Key messageSix stable QTL for resistance againstL. maculans(phoma stem canker) have been identified by QTL × environment interaction analysis using data from five winter oilseed rape field experiments.AbstractPhoma stem canker, caused by Leptosphaeria maculans, is a disease of worldwide importance on oilseed rape (Brassica napus). Quantitative trait loci (QTL)-mediated resistance against L. maculans in B. napus is considered to be race non-specific and potentially durable. Identification and evaluation of QTL for resistance to L. maculans is important for breeding oilseed rape cultivars with durable resistance. An oilseed rape mapping population was used to detect QTL for resistance against L. maculans in five winter oilseed rape field experiments under different environments. A total of 17 QTL involved in ‘field’ quantitative resistance against L. maculans were detected and collectively explained 51 % of the phenotypic variation. The number of QTL detected in each experiment ranged from two to nine and individual QTL explained 2–25 % of the phenotypic variation. QTL × environment interaction analysis suggested that six of these QTL were less sensitive to environmental factors, so they were considered to be stable QTL. Markers linked to these stable QTL will be valuable for selection to breed for effective resistance against L. maculans in different environments, which will contribute to sustainable management of the disease.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2620-z) contains supplementary material, which is available to authorized users.

Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca 2+ transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis-and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 3 R500); 23 cis-and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca 2+ transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization.

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