Pre-maturity α-amylase and incipient sprouting in UK winter wheat, with special reference to the variety Rialto

Abstract

In 1998 and 1999 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 pre-maturity α-amylase activity (PMAA). The problem was not identified during the selection and commercial development stages. Our study tested the hypothesis that the variety Rialto is PMAA-susceptible. 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 10-44% of the grain from the 13 samples, leading to the conclusion that Rialto is PMAA-susceptible. Diurnal temperature range accumulated for an 11 day period during a warm spell in early simulated grain development displayed a significant but negative correlation with the number of grains showing clear PMAA discoloration patterns on Phadebas gel. The number of clear PMAA grains correlated positively with rainfall accumulated over 11 days. These results suggest that PMAA can increase under conditions similar to those conducive to pre-harvest sprouting. It is however also possible that in some instances both PMAA and incipient sprouting could have produced similar patterns of α-amylase activity. In addition to tests with Rialto, Phadebas gel tests were therefore also done with the known high Hagberg varieties Option and Malacca, sprouted in a controlled environment. Results from the additional gel tests suggest that visual and chemical assessments of sprouting in the grain combined with Phadebas gel analysis could identify PMAA more reliably in grain sub-samples than Phadebas gel analysis alone.

Impact of Cultivar and Growing Conditions on Alpha‐Amylase Properties in Wheat

“…In addition, it was suggested that the elevated temperatures during harvest period promoted grain drying by rapid evaporation. [ 48 ] Such conditions may favor the harvest of mature grains before the induction of α‐amylase by precipitation at harvest time. [ 45 ] Another possible explanation is that a temperature of 15 °C lead to delay in wheat germination compared to 20 °C, [ 49 ] since the germination inhibitor (e.g., abscisic acid) is maintained in the embryo.…”

Detection of the quantitative trait loci for α-amylase activity on a high-density genetic map of rye and comparison of their localization to loci controlling preharvest sprouting and earliness

“…Premature breaking of dormancy can result in PHS of spikes in wet weather conditions. PHS is a major cause of excess α-amylase activity (AA), which impairs grain quality since enzymatic hydrolysis of starch during food manufacture can lead to processing problems and unsatisfactory end products (Graybosch et al 2000; Lunn et al 2001; Mares et al 2002; Tjin Wong Joe et al 2005). Much research on wheat grains has proved that there are a number of additional causes for the deterioration of meal properties, which reflects low falling number.…”

“…Much research on wheat grains has proved that there are a number of additional causes for the deterioration of meal properties, which reflects low falling number. These include late maturity α-amylase (LMA) (Mrva and Mares 1996a, b, 1999, 2002, 2008), also known as prematurity α-amylase (PMAA) in the UK (Lunn et al 2001; Tjin Wong Joe et al 2005), and retained pericarp α-amylase (RPAA) (Lunn et al 2001). …”

Late-maturity α-amylase (LMA): exploring the underlying mechanisms and end-use quality effects in wheat

“…In LMA-susceptible varieties, PCD symptoms are present in individual cells or cell patches in random locations throughout the aleurone (Mrva et al 2006). Previous studies have also shown that LMA initially affected cells near the grain crease in UK varieties (Major 1999;Lunn et al 2001;Joe et al 2005). The low percentage of affected cells agrees with the relatively lower levels of α-amylase when mature LMA-affected varieties are compared to sprouted grain over time.…”

“…The underlying biochemical mechanisms associated with the induction of LMA are currently unknown. Studies have provided insights into the expression and protein accumulation of α-amylase during this developmental event (Gale et al 1987;Mrva and Mares 1996c, 1999, 2001aJoe et al 2005;Mrva et al 2006Mrva et al , 2009Farrell and Kettlewell 2008;Barrero et al 2013Barrero et al , 2020Farrell et al 2013;Kondhare et al 2013Kondhare et al , 2014Cheng et al 2014;Mieog et al 2017;Derkx and Mares 2020). In LMA-susceptible wheat varieties, the relative expression and protein abundance of high pI α-amylase increased during late grain development, at 20 days postanthesis (dpa) (Barrero et al 2013).…”