Genetics of Germination and Seedling Traits under Drought Stress in a MAGIC Population of Maize

Abstract

Drought is one of the most detrimental abiotic stresses hampering seed germination, development, and productivity. Maize is more sensitive to drought than other cereals, especially at seedling stage. Our objective was to study genetic regulation of drought tolerance at germination and during seedling growth in maize. We evaluated 420 RIL with their parents from a multi-parent advanced generation inter-cross (MAGIC) population with PEG-induced drought at germination and seedling establishment. A genome-wide association study (GWAS) was carried out to identify genomic regions associated with drought tolerance. GWAS identified 28 and 16 SNPs significantly associated with germination and seedling traits under stress and well-watered conditions, respectively. Among the SNPs detected, two SNPs had significant associations with several traits with high positive correlations, suggesting a pleiotropic genetic control. Other SNPs were located in regions that harbored major QTLs in previous studies, and co-located with QTLs for cold tolerance previously published for this MAGIC population. The genomic regions comprised several candidate genes related to stresses and plant development. These included numerous drought-responsive genes and transcription factors implicated in germination, seedling traits, and drought tolerance. The current analyses provide information and tools for subsequent studies and breeding programs for improving drought tolerance.

Endophytic and rhizobacteria functionalities in alleviating drought stress in maize plants

“…This involves plant breeding techniques which utilise procedures of cultivating better wild-type species of maize plants that can withstand harsh drought conditions (Chandra et al 2021). The application of this method in maize plant production will ensure that the potential of a high plant yield as well as improving the crop for drought tolerance are harnessed, which is the major focus of breeding programmes as it is critical to guarantee the stabilised global maize production (Rida et al 2021). Breeding for stress tolerance requires care-ful consideration of the selection technique to be used.…”

“…Drought has been noted to be a key factor that affects the yield of maize and, as such, whatever strategy to address it will be of immense benefit (Siddique et al 2022). While most crops are susceptible to drought conditions and may experience losses in yield of more than 50%, maize has been reported to be more sensitive to drought than other grains (Rida et al 2021). In fact, the occurrence of drought stress conditions especially at the vegetative and reproductive phases of maize reduces yields by 39.3% (Lunduka et al 2019).…”

BREEDIT: A novel multiplex genome editing strategy to improve complex quantitative traits in maize (Zea mays L.)

“…For SCRIPT 2 and SCRIPT 3, when tested in experiment WW001, significant increases of about 5% relative to controls could be detected only for FLL3 and only in one of the two populations of each group (P108 for SCRIPT 2, and P033 for SCRIPT 3), while FLW3 remained unaffected in SCRIPT 2 populations or decreased for both populations of SCRIPT 3 (Supplemental Figure S9B-C). Because the genes targeted in SCRIPT 2 are involved in cytokinin metabolism, previously implicated in drought tolerance (Rida et al, 2021), and some of the genes targeted in SCRIPT 3 are drought responsive (Li et al, 2016; Hai et al, 2020), these populations were phenotyped under WD conditions (Supplemental Figure S9B-C). Under WD, the SCRIPT 2 populations showed an enhanced growth (Supplemental Figure S10A), which is reflected by a significant increase in FLL3, FLW3, FW and DW compared with control EDITOR 1 (Supplemental Figure S9B, Supplemental Figure S10 A-C).…”

“…A gain-of-function mutation in D8 (SCRIPT 1), encoding a DELLA maize protein ortholog, is causative of dwarf phenotypes (Winkler and Freeling, 1994; Lawit et al, 2010). Zm CKX-4B (SCRIPT 2) plays a role in both drought (Rida et al, 2021) and heat shock stress (Wang et al, 2020). Downregulation of ZmHB124B and ZmHB124C induces the formation of additional protoxylem files in the vasculature (Bloch et al, 2019), which could prevent vascular embolism and water retention under water-limiting conditions (Hwang et al, 2016).…”

BREEDIT: Fast breeding tools to match the fast pace of climate change

“…Nevertheless, multiple knockouts generated by SCRIPT1 -which targets genes involved in the catabolism of Gibberellic Acid (Huang et al, 2015) -caused enhanced growth of vegetative organs but abnormalities in reproductive organs that led to male sterility in transformed generations. On the other hand, multiple knockouts generated by SCRIPT2 -which targets genes involved in the metabolism of cytokinin, previously shown to be involved in plant response to drought at early developmental stages (Rida et al, 2021) -displayed increased growth under water-deficient conditions.…”