Genetic mapping and development of near-isogenic lines for genes governing a liguleless phenotype in tetraploid wheat

The liguleless phenotype in wheat lacks ligules and auricles on all plant leaves. Two duplicate dominant genes (Lg (1) and Lg (3) ) principally control the presence of ligules in tetraploid wheat. Although the Lg (3) gene was tentatively located in chromosome 2A, a genetic stock of Triticum durum Desf. (2n = 4x = 28, BBAA genome) having genotype lg (1) lg (1) Lg (3) Lg (3) has not been available. We speculated that a wild emmer (T. dicoccoides Korn., 2n = 4x = 28, BBAA genome) could be a possible source of the Lg (3) gene. In the present study near-isogenic lines (NIL's) ANW 12E for genotype lg (1) lg (1) Lg (3) Lg (3) and ANW 12F for genotype Lg (1) Lg (1) lg (3) lg (3) were developed from a cross between ANW 12A (lg (1) lg (1) lg (3) lg (3) ), a liguleless NIL of T. durum LD222, and LDN(DIC 2A) (Lg (1) Lg (1) Lg (3) Lg (3) ) through backcrossing to ANW 12A. LDN(DIC 2A) is a chromosome substitution line in which a pair of T. durum cv. Langdon (LDN) 2A chromosomes is replaced with a pair of chromosomes 2A from T. dicoccoides (DIC) line Israel A. Molecular mapping using the F-2 of liguleless durum PI 370751/ANW 12F revealed that the Lg (1) gene was 17.5 cM distal to Xgwm47 in chromosome 2BL. In the F-2 of PI 370751/ANW 12E the Lg (3) gene was located 18.6 cM distal to Xgwm312 in chromosome 2AL. These results confirmed that the Lg (3) locus was present in chromosome 2A, and dominant alleles at the homoeologous Lg loci determine the presence of ligules in polyploid wheat.