Identification and mapping of a tiller inhibition gene (tin3) in wheat

Tillering is one of the most important agronomic traits in cereal crops because tiller number per plant determines the number of spikes or panicles per plant, a key component of grain yield and/or biomass. In order to characterize the underlying genetic variation for tillering, we have isolated mutants that are compromised in tillering ability using ethyl methanesulphonate (EMS)-based mutagenesis in diploid wheat (Triticum monococcum subsp. monococcum). The tillering mutant, tiller inhibition (tin3) produces only one main culm compared to the wild type with many tillers. The monoculm phenotype of tin3 is due to a single recessive mutation. Genetic and molecular mapping in an F(2) population of diploid wheat located the tin3 gene on the long arm of chromosome 3A(m). One codominant RFLP marker Xpsr1205 cosegregated with tin3 in the F(2) population. Physical mapping of PSR1205 in a set of Chinese Spring deletion lines of group-3 chromosomes placed the tin3 gene in the distal 10% of the long arm of chromosome 3A, which is a recombination-rich region in wheat. The implications of the mapping of tin3 on chromosome arm 3A(m)L are discussed with respect to putative orthologs of tin3 in the 3L colinear regions across various cereal genomes and other tillering traits in grasses.