Enhancement and selection of renewal crops in low impact systems in anticipation of future climate change

Nowadays, the need to increase crop production and sustainability of farming systems is a main issue at global level, involving private and public sectors. Consequently, the future challenge of agriculture will be to improve food production while maintaining high nutritional quality and counteracting the effects of climate change already underway in the Mediterranean basin. The scientific community is pushing for the development and cultivation of climate resilient crops (CSC) that may be able to efficiently utilize the natural resources ensuring improved nutritional values and crop diversification for a sustainable rotational program. Among these crops, proso millet (Panicum miliaceum L.) might be a promising candidate thanks to its heat stress resistance, its limited water demand and its high-quality nutritional traits, although it is characterized by low yields. To date, the only way to increase the grain yield and improve other agronomic important traits is through an efficient breeding program based on a wide genetic variability of parental germplasm. The aim of this thesis was to evaluate the impact and re-introduction of this minor cereal in the agricultural systems of the Mediterranean basin as renewal crop. For this purpose, agronomic and genetic traits of a germplasm collection of wild and domesticated proso millet accessions, obtained from the United States Department of Agriculture (USDA) bank, was cultivated over 2 years’ field experiment under Mediterranean pedoclimatic conditions. The agronomic traits characterization of the germplasm collection resources is considered an important step to select genotypes adaptable to such environment and with desirable productive traits to be used in future breeding programs for the constitution of new improved varieties. The first study showed a morphological characterisation and a preliminary evaluation of the agronomical performances of a world collection of 80 proso millet (P. miliaceum) accessions. Overall, all the germplasm resources evaluated exhibited a wide range of variability for plant height, grain yield, total dry biomass, Harvest Index (HI), Growing Degree Days (GDD) to flowering and days to maturity, providing valuable information that could support future researchers. The second study was carried out to research the genomic base of the phenotypic seed traits diversity through a genome-wide association study (GWAS). Phenotypic diversity of seed size, shape, and colour has been evaluated in the fields, to characterise the diversity on germination physiology, nutrient quality, and yield of the different accessions studied. Then DNA of each accession was extracted from a pool of seed and analysed with a RAD sequencing approach to 8 screen and identify single nucleotide polymorphism (SNPs) markers. Association between phenotypic and molecular markers were than carried out using the model implemented in the R package qqman The high variation and strong association signals obtained for some of these traits, support the use of genomics and phenotypic screening to rapidly detect marker-trait associations (MTAs) to be employed in specific breeding program. Although the size of the population used in our study was small and this may shrink a bit our results. In the third study we evaluated the agronomic performances of proso millet varieties Sunrise in two consecutive cultivation years (2018 and 2019) under Mediterranean pedoclimatic conditions. Different Plants Densities (D) and Nitrogen Fertilisation (N) were tested, and plants performance were evaluated measuring several agronomic traits. The identification of the best combination of D and N represented an important information to set up an optimised protocol to improve proso millet yields.