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Accueil > Animation scientifique > Séminaires passés

Séminaire hebdomadaire UGSF - Jean-Philippe Ral - 13 avril 2018 - C9 - André Verbert


"The Breeder Digest : "Legend of the Falls" or impact of elevated level of alpha-amylase on wheat end product "

Animé par : Jean-Philippe Ral, CSIRO Agriculture and Food Black Mountain Canberra - Invitée de l’Equipe "Glycobiologie végétale" Fabrice Wattebled, de l’UMR 8576 - Université de Lille

Synopsis :

Alpha-amylase has been recently described as the “best known amylolytic enzyme”, title well deserved for its role in 2 pillars of our civilization : Baking and Brewing !

In non-photosynthetic organs, high levels of reserve starch need to be mobilized very rapidly during germination and early seedling growth. For most cereals, these endo-hydrolases are primarily responsible for starch breakdown during germination. Unfortunately, wheat alpha-amylases have also been known among the cereal community for their involvement in 2 of the current major wheat genetic defects, the Late Maturity Alpha-amylase (LMA) and pre Harvest Sprouting (PHS).

Late maturity α-amylase is a recently identified quality issue that is now receiving increasing attention and whose prevalence is now seen as impeding the development of superior quality wheat varieties worldwide. LMA is a genetic defect present in specific wheat genotypes and is characterized by abnormally elevated levels of the high pI TaAMY1 alpha-amylase, triggered by environmental stress at precise grain developmental stage. TaAMY1 remains present in the aleurone layer throughout grain maturity and harvest. To the exception of the elevated level of alpha-amylase, LMA affected grain does not present any visible detrimental effect on grain morphology, properties or germination. However, elevated level of alpha-amylase lowers Falling Number (FN) test (a test used to detect sprouted grain) at receival, causing a down-grading of the grain, often to feed grade, thus reducing the farmers’ income. In Australia, if grains present a low FN (below 300), there is a potential $20-50/t penalty to growers due to discounting superior milling wheat classes to feed grade. In the United States, the Pacific North West was severely affected during the 2016 harvest—with losses estimated to be in the order of $US140 millions. This severely impacts grower profitability through increasing risk of a reduced grain value. This downgrading is based on the assumption within the grain industry that a low FN represents poor quality grain. Consequently any wheat line possessing low FN or high alpha-amylase levels is automatically considered a poor bread wheat despite there being no published evidence to date, to show that LMA is detrimental to end product quality.

Despite being thoroughly characterized in plant model such as Arabidopsis, alpha-amylases and starch degradation in non-photosynthetic tissues have been very often targeted in a view to mitigate their effects rather that understanding their fundamental role in biological or industrial processes. Our research on wheat reserve starch degradation during grain development and germination has suggested that starch degradation in cereal grains has a hitherto unsuspected role in starch synthesis and deposition throughout grain maturation. Finally, the impact of wheat alpha-amylase on end-use applications is being investigated.

Le vendredi 13 avril 2018 à 11h00 - Bât. C9 - Salle André Verbert