Genetic Analysis of Agro-Morphological Traits and Molecular Diversity Study (ISSR and Snps) of Quality Protein Maize (Zea Mays L.) Inbred Lines in Drought Stressed Areas of Ethiopia
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Date
2017-11-05
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Addis Ababa University
Abstract
Genetic studies along with characterization of elite breeding lines provide understanding of
the genetic diversity and relationship among the inbred lines. They also offer information on
the type of gene action controlling the inheritance of desirable quantitative traits. The
information enables breeders to define a systematic breeding strategy and to select suitable
parents and hybrids for further breeding activities and commercialization. Thus, the
purposes of this study were to estimate combining abilities and heterosis and to determine
genetic variation, correlation, heritability and expected genetic advance of elite quality
protein maize (QPM) inbred lines for grain yield and other agronomic traits as well as to
investigate their genetic diversity and relationship using SNP and ISSR markers. A total of
116 QPM test cross hybrids developed by crossing 58 QPM inbred lines with two QPM
testers was evaluated for 17 morphological traits along with two conventional maize (CM)
and two QPM standard checks in drought stressed areas of eastern Ethiopia – Melkassa
Agricultural Research Center (MARC), Edo Gojola and Mieso. The inbred lines were also
evaluated separately adjacent to the hybrid trial at each site and the inbred lines were
genotyped by SNP and ISSR markers. Significant differences were observed among the
inbred lines and hybrids for grain yield and most considered agronomic traits indicating that
genetic variations existed among the genotypes to allow good progress from selection for
improvements of those traits. Across sites, the highest mean grain yield was observed for the
hybrid L52/CML159 (5.38 t ha-1) followed by L18/CML159 (5.07 t ha-1) and L35/CML159
(5.02 t ha-1) in the hybrid trial while inbred line L52 showed the highest mean GY which
was 3.15 t ha-1 followed by L38 (2.94 t ha-1), L47 (2.88 t ha-1), L17 (2.43 t ha-1), L48 (2.33 t
ha-1) and L40 (2.06 t ha-1) in the inbred line trial. The combining ability analysis showed
that general combining ability (GCA) of lines was significant while specific combining
ability (SCA) was non-significant for grain yield, anthesis date, plant height, ear height,
plant aspect, ear length and thousand kernel weight indicating that the variability observed
among the hybrids was attribuable to additive effects for most traits. The contribution of line
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GCA was found to be higher than the contribution of tester GCA and line tester SCA for
all considered traits except for thousand kernel weight where the contribution of tester GCA
was higher. Inbred lines L35 (0.83 t ha-1), L45 (0.68 t ha-1), L53 (0.63 t ha-1), L4 (0.57 t
ha-1), L21 (0.56 t ha-1), L52 (0.54 t ha-1) and L32 (0.49 t ha-1) had significant positive GCA
effects for grain yield. Hybrid combination L52/CML159 had the best SCA effects for grain
yield and other most important traits and the maximum standard heterosis over MH140
(19.7%) and MH130 (21.4%). Grain yield had positive and highly significant genotypic and
phenotypic correlations with plant height, ear length and thousand kernel weight while
negative and highly significant with days to 50% anthesis, anthesis-silking interval, ear
position, shoot lodging and ear aspect. The present study showed that root lodging was not
important characteristics to be considered while shoot lodging played an important role in
determining grain yield. It also showed that ear height is more important than plant height to
develop high yielding hybrids and that it is possible to select high yielding varieties which
are early but tall with low ear placement. The ISSR markers were found to be as effective as
SNP markers in clustering inbred lines into seven sub-groups which are in agreement with
pedigree information. All the three multivariate analyses viz. cluster analysis, model-based
population structure analysis and principal component analysis using SNPs consistently
identified the same seven distinct populations and revealed similar membership of inbred
lines in each population. In general, the results from this diversity study based on SNP and
ISSR markers will be useful to breeders in selecting best parental combinations for starting
new breeding populations, mapping population and marker assisted breeding.
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Keywords
Quality Protein Maize, QPM, Combining Ability, GCA, SCA, Heterosis, Correlation, Heritability, Genetic Advance, Diversity, SNP, ISSR