Genetic analysis of drought response of wheat following either chemical desiccation or the use of a rain-out shelter.

Simulating drought stress during the breeding process has been proposed as a way to select varieties under naturally non-stressful conditions. The aim of the study was to characterise the genetic basis of the response of 111 spring wheat (Triticum aestivum L.) varieties and landraces to chemical desiccation and to rain-out shelter drought. The effect of the rain-out shelter was a 15% reduction in plant height, spike length and thousand seed weight (TSW); in contrast, the desiccant treatment induced a 15% reduction in seed number, a 35-72% loss in TSW and a reduction in subsequent germination of 12%. A genome-wide association analysis revealed 263 significant marker-trait associations (MTAs), of which 246 involved days to anthesis, plant height, spike length, number of spikelets, seed number, TSW and germination from the non-treated plants. Only four and five MTAs involved TSW from plants grown under the rain-out shelter and the chemical desiccation, respectively, and harboured the Sugar-Dependent6 gene. Seven MTAs involved seed number for chemical desiccated plants. Both, chemical desiccation and rain-out shelter drought identified same tolerant genotypes. Concluding, both approaches are suitable to simulate different drought scenarios. However, there was a strong environmental impact for chemical desiccation which may increase the complexity of this tolerance mechanism.

Genome-wide association study and genetic diversity analysis on nitrogen use efficiency in a Central European winter wheat (Triticum aestivum L.) collection.

To satisfy future demands, the increase of wheat (Triticum aestivum L.) yield is inevitable. Simultaneously, maintaining high crop productivity and efficient use of nutrients, especially nitrogen use efficiency (NUE), are essential for sustainable agriculture. NUE and its components are inherently complex and highly influenced by environmental factors, nitrogen management practices and genotypic variation. Therefore, a better understanding of their genetic basis and regulation is fundamental. To investigate NUE-related traits and their genetic and environmental regulation, field trials were evaluated in a Central European wheat collection of 93 cultivars at two nitrogen input levels across three seasons. This elite germplasm collection was genotyped on DArTseq® genotypic platform to identify loci affecting N-related complex agronomic traits. To conduct robust genome-wide association mapping, the genetic diversity, population structure and linkage disequilibrium were examined. Population structure was investigated by various methods and two subpopulations were identified. Their separation is based on the breeding history of the cultivars, while analysis of linkage disequilibrium suggested that selective pressures had acted on genomic regions bearing loci with remarkable agronomic importance. Besides NUE, genetic basis for variation in agronomic traits indirectly affecting NUE and its components, moreover genetic loci underlying response to nitrogen fertilisation were also determined. Altogether, 183 marker-trait associations (MTA) were identified spreading over almost the entire genome. We found that most of the MTAs were environmental-dependent. The present study identified several associated markers in those genomic regions where previous reports had found genes or quantitative trait loci influencing the same traits, while most of the MTAs revealed new genomic regions. Our data provides an overview of the allele composition of bread wheat varieties anchored to DArTseq® markers, which will facilitate the understanding of the genetic basis of NUE and agronomically important traits.