Genetic variation and inheritance of root system architecture (RSA) in Italian maize inbred lines

Genetic variation and inheritance of root system architecture (RSA) in Italian maize inbred lines G Mazzinelli1 , F Solimei2 , M De Biasi2 , C Gagliardi2 , H Hartings1 , C Lanzanova1 , C Balconi1 , A Torri1 , A Tassinari2 , S Salvi2 , E Frascaroli2 1 CREA Research Centre for Cereal and Industrial Crops; 2 Department of Agricultural and Food Sciences, DISTAL, University of Bologna, Italy Maize genotypes exhibiting efficient root systems are deemed to possess superior adaptability to environments characterized by dry seasons. Initial investigations indicate that a considerable degree of genetic variability for root system architecture (RSA) persists within both elite cultivars and germplasm collections, serving as a reservoir of valuable alleles conferring stress tolerance. The assessment of RSA can facilitated the delineation of root ideotypes pertinent to both yield and stress tolerance. Preliminary investigations unveil extensive genetic and phenotypic diversity in root traits across elite cultivars and germplasm populations. This research aims to establish phenotypic and genomic selection criteria to identify drought-tolerant RSA. Objectives include assessing RSA variability in Italian maize germplasm, investigating its inheritance and formulating selection criteria for developing resilient varieties tailored for cultivation in Northern Italy. This study was conducted on 340 inbred lines: 90 lines derived from historical varieties maintained by local farmers before the 1950s (GRM) and adapted to Northern Italy climates, and 250 elite lines (ELT) selected over the past 25 years through the CREA breeding programs. All lines were evaluated in rhizotrons for 10 days in optimal conditions and revealed substantial variations for root traits, with medium-high heritabilities. Genome-wide association mapping was performed with 20.397 SNPs, and preliminar analyses did not reveal major factors controlling the traits. Inbred lines were then classified as shallowrooted (S) or deep-rooted (D) according to a multi-trait linear phenotypic selection index (LPSI). Those lines were also evaluated as mature plants in field condition through shovelomics analysis and confirmed their predicted RSA. About 60 hybrids between S lines and about 60 between D lines were obtained and were evaluated in rhyzotrons and in the field for agronomic traits under two water regimes. Preliminary results will be discussed. As applied output, this study may contribute to the setting of a selection criteria to identify hybrid combinations with improved root efficiency and stress tolerance. Financial support of Regione Lombardia -Progetti di ricerca in campo agricolo e forestale Bando 2018 d.d.s. n. 4403 del 28/03/2018). Project “MIRALO (2020 – 2024) Analisi di linee di Mais per lo sviluppo di Ibridi con efficiente apparato RAdicale da utilizzare nell’areale Lombardo”