Validation of Diaporthe toxica resistance markers in European Lupinus angustifolius germplasm and identification of novel resistance donors for marker-assisted selection

M Książkiewicz,E Rudy,M Jędryczka,S Rychel,W Irzykowski,K Wójcik,J Kaczmarek,W Bielski,P Plewiński

doi:10.1007/s13353-019-00521-y

Abstract

The fungus, Diaporthe toxica, anamorph Phomopsis sp., 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. angustifolius was 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 Phr1 and PhtjR. Molecular markers PhtjM7, InDel2, and InDel10, tagging PhtjR gene, were applicable for marker-assisted selection targeting the European gene pool with an expected accuracy of 95%. None of diagnostic markers for the Phr1 locus 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%).

Highlights

The legume Lupinus angustifolius L. belongs to the genus Lupinus
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 Phr1 and PhtjR
The other five isolates were obtained from L. angustifolius, all of them were collected in Australia, mostly in Western Australia (4 sites) and one isolate was obtained from L. angustifolius collected in South Eastern Australia

Summary

Introduction

The legume Lupinus angustifolius L. (narrow-leafed lupin) belongs to the genus Lupinus (tribe of Genisteae, family Fabaceae, subfamily Faboideae). (narrow-leafed lupin) belongs to the genus Lupinus (tribe of Genisteae, family Fabaceae, subfamily Faboideae). It is well known as a source of protein for food and feed, as well as being a crop that contributes to the improvement of soil structure and fertility, increasing yields of succeeding crops (Peoples et al 2009). Due to its relatively low chromosome number (2n = 40) and small genome size (2C = 1.89 pg), compared with other lupins (Naganowska et al 2003), L. angustifolius became the species of choice for extensive molecular studies. Molecular research has been greatly facilitated by the development of bacterial artificial chromosome (BAC) libraries of the nuclear genomes for two L. angustifolius cultivars: Polish cv. Exploitation of BAC resources for cytogenetic mapping resulted in the integration of all linkage groups with the corresponding chromosomes, as well as in the identification of

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