Genetic Gains in Yield and Yield Related Traits under Drought Stress and Favorable Environments in a Maize Population Improved Using Marker Assisted Recurrent Selection.

Folusho Bankole,Abebe Menkir,Sarah Hearne,Nnanna Unachukwu,Jose Crossa,Melaku Gedil,Gbadebo Olaoye

doi:10.3389/fpls.2017.00808

Abstract

The objective of marker assisted recurrent selection (MARS) is to increase the frequency of favorable marker alleles in a population before inbred line extraction. This approach was used to improve drought tolerance and grain yield (GY) in a biparental cross of two elite drought tolerant lines. The testcrosses of randomly selected 50 S1 lines from each of the three selection cycles (C0, C1, C2) of the MARS population, parental testcrosses and the cross between the two parents (F1) were evaluated under drought stress (DS) and well watered (WW) well as under rainfed conditions to determine genetic gains in GY and other agronomic traits. Also, the S1 lines derived from each selection types were genotyped with single nucleotide polymorphism (SNP) markers. Testcrosses derived from C2 produced significantly higher grain field under DS than those derived from C0 with a relative genetic gain of 7% per cycle. Also, the testcrosses of S1 lines from C2 showed an average genetic gain of 1% per cycle under WW condition and 3% per cycle under rainfed condition. Molecular analysis revealed that the frequency of favorable marker alleles increased from 0.510 at C0 to 0.515 at C2, while the effective number of alleles (Ne) per locus decreased from C0 (1.93) to C2 (1.87). Our results underscore the effectiveness of MARS for improvement of GY under DS condition.

Highlights

Maize is a staple crop in sub-Saharan (SSA) Africa consumed by over 300 million people
Testcrosses of the S1 lines derived from C0, C1, and C2 of the marker assisted recurrent selection (MARS) population were evaluated at Ikenne for 2 years under both Drought Stress stress (DS) and well watered (WW) conditions
The observed higher mean grain yield (GY) of the testcrosses at C2 over that at C0, parental testcrosses and commercial checks under DS and well-watered condition suggest that MARS was effective for the improvement of complex traits such as tolerance to DS consistent with the findings of Beyene et al (2015, 2016)

Summary

Introduction

Maize is a staple crop in sub-Saharan (SSA) Africa consumed by over 300 million people. The rapidly growing population in the SSA has necessitated the need to increase maize production in the region ; the development of maize varieties with enhanced performance under biotic and abiotic stresses continues to be an important objective (Boomsma and Vyn, 2008). The average yield of maize are significantly lower in Africa compared with the other parts of the world as a result of a host of abiotic and biotic stress factors that affects the crop (FAO, 2010). Genetic Gains under Drought Stress stress (DS) and sub-optimal soil nitrogen conditions, the yield of maize is reduced by up to 80% (Bänziger and Lafitte, 1997; Betran et al, 1997; Bänziger et al, 2006). The change in the climate is expected to increase the occasions of drought in Africa (Williams and Funk, 2011), coupled with the expansion of maize production into drought prone regions

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