Diallel analysis of corn for special use as corn grits: determining the main genetic effects for corn gritting ability.

Corn grits are used for various purposes such as flakes, snacks, livestock feed, hominy, extruded products, beer, etc. The grit size proportion varies according to the hybrid, and thus, once the use of the grits is linked to the particle size, determining the genetic effects is essential to develop hybrids for any specific use. For this purpose a complete diallel series of crosses, involving eight parents, was performed near Maringá, PR, Brazil. The objective of this study was to evaluate the general (GCA) and specific (SCA) combining abilities of 28 progeny for selection of hybrids for breeding programs and extraction of inbred lines for hybrid development. The response variables, such as plant height, ear insertion height, crop stand, grain yield, and grits, small grits and bran production, were gauged and appraised for each of the 28 progeny. The trait effects and GCA were significant for all response variables, while for SCA, only grain yield and crop stand showed significance (P < 0.05), according to Griffing (1955) analysis. A significant weak negative partial correlation was found between grain yield and grits conversion. In relation to the hybrid selection for breeding programs, the parent IAC Nelore was highly recommended for recurrent selection and the hybrids IPR 119 x HT 392 and IAC Nelore x HD 332 for the extraction of pure lines for hybrid development.

Combining ability of tropical maize lines for seed quality and agronomic traits.

Studies of genetic effects of early selection of maize based on seed quality traits are rare, especially those that use materials from different heterotic groups. These studies are also useful in tropical environments and for the advancement of sustainable agriculture with cropping during seasons not commonly used for cultivation. We estimated, through diallel crosses, the predominant genetic effects on the expression of agronomic traits and seed quality and on the general combining ability of nine maize lines from commercial hybrids and the specific combining ability of hybrid combinations among them. In the evaluation of seed quality, seven tests were used: first count and final count of seed germination, seedling vigor classification, cold tolerance, seedling emergence rate in a sand seedbed, speed of emergence in a sand seedbed, and speed of emergence index. Plant height, first ear height and grain yield were the estimated agronomic traits. In the diallel analysis, method 3 (model I) proposed by Griffing was used. There was a greater significance of non-additive genetic effects in the genetic control of seed quality of the various lines. The Flash, Dekalb 350 and P 30F80 lines combined high seed quality and high grain yield. For growth during the normal planting season, the combinations CD 3121-1 x P 30F80, Speed x CD 3121-2, Dow 8330 x AG 8080 and Dekalb 350 x CD 3121-2 were the most promising for both seed quality and agronomic traits.