ABSTRACT
Field were conducted at the and 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 were to (i) screen some maize genotypes for agronomic 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).
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 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 < 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 %), a number of exit holes (2.83), and tunnel damage length (7.37 cm). The 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 a significantly higher ear weight (350 g) and grain yield (11.35 ton/ha). The hybrid UM x B43 obtained a significantly higher number of ears per plant (1.83) while UM x OB hybrid gave the highest number of kernels per cob (611.30).
The hybrid B28 x B43 had the 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 the number of kernels per cob while UM x B43 (26.88%) was higher on the number of ears 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 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.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgment iv
Table of content v
List of tables vii
Abstract ix
INTRODUCTION 1 LITERATURE REVIEW
Origin and Distribution of maize 3
Climatic and soil requirement 3
Production constraint 4
Maize disease 4
Maize stem borers 4
Genetic diversity and improvement on maize 5
Breeding methods 6
Recurrent selection 6
Phenotypic or simple recurrent selection 8
Combining ability 8
Heterosis 10
MATERIALS AND METHODS
Site Location 12
Land preparation and planting 12
Fertilizer application and weeding 12
Materials 12
Experiment 1 12
Experiment 2 13
Experiment 3 14
Statistical analysis 16
RESULTS
Evaluation of the maize parents 20
Evaluation of the maize parent on the incidence of brown spot disease, stem borer infestation, and lodging. 23
Principal components analysis for the maize parents studied. 25
The correlation coefficient of the maize genotypes was studied. 27
Path coefficient analysis of the maize genotypes studied. 29
The mean square and genetic parameters for some of the quantitative traits studied on the maize genotypes 31
Evaluation of phonological, morphological, yield, and yield component traits of the maize inbred parent 33
Evaluation of the incidence of brown spot disease, lodging, stemborer infestation, and stemborer related traits 36
Evaluation of the parent and F1 on phenological, morphological, yield, and yield components traits of the maize genotypes 38
Evaluation of brown spot disease incidence, lodging, stem borer infestation, number of the exit hole,s, and tunnel length on F1 hybrids and the parents of the maize studied. 43
Estimates of Better Parent Heterosis (BPH) on the phenological, morphological, yield, and component traits of the maize hybrid studied. 46
Estimates of Better Parent Heterosis (BPH) on brown spot disease incidence, lodging incidence, and stem borer infestation and stem borer related traits on the maize genotypes 49
The variance component of the General Combining Ability of (GCA)
and Specific Combining Ability (SCA) of the maize traits studied. 51
Estimate of General Combing Ability (GCA) of the maize parents. 55
Estimate of the specific combining ability (SCA) of the maize hybrid use in study 60
DISCUSSION 64
Conclusion and recommendation 71
REFERENCES 72
Appendix
INTRODUCTION
Maize (Zea mays L.) belongs to the family of grass Gramineae (Poaceae). It is a tall, monoecious annual plant with male and female flowers in separate places on the same plant with an extensive fibrous root system.
Its center of origin is a Mesoamerican region, now Mexico and Central America (Doebley, 1994), and its domestication started at least 6000 years ago. Maize is one of the most productive and widely adapted crop species in the world.
It is cultivated in all parts of the world except Antarctica. Loamy or silty loam soil or silty clay loam is the ideal soil type for its cultivation and a pH of 6.5 to 7.5 is the most preferred for its growth.
It is among the leading cereal crops after wheat and rice with regard to cultivation area, total production, and consumption (Olakojo and Akinlosotu, 2004; CIMMYT, 2004; Olawuyi et al., 2010). Global production amounted to 130 million hectares with an output of 574 million metric tons (Ito, 1998).
Maize is an important staple food crop for millions of both in developed and developing countries. It is relatively high-yielding, easy to digest, easily processed, and cheaper than other cereals.
In Nigeria, maize is used directly for human consumption as well as infant nutrition in the form of porridge during the weaning period, without any protein supplement such as egg, meat, or beans which are comparatively expensive especially for poor-resource families in the rural areas (Yusuf, 2010).
In Africa, maize is consumed as a starchy base in a wide variety of porridges, pastes, grits, and beer. Freshly harvested is eaten parched, baked, roasted, or boiled and plays an important role in filling the hunger gap after the dry season.
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