Identification of QTLs for grain yield and other traits in tropical maize under Striga infestation.
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Strigais 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 improvingStrigaresistance but requires identification and use of markers associated withStrigaresistance for adequate genetic gains from selection. However, there is no report on the discovery of quantitative trait loci (QTL) for resistance toStrigain maize under artificial field infestation. In the present study, 198 BC(1)S(1)families obtained from a cross involving TZEEI 29 (Strigaresistant inbred line) and TZEEI 23 (Strigasusceptible inbred line) plus the two parental lines were screened under artificialStriga-infested conditions at twoStriga-endemic locations in Nigeria in 2018, to identify QTL associated withStrigaresistance indicator traits, including grain yield, ears per plant,Strigadamage and number of emergedStrigaplants. 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 keyStrigaresistance/tolerance indicator traits: 3 QTL for grain yield, 4 for ears per plant and 7 forStrigadamage 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 forStrigaresistance/tolerance indicator traits. The QTL detected in the present study would be useful for rapid transfer ofStrigaresistance/tolerance genes intoStrigasusceptible 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 forStrigaresistance/tolerance.
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