Molecular Plant Breeding 2015, Vol.6, No.17, 1
-
22
1
Research Article
Open
Access
Genetic Diversity Analysis in Tropical Maize Germplasm for Stem Borer and
Storage Pest Resistance using Molecular Markers and Phenotypic traits
Mwololo J.K.
1
, Munyiri S.W.
2
, Semagn K.
3
, Mugo S.
3
, Okori p.
4
1. Pwani University, P.O Box 195 Kilifi, Kenya
2. Chuka University, P.O. Box 109-60400, Chuka, Kenya.
3. International Maize and Wheat Improvement Center (CIMMYT), P. O. Box 1041, 00621, Nairobi, Kenya
4. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), P. O. Box 1096, Lilongwe, Malawi, Kenya
Corresponding
authors
email:
Molecular
Plant
Breeding,
2015,
Vol.6,
No.17
doi:
10.5376/mpb.2015.06.0017
Received:
07
Jul.,
2015
Accepted:
11
Aug.,
2015
Published:
30
Sep.,
2015
Copyright
© 2015 Mwololo et al,
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Preferred
citation
for
this
article:
Mwololo J.K., Munyiri S.W., Semagn K., Mugo S. and Okori p., 2015,
Genetic Diversity Analysis in Tropical Maize Germplasm for Stem Borer and Storage
Pest Resistance using Molecular Markers and Phenotypic traits,
Molecular
Plant
Breeding,
6(17)
1
-
22(doi:
Abstract
One hundred maize inbred lines and eighty four hybrids were characterized for resistance to maize stem borer and
post-harvest insect pests. This was achieved using genetic distance and population structure based on simple sequence repeat (SSR)
markers and biophysical traits. The test materials were evaluated for stem borer, maize weevil and larger grain borer (LGB)
resistance. Leaf samples were harvested from 10 healthy plants per genotype and bulked. Genomic DNA was extracted using a
modified version of mini-prep Cetyl Trimethyl Ammonium Bromide (CTAB) method. The samples were genotyped with 55 SSRs
makers. Univariate analysis of variance was done using the general linear model procedure of SAS statistical package. Rodgers
genetic distance was calculated for all data sets as a measure of genetic distance using NTSYS-pc for Windows. The distance
matrices were used to generate phenograms using the unweighted pair group method based on arithmetic average (UPGMA) method
in MEGA5. The genotypes were assigned into different populations using population structure software. The data was further
subjected to discriminant and principal component analysis to group the gnotyoes. Analysis of molecular variance within and among
the different populations was done using arlequin. There were significant differences (P ≤ 0.001) for all the biophysical traits
evaluated. The SSR marker data estimated successfully the close relationship among different hybrids and inbred lines within clusters.
Comparisons of the different multivariate analyses revealed high concordance among the different approaches of analyses. The
results of this study can be directly used by breeding programs to develop resistant genotypes.
Keywords
Resistance; Maize insect pests; Genetic distance; Breeding, Molecular marker
s
Introduction
Maize is a staple food for more than 300 million
people in sub Saharan Africa (SSA) and is commonly
grown by small-scale and resource poor farmers in
rural areas (Shiferaw et al., 2011). However, the
average maize yield in SSA was estimated at 1.4 t/ha,
which is extremely low as compared to the 3.3 t/ha
reported in developing countries in other parts of the
world, the 4.9 t/ha worldwide production and the 8.4
t/ha in industrialized countries. Several factors,
including a wide range of pests and diseases, periodic
drought, scarcity of irrigation water, low soil fertility
and farmers inability to use farm inputs contribute to
low productivity in SSA. Insect pest in the field and in
storage are among the factors that reduce yields and
food availability in the region. Maize stem borers
cause maize losses of up to 15% in susceptible
germplasm in the infested ecologies, while the storage
pest, such as maize weevil and larger grain borer (LGB)
cause 20-30% yield loss
.
Although there are different possible methods that
help in minimizing yield loss by insect pest (e.g.
chemical, biological and cultural methods), host plant
resistance developed through breeding is a preferred
method to disseminate improved maize varieties due
to its environmental and human safety, relatively low
cost, and ease of use by farmers. However, there is
very little effort in breeding for insect pest resistance
in SSA which may be due to the genetic and logistical
challenges associated with insect pest and hosts
(screening and selecting for insect resistance).
Nevertheless, CIMMYT and partners have developed
various multiple borer resistance (MBR) lines and
population using conventional breeding methods
under artificial infestation. Some of the MBR
germplasm have been released and disseminated in
some countries.
