Osuman AS, Badu-Apraku B, Karikari B, Ifie BE, Tongoona P, Danquah EY.

Genes (Basel). 2022 Feb 15;13(2):349. doi: 10.3390/genes13020349.

Abstract

Maize (Zea mays L.) production is constrained by drought and heat stresses. The combination of these two stresses is likely to be more detrimental. To breed for maize cultivars tolerant of these stresses, 162 tropical maize inbred lines were evaluated under combined heat and drought (CHD) and terminal drought (TD) conditions. The mixed linear model was employed for the genome-wide association study using 7834 SNP markers and several phenotypic data including, days to 50% anthesis (AD) and silking (SD), husk cover (HUSKC), and grain yield (GY). In total, 66, 27, and 24 SNPs were associated with the traits evaluated under CHD, TD, and their combined effects, respectively. Of these, four single nucleotide polymorphism (SNP) markers (SNP_161703060 on Chr01, SNP_196800695 on Chr02, SNP_195454836 on Chr05, and SNP_51772182 on Chr07) had pleiotropic effects on both AD and SD under CHD conditions. Four SNPs (SNP_138825271 (Chr03), SNP_244895453 (Chr04), SNP_168561609 (Chr05), and SNP_62970998 (Chr06)) were associated with AD, SD, and HUSKC under TD. Twelve candidate genes containing phytohormone cis-acting regulating elements were implicated in the regulation of plant responses to multiple stress conditions including heat and drought. The SNPs and candidate genes identified in the study will provide invaluable information for breeding climate smart maize varieties under tropical conditions following validation of the SNP markers.

See https://pubmed.ncbi.nlm.nih.gov/35205393/

Figure 4: Manhattan plots (left) and quantile–quantile (QQ) plots (right) for ears per plant across the three treatments (a,b). Manhattan and QQ plot under combined heat and drought conditions (CHD). (c,d). Manhattan and QQ plot under terminal drought conditions (TD) (e,f). Manhattan and QQ plot for means obtained under CHD and TD. The threshold of 3.89 (Bonferroni correction) was adopted with the red line in the Manhattan plots. The X-axis represents chromosome number while the Y-axis represents −log10(P). The X and Y axes in the QQ plots represent the expected and observed −log10(P), respectively. The red line in the QQ-plots with the shaded regions indicates a 95% confidence interval.