Phenotypic characterisation and fine genetic mapping of the tomato bushy root (brt) mutant. bushy root (brt) mutant

The tomato mutant bushy root (brt) arose from a cross between tomato accessions “Stock No. 1” and cultivar “Red Cherry” following EMS mutagenesis of pollen. Micro-Tom (MT) was used to produce a homozygous near isogenic line (brtNIL). The mutation has a pleiotropic phenotype: small seed size was observed, and it was determined that this phenotype is controlled by the maternal tissue; the small seed size is likely to explain, the slow early development exhibited by brtNIL. The mutant root system was characterised by image analysis and can be described as a compact root system with fewer and smaller lateral roots and shorter tap root. The brtNIL genome was re-sequenced and assembled in comparison to MT, against the reference S. lycopersicum Heinz 1706 (version SL2.50); this shows that the introgression spans 64 Mbp of the 67 Mbp. In the current mapping interval, i.e. 137 kbp, 9 genes were found. The transcriptomics data of the pirin gene (Solyc12g014590), homologue to PRN1 in Arabidopsis, suggest Solyc12g014590 as a strong candidate for the brtNIL phenotype.