Forage aptitude in maize populations
--Torrecillas, M, Bertoia, LM
Landraces without improvement and composites with few cycles of selection constitute a source of important variability to be used as a base in improvement programs, directed to the synthesis of hybrids with forage aptitude.
Four populations and two improved composites, per se and their crosses with selected inbred lines PR4 and PR10 were evaluated. These materials showed diversity in origin, cycle and plant architecture. Trials were performed in two environments located in the Buenos Aires milk belt. A complete block design with three replications was used, Morgan 369, Funk's Tilcara and Pioneer 3452 being the commercial checks. The experimental unit consisted of two 5-m rows, spaced 0.7 m apart. Combined analyses were computed to determine the effects of general combining ability (GCA) and specific combining ability (SCA).
The studied variables were Ear Dry Matter Yield (EDMY); Stover Dry Matter Yield. (SDMY); Whole Plant Dry Matter Yield (WPDMY).
In the combined analysis for SDMY and WPDMY, GCA effects in populations and composite were detected. No significant effects of GCA for the inbred lines were found. Significant effects of SCA for the variable SDMY were observed, the interaction of this effect with the environment for the same variable being significant. In two environments evaluated, the populations 1 and 4 had the greater values of GCA for SDMY and WPDMY.
The superiority shown by some crosses upon the commercial hybrids for the variable WPDMY indicates the feasibility of using that germplasm in improvement programs directed to forage production.
Table 1. SDMY
| Material | Mean1 | GCA |
| Population 1 | 9.63 | 6.55 * |
| Population 2 | 8.92 | -0.6 |
| Population 3 | 7.80 | -11.74 |
| Population 4 | 9.61 | 6.30 * |
| Composite Pitagu· | 9.08 | 1.08 |
| Composite Semiflint | 8.82 | -1.6 |
Table 2. WPDMY
| Material | Mean1 | GCA |
| Population 1 | 21.08 | 9.52 * |
| Population 2 | 20.46 | -0.85 |
| Population 3 | 18.68 | -14.45 |
| Population 4 | 20.54 | 4.16 * |
| Composite Pitagu· | 20.51 | 3.76 * |
| Composite Semiflint | 19.92 | -2.14 |
1Yield in Tn ha-1
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