Combining Ability for Yield and Protein Quality among Modified Endosperm opaque‐2 Tropical Maize Inbreds

Abstract

The opaque‐2 mutation has been used in maize (Zea mays L.) breeding to develop cultivars with increased concentrations of lysine and tryptophan. Very little information is available, however, about combining ability for protein quality traits for modified/vitreous‐endosperm opaque‐2 maize (quality protein maize, or QPM), although such information is essential for planning an effective hybrid development program. This research assessed the relative importance of general and specific combining ability effects (GCA and SCA) for grain yield, protein concentration in grain, tryptophan concentration in grain, and tryptophan concentration in protein for various tropical, late maturity, white grained QPM lines. Four diallel trials, involving a total of 28 lines from five populations, were evaluated from 1988 to 1990, each at two to five locations during 1 yr. The best QPM hybrid in each trial exceeded the best normal‐endosperm maize check by an average of 14% for grain yield, 48% for tryptophan concentration in grain, and 60~ for tryptophan concentration in protein. Mean squares for GCA effects in across‐location analyses were significant (P < 0.05) for grain yield, protein concentration in grain, and tryptophan concentration in protein for three of the four trials, and for tryptophan concentration in grain in two trials. Mean squares for SCA effects were not significant except for grain yield in one diallel. Location × GCA interaction was generally significant for all traits except tryptophan concentration in protein. Our results suggest that QPM hybrids with the highest values for protein quality traits will be crosses between lines with the highest GCA values. Concurrent improvement of yield and protein quality should be possible for this germplasm because phenotypic correlation coefficients were not significant for grain yield with concentration of protein in grain, concentration of tryptophan in grain, and concentration of tryptophan in protein.

Genetic analysis of tropical quality protein maize (Zea mays L.) germplasm

“…The QPM inbred lines used in this study were developed from conversion of a variety of mid-altitude normal endosperm inbred lines and OPVs to QPM and this explained the observed large genetic variability for various traits. This result is consistent with reports of genetic variability in tropical and temperate QPM germplasm (Spaner et al 1992;Vasal et al 1993a;Pixley and Bjarnason 1993;Bhatnagar et al 2004;Musila et al 2010;BaduApraku and Lum 2010;Badu-Apraku et al 2016) and in opaque-2 types (Motto et al 1978;Wessel-Beaver et al 1985).…”

“…This result suggested that inheritance of GY and some agronomic traits in these QPM inbred lines is largely controlled through additive genetic effects under optimal conditions. This result is consistent with findings in several studies with QPM germplasm (Pixley and Bjarnason 1993;Vasal et al 1993a, b;Musila et al 2010;Wegary et al 2014). In contrast, studies by Bhatnagar et al (2004) and Machida et al (2010) showed that nonadditive genetic effects were more important than additive genetic effects for control of GY in QPM germplasm.…”

Análise dialélica de linhagens de milho na safrinha

“…Também, a interação CEC x locais foi significativa (P<0,05) para todos os caracteres, com exceção de altura de espigas, permitindo inferir que houve resposta diferenciada das combinações híbridas frente aos locais. Essas interações são relatadas na literatura por diversos autores (ROJAS & SPRAGUE, 1952, MATZINGER et al, 1959, PIXLEY & BJARNASON, 1993, NASS et al, 2000, LOCATELLI et al, 2002.…”

Capacidade de combinação e heterose para resistência a Puccinia polysora Underw. em milho

“…No primeiro caso foi utilizada a escala diagramática de Rezende et al (1994) e no segundo a de Fantin (1997).…”

“…Trabalhos prévios para produtividade de grãos e resistência a doenças mostraram que CGC e CEC podem interagir com o ambiente (Rojas & Sprague, 1952;Matzinger et al, 1959;Parodas & Hayes, 1971;Pixley & Bjarnason, 1993;Nelson & Scott, 1973). Em regiões tropicais, esta interação é de particular interesse pois há uma expressiva variação entre locais, mesmo entre locais próximos.…”