title: Manifestation of heterosis during early maize (Zea mays L.) root development.
abstract: Heterosis is typically detected in adult hybrid plants as increased yield or vigor compared to their parental inbred lines. Only little is known about the manifestation of heterosis during early postembryonic development. Objective of this study was to identify heterotic traits during early maize root development. Four German inbred lines of the flint (UH002 and UH005) and dent (UH250 and UH301) pool and the 12 reciprocal hybrids generated from these inbred lines were subjected to a morphological and histological analysis during early root development. Primary root length and width were measured daily in a time course between 3 and 7 days after germination (DAG) and displayed average midparent heterosis (MPH) of 17-25% and 1-7%, respectively. Longitudinal size of cortical cells in primary roots was determined 5 DAG and displayed on average 24% MPH thus demonstrating that enlarged primary roots of hybrids can mainly be attributed to elongated cortical cells. The number of seminal roots determined 14 DAG showed on average 18% MPH. Lateral root density of all tested hybrids was determined 5 DAG. This root trait showed the highest degree of heterosis with an average MPH value of 51%. This study demonstrated that heterosis is already manifesting during the very early stages of root development a few days after germination. The young root system is therefore a suitable model for subsequent molecular studies of the early stages of heterosis manifestation during seedling development.
authors.affiliation: Department of General Genetics, Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Hoecker
authors.forename: Barbara
authors.initials: B
authors.lastname: Keller
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Piepho
authors.forename: Frank
authors.initials: F
authors.lastname: Hochholdinger
mesh_terms: D005838:Genotype; D006823:Hybrid Vigor; D018613:Microscopy, Confocal; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development*; D012394:Rosaniline Dyes; D003313:Zea mays / Q000033:anatomy & histology / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*
chemical_list: C007722:Feulgen stain; D012394:Rosaniline Dyes