Linkage of AFLP markers to lhd 1, a recessive heterochronic gene in Italian ryegrass

A mutant, leafy head 1 (lhd 1), was discovered in Japan from the progeny of Italian ryegrass (Lolium multiflorum Lam.) 'Nioudachi' and local line 'Aichikei #3'. Compared with normal plants, the mutant plant is a dwarf with a larger number of internodes per stem, shorter internodes, and smaller leaves. The plants also head later in the season. Aerial roots are usually produced from the stem nodes during rainy seasons. In characterizing lhd 1, it was found to have many branches with small leaves and many small panicles on the upper part of the plant. Panicle development was severely disturbed in lhd 1 mutants, and the number of leaves produced in the vegetative phase was nearly twice that produced in the wild-type counterpart. The lhd 1 mutant appears to be a heterochronic mutation that is able to extend the vegetative period during development. The frequency of mutants in segregating populations indicated that lhd 1 is a recessive allele. To determine the linkage relationship between the lhd 1 gene and AFLP markers, 768 primer combinations were screened for polymorphisms using bulked segregant analyses in two populations with 316 and 30 plants, respectively. Five AFLP markers were linked to the lhd 1 locus. E3/M41-1 and E16/M14-2 cosegregated with lhd 1. E16/M14-1 and E30/M10-1 flanked the gene at a distance of 0.3 cM and E30/M14-2 was linked to lhd 1 at a distance of 0.6 cM.