per panicle accounted for 37% and 25% across no drought stress, 58% and 48% under random drought stress and 56% and 39% across environments, respectively. For grain phenotypic acceptability, additive genetic variance accounted for 83% across no drought stress, 40% under random stress and 78% across environment.
In general the results revealed that non-additive gene action was more important than additive gene action for grain yield, spikelet fertility, grains per panicle, and weight of grains per panicle under no drought and drought stress conditions. In contrast, additive gene action was more important for a thousand grain weight under no drought and drought stress condition. For panicle weight non additive gene action was more important under no drought stress while both additive and non-additive gene action prevailed under drought stress. For grain phenotypic acceptability, additive gene action was more important under no drought stress while non-additive gene action prevailed under drought stress conditions.
Table 5.6: Ratio of additive genetic variance to total genetic variance (based on Baker’s ratio) for grain yield and yield contributing traits at each and across no drought stress, under random managed drought stress and across environments
Traits ‡MTG MTP MSMLR Across MSMSR Across
No drought condition RDS
Grain yield 0.23 0.15 0.78 0.01 0.02 0.11
Spikelet fertility 0.29 0.08 0.10 0.06 0.04 0.05
1000 grain weight 0.98 0.97 0.51 0.98 0.99 0.99
Grains per panicle 0.21 0.41 0.35 0.23 0.09 0.20
Panicle weight 0.53 0.33 0.21 0.37 0.58 0.56
Weight of grains per panicle 0.55 0.20 0.12 0.25 0.48 0.39 Grain phenotypic acceptability 0.59 0.93 0.73 0.83 0.40 0.78
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random managed drought stress
Bakers ratio: 2σ2GCA/(2σ2GCA + σ2SCA)
environments, once more Vandana displayed the highest significantly positive GCA effects (0.33 t ha-1). The GCA estimates for spikelet fertility were inconsistent in the sign under no drought stress environments for all lines with exception of Vandana which showed consistently positive GCA effects contributing to the highest highly significant positive GCA estimate of 4.22% across no drought stress environments (Table 5.8). Under random stress the estimates were significant (p<0.01) and negative for NERICA-L-25 only. Across environments Vandana showed the highest highly significant positive GCA estimate of 3.96%.
There was consistency in GCA estimates for a thousand grain weight (Table 5.9). The estimates were positive for all the interspecific lines with exception of NERICA-L-25 and negative for all the Oryza sativa lines with exception of Duorado. All the lines showed highly significant GCA estimates across no drought stress, under random drought stress and across environments. The line Duorado followed by CT16323-CA-25-M showed the highest positive effects at each and across environments while NERICA-L-25 had the lowest negative effects. The GCA effects for grains per panicle at and across environments were consistently positive for NERICA 2 and IR55423-01 and consistently negative for Duorado (Table 5.10). Across no drought stress the estimates were significant and positive for IR55423-01 and significant and negative for NERICA-L-25. Under random drought stress the estimates were significant and positive for NERICA 1 and NERICA 2 and significant and negative for NERICA-L-25 and Duorado. Across environments NERICA 2 displayed the highest positive estimate followed by IR55423-01 and NERICA 1 while Duorado showed the lowest negative estimates.
The GCA estimates for panicle weight and weight of grains per panicle were consistent at and across environments (Table 5.11 and 5.12). Once more, the estimates were positive for all the interspecific lines with exception of NERICA-L-25 and negative for all the Oryza sativa lines with exception of Duorado. Under random drought stress and across environments the lines NERICA 1 and NERICA 2 consistently showed the highest significant positive effects while NERICA-L-25 showed the lowest significant negative effects for panicle weight and weight of grains per panicle. The GCA estimates for grain phenotypic acceptability were consistently positive for all the interspecific lines with exception of NERICA-L-25 and negative for all the Oryza sativa lines with exception of Duorado (Table 5.13). Under random drought NERICA 1 followed by CT16323-CA-25-M showed the highest highly significant (P<0.001) negative estimates. Across no drought stress and across environments, NERICA 1 followed by NERICA 2 showed the highest highly significant (P<0.001) negative estimates.
NERICA-L-25 followed by Vandana had the lowest significant GCA estimate.
Table 5.7 The general combining ability effects (GCA) of parents for grain yield (t ha-1) Grain yield
Parents MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 0.22* -0.15 -0.14 -0.03 0.18 0.03
NERICA 2 0.10 0.10 0.23 0.14 0.02 0.11
CT16323-CA-25-M -0.03 -0.04 -0.71*** -0.26* 0.01 -0.19*
CT16333(1)-CA-22-M 0.14 -0.17 -0.63*** -0.22* -0.21 -0.22*
NERICA-L-25 -0.44*** 0.21* 0.45* 0.07 0.05 0.07
Oryza sativa L.
Vandana 0.58*** -0.09 0.86*** 0.45** -0.05 0.33***
Duorado 0.15 -0.30*** -0.76*** -0.30** 0.03 -0.22*
IR74371-54-1-1 -0.34*** 0.45*** -0.3 -0.06 0.21 0.01
Luyin 46 -0.42*** -0.28** 1.05*** 0.12 -0.16 0.05
IR55423-01 0.04 0.27** -0.06 0.09 -0.08 0.04
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random managed drought stress
Table 5.8: The general combining ability effects (GCA) of parents for spikelet fertility (%) Parents
Spikelet fertility
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 5.33*** -2.08* -0.49 0.92 2.72 1.37
NERICA 2 2.72 -0.58 -1.33 0.27 1.47 0.57
CT16323-CA-25-M 2.92 2.10* -2.38 0.88 2.11 1.19
CT16333(1)-CA-22-M 1.98 -1.2 -0.33 0.15 -2.37 -0.48
NERICA-L-25 -9.72*** 2.21* 0.16 -2.45* -4.99** -3.09**
Oryza sativa L.
Vandana 5.39*** 3.17** 4.09** 4.22*** 3.18 3.96***
Duorado 2.11 -5.38*** -4.71*** -2.66* -0.03 -2.00*
IR74371-54-1-1 -7.27*** 1.7 2.05 -1.17 2.39 -0.28
Luyin 46 -5.62*** -0.33 1.85 -1.37 -3.42 -1.88
IR55423-01 2.16 0.38 1.09 1.21 -1.07 0.64
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress
Table 5.9: The general combining ability effects (GCA) of parents for a thousand grain weight (g)
Parents
A thousand grain weight
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 1.55*** 1.11** 1.08 1.22*** 1.99*** 1.43***
NERICA 2 1.06** 1.31*** 1.04 1.02*** 1.80*** 1.30***
CT16323-CA-25-M 2.42*** 2.36*** 2.13*** 2.44*** 2.54*** 2.36***
CT16333(1)-CA-22-M 2.31*** 1.82*** 0.94 1.76*** 1.63*** 1.68***
NERICA-L-25 -3.88*** -3.51*** -2.28*** -3.17*** -3.71*** -3.35***
Oryza sativa L.
Vandana -1.22*** -1.68*** -0.91 -1.34*** -2.41*** -1.55***
Duorado 3.17*** 3.57*** 2.53*** 3,23*** 3.72*** 3.25***
IR74371-54-1-1 -1.57*** -1.50*** -2.01*** -1.93*** -1.82*** -1.73***
Luyin 46 -2.00*** -1.32*** -1.53** -1.70*** -1.60*** -1.61***
IR55423-01 -1.85*** -2.15*** -0.99 -1.69*** -2.14*** -1.78***
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress
Table 5.10: The general combining ability effects (GCA) of parents for grains per panicle (g) Parents
Grains per panicle
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 6.89* -0.91 -6.6 -0.21 9.96*** 2.34*
NERICA 2 10.58** 2.53 3.12 5.41 6.38* 5.04**
CT16323-CA-25-M -1.14 -4.88* -1.82 -2.61 0.65 -1.76
CT16333(1)-CA-22-M 1.96 1.38 -13.10*** -3.25 1.87 -0.79
NERICA-L-25 -10.40** 9.19*** 0.49 -0.24 -10.48*** -4.10*
Oryza sativa L.
Vandana 3.61 -3.85 8.07* 2.61 -3.79 0.08
Duorado -0.41 -17.00*** -12.30** -9.90*** -7.93** -8.12***
IR74371-54-1-1 -8.31* 11.03*** 4.06 2.26 3.02 2.98
Luyin 46 -9.13** -1.03 10.34** 0.06 -0.58 0.04
IR55423-01 6.36 3.52 7.74* 5.87* 0.91 4.30*
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress
Table 5.11: The general combining ability effects (GCA) of parents for panicle weight (g)
Parents Panicle weight
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 0.42*** 0.15* 0.24* 0.27** 0.58*** 0.35***
NERICA 2 0.36*** 0.23*** 0.43*** 0.34*** 0.30** 0.33***
CT16323-CA-25-M 0.17 0.04 0.06 0.09 0.26* 0.14*
CT16333(1)-CA-22-M 0.34*** 0.26*** -0.33** 0.09 0.13 0.10
NERICA-L-25 -0.60*** -0.08 -0.21 -0.30*** -0.45*** -0.34***
Oryza sativa L.
Vandana -0.17 -0.25*** 0.15 -0.09 -0.39*** -0.17*
Duorado 0.33*** -0.20** -0.28** -0.05 0.14 0.00
IR74371-54-1-1 -0.35*** 0.01 -0.11 -0.15 -0.25* -0.18*
Luyin 46 -0.39*** -0.09 -0.04 -0.17* -0.13 -0.16
IR55423-01 -0.10 -0.07 0.09 -0.03 -0.20* -0.07
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress
Table 5.12: The general combining ability effects (GCA) of parents for weight of grains per panicle (g)
Parents
Weight of grains per panicle
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 0.45*** 0.08 0.24** 0.25*** 0.53*** 0.32***
NERICA 2 0.37*** 0.25*** 0.11 0.24*** 0.29** 0.26***
CT16323-CA-25-M 0.21* 0.10 0.05 0.12 0.31** 0.17**
CT16333(1)-CA-22-M 0.32*** 0.22** -0.31*** 0.08 0.02 0.06
NERICA-L-25 -0.66*** -0.10 -0.17* -0.31*** -0.50*** -0.36***
Oryza sativa L.
Vandana -0.12 -0.16* 0.22** -0.02 -0.27** -0.08
Duorado 0.35*** -0.21** -0.26** -0.04 0.11 0.00
IR74371-54-1-1 -0.37*** -0.01 -0.06 -0.15* -0.21* -0.16*
Luyin 46 -0.43*** -0.10 0.11 -0.14 -0.06 -0.12
IR55423-01 -0.13 -0.07 0.06 -0.04 -0.23* -0.09
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress
Table 5.13: The general combining ability effects (GCA) of parents for grain phenotypic acceptability (g)
Parents
Grain phenotypic acceptability
MTG‡ MTP MSMLR Across MSMSR Across
No drought stress RDS
Interspecific
NERICA 1 -1.25*** -0.84*** -0.91*** -1.00*** -1.08*** -1.02***
NERICA 2 -0.95*** -1.04*** -0.86*** -0.95*** -0.58* -0.86***
CT16323-CA-25-M -0.65*** -0.84*** -0.81*** -0.77*** -0.88*** -0.79***
CT16333(1)-CA-22-M -0.55** -1.44*** -0.26 -0.75*** 0.22 -0.51***
NERICA-L-25 1.35*** 1.36*** 0.80*** 1.17*** 0.72** 1.06***
Oryza sativa L.
Vandana 0.85*** 1.36*** 1.05*** 1.09*** 0.72** 0.99***
Duorado -0.55** -0.74*** -0.66*** -0.65*** -0.48* -0.61***
IR74371-54-1-1 0.75*** 0.56*** 0.35* 0.55*** 0.22 0.47***
Luyin 46 0.45** 0.76*** 0.55** 0.59*** 0.32 0.52***
IR55423-01 0.55** 0.86*** 0.75*** 0.72*** 0.82*** 0.74***
‡MTG, Matuga; MTP, Mtwapa, MSMLR, Msambweni long rain; MSMSR, Msambweni short rain: RDS, Random drought stress