Dissection of Maize Drought Tolerance at the Flowering Stage Using Genome-Wide Association Studies

Abstract

Drought is one of the most critical environmental factors constraining maize production. When it occurs at the flowering stage, serious yield losses are caused, and often, the damage is irretrievable. In this study, anthesis to silk interval (ASI), plant height (PH), and ear biomass at the silking date (EBM) of 279 inbred lines were studied under both water-stress (WS) and well-water (WW) field conditions, for three consecutive years. Averagely, ASI was extended by 25.96%, EBM was decreased by 17.54%, and the PH was reduced by 12.47% under drought stress. Genome-wide association studies were carried out using phenotypic values under WS, WW, and drought-tolerance index (WS-WW or WS/WW) and applying a mixed linear model that controls both population structure and relative kinship. In total, 71, 159, and 21 SNPs, located in 32, 59, and 12 genes, were significantly (P < 10−5) associated with ASI, EBM, and PH, respectively. Only a few overlapped candidate genes were found to be associated with the same drought-related traits under different environments, for example, ARABIDILLO 1, glycoprotein, Tic22-like, and zinc-finger family protein for ASI; 26S proteasome non-ATPase and pyridoxal phosphate transferase for EBM; 11-ß-hydroxysteroid dehydrogenase, uncharacterised, Leu-rich repeat protein kinase, and SF16 protein for PH. Furthermore, most candidate genes were revealed to be drought-responsive in an association panel. Meanwhile, the favourable alleles/key variations were identified with a haplotype analysis. These candidate genes and their key variations provide insight into the genetic basis of drought tolerance, especially for the female inflorescence, and will facilitate drought-tolerant maize breeding.

Linkage Mapping Reveals QTL for Flowering Time-Related Traits under Multiple Abiotic Stress Conditions in Maize

“…3: 196.14–199.89 Mb ( Table 1 ). Recently, an uncharacterized protein and pectin-esterase were found to be associated with ASI-Delay-17 and ASI-Delay-20 through GWAS, respectively [ 42 ]. The ASI-delay was caused by drought stress under the same experimental design as in this study.…”

“…The field trials with WW (well-water) and WS (water-stress) treatments were conducted in Urumqi (Xinjiang province, 43°57′ N, 87°49′ E), as described by Khan et al [ 42 ]. The RIL population was tested in 2019 and 2020.…”

“…The spacing between the rows was 1.1 m. Every line was planted in two adjacent rows, one for WS and the other for WW, each with its own irrigation valve. Managed stress management was described by Khan et al [ 42 ]. Briefly, irrigation was withdrawn at −21 D (days before flowering), estimated according to the Growing Degree Days (GDD), and soil moisture was maintained at 150–200 centibars from −7 D to 14 days post flowering.…”

“…Meta-analysis aids in the identification and detection of some of the common QTLs across studies, resulting in interesting candidates for maize flowering time [ 34 , 35 , 36 , 37 ]. Multi-population mapping studies have increasingly evolved, as molecular marker technology has matured and the cost of genotyping has decreased [ 2 , 21 , 35 , 38 , 39 , 40 , 41 , 42 ].…”

Improving drought tolerance in maize: Tools and techniques

“… Wang et al (2022) identified and reported the overexpression of a transcription factor, ZmERF21 , is tightly associated with drought tolerance in maize seedlings, expressed by significantly increased chlorophyll content and activities of antioxidant enzymes under drought conditions. Another GWAS study ( Khan et al, 2022 ) identified candidate genes and their key variations that will contribute to an understanding of the genetic basis of drought tolerance, especially for the female inflorescence, and will be important in facilitating drought-tolerant maize breeding.…”