Abstract
High seed vigor is important for agricultural production due to the associated potential for increased growth and productivity. However, a better understanding of the underlying molecular mechanisms is required because the genetic basis for seed vigor remains unknown. We used single-nucleotide polymorphism (SNP) markers to map quantitative trait loci (QTLs) for four seed vigor traits in two connected recombinant inbred line (RIL) maize populations under four treatment conditions during seed germination. Sixty-five QTLs distributed between the two populations were identified and a meta-analysis was used to integrate genetic maps. Sixty-one initially identified QTLs were integrated into 18 meta-QTLs (mQTLs). Initial QTLs with contribution to phenotypic variation values of R2>10% were integrated into mQTLs. Twenty-three candidate genes for association with seed vigor traits coincided with 13 mQTLs. The candidate genes had functions in the glycolytic pathway and in protein metabolism. QTLs with major effects (R2>10%) were identified under at least one treatment condition for mQTL2, mQTL3-2, and mQTL3-4. Candidate genes included a calcium-dependent protein kinase gene (302810918) involved in signal transduction that mapped in the mQTL3-2 interval associated with germination energy (GE) and germination percentage (GP), and an hsp20/alpha crystallin family protein gene (At5g51440) that mapped in the mQTL3-4 interval associated with GE and GP. Two initial QTLs with a major effect under at least two treatment conditions were identified for mQTL5-2. A cucumisin-like Ser protease gene (At5g67360) mapped in the mQTL5-2 interval associated with GP. The chromosome regions for mQTL2, mQTL3-2, mQTL3-4, and mQTL5-2 may be hot spots for QTLs related to seed vigor traits. The mQTLs and candidate genes identified in this study provide valuable information for the identification of additional quantitative trait genes.
Highlights
Seed vigor, an important and complex agronomic trait, is controlled by multiple factors such as genetic and physical purity, mechanical damage, and physiological conditions [1,2,3]
Similar trends for changes in germination energy (GE), germination percentage (GP), seedling dry weight (SDW), and root dry weight (RDW) in response to artificial aging treatments were observed in the recombinant inbred line (RIL) populations relative to the parents
Producing high-quality seeds to stabilize crop yield poses a challenge for crop breeders, and a key to meeting this challenge is the elucidation of the molecular mechanisms underlying seed vigor traits
Summary
An important and complex agronomic trait, is controlled by multiple factors such as genetic and physical purity, mechanical damage, and physiological conditions [1,2,3]. Highquality seeds that ensure uniform germination and growth that lead to increased production are important to growers, and seed vigor depends fundamentally on the potential of the seed itself to grow under favorable growth conditions and under adverse stress conditions. Antioxidants, heat shock proteins (HSPs), and enzymes that repair protein damage may be involved in ameliorating the effects of artificial aging on seed vigor [7,9,10,11]. Overaccumulation of protein-L-isoaspartate O-methyltransferase (PIMT1, encoding IAMT in Arabidopsis) reduced the accumulation of L-isoaspartyl residues in seed proteins and increased germination vigor. Reduced PIMT1 accumulation was associated with an increase in the accumulation of L-isoaspartyl residues in the proteome of freshly harvested dry mature seeds, resulting in heightened sensitivity to aging treatments and the loss of seed vigor under stressful germination conditions [7]
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