Genetic Diversity and Population Structure of Maize Inbred Lines with Varying Levels of Resistance to Striga Hermonthica Using Agronomic Trait-Based and SNP Markers.

Adekemi Stanley,Pangirayi Tongoona,Silvestro Meseka,Abebe Menkir,Beatrice Ifie,Melaku Gedil,Wende Mengesha,Nnanna Unachukwu,Agre Paterne

doi:10.3390/plants9091223

Abstract

Striga hermonthica is a serious biotic stress limiting maize production in sub-Saharan Africa. The limited information on the patterns of genetic diversity among maize inbred lines derived from source germplasm with mixed genetic backgrounds limits the development of inbred lines, hybrids, and synthetics with durable resistance to S. hermonthica. This study was conducted to assess the level of genetic diversity in a panel of 150 diverse maize inbred lines using agronomic and molecular data and also to infer the population structure among the inbred lines. Ten Striga-resistance-related traits were used for the phenotypic characterization, and 16,735 high-quality single-nucleotide polymorphisms (SNPs), identified by genotyping-by-sequencing (GBS), were used for molecular diversity. The phenotypic and molecular hierarchical cluster analyses grouped the inbred lines into five clusters, respectively. However, the grouping patterns between the phenotypic and molecular hierarchical cluster analyses were inconsistent due to non-overlapping information between the phenotypic and molecular data. The correlation between the phenotypic and molecular diversity matrices was very low (0.001), which is in agreement with the inconsistencies observed between the clusters formed by the phenotypic and molecular diversity analyses. The joint phenotypic and genotypic diversity matrices grouped the inbred lines into three groups based on their reaction patterns to S. hermonthica, and this was able to exploit a broad estimate of the actual diversity among the inbred lines. The joint analysis shows an invaluable insight for measuring genetic diversity in the evaluated materials. The result indicates that wide genetic variability exists among the inbred lines and that the joint diversity analysis can be utilized to reliably assign the inbred lines into heterotic groups and also to enhance the level of resistance to Striga in new maize varieties.

Highlights

Maize (Zea mays L.) is an important cereal crop playing a crucial role in global food security and as a source of income for smallholder farmers in sub-Saharan Africa (SSA)
Assessment of the phenotypic diversity using the agronomic traits grouped the inbred lines into five clusters based on their reaction pattern to S. hermonthica (Figure 1)
The hierarchical cluster analysis based on agronomic characteristics under Striga infestation grouped the inbred lines according to their reaction pattern to S. hermonthica, with most of the inbred lines in each group emanating from different source populations

Summary

Introduction

Maize (Zea mays L.) is an important cereal crop playing a crucial role in global food security and as a source of income for smallholder farmers in sub-Saharan Africa (SSA). It is referred to as the queen of cereals because of its high yield potential, ease in processing, and low cost [1]. Maize is a major source of food and livelihood for over 900 million people in Africa [2]. Maize has enormous genetic diversity due to its prolonged selection [4,5,6], and it has become a model crop for major cereals [7] because its genome harbors tremendous phenotypic and molecular diversity [8]. Its molecular diversity is about fivefold higher than other domesticated crops [8,9]

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Conclusion