Rhizomes and tillers grow from underground axillary meristems, which are important determinants of perennial growth habit and architecture in grasses. Leymus cinereus grows from intravaginal axillary meristems (tillers), forming a compact tussock year after year. Conversely, L. triticoides grows from creeping underground rhizomes, capable of forming extensive sods and substantial spreading year after year. Homologous and possibly homoeologous QTLs have been detected on LG3a and LG3b chromosomes in the 164-sib TTC1 and 170-sib TTC2 Leymus triticoides x (L. triticoides x L. cinereus) mapping families, using high-density molecular genetic linkage maps with 1583 AFLP markers and 64 anchor loci. In this report, we describe fine genetic mapping of the LG3a and LG3b QTLs using the 192-sib TTTC1-168, 96-sib TTC2.1-045, 96-sib TTC2.1-111, 192-sib TTTC2.2-002, 87-sib TTTC2.2-005, and 96-sib TTTC2.2-063 advanced backcross families evaluated in clonally replicated field trials. Fine-genetic mapping will be used to identify Leymus BAC clones containing these rhizome QTLs.