Phytophthora resistant asparagus variety to be released in NZ and Europe

New Zealand asparagus growers will shortly have access to the first asparagus variety that is tolerant of the soil fungus Phytophthora. This is the first disease tolerant asparagus variety produced in 100 years since tolerance to asparagus rust was developed in USA.

New Zealand grower and breeder Dr Peter Falloon, together with NZ Asparagus Council (NZAC) has identified at least one hybrid that shows higher yields under high disease pressure from Phytophthora rot than the best commercial varieties during evaluation trials.

The Phytophthora-resistant asparagus breeding programme started in 1985 when a search was made for a source of resistance to Phytophthora in asparagus.

Asparagus varieties from every breeding programme in the world were tested but none were found that had high levels of resistance. However, a few plants were found that resisted the disease when exposed to several isolates of P. asparagi and P . cryptogea that had been collected from asparagus from many different fields.

The work continued at Lincoln from 1990 with support from the Foundation for Research, Science and Technology (FRST) and the NZ Asparagus Council. Funding from the Sustainable Farming Fund (SFF) together with assistance from the NZ Asparagus Council helped establish national cultivar evaluation trials in the main asparagus producing regions so the Phytophthora-tolerant hybrids could be compared to the best non-tolerant commercial varieties.

Falloon explained that Phytophthora is a signifcant disease in asparagus in most countries around the world, he spent 3 years in California where he saw establishment failures as high as 80% and yield losses of over 50%. The disease has traditionally been treated with chemicals, which not only are expensive but cease to work after around 7 years as the disease builds resistance to them.

"There is lot of replanting of asparagus in the same fields due to limited areas of suitable soil, this causes higher disease levels in the soil, our trials have shown better yields than standard varieties, they also last 3 or 4 years longer than current varieties meaning that the growers won't have to replant so often." Current varieties in New Zealand have a life span of about 10-12 years, depending on the conditions, and in Europe 7 years, if this can be extended it would save growers a lot of expense as planting is the biggest cost after harvest labour. This new variety is also good news for organic growers who are unable to use any chemicals to fight Phytophthora.

The new variety, Pacific Challenger, will be released to New Zealand growers later this year, a small amount of seeds have been sent to European plant breeder Hargreaves Plants. At the moment there is only a small volume but Falloon says that he hopes to increase the amount by 15-20 times next year.