Table 1.
List of the extra-early maturing PVA maize inbred lines used for the North Carolina design II studies, the pedigree information, reactions to Striga and provitamin A contents in preliminary studies.
Table 2.
Observations made on the agronomic traits and the mode of determination.
Table 3.
Mean squares of grain yield and other agronomic traits of extra-early maturing PVA maize hybrids evaluated under Striga conditions.
Table 4.
Mean squares of grain yield and other agronomic traits of extra-early maturing PVA maize hybrids evaluated under low-N environments in 2018 (Ile-Ife and Mokwa) and 2019 (Mokwa).
Table 5.
Mean squares of grain yield and other agronomic traits of extra-early maturing pro-vitamin A maize hybrids evaluated under optimal environments at Mokwa (2018 and 2019), Ile-Ife and Abuja (2018).
Table 6.
Proportion of total-genotypic sums of squares for grain-yield and other agronomic traits of extra-early maturing provitamin A maize-inbred lines attributable to general combining ability (GCA-male and GCA-female) and specific combining-ability (SCA) effects of the inbred lines and hybrids, respectively under Striga, low-N and optimal conditions in Nigeria, 2018–2019.
Table 7.
General combining ability effects of grain yield and other agronomic traits of PVA maize inbred lines evaluated under Striga, low-N and optimal conditions.
Table 8.
Grain yield of selected PVA maize hybrids across Striga, low-N and optimal conditions.
Fig 1.
Dendogram of 30 extra-early maturing PVA inbred lines constructed based on the GCA effects of multiple traits (HGCAMT) method across Striga, low-N and optimal environments in Nigeria, 2018–2019.
Table 9.
The PVA contents of selected extra-early single-cross hybrids.
Fig 2.
Path analysis model diagram showing causal relationships of measured traits of early maturing provitamin A maize hybrids evaluated under Striga infested conditions in Mokwa and Abuja.
R2 = co-efficient of determination; R1 = residual effects; YIELD = grain yield; EASP = ear aspect; EPP = ears per plant; ANTH = days to 50% anthesis; SL = stalk lodging; ASI = anthesis–silking interval; PASP = plant aspect; DYSK = days to 50% silking; RAT1 and RAT2 = Striga damage rating at 8 and 10 WAP, respectively; C01 and C02 = number of emerged Striga plants at 8 and 10 WAP, respectively; PHT = plant height; EHT = ear height; HC = husk cover; RL = root lodging; EROT = ear rot.
Fig 3.
Path analysis model diagram showing causal relationships of measured traits of extra-early maturing provitamin A maize hybrids evaluated under low-N environments in Ile-Ife and Mokwa.
R2 = co-efficient of determination; R1 = residual effects; YIELD = grain yield; EASP = ear aspect; EPP = ears per plant; ANTH = days to 50% anthesis; SL = stalk lodging; ASI = anthesis–silking interval; PASP = plant aspect; DYSK = days to 50% silking; STGR = stay green characteristics; PHT = plant height; EHT = ear height; HC = husk cover; RL = root lodging; EROT = ear rot.
Fig 4.
Path analysis model diagram showing causal relationships of measured traits of extra-early maturing provitamin A maize hybrids evaluated under optimal environments in Abuja, Ile-Ife and Mokwa.
R2 = co-efficient of determination; R1 = residual effects; YIELD = grain yield; EASP = ear aspect; EPP = ears per plant; ANTH = days to 50% anthesis; SL = stalk lodging; ASI = anthesis–silking interval; PASP = plant aspect; DYSK = days to 50% silking; PHT = plant height; EHT = ear height; HC = husk cover; RL = root lodging; EROT = ear rot.
Fig 5.
An entry/tester genotype main effect plus genotype x environment biplot showing mean versus stability of grain yield for 30 (best 20 and worst 10 based on the combined Striga and low-N base index) selected extra-early maturing provitamin A maize hybrids plus six checks evaluated across Striga, low-N and optimal environments from 2018 to 2019 in Nigeria.
Table 10.
(a): List of selected hybrids for stability analysis; (b) The description of the test environments used for the biplot analysis.