SELECTION OF MAIZE LINES AND CROSSES BY COMBINING TOP CROSS AND DIALLELIC CROSS TESTS

Obtaining competitive commercial maize (Zea mays L.) hybrids requires efficient selection strategies to improve populations and develop elite parents. The objective of this research was to select lines and crosses with high general (GCA) and specific (SCA) combining ability for grain yield (GR) and agronomic characteristics, by combining top crosses (line x tester) and diallel crosses. In the Autumn-Winter 2010-2011 agricultural season, 144 top crosses were formed with S-2 inbred lines from the ST C-2 F-2 subtropical population, and as a tester, the subtropical population PABGT-CE C-9 F-2. Top crosses were evaluated under rainfed conditions in the 2012 Spring-Summer (SS) agricultural season at Tlajomulco and Tepatitlan, Jalisco, Pena del Panel, Michoacan, and Santa Maria del Oro, Nayarit, covering a range from 1100 to 1900 m of altitude. In this test, nine top crosses were selected by GCA across locations for GY and lodging tolerance. With the remaining seed of lines of the selected top crosses diallel crosses were formed in SS 2015. Crosses were evaluated in SS 2016 in the previous locations and Iguala, Guerrero. Lines ST C-2 F-2-21-2-1 and ST C-2 F-2-29-2-1 stood out in both tests by virtue of their high GCA for GY, but the last one was eliminated because in diallel crosses its GCA and SCA for lodging were positive and significant (P <= 0.05). The SCA of the cross ST C-2 F-2-33-1-1 x ST C-2 F-2-49-2-1 for GY was significant (P <= 0.05), yet in lodging it was negative but not significant. Associating top cross and diallel cross tests allowed to select in a more rigorous way lines with high GCA and SCA for GY and agronomic characteristics; in addition, it allowed to eliminate lines before forming the synthetic and obtaining single crosses that could be used to develop hybrids with elite progenitors of the other heterotic component.