When the UK winter wheat variety Rialto produced unexpected low Hagberg falling numbers that could not be directly linked to sprouting, it was proposed that these reductions in quality could be due to PMAA. The problem was not identified during the selection and commercial development stages.
In this project the hypothesis was tested that the variety Rialto is PMAA-susceptible. In addition, the effect of a previously proposed high temperature stimulus for PMAA followed by slow grain drying was assessed on plants grown in a controlled environment, throughout. This was done to eliminate any distorting effects the temperature history of plants grown in field or glasshouse had in previous studies. The identification of an effective and reliable PMAA stimulus could facilitate the development of a screening method for PMAA.
Analysis was done on 13 year-location combinations of field grown Rialto. Together, visual and chemical assessments of sprouting and iso-electric focusing of α-amylase isozymes identified several samples with significant α-amylase activity in the apparent absence of sprouting. In addition, tests with α-amylase sensitive Phadebas gel revealed distinctive PMAA discoloration patterns in 10% to 44% of the grain from the 13 samples, leading to the conclusion that Rialto is PMAA-susceptible. Results from a controlled environment experiment confirmed the ability of a high temperature treatment to induce increased amylase production in the grain. However, the increase occurred in low humidity, considered to promote grain drying. Other results suggested that induction transpires during an earlier grain development stage than proposed in previous studies. Further work revealed the potential of a detached tiller technique to be used in a prospective fast and reliable screening method for PMAA
