Mapping Qtls for Grain Yield and Yield Components in Kenyan Maize (<i>Zea mays</i>L.) Under Low Phosphorus Using Single Nucleotide Polymorphism (SNPS)

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 western Kenya.