Genetic Diversity and Inter-Trait Relationships among Maize Inbreds Containing Genes from Zea diploperennis and Hybrid Performance under Contrasting Environments&#x0D; &#x0D;

Ijeoma Chinyere Akaogu,Nnanna Unachukwu,Ana Luisa Garcia-Oliveira,Samuel Kwame Offei,Vernon Gracen,Baffour Badu-Apraku,Melaku Gedil,Daniel Kwadjo Dzidzienyo,Pangirayi Tongoona,Sarah Hearne

doi:10.3390/agronomy10101478

Abstract

Accurate estimation of genetic variability present in tropical maize inbreds with varying reactions to Strigahermonthica infestation is essential for efficient and sustainable utilization to ensure increased genetic gain in a breeding program. Thirty-six early maturing maize inbred lines and 156 single cross hybrids were evaluated under Striga-infested and non-infested conditions in Nigeria during the 2014 and 2015 cropping seasons. Under Striga infestation, grain yield ranged from 1134 kg ha−1 for TZEI 26 × TZEI 5 to 5362 kg ha−1 for TZdEI 173 × TZdEI 280. The average yield reduction of the hybrids under Striga infestation was 44% relative to the performance under non-infested environments. Using 4440 high-quality DArT markers, clustering and population structure analyses separated the inbred lines into three distinct groups based on the genetic distance indicating high level of genetic variability among the lines. The base index of the International Institute of Tropical Agriculture (IITA) identified 50% of the inbred lines as Striga resistant. The genetic diversity study provided an opportunity for selecting divergent parents for tagging candidate genes and quantitative trait loci for marker-assisted introgression of Striga resistance genes into early maturing tropical maize breeding populations. The most reliable secondary trait for indirect selection for grain yield under Striga infestation was the ear aspect.

Highlights

The introgression of novel genes for Striga resistance from the wild relative of maize, Zea diploperennis L., into the background of cultivated maize is a resourceful approach for genetic and Agronomy 2020, 10, 1478; doi:10.3390/agronomy10101478 www.mdpi.com/journal/agronomyAgronomy 2020, 10, 1478 physiological studies [1,2,3]
Significant (p < 0.01) sets and environment–sets interaction effects were obtained for most measured traits except sets mean squares for Striga damage at eight weeks after planting (WAP); environments–sets interactions mean squares for anthesis-silking interval (ASI) and Ears per plant (EPP)
Interactions of the general combining ability (GCA)-male and GCA-female with the environment were highly significant for grain yield and other agronomic traits, except E–GCA-male for Striga damage at eight WAP

Summary

Introduction

The introgression of novel genes for Striga resistance from the wild relative of maize, Zea diploperennis L., into the background of cultivated maize is a resourceful approach for genetic and Agronomy 2020, 10, 1478; doi:10.3390/agronomy10101478 www.mdpi.com/journal/agronomyAgronomy 2020, 10, 1478 physiological studies [1,2,3]. A thorough understanding of the genetic diversity in the maize inbred lines and assessment of their reactions to Striga are essential for systematic exploitation, to provide the capacity to meet changing environments and market requirements [4]. Genetic diversity in maize has been assessed using several types of DNA markers including restriction fragment length polymorphism (RFLP), randomly amplified polymorphism DNA (RAPD), simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers. These markers have provided effective genotyping and are not affected by the different processes of plant physiology or the environment [8,9,10,11].

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Discussion

Conclusion