Materials and methods
2.1. Field experiment
Ninety-six (96) newly developed single- cross maize hybrids of IITA-bred adapt ed and CIMM YT-bred exotic inbred
lines [2] plus four (4) hybrid checks (Table 1) were evaluated
under drought stress and full irrigation conditions at Ikenne
(latitude 6 54 0N, longitude 3 42 0E, altitude 60 masl), in
Nigeria during the dry seasons of 2010 and 2011. Ikenne receives little rainfall from November to March of the year,
making the site suitable for conducting drought tolerance experiments because maize crops planted at this period must be
supported with irrigation. The soil at this site is eutricnitrosol
(FAO classification). The experimental fields are flat and
reasonably uniform, with high water-holding capacity [9].
Two out of the four checks are commercial hybrid maize varieties being marketed in Nigeria (Oba Super 1 and Oba 98)