Factors affecting durm wheat grain color.

RONCALLO, P.F.; AKKIRAJU P; CARRERA, A.; HELGUERA, M.; CERVIGNI, G.; MIRANDA R; JENSEN C; ECHENIQUE V

Rosario, Argentina

Conferencia; 1 Conferencia latinoamericana ICC 2007; 2007

Asoc. Internacional de Qcos, Cerealistas

The bright yellow colour of durum wheat grain and products is due to the presence of carotenoid pigments of the xanthophylls type, mainly lutein, and their enzymatic degradation, where a major role appear to be played by the lipoxygenase-linoleate system over other enzymes like peroxidases and polyphenol oxidases. Colour is an important quality trait in pasta wheat. The aim of this work was the characterization of the more common Argentinean pasta wheat varieties according to its carotenoid pigment content, using different biochemical methods and their association with the yellow colour index (b value). Field trails were conducted in three locations using 8 varieties from Argentina and two from US, using a complete randomized block design with 3 replicates (N=90). Whole meal samples were obtained with a cyclonic mill. Each sample was evaluated for carotenoid pigment content (lutein and ß-carotene) using the standard AACC 14-50 method and the microtest described by Fares et al.(1991; Molini d’Italia, Anno XLII 12:19-21), the yellow index using reflectance spectrophotometry (CIE L*a*b*) and the thousand-kernel-weight. The ß-carotene content ranged from  4,61 to 13,03 p.p.m. The analysis of variance showed that the pigment content, measured by both methods, and the yellow index were affected by the genotype (p<0,0001) and the environment (p<0,0001), obtaining higher ß-carotene and  lutein contents and yellow index values in Cabildo than Balcarce and Tres Arroyos. The genotype-by-location interaction was highly significant for all the parameters analyzed (p<0,0001). Multiple rank Duncan test showed that Buck Topacio followed by the US variety Kofa had the highest ß-carotene and lutein content, whereas Buck Ámbar and B.I. Cumenay were the varieties with the lowest yellow pigment content in the three locations. The microtest underestimated the yellow pigment content (p.p.m.), but was strongly correlated to both ß-carotene (r=0,94) and lutein (r=0,92) contents, measured by the AACC 14-50 method. The yellow index was highly correlated with the standard ß-carotene (r=0,85) and lutein (r=0,74) content and ß-carotene content (r=0,84), performed by the microtest. Thousand-kernel-weight was negatively correlated with ß-carotene content (-0,43) and yellow index (-0,53) and the correlation between ß-carotene and lutein content was strongly high (r=0,962). All of the Pearson’s simple correlations were highly significant. We can conclude that the grain bright yellow color is strongly affected by the genotype, followed by a location effect. The microtest is a useful tool to predict the carotenoid pigment content at early generations in breeding programs, having the advantage of saving time and reducing the sample size. The yellow index is an accurate estimate of carotenoid pigment content and the grain size has a secondary but highly significant effect on the pigment content. We continue evaluating the varieties for lipoxigenase activity and pigment content in semolina and whole meal and looking for molecular markers associated to these traits.