Abstract
Drought remains the primary abiotic constraint to maize (Zea mays L.) productivity globally. Maize drought response involves several regulatory quantitative traits and complex gene networks. Therefore, precise location of drought-related quantitative trait loci (QTL) is imperative for drought tolerance breeding. Despite numerous studies identifying several drought-related maize QTLs, some QTL from particular genetic backgrounds showed smaller effects or could not be identified at all in different backgrounds, affected by marker sets, experimental design, mapping populations and statistical methods. Herein, therefore; using 457 published maize QTLs conferring for 18 traits, we have performed meta-analysis of data from various experiments to obtain meta-QTL (MQTL), integrate these fruitful QTL and to mine candidate genes related to drought. Resultantly, 24 MQTL with confidence interval (CI) < 5 cm were identified to be hot regions. Additionally, 47 drought related gene loci were observed and several candidate genes of the hot MQTL were reorganized by bioinformatics techniques. Thirteen gene (sod4, taf1, rps1, nthr3, oc13, bas, apx1, asn4, pck2, nac1, gst2, ao1 and kch4) loci of hot MQTL regions were homologous to their corresponding gene sequences from the PlantGDB database (http://www.plantgdb.org/search/). Further, we used a comparative genomics approach to identify the homologous regions of MQTL in rice (Oryza sativa Japonica) database (http://www.gramene.org) and observed that drought-related rice gene ATG6 was homologous to maize candidate genes GRMZM2G027857_T01 and GRMZM2G027857_T02. Conclusively, our identified MQTLs with narrowed CI could be useful for marker-assisted selection and the candidate genes harnessed for maize drought tolerance breeding.
Highlights
Maize (Zea mays L.) is the third most important cereal in the world after wheat (Triticum aestivum L.) and rice (Orzya sativa L., Golam et al, 2011)
Amongst the 457 quantitative trait loci (QTL), 207 from 22 researches and 18 populations were related to grain yield, 130 from 17 published papers and 12 populations were related to flowering date, whereas 94 from 14 papers and 11 populations were related to plant morphology
A total of 47 drought related gene loci were identified and several candidate genes of the hot MQTL were reorganized by bioinformatics techniques
Summary
Maize (Zea mays L.) is the third most important cereal in the world after wheat (Triticum aestivum L.) and rice (Orzya sativa L., Golam et al, 2011). The continued rise in world human population and consequent food demands against the backdrop of worsening global climate change has prompted greater need for the crop (Xu et al, 2014; Maazou et al, 2016). As a result of the continuing climate change phenomenon, drought stress will remain the primary environmental limitation to maize productivity (Rao et al, 2016). Maize breeders have the burden of developing drought resilient crop varieties in order to sustain higher yields and global food security under the ravaging climate change conditions. Quantitative trait loci (QTL) analysis of maize drought tolerance involves various aspects, including morphological traits (such as plant height, ear position, and branches per tassel etc.), root, physiological, and biochemical related traits (ABA, degree of leaf senescence, photosynthesis parameters, protein content, stomatal conductance, osmotic adjustment etc.), and yield traits (ear length, 100-kernel weight, ears per plant, and grain yield etc.) among others (Lu et al, 2006; Edmeades, 2013)
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