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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Addis Ababa University


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 iv 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.



Quality Protein Maize, QPM, Combining Ability, GCA, SCA, Heterosis, Correlation, Heritability, Genetic Advance, Diversity, SNP, ISSR