Sprouting race hots up: Late-maturing varieties seem least affected by sprouting. by Eammon Conaghan
AS THE race heats up to develop pre-harvest sprouting-tolerant white wheat varieties, WA graingrowers have been updated on how to reduce their exposure to the problem and how to manage sprouted grain.
In a bad year, pre-harvest sprouting can cost Australia $100 million and in 2001 it was nature's cruel encore to bring down the curtain on a season of climatic calamity in the west.
In fact, WA's remarkable recovery from a harvest projection, at one stage, of just 4 million tonnes, to post its fourth all-time largest yield (more than 11 million tonnes), was tempered by the downgrading of wheat at receival, as record rainfall washed over south and north-west coastal growing regions.
At the recent GRDC-supported 2002 Agribusiness Crop Updates, Tim Setter, of the WA Department of Agriculture, outlined work by the Department's team of breeders, physiologists, cereal chemists, agronomists and molecular biologists in developing sprouting-tolerant varieties.
"In 2001, we made 33 crosses to locally adapted material, using lines supplied by Frank Ellison of the University of Sydney, which will allow us to develop substantially more sprouting-tolerant varieties than we previously had available," Dr Setter explained.
"The most sprouting-resilient commercial white-grained varieties available in Australia had been Sunlin and Sunelg in the east and Camm in the west, but new varieties SUN325 and SUN326 should equip us to deliver superior varieties."
SUN325 and SUN326 were derived from AUS1408, with a Hartog or Janz background, neither of which is well adapted to WA, but they should be good parents in local programs breeding for tolerance.
Work is underway to identify molecular markers for the two genes that confer sprouting resistance in AUS1408.
While breeding programs strive for tolerant varieties, Dr Setter recommended WA growers stick with the more sprouting-tolerant varieties such as Camm or Wyalkatchem, which displayed reasonable sprouting resistance in trials at Merredin and Katanning in 2001. (See rust warning on Camm p21 — Ed.)
The recently released Clearfield STL also has some tolerance, returning falling number results higher than the moderately-tolerant Spear in eight out of eight trials.
Late-maturing varieties seem the least affected by sprouting, while delaying seeding for susceptible short-medium maturity varieties may also help reduce damage.
Handling rain-damaged seed
Until new varieties have proven themselves, management remains the key. "Growers who retained damaged seed from last year to plant this year's crop should put them through a germination test to ensure they are viable and have good vigour," Dr Setter advised.
Weather-damaged seed should not be retained for more than one season; handling of damaged seed should be kept to a minimum; and growers need prime sowing conditions to achieve good emergence.
While sowing damaged seed was risky, growers could minimise the risk of weed competition by using pre- and post-emergent herbicides and increasing seeding rates to account for reduced seed viability and vigour. The possible adverse effects of herbicides on sprouted seeds need to be determined.
"In preliminary trials, grain with a falling number down to 180 seconds had good germination and vigour. However, after 1-4 months of storage, or when grain has a falling number below 180, growers could start to experience real problems with germination and vigour.
"Trials on falling numbers will continue, but the take-home message is to be careful and adopt all available identified precautions to hedge your bets," Dr Setter said.
Growers and the Federal Government through the GRDC have set their sights on eliminating pre-harvest sprouting within 10 years.
By 2004 the GRDC, in association with its research partners, hopes to develop management strategies to reduce sprouting risks faced by growers and the techniques to screen breeding material to select against sprouting defects.
It also hopes to have resistant milling-grade, white-grained wheat varieties available by 2010.
Program 1 Contact: Dr Tim Setter 08 9368 3289