Genetic variability for root system architecture (RSA) in Italian maize inbred lines

Genetic variability for root system architecture (RSA) in Italian maize inbred lines Gianfranco Mazzinelli a, Francesco Solimei b, Matteo De Biasi b, Hans Hartings a, Chiara Lanzanova a, Carlotta Balconi a, Alessio Torri a, Alberto Tassinari b, Silvio Salvi b, Elisabetta Frascaroli b a) CREA-Centro di ricerca Cerealicoltura e Colture Industriali/Research Centre for Cereal and Industrial Crops, Via Stezzano 24, 24126, Bergamo (Italy) b) Department of Agricultural and Food Sciences, University of Bologna, viale Giuseppe Fanin 44, 40127, Bologna (Italy). Corresponding author: Elisabetta Frascaroli (elisabetta.frascaroli@unibo.it) Keywords: root system architecture RSA, selection criteria, maize germplasm, drought Maize genotypes with efficient root systems are thought to better adapt to environments with frequent dry seasons. Preliminary investigations suggested that a fair amount of genetic variability for root system architecture (RSA) is still present among elite cultivars as well as in germplasm collections, which may result in drought stress tolerance. The evaluation of RSA led to the development of root ideotypes related to yield and stress tolerance. The objectives of the study are to explore variability for RSA in Italian maize germplasm and to develop phenotypic and genomic selection criteria for obtaining resilient varieties adapted to Northern Italy. We studied 340 inbreds, 90 of which derived from local varieties grown in Italy before the 1950s and 250 elite inbred lines selected in the last 25 years within the CREA breeding programs and belonging to two breeding groups. In this study, all lines were evaluated for RSA in rhizotrones under controlled condition. Genome-wide association was performed with 20.397 SNPs. The results showed substantial variations for root traits, with medium-high heritabilities. Inbred lines were classified as shallow or deep rooted according to a multi-trait index, and crossed in partial North Carolina mating designs II. About 60 hybrids between shallow and about 60 between deep inbred groups were obtained and were evaluated 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”