Synthesis of Flavonoid Pigments in Grain of Representatives of Poaceae: General Patterns and Exceptions in N.I. Vavilov’s Homologous Series

Abstract

Flavonoid pigments are a group of secondary plant metabolites. Interest in these compounds is determined by a wide range of their biological properties; thus the saturation of edible parts of plants, in particular, cereal grains, with flavonoids is an urgent task today. The synthesis of flavonoid pigments can be observed in the testa, pericarp, aleurone layer, and grain endosperm in representatives of most cereal crops (maize Zea mays L., rice Oryza sativa L., bread wheat Triticum aestivum L., barley Hordeum vulgare L., rye Secale cereale L., sorghum Sorghum bicolor (L.) Moench., etc.), which is consistent with N.I. Vavilov’s law of homologous series in hereditary variation. However, according to some features, certain types of variability are not observed: for example, in some representatives of the tribe Triticeae, no forms synthesizing anthocyanins in the aleurone layer are found. Homologous series have not been identified for some unique features. For example, compounds belonging to the group of 3-deoxyanthocyanidins having a yellow-orange color uncharacteristic of cereal crops are synthesized in the pericarp only in sorghum. This review provides information on the genetic diversity and biosynthesis of flavonoid pigments in the cereal grains, characterizing the nature of the observed patterns and exceptions to Vavilov’s law.