INTERACTIONS BETWEEN TESTERS AND ARGENTINE MAIZE LANDRACES

Exploitation of maize (Zea mays L.) landraces is far from having reach ed its potential impact on breeding programs in Argentina. The search for alternative hererotic patterns and concerns about kernel physical quality constitute a new scenario. This research was aimed at characte rizing 79 landraces for their interactions with testers, and identifyi ng those to be composited in mio populations to form an alternative fl int x flint heterotic pattern. The landraces were testcrossed with two pairs of divergent testers. Testcrosses were evaluated in three envir onments during the 1991/1992 season. A split-plot arrangement of entri es, where main plots corresponded to landraces and subplots to landrac e x tester combinations, was used. Differences for landraces, testers, and landrace x tester interactions were detected for days to anthesis , ear height, grain yield, and relative grain yield. Yield data were f urther ana lyzed following additive main effects (landrace and tester) and multiplicative interaction (landrace x tester) models. The first mio principal components were significant and accounted for 74% of tha t interaction. The first axis was consistent with the Argentine flint vs. U.S. dent major heterotic pattern. The second axis exhibited a con trast between the local flint heterotic groups. The mean yield perform ance in test-crosses and the first two principal components of the lan drace x tester interaction were considered to identify five landraces to form each composite.