With good rainfall this season, Australia’s wheat crop is set for an exceptional year. However, if rainfall continues during grain ripening and harvest, it could have devastating effects and significantly reduce growers’ returns due to pre-harvest sprouting (PHS).
PHS occurs with prolonged rainfall, high humidity and/or low drying conditions when the grain is harvest ripe. The impact of PHS of grain is assessed as low falling numbers at receival points. Sound grain has a falling number >350. If an APH line has a falling number of 300-350, this triggers a price downgrade. If falling number is <300, the grain is graded as ‘feed’.
2010 was the last widespread ‘wet harvest’, with GRDC estimating losses of approximately $100 million due to PHS, but there are localised losses due to PHS every year, with individual farmers losing 20-40% of their profit.
PHS in wheat is where germination begins within the spike before harvest (Fig. 1). During germination, enzymes begin to break down starch, which reduces applications for which the flour is useful. “You cannot bake bread with grain affected by pre-harvest sprouting” reported Dr Al Rattey, Expert Breeder for Dow Seeds. “It just falls over like a wet sack.”
There are several methods for estimating PHS, with germination index (GI) the most common. GI is estimated on harvest ripe seeds in a Petri dish and assessed for sprouting over a number of days; lower GI indicates better tolerance to PHS.
Tolerance to PHS should be seen as an ‘insurance’. Currently, limited genetic tolerance to PHS exists amongst Australian wheat lines.
“The falling number of DS Pascal was sufficient to attain milling status across both trials, whilst Chara would have been downgraded to feed on both occasions. Sunvale was downgraded to feed once, and EGA Wedgetail and Sunvale would not have been eligible for APH status in one trial” explained Dr Rattey.
DS Pascal is an early season variety that has been classified APW for SNSW, Vic and SA. It is best suited to medium-high yield potential areas, and is excellent under irrigation. DS Pascal has excellent standability and harvestability, with strong yellow leaf spot (MRMS) and rust resistance.
“PHS tolerance in DS Pascal is the result of targeted, intensive phenotyping. This involved sourcing and introgressing targeted novel germplasm, followed by multiple breeding rounds and selection in the field, and under a rain simulator. Through this process, Dow Seeds has a robust suite of alleles underpinning superior PHS within our breeding germplasm. Whilst DS Pascal marks our first launch of the PHS trait, we will soon be launching a new variety for northern Australia with this tolerance as well” announced Dr Rattey. “The release of DS Pascal in 2016 provides growers with a new benchmark for PHS tolerance, which brings the potential of saving growers significant grain quality downgrades due to PHS in wet harvests” he added.