Validation of Diaporthe toxicaresistance markers in European Lupinus angustifoliusgermplasm and identification of novel resistance donors for marker-assisted selection

The fungus, Diaporthe toxica, anamorph Phomopsissp., previously classified as P. leptostromiformis, is a plant endophyte and occasional pathogen, causing Phomopsis stem blight. This disease is damaging not only to lupins but also to the animals grazing on infected plants, due to the toxic secondary metabolites called phomopsins. The aim of this work was to validate markers for resistance to Phomopsis stem blight in narrow-leafed lupins and identify novel germplasm with increased levels of resistance to the disease. Plant inoculations were performed using ten isolates of D. toxica, originating from Australia and Poland. The European core collection of L. angustifoliuswas evaluated both in a controlled environment and with field experiments to classify the accessions based on their resistance to the disease. Simultaneously, the accessions were assayed with disease resistance markers to identify donors of hypothetical resistance alleles. We have found that the European lupin germplasm collection preserves wild and domesticated donors of at least two resistance genes to Phomopsis stem blight, including Phr1and PhtjR. Molecular markers PhtjM7, InDel2, and InDel10, tagging PhtjRgene, were applicable for marker-assisted selection targeting the European gene pool with an expected accuracy of 95%. None of diagnostic markers for the Phr1locus was found useful for European breeding programs; two existing markers Ph258M1 and Ph258M2 were unreliable, due to a high percentage of false-positive results (up to 58%) and a high recombination rate between markers (~ 30%).