa Baker's Gayndah property to launch the variety, Barkley.

The plant was named after Patricia Barkley, a retired citrus pathologist who was instrumental in bringing new genetic material (rootstocks), including this particular rootstock, to Australia.

Queensland Department of Agriculture and Fisheries (QDAF) citrus breeder, Malcolm Smith, said the Barkley rootstock showed solid performance over the past 10 years of production in an Imperial mandarin rootstock experiment planted at Gayndah in 2004.

“It was one of 33 different rootstocks tested in this experiment and will now be established by AusCitrus for distribution to Australian growers," Mr Smith said.

“The field day was the first opportunity for growers to see mature trees on these different rootstocks, and consider their suitability for commercial use ahead of anticipated seed availability in a few years’ time.”

The field day was a joint collaboration between the Queensland Citrus Improvement Scheme, Citrus Australia and QDAF.

Mr Smith spoke on rootstocks, including Barkley, at the Citrus Technical Forum and Field Day in Mildura this month.

He said there was a lot going for the new variety.

"We think it's got some quite good promise, mainly in terms of orchard longevity but also the fruit quality's been good, the timing has been good and in low production it has been good," he said. 

"Rootstocks are really critical in terms of tree health. If you don't have good tree health, you don't have good quality.

"Our objective in all our rootstock breeding work is better fruit quality."

But he said there was a major caveat with that statement. 

"We can't just choose for better fruit quality because when we're choosing for rootstocks we are looking for a whole host of things," he said.

Breeders are working off a 1985 "wish list" of traits which has essentially remained unchanged.

An ever-present challenge to rootstock breeding is ensuring it is resistant to citrus tristeza virus (CTV).

"It would be very easy to go and breed new rootstocks and then all of sudden find out in 10 years time they are susceptible to tristeza. That would be really quite a disaster," Mr Smith said.

"So all of our hybrids really need to be CTV resistant and we've developed a much faster method of doing that by direct budding onto infected rootstocks instead of   putting an infected bud onto our hybrids."

He said there were about 800 hybrids that were now CTV resistant.

Molecular work could also improve efficiency when it comes to variety screening.

"We hope that we will be able to screen our seedlings to see whether they're going to come true to type from seed and be able to do that when they are a seedling rather having to wait for five years for it to produce fruit," he said.