Efforts towards the development of high yielding and stem borer resistant maize in a humid environment

Thesis Abstract

Field experiments were conducted at the Teaching and Research Farm of the Department of Crop Science, Faculty of Agriculture, University of Nigeria, Nsukka to commence the process of developing high yielding maize with resistance to stem borers in a humid environment. The specific objectives were to (i) screen some maize genotypes for agronomic traits and stem borer resistance (ii) estimate some genetic parameters of the genotypes studied. Twenty maize genotypes used comprised twelve maize genotypes collected from the International Institute of Tropical Agriculture (IITA) namely (2009 TZE OR1 DT STR QPM (TOR1), AMA TZBR – Y – F2 (AMA), TZBR COMP – 2 – YC1F2 (COMP2), BR 9928 DMRSR (B28), DMR – LSR – Y (DMR), TZE – Y – POP DT STR QPM (POP), 2009 TZE OR2 DT STR QPM (TOR2), 99 TZE Y – STR QPM (99 TZE), BR 9943 DMRSR (B43), TZBR COMP – YC1F2 (COMP1), EV DT – Y – 2000 STR QPM (EVDT) and TZEE – Y -POR STR QPM CO (PORC)) and eight (8) local accessions (Ugwuachara (UG), Umukasi (UM), ORBA1, Obukpa (OB), ORBA2, Edem Ani (EA), Isakpu (IS) and Ajuona (AJ)) from Enugu state, Nigeria. The parameters measured include days to tasselling, silking, maturity, stem girth, number of leaves, ear height, plant height, ear length, ear diameter, number of kernel per row, number of rows per ear, number of kernel per cob, number of ear per plant, shelling percentage, ear weight, grain yield, brown spot disease, lodging incidence, stem borer infestation, number of exit holes and tunnel damage length. General combining ability (GCA) of the parents and specific combining ability (SCA) of the hybrids were estimated using Graffings’ model 1 method 2 in a 10 x 10 diallel cross. Among the parents, POP and PORC had significantly (p < 0.05) shorter days to tasselling (55.67 and 56.00) and silking (57.00 and 58.33), respectively than other genotypes. The parent UG had significantly (p < 0.05) higher ear weight (209.40 g) and grain yield (6.23 ton/ha) among other genotypes. The ORBA2 parents gave significantly (p r< 0.05) higher number of kernel per cob (419.50) and hundred grain weights (33.60 g) while the parent UM gave the highest number of ears per plant (1.48). The parent OB obtained the highest stem borer infestation (20 %), number of exit hole (2.83) and tunnel damage length (7.37 cm). Majority of the hybrids produced performed significantly (p < 0.05) higher than the parents in most of the traits. The hybrid UG x ORBA2 had significantly higher ear weight (350 g) and grain yield (11.35 ton/ha). The hybrid UM x B43 obtained significantly higher number of ear per plant (1.83) while UM x OB hybrid gave highest number of kernels per cob (611.30). The hybrid B28 x B43 had highest positive better parent heterosis (BPH) for ear weight (136.56 %) and grain yield (193.83 %). The hybrid UG x B28 (101.16 %) obtained higher BPH on number of kernel per cob while UM x B43 (26.88%) was higher on number of ear per plant. The hybrid PORC x B28 had the least stem borer infestation (6.14 %) while TOR1 x B43 obtained lower number of exit holes (1.00) and tunnel damage length (7.12 cm). The ORBA1 parent was the best combiner among all the parents while POP x PORC was the best combiner among all the hybrids in yield and yield attributes. A cross involving B28 x B43, ORBA1 x B28, ORBA1 x ORBA2, ORBA2 x B43, PORC x B28, TOR1 x B43, TOR1 x POP, TOR1 x PORC, TOR1 x UM, UG x B43, UG x UM, UM x B28, UM x B43 and UM x OB could be resistant to stem borer while a cross involving UG x ORBA2, ORBA2 x B43, ORBA2 x UM, PORC x B43, UG x B43 and UM x B28 could also serve as potential hybrids for improving maize yield.