Heterotic grouping of selected inbred lines of maize (zea mays l.) using two testers in Kiambu And Embu Counties, Kenya
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Date
2016-02
Authors
Chemeli, Jane
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Maize is an important staple food for most Kenyans. The increasing population trend in the face
of declining yields in maize production has intensified food insecurity countrywide. The low
grain yield can be attributed to foliar diseases mainly gray leaf spot and maize streak virus and
expensive hybrid seeds. Hybrid testing is expensive and limited in number of hybrids that can be
generated and tested each year. This has increased the need to improve maize production
techniques to meet the high demand. Assigning germplasm into different heterotic groups is
fundamental for exploitation of heterosis for hybrid development within a shorter period thus
reducing the cost. The objectives of this study were to identify good hybrids based on grain yield
data and other yield related traits, to estimate the specific combining ability and percentage
heterosis of hybrids formed and identify lines with good combining that can be used as parents in
hybrid combination and classify the selected KALRO lines into heterotic groups. Eleven inbred
lines were crossed with two single cross testers MU021 and MU022 developed by Kenya
Agricultural and Livestock Research Organization (KALRO) Muguga South and belonged to
heterotic groups A and B respectively. Line by tester design was used for making crosses.
Twenty two crosses were evaluated in a randomized incomplete block design (RIBD) with two
replications during the long rainy seasons between March and November 2012.The study was
carried out in two different sites, at KALRO Muguga South and KALRO Embu. The parameters
measured included plant height (cm), ear height (cm) and grain weight per plot in grams. Disease
scores for gray leaf spot (GLS) and maize streak virus (MSV) were recorded and analyzed using
Kruskal-Wallis Test. Data collected on plant height, ear height and yield were analyzed by
Analysis of Variance (ANOVA) using Genstat programme 2012 and means separation was done
using Tukey‘s 95% confidence intervals. Heterosis, general combining ability (GCA) and
specific combining ability (SCA) were calculated using line by tester analysis. GCA mean
squares due to lines and testers were highly significant p< 0.01 for plant height and ear height.
GCA effects indicated that V217-48, Z426-43Z387-4-1 and Z419-5Z443-3 were the best general
combiners for grain yield. V131-303 showed significant negative GCA effects. The good
yielders in Embu were Z426-43Z387-4-1 X MU021, Z419-5Z443-3 X MU022,V217-48 X
MU021, V217-48 X MU022 S458-2-2-2 X MU022 and V131-201 X MU021. In Muguga, the
best performance were EC573(R12) Cross combinations S458-2-2-2 X MU021 or S458-2-2-2 X
MU022 did well in the two counties. Inbred lines; V217-48 and V265-4-1 were resistant to both
maize streak virus and Gray leaf spot in Muguga while inbred lines: Z419-5Z443-3, S458-2-2-2
and V131-201 showed resistance to both MSV and GLS. Total GCA mean squares were greater
than SCA mean squares (GCA/SCA ratios of >1) indicating a preponderance of additive over
non additive gene action. The basis of grouping the germplasm into different heterotic groups
was specific combining ability (SCA) effects for grain yield. V131-303, Z426-43Z387-4-1,
V217-48 and V131-201 showed negative SCA effects for grain yield with MU022 and were
place into heterotic group B. EC573(R12)C853-14, V265-4-1, Z419-5Z443-3, V217-5, V265-
80, REGN99/48-2 and S458-2-2-2 showed negative SCA effects for grain yield with MU021 and
were placed into heterotic group A. The general, specific combining abilities and heterotic
groups showed that these genotypes had a potential hybrids for advanced yield testing and
subsequent release in the specific locations.
Description
A thesis submitted in partial fulfillment of the requirements for the award of the degree of Master of Science (Genetics) in the School of Pure and Applied Sciences of Kenyatta University. February 2016