Forage production in Argentine land races
--R. Burak, L. Bertoia and C. López

The increase in demand for dairy products, mainly due to the new MERCOSUR, has led to the need to incorporate high technology in the dairy farm, with the aim of improving productivity. The use of maize silage is standard practice, because it allows the harvested forage to be used strategically in times when grass production is low. The scarcity of improved maize forage in the Argentine market shows the need to develop plans for investigation in this area. Following this criterion, the aim of our work was to find out about forage behavior of maize land races and its crosses, and the detection of materials for starting a breeding program.

Eight (1 to 8) land races from the germplasm bank of INTA Pergamino, their 28 crosses and 4 checks, which have shown to be good dry matter producers (Morgan 369, Dekalb 4F37, Funk's Tilcara and Cargill Semiden 5) were evaluated. The experimental design used was alpha lattice 8x5 with 4 replications. The planting was carried out in Esteban Echeverría and Cañuelas locations, which form part of the Buenos Aires milk-belt. The variables analysed were: Total dry matter yield (TDMY), ear dry matter yield (EDMY) and stover dry matter yield (SDMY). The averages adjusted by lattice for the land races and crosses of EDMY and SDMY were analysed following Gardner and Eberhart's model II for diallel crosses. In the ANOVA, an error probability (P < 0.05) was used.

The combined ANOVA (Table 1) detected significance for genotypes in TDMY, EDMY and SDMY, for populations in SDMY and for their interactions with locations in all the studied variables.

Taking EDMY into account, the heterosis parameter and its components average heterosis, varietal heterosis and specific heterosis are significant, while their respective interaction with locations is not. The sum of squares of heterosis was the most important source of variation. The crosses with major EDMY were 2x7 and 2x4, showing high percentages of high parent heterosis (52% and 31% respectively) and similar values to the check hybrids.

Table 1:. ANOVA for a diallel set of eight land races.
 
S.V.
D.F.
M.S.
 
TDMY
EDMY
SDMY
Genotypes 35
*
*
*
Populations
7
*
ns
*
Heterosis 28
*
*
ns
Average Het. 1
*
*
ns
Variety Het. 7
ns
*
ns
Specific Het. 20
ns
*
ns
Gen.* Loc. 35
*
*
*
Pop.* Loc. 7
*
*
*
Het.* Loc. 28
ns
ns 
*
Av.Het.* Loc. 1
ns
ns
ns 
Var.Het.* Loc. 7
ns
ns
ns 
Spec.Het.* Loc. 20
ns
ns 
ns
Combined Error 202
*Indicates significance at the 5% level of probability.
ns Indicates no significance.

For SDMY the heterosis parameter did not show significance in the combined analysis or in the individual one corresponding to Esteban Echeverría, while in Cañuelas the three heterotic components turned out to be significant. In both locations the sum of squares of populations was the most important source of variation. The crosses with the best SDMY were 1x3 and 1x4. The crosses 2x7, 2x4 and 1x3 showed the greatest TDMY after taking the average of the yield in both locations.

The heterosis expressed by some crosses, with yields in certain cases greater than that of the checks, indicates the possibility of deriving inbreds of their progenitor land races. That will depend upon these results being repeated in future evaluations. 


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