Meta-analysis steps from QTL-projection on the consensus map to clustering into meta-QTLs: chromosome IV example. Projected QTLs (quantitative trait loci) are represented by vertical bars to the left of the consensus chromosome IV. Their length is representative of their confidence interval once projected on the consensus map. They are sorted into assessment type, within late blight resistance traits (Leaf disc, Leaflet, Whole tuber, Tuber slice, Stem, Foliage in field), on one hand, and within maturity traits (Maturity, Vigour), on the other hand. QTL names are written to the left of the bars. QTL nomenclature is as follows: the name of the first author of the original publication juxtaposed to the last two digits of the publication year, the name of the population consensus map or of the parental map where the QTL was detected, and an Arabic number that can be followed by a letter. This latter Arabic number is the number of the chromosome juxtaposed to the QTL mapping order on the chromosome; a letter was sometimes added to distinguish colocalizing QTLs that were detected with different traits. For Leonards-Schippers et al.'s study, the original name of the QTL was added . Ticks on the consensus chromosome indicate marker positions. Marker names are only shown for markers that occur at least in four maps out of the 21 compiled maps. Vertical thick bars to the right of the consensus chromosome indicate Meta-QTLs. Late blight meta-QTLs are in black and maturity meta-QTLs are in grey. Their length is representative of their confidence interval. To show clearly the results of the clustering step, the QTLs or part of the QTLs that were assigned to the 'MQTL_1_Late_blight' meta-QTL are in plain line and those assigned to the 'MQTL_2_Late_blight' meta-QTL are in dotted line. The QTL Collins99_I88_42 was not clustered to any late blight meta-QTL and was reported as an outlayer QTL in Additional file 1.