Mapping QTLs Regulating Morpho-physiological Traits and Yield: Case Studies, Shortcomings and Perspectives in Drought-stressed Maize

Abstract

Comparative analysis of a number of studies in drought-stressed maize (Zea mays L.) reporting quantitative trait loci (QTLs) for abscisic acid concentration, root characteristics, other morpho-physiological traits (MPTs) and grain yield (GY) reveals their complex genetic basis and the influence of the genetic background and the environment on QTL effects. Chromosome regions (e.g. near umc11 on chromosome 1 and near csu133 on chromosome 2) with QTLs controlling a number of MPTs and GY across populations and conditions of different water supply have been identified. Examples are presented on the use of QTL information to elucidate the genetic and physiological bases of the association among MPTs and GY. The QTL approach allows us to develop hypotheses accounting for these associations which can be further tested by developing near isogenic lines (NILs) differing for the QTL alleles. NILs also allow for a more accurate assessment of the breeding value of MPTs and, in some cases, may allow for the map-based cloning of the gene(s) underlying the QTL. Although QTL analysis is still time-consuming and resource-demanding, its integration with genomics and post-genomics approaches (e.g. transcriptome, proteome and metabolome analyses) will play an increasingly important role for the identification and validation of candidate genes affecting MPTs and GY.

QTL controlling root and shoot traits of maize seedlings under cold stress

“…The third major QTL detected by Tuberosa et al (2002b) for PrAx diameter on chromosome 1(89) fell just below the LOD threshold in the present study. QTL for root traits have been identified in various other populations at the same positions that we found to control the primary root weight at 38 cM (bin 1.03) and the PrAx diameter at 89 cM (bin 1.06) (Tuberosa et al 2002a). Apart from the above mentioned loci on chromosome 1, five others were detected in both studies: one on chromosome 2(56-57) for PrAx diameter, two on chromosome 7(12-22) for PrAx length and the seminal root weight, one on chromosome 9 (10-13) for primary root weight, and one on chromosome 10(74-76) for seminal root weight.…”

Discovery, Biosynthesis and Stress-Related Accumulation of Dolabradiene-Derived Defenses in Maize

“…In contrast, the induced accumulation of kauralexins was shown previously in stems and scutella tissues to exceed 100 mg g 21 fresh weight as compared with the 10 mg g 21 fresh weight currently detected in mature roots . Notably, ZmAN2 is located proximal to a quantitative trait locus mapped to bin 1.03 that is associated with root growth (Rahman et al, 2011), and ZmKSL4 colocates in bin 1.08 with quantitative trait loci associated with both drought tolerance (Tuberosa et al, 2002) and abscisic acid biosynthesis, which can further mediate drought-induced phytoalexin biosynthesis in maize roots (Vaughan et al, 2015). Our findings here contribute to a growing body of knowledge demonstrating roles for root diterpenoids, including momilactone phytoalexins in rice (Toyomasu et al, 2008), the antiherbivory activity of rhizathalene in Arabidopsis (Arabidopsis thaliana; Vaughan et al, 2013), and drought tolerance mediated by isorosmanol in rosemary (Rosmarinus officinalis; Munné-Bosch and Alegre, 2000).…”

Changes in gene expression in maize kernel in response to water and salt stress

“…Major progress in microarray analysis has provided made possibilities for more practical application of the results (Kawasaki et al 2001;Ozturk et al 2002) including the possibility of identifying TQL (transcript quantity loci) and to connect with QTL of interest or to associate clusters of genes with QTLs (Khavkin and Coe 1997;Tuberosa et al 2002).…”