Dissection of mechanisms of maize resilience to combined drought and high temperature using high-throughput phenotyping platforms.

Dissection of mechanisms of maize resilience to combined drought and high temperature using high-throughput phenotyping platforms R Shi1 , A L Malvar2 , D Knoch1 , H Tschiersch1 , M C Heuermann1 , S Shaaf1 , D Madur3 , V Combes3 , S Nicolas3 , R Santiago4 , C Balconi5 , E Frascaroli6 , S Erdal7 , C Palaffre8 , C Bauland3 , C Welcker9 , A Charcosset3 , P Revilla4 , T Altmann1 1 Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Seeland OT Gatersleben, Corrensstrase 3, 06466 Seeland, Germany; 2 Universidad de Vigo, As Lagoas Marcosende, 36310, Vigo, Spain Agrobiología Ambiental, Calidad de Suelos Y Plantas (UVIGO), Unidad Asociada a La MBG (CSIC), Vigo, Spain; 3 Université Paris-Saclay, INRAE, CNRS, AgroParisTech, Génétique Quantitative et Evolution (GQE) - Le Moulon, 91190, Gif-Sur-Yvette, France; 4 Misión Biológica de Galicia (CSIC), Carballeira 8, 36143, Pontevedra, Spain; 5 Research Centre for Cereal and Industrial Crops (CREA), Via Stezzano, 24, 24126 Bergamo, Italy; 6 Department of Agricultural and Food Sciences, Università di Bologna, Viale Fanin, 44 - 40127 Bologna, Italy; 7 Bati Akdeniz Agricultural Research Institute, Antalya, Turkey; 8 Unité Expérimentale du Maïs, INRAE, 2297 Route de l’INRA, F-40390 Saint-Martin-deHinx, France; 9 LEPSE, Univ Montpellier, INRAE, Montpellier, France Climate models predict increases in average temperature with higher risks of severe heat and drought stress periods. It negatively impacts plant growth and decreases crop productivity. The development of genotypes which are resilient to combined drought and high temperatures becomes increasingly important. Mediterranean countries conserve maize with a wide genetic diversity as a consequence of its adaptation to conditions very different from those of its center of origin and domestication. Within the DROMAMED project, 116 maize inbred lines provided by germplasm banks from different Mediterranean countries (Spain, France, Italy and Turkey) were studied under non-stress (control) and stress (combined drought and heat, 30% field capacity and 35 °C day temperature, for two weeks followed by two weeks recovery) conditions (45 days after sowing). An automated high-throughput shoot phenotyping facility was used to investigate the physiological and morphological mechanisms involved in maize resilience to drought and high temperature stress under controlled environmental condition. Image-derived phenotypic traits enable us to quantify shoot growth dynamics over time. The results showed that combined drought and high temperature (D-HT) decreased plant height and shoot area and volume, as well as the relative shoot growth rate during the vegetative phase. Color-related traits suggest that leaf chlorophyll decreased under D-HT stress. Additionally, photosynthetic parameters decreased significantly under D-HT, but were then normalized during the recovery stage. Genotypic variation of shoot biomass among the tested inbred lines was also observed. Stress indices, namely stress resistance, stress recovery and stress adaptability, were calculated based on the estimated shoot volume data. Both stress resistance and recovery contribute to maize resilience to D-HT stress, while it seems that they are differently affected. Keeping a high growth rate is important for stress resistance, while maintaining a large biomass until the end of the stress period appears favorable for the recovery process. Genome Wide Association analysis (GWAS) was performed on 100 tested maize lines to identify SNP markers associated to the traits of interest and to dissect the genetic basis of maize resilience to D-HT-stress.