Evaluation and comparison of protein composition and quality in half-sib families of opaque-2 maize (Zea mays L.) from Argentina

Abstract

El objetivo fue caracterizar y comparar la composición proteica de familias de medios hermanos de maíz opaco-2 de Argentina mediante prueba de progenie. Se determinó dureza del grano, contenido de fracciones proteicas, aminoácidos y digestibilidad in vitro de proteína (PD) de la harina integral. Se usaron genotipos no-opacos como control. El contenido total de proteína de los genotipos o2 correlacionó negativamente con la dureza del grano (r=-42 en 2012 y r=-0.32 en 2013) y no mostró diferencias significativas respecto a los genotipos no-opacos; sin embargo, los genotipos o2 mostraron mayor PD, menor proporción de zeína y mayor de albúminas, globulinas y glutelinas. Las progenies o2 mostraron mayor contenido de lisina, isoleucina y treonina en comparación con el maíz blanco. El contenido de lisina, el de fracciones proteicas y la PD mostraron una mayor contribución de la varianza genética, a pesar de la alta contribución de la varianza del año observada en el contenido total de proteínas. Las diferencias mostradas por los perfiles de proteínas de las progenies permitirán identificar genotipos o2 con menor nivel de zeína y mayor contenido de lisina. Esto permitirá continuar con la selección y la mejora genética para obtener variedades con calidad proteica superior.

The objective of this study was to characterize and compare the protein composition of half-sib families of opaque-2 maize from Argentina through progeny testing. Grain hardness, protein fractions, amino acid content and in vitro protein digestibility (PD) of whole grain flour were determined. Nonopaque genotypes were used as control. Total protein content of o2 genotypes correlated negatively with the grain hardness (r=-42 in 2012 and r=-0.32 in 2013) and did not show significant differences in relation to non-opaque genotypes; however, o2 genotypes showed significantly higher PD, lower zein proportion, and higher albumin, globulin and glutelin contents. The o2 progenies showed significantly higher lysine content and higher levels of other essential amino acids, such as isoleucine and threonine compared to white corn. Lysine content, protein fraction contents and PD showed a higher contribution of genetic variance to the total variability, despite the high contribution of crop year variance obtained by total protein content. The differences shown by progeny protein profiles would enable the identification of o2 genotypes with lower zein level and higher lysine content; this allows us to continue the selection and improvement to obtain open-pollination varieties enhanced in terms of protein quality.