Abstract
The comparison of different methods of estimating the genetic diversity could define their usefulness in plant breeding and conservation programs. In this study, a total of 15 morphological traits, eight AFLP-primer combinations and 20 simple sequence repeat (SSR) loci were used (i) to study the morphological and genetic diversity among 62 selected highland maize accessions, (ii) to assess the level of correlation between phenotypic and genetic distances, and (iii) to classify the accessions into groups based on molecular profiles and morphological traits. The analysis of variance of the morphological data revealed significant differences among accessions for all measured traits. The mean morphological dissimilarity (0.3 with a range of 0.1-0.68) was low in comparison to dissimilarity calculated using SSR markers (0.49 with a range 0.27-0.63) and AFLP markers (0.57 with a range 0.32-0.69). The correlation between the morphological dissimilarity matrix and the matrices of genetic dissimilarity based on SSR and AFLP markers was 0.43 and 0.39, respectively (p = 0.001). The correlation between SSRs and AFLPs dissimilarity matrices was 0.67 (p = 0.001). This congruence indicates that both marker systems are equally suited for genetic diversity study of maize accessions. Cluster analysis of morphological and marker distances revealed three groups of maize accessions with distinctive genetic profiles and morphological traits. This information will be useful for collections, conservation and various breeding programs in the highlands of Ethiopia. Key words: AFLP, correlation, phenotypic diversity, SSR.
Highlights
Knowledge of genetic variation and relationships between accessions or genotypes is important: (i) to understand the genetic variability available and its potential use in breeding programs, (ii) to estimate any possible loss of genetic diversity, (iii) to offer evidence of the evolutionary forces shaping the genotypic diversities, and (iv) to choose genotypes to be given priority for conservation (Thormann et al, 1994)
The objectives of this study were (i) to investigate genetic diversity and relationships among 62 selected highland maize accessions using morphological, AFLP and simple sequence repeat (SSR) markers, (ii) to assess the correlation between distance estimates based on morphological traits and molecular markers, and (iii) to classify the accessions into groups based on a combination of molecular profiles and morphological traits
The third principal component, which accounted for 10.5% of the total variation, was dominated by traits such as number of leaves, ear diameter, yield and ear length, while days to maturity, leaf width and number of leaves were important delineating traits associated with the fourth principal component, which accounted for 6.7% of the total variation
Summary
Knowledge of genetic variation and relationships between accessions or genotypes is important: (i) to understand the genetic variability available and its potential use in breeding programs, (ii) to estimate any possible loss of genetic diversity, (iii) to offer evidence of the evolutionary forces shaping the genotypic diversities, and (iv) to choose genotypes to be given priority for conservation (Thormann et al, 1994). Characterization of genetic resource collections has been greatly facilitated by the availability of a number of molecular marker systems. Morphological traits were among the earliest markers used in germplasm management, but they have a number of limitations, including low polymorphism, low heritability, late expression, and vulnerability to environmental influences (Smith and Smith, 1992). DNA markers do not have such limitations. They can be used to detect variation at the DNA level and have proven to be effective tools for distinguishing between closely related genotypes. Different types of molecular markers have been used to assess the genetic diversity in crop species, but no single technique is universally ideal. Amplified fragment length polymorphisms (AFLPs; Vos et al, 1995) and microsatellites, or simple sequence repeats
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