The effect of a cool temperature treatment during grain filling on falling number as an indicator of late maturity alpha-amylase (LMA) presence in wheat: Southern NSW research results 2022

Key findings
• Late maturity alpha-amylase (LMA) is a genetic defect, commonly observed in
Australian wheat breeding germplasm, that can cause low falling numbers (FN) at grain receivals.
• Twenty-four cultivars considered to range in susceptibility to LMA expression were subjected to a simulated ‘cool shock’ temperature treatment under controlled conditions (24 hours of 23 °C day/19 °C night, then 48 hours of 16 °C day/11 °C night) during a critical period of grain filling and were tested for FN for an indication of LMA expression.
• Under controlled conditions (without ‘cool shock’ temperature treatment), 71% of the cultivars tested exceeded a threshold FN of 250 seconds. In comparison, the effect of the ‘cool shock’ temperature treatment reduced the proportion of cultivars exceeding the FN threshold to 42%.
• In general, the FN response of the cultivars to the cool shock reflected their anticipated LMA sensitivity. A simulated cool shock treatment under controlled conditions could provide a rapid phenotyping methodology to identify wheat germplasm with high LMA susceptibility, earlier in a breeding program.