Distribution of genes producing phenol colour reaction in grains of wheat and its related species, mode of inheritance and breeding for low polyphenol activity

Abstract

One of the important chapati quality traits pertains to the darkening of whole meal dough and its subsequent effect on browning of chapatis (unleavened Indian bread). The grain pericarp of most of the bread wheat varieties grown in India reacts to phenolic compounds and produce dark brown or brown colour. The present investigation undertook a most intriguing challenge to breed a variety, which do not react to phenol and does not darken the dough. A large number of wild wheat species, bread wheat cultivars, durum wheat and synthetic hexaploid (SH) wheat were screened to identify wheat genotype(s) with negative reaction to phenol. A variety of phenol reactions were recorded among the wheat species having different genomes. Most of the Aegilops squarrosa and Triticum timopheevi accessions showed negative colour reaction. Two phenol non-reactive (–ve) SH wheats (SH26 and SH32) were crossed with hexaploid bread wheat variety, HD 2851 with positive reaction (+ve) to phenol. Phenol test of F1 grains reacted positively and produced dark brown colour on pericarp indicating that the phenol colour reaction is a dominant trait. The F2 population segregated into two categories where the grains of 746 plants developed colour and 13 were non reactive (-ve colour or no colour). The Chisquare analysis revealed that development of phenol colour in grains is governed by three dominant alleles as the observed frequency of plants fit well into theoretical ratio of 63 (+ve) : 1 (–ve). The subsequent BC1-F2 and BC2-F2 generations were simultaneously tested with phenol to facilitate selection of the genotypes with –ve reaction. A few genetic stocks and selections derived from multiparent- cross did not develop colour upon testing with polyphenol. These genetic stocks have been improved further in respect of other agronomic traits. In Addition, an alternative chemical to phenol was discovered, which gave comparable results, safer to use, would not affect germinability adversely and thus amenable to high through put application in breeding programme.