Abstract
Striga is an important biotic factor limiting maize production in sub-Saharan Africa and can cause yield losses as high as 100%. Marker-assisted selection (MAS) approaches hold a great potential for improving Striga resistance but requires identification and use of markers associated with Striga resistance for adequate genetic gains from selection. However, there is no report on the discovery of quantitative trait loci (QTL) for resistance to Striga in maize under artificial field infestation. In the present study, 198 BC1S1 families obtained from a cross involving TZEEI 29 (Striga resistant inbred line) and TZEEI 23 (Striga susceptible inbred line) plus the two parental lines were screened under artificial Striga-infested conditions at two Striga-endemic locations in Nigeria in 2018, to identify QTL associated with Striga resistance indicator traits, including grain yield, ears per plant, Striga damage and number of emerged Striga plants. Genetic map was constructed using 1,386 DArTseq markers distributed across the 10 maize chromosomes, covering 2076 cM of the total genome with a mean spacing of 0.11 cM between the markers. Using composite interval mapping (CIM), fourteen QTL were identified for key Striga resistance/tolerance indicator traits: 3 QTL for grain yield, 4 for ears per plant and 7 for Striga damage at 10 weeks after planting (WAP), across environments. Putative candidate genes which encode major transcription factor families WRKY, bHLH, AP2-EREBPs, MYB, and bZIP involved in plant defense signaling were detected for Striga resistance/tolerance indicator traits. The QTL detected in the present study would be useful for rapid transfer of Striga resistance/tolerance genes into Striga susceptible but high yielding maize genotypes using MAS approaches after validation. Further studies on validation of the QTL in different genetic backgrounds and in different environments would help verify their reproducibility and effective use in breeding for Striga resistance/tolerance.
Highlights
In sub-Saharan Africa (SSA), maize (Zea mays L.) is the most widely cultivated cereal crop, playing important food and nutritional roles in the livelihoods of over 300 million households in the sub-region [1,2,3]
Significant positive genotypic correlations were recorded between grain yield and ears per plant while significant negative genotypic correlations were observed between grain yield and Striga damage at 10 weeks after planting (WAP) as well as ears per plant and Striga damage at 10 WAP (Table 2)
Significant positive phenotypic correlations were obtained between grain yield and ears per plant while significant negative correlations were observed between grain yield and Striga damage at 10 WAP
Summary
In sub-Saharan Africa (SSA), maize (Zea mays L.) is the most widely cultivated cereal crop, playing important food and nutritional roles in the livelihoods of over 300 million households in the sub-region [1,2,3]. The parasitic purple witchweed Striga hermonthica (Del.) Benth. Identification of QTLs under Striga infestation in tropical maize [OPP1134248]. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript
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