Demand-Driven Technologies for Sustainable Maize ... - IITA

50Table 4. Estimates of GCA effects for grain yield of 24 maize inbredlines evaluated under water stress and well-wateredcondition at Ikenne in 2002.Water stress Well-wateredInbred Category † male female male femaleGCA-GCA-GCA-GCA-9613 T 0.05 -0.02 0.17 0.129006 T 0.16* 0.39** 1.06** 0.71**4058 T 0.10 -0.12 0.03 -0.21*POP 10 T 0.20* -0.05 0.38** 0.86**1824 T -0.12 0.42** 0.11 0.56**4001 T 0.20* -0.05 0.18 -0.54**KU1409 T 0.34** 0.08 0.24* 0.03(POOL 26 Sequia)C3F2 T -0.12 -0.16* 0.38** 0.45**9450 T -0.40** 0.11 -0.80** 0.06161 T 0.12 -0.03 0.69** 0.37**(KU1403x1368)STR T 0.04 -0.21** -0.57** -0.76**(TZMI501xKU1414x501) T 0.08 0.10 -0.09 0.78**5012 S -0.26* 0.26** -0.03 -0.36**5057 S -0.06 -0.62** -0.37** -0.79**Fun.47-3 S 0.11 0.10 -0.25* 0.50**9432 S -0.13 0.39** 0.17 -0.13GH 24 S 0.10 0.13 0.47** 0.43**(KU1403x1368) S 0.20* 0.08 -0.95** -0.161808 S -0.35** -0.39** -0.61** -0.89**9071 S -0.01 -0.09 0.50** 0.34**9485 S -0.30** 0.01 -0.26* 0.124008 S 0.13 -0.05 0.48** -0.54**Mok Pion-Y-S4 S 0.10 0.07 -0.38** 0.31**(KU1403x1368)BC2 S -0.08 -0.25** -0.51** -1.21**SED 0.04 0.05 0.10 0.12†T = tolerant and S = susceptible.*, ** Signifi cant at 0.05 and 0.01 levels of probability, respectively.SED = standard error of the difference between estimates of two GCA estimates.importance of GCA effects was greater than SCA effects, indicatingthe importance of additive gene effect in the inheritance of yield andother traits under drought stress. The signifi cant SCA mean squaresuggests that hybrid development could be employed to exploit nonadditivegene action to improve drought tolerance in this set of maizelines. Menkir and Akintunde (2001) had earlier noted the superiorityof hybrids over other genotypes under WS conditions.Most tolerant parental lines had positive GCA effects for grain yield,while most susceptible lines showed consistently negative GCA effectsfor grain yield under both WS and WW conditions. Inbred lines KU1409and 9006 had the highest positive GCA-male effects under WS andWW, while 1824 and POP10 had the highest positive GCA-female effectsunder WS and WW (Table 4). The estimates of SCA effects werepositive for 56% of T x T, 52% of T x S and 50% of the S x T crosses,while more than 50% of S x S crosses had consistently negative SCAeffects for both irrigation treatments (Table not presented).