First steps to understand heat tolerance of temperate maize at adult stage: identification of QTL across multiple environments with connected segregating populations

Theoretical and Applied Genetics, Feb 2016

Key message Dents were more heat tolerant than Flints. QTL for heat tolerance with respect to grain yield at field conditions were identified considering multiple populations and environments. Abstract High temperatures have the potential to cause severe damages to maize production. This study aims to elucidate the genetic mechanisms of heat tolerance under field conditions in maize and the genome regions contributing to natural variation. In our study, heat tolerance was assessed on a multi-environment level under non-controlled field conditions for a set of connected intra- and interpool Dent and Flint populations. Our findings indicate that Dent are more heat tolerant during adult stage than Flint genotypes. We identified 11 quantitative trait loci (QTL) including 2 loci for heat tolerance with respect to grain yield. Furthermore, we identified six heat-tolerance and 112 heat-responsive candidate genes colocating with the previously mentioned QTL. To investigate their contribution to the response to heat stress and heat tolerance, differential expression and sequence variation of the identified candidate genes should be subjected to further research.

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First steps to understand heat tolerance of temperate maize at adult stage: identification of QTL across multiple environments with connected segregating populations

Theor Appl Genet First steps to understand heat tolerance of temperate maize at adult stage: identification of QTL across multiple environments with connected segregating populations Felix P. Frey 0 1 2 3 4 0 Communicated by N. de Leon 1 Group Limagrain , Fehrpart u. 80, 6710 Szeged , Hungary 2 Group Limagrain , Am Eggenkamp 1, 48268 Greven , Germany 3 KWS SAAT SE , Grimsehlstrasse 31, 37555 Einbeck , Germany 4 Max Planck Institute for Plant Breeding Research , Carl-von-Linné-Weg 10, 50829 Cologne , Germany High temperatures have the potential to cause severe damages to maize production. This study aims to elucidate the genetic mechanisms of heat tolerance under field conditions in maize and the genome regions contributing to natural variation. In our study, heat tolerance was assessed on a multi-environment level under non-controlled field conditions for a set of connected intra- and interpool Dent and Flint populations. Our findings indicate that Dent are more heat tolerant during adult stage than Flint genotypes. We identified 11 quantitative trait loci (QTL) including 2 loci for heat tolerance with respect to grain yield. Furthermore, we identified six heat-tolerance and 112 - * Benjamin Stich heat-responsive candidate genes colocating with the previously mentioned QTL. To investigate their contribution to the response to heat stress and heat tolerance, differential expression and sequence variation of the identified candidate genes should be subjected to further research. Maize (Zea mays L.) was grown on 184 million hectares in 2013 and was, thus, the second most widely cultivated crop after wheat (FAOSTAT 2014). In temperate regions of Europe, maize is of increasing importance as fodder for animal production and, lately, for biogas production (Deutsches Maiskomitee 2013). With the progress of climate change, the global mean temperature and variance are expected to increase in the future (IPCC 2013). Lobell and Field (2007) observed a negative correlation of the yields of major crops, including maize, and an increasing global mean temperature. The effects of heat stress on plants are yield losses, growth inhibition and leaf scorching (Wahid et al. 2007), which was also reported for maize in temperate regions (Giaveno and Ferrero 2003). Especially during flowering and grain filling, heat stress has severe impacts on maize plants (Barnabás et al. 2008). Thus, breeding heat-tolerant cultivars is crucial to sustain crop production in the future (Chen et al. 2012). Two complementary approaches are conceivable to increase heat tolerance in European maize germplasm. One possibility is to introgress exotic germplasm as described by Giaveno and Ferrero (2003). The second approach, which is described in this present study, has the potential to reduce the introgression of alleles which are associated with non-adaptedness to a temperate climate. It consists in assessing heat-tolerance variation in local germplasm and enhancing the frequency of the present positive alleles. The molecular and physiological basis of heat tolerance in maize was studied intensively by Crafts-Brandner and Salvucci (2002), Ashraf and Hafeez (2004) and Sinsawat et al. (2004). Further, Ottaviano et al. (1991), Frova and Sari-Gorla (1994), Reimer et al. (2013) and Frey et al. (2015) investigated this question with a focus on natural variation. All these mentioned studies examined the heat tolerance of seedlings or pollen grains grown under controlled conditions. Nevertheless, experiments on seedlings can never substitute experiments on adult plants grown under field conditions (Roy et al. 2011) and can only be an auxiliary means to study the phenotypic and genotypic response to heat stress. Chen et al. (2012), Cairns et al. (2013) and Rattalino Edreira and Otegui (2013) examined heat tolerance of maize in adult stage and measured yield potential under field conditions. However, to the best of our knowledge, no previous study has used natural variation to genetically dissect heat tolerance under field conditions. Earlier studies used different approaches to quantify the effect of a certain level of heat stress on the occurrence of phenotypic heat stress symptoms. Chen et al. (2012) and Cairns et al. (2013) described the heat tolerance of a genotype as the performance at high temperature conditions, without considering the relation of the performance at heat conditions to a control environment. Fokar et al. (1998) estimated heat tolerance in wheat by the reduction of trait values at heat conditions compared to a control condition. A more advanced approach was pursued by Mason et al. (2010) and Paliwal et al. (2012), who calculated heat susceptibility for wheat on a one-trait basis for yield components, relating the trait value of plants grown under heat conditions with their trait value at control conditions, taking into account the stress intensity at the heat conditions across all genotypes. However, to the best of our knowledge, (...truncated)


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Felix P. Frey, Thomas Presterl, Patrick Lecoq, András Orlik, Benjamin Stich. First steps to understand heat tolerance of temperate maize at adult stage: identification of QTL across multiple environments with connected segregating populations, Theoretical and Applied Genetics, 2016, pp. 945-961, Volume 129, Issue 5, DOI: 10.1007/s00122-016-2674-6