Abstract
Identifying quantitative trait loci (QTL) of sizeable effects that are expressed in diverse genetic backgrounds across contrasting water regimes particularly for secondary traits can significantly complement the conventional drought tolerance breeding efforts. We evaluated three tropical maize biparental populations under water-stressed and well-watered regimes for drought-related morpho-physiological traits, such as anthesis-silking interval (ASI), ears per plant (EPP), stay-green (SG) and plant-to-ear height ratio (PEH). In general, drought stress reduced the genetic variance of grain yield (GY), while that of morpho-physiological traits remained stable or even increased under drought conditions. We detected consistent genomic regions across different genetic backgrounds that could be target regions for marker-assisted introgression for drought tolerance in maize. A total of 203 QTL for ASI, EPP, SG and PEH were identified under both the water regimes. Meta-QTL analysis across the three populations identified six constitutive genomic regions with a minimum of two overlapping traits. Clusters of QTL were observed on chromosomes 1.06, 3.06, 4.09, 5.05, 7.03 and 10.04/06. Interestingly, a ~8-Mb region delimited in 3.06 harboured QTL for most of the morpho-physiological traits considered in the current study. This region contained two important candidate genes viz., zmm16 (MADS-domain transcription factor) and psbs1 (photosystem II unit) that are responsible for reproductive organ development and photosynthate accumulation, respectively. The genomic regions identified in this study partially explained the association of secondary traits with GY. Flanking single nucleotide polymorphism markers reported herein may be useful in marker-assisted introgression of drought tolerance in tropical maize.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-014-0068-5) contains supplementary material, which is available to authorized users.
Highlights
Maize (Zea mays L.) is an important economic crop and, due its high yield potential, is currently recognised as a major crop that can ensure food security worldwide
We identified eight meta-QTL analysis (mQTL) for SG traits, two for ears per plant (EPP) and four for plant-to-ear height ratio (PEH), respectively, with a confidence interval of 95 % (Table 5), which are plotted in the consensus map (Fig. 1)
While the heritability estimates considerably decreased for grain yield (GY) under WS conditions, the secondary traits tended to have similar or substantially higher heritability estimates under WS than WW conditions, indicating their potential to aid in selection decisions when selections based on GY under WS alone may not be reliable due to the quality of the trial measurements
Summary
Maize (Zea mays L.) is an important economic crop and, due its high yield potential, is currently recognised as a major crop that can ensure food security worldwide. It has been projected that by the year 2050, a 70 % increase in global food production must occur, while the global climate change scenario tends to increase the problems of food insecurity (Varshney et al 2010). This grim forecast has forced plant scientists to breed cultivars that can be grown in marginal areas with limited water availability. Drought stress can adversely affect many aspects of maize physiological metabolism and growth, including photosynthesis, plant height, dry matter production, leaf area and grain yield (Ge et al 2012). Biochemical and physiological changes to respond and adapt in order to survive under drought stress (Lu et al 2011)
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