Mapping Qtls for Grain Yield and Yield Components in Kenyan Maize (Zea mays L.) Under Low Phosphorus Using Single Nucleotide Polymorphism (SNPS)
Abstract
Selection for tolerance to low phosphorus (P) using morphological traits alone
is slow and often confounded by environmental effects. This study identified
some Quantitative Trait Loci (QTLs) associated with grain yield (GYLD),
Plant (PHT) and Ear heights (EHT) under low P in maize using single nucleotide polymorphic markers. 228 F2:3 individuals derived from a cross between two contrasting maize inbred lines together with 239 SNPs were
mapped onto ten linkage groups (LGs) spanning 2255 centiMorgans (cM)
with an average inter-marker distance of 9.44 cM. Majority of the SNP markers (63%) followed the Mendelian segregation and were fairly distributed in
all the LGs. Mean performance for all the traits in the F3 population was
higher than the parental values, which suggested transgressive segregation for
all traits. Low to moderate broad sense heritability (0.35 - 0.50) in the F3
population for GYLD, PHT and EHT indicated that tolerance to low P is
controlled by complex multi genetic factors. A full multi-QTL model analysis
suggested six QTLs (2 QTLs each for GYLD, PHT and EHT) located on
chromosomes 1, 3, 4 and 8. The two QTLs for GYLD increased maize yield
under low P soils by 173 kg/ha while the 2 QTLs for PHT increased plant
growth by 18.14 cm. The % phenotypic variance explained by these QTLs
under low P environments had a wide range (0.242% - 53.34%) and was
much lower for GYLD compared to plant growth. Both additive and dominance gene actions contributed differentially to the observed phenotypic
variance for tolerance to low P soils with dominance contributing more genetic effects compared additive effects for majority of the QTLs. The findings
of this study will provide some basis for marker-assisted selection for yield
improvement and further guide breeding strategies under low P soils of west ern Kenya
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