Unraveling the Genetic Basis of Key Agronomic Traits of Wrinkled Vining Pea (Pisum sativum L.) for Sustainable Production

Estimating the allelic variation and exploring the genetic basis of quantitatively inherited complex traits are the two foremost breeding scenarios for sustainable crop production. The current study utilized 188 wrinkled vining pea genotypes comprising historical varieties and breeding lines to evaluate the existing genetic diversity and to detect molecular markers associated with traits relevant to vining pea production, such as wrinkled vining pea yield (YTM100), plant height (PH), earliness (ERL), adult plant resistance to downy mildew (DM), pod length (PDL), numbers of pods per plant (PDP), number of peas per pod (PPD), and percent of small wrinkled vining peas (PSP). Marker-trait associations (MTAs) were conducted using 6902 quality single nucleotide polymorphism (SNP) markers generated from the diversity arrays technology sequencing (DArTseq) and Genotyping-by-sequencing (GBS) sequencing methods. The best linear unbiased prediction (BLUP) values were estimated from the two-decadeslong (1999–2020) unbalanced phenotypic data sets recorded from two private breeding programs, the Findus and the Birds eye, now owned by Nomad Foods. Analysis of variance revealed a highly significant variation between genotypes and genotype-byenvironment interactions for the ten traits. The genetic diversity and population structure analyses estimated an intermediate level of genetic variation with two optimal subgroups within the current panel. A total of 48 significant (P < 0.0001) MTAs were identified for eight different traits, including five for wrinkled vining pea yield on chr2LG1, chr4LG4, chr7LG7, and scaffolds (two), and six for adult plant resistance to downy mildew on chr1LG6, chr3LG5 (two), chr6LG2, and chr7LG7 (two). We reported several novel MTAs for different crucial traits with agronomic importance in wrinkled vining pea production for the first time, and these candidate markers could be easily validated and integrated into the active breeding programs for marker-assisted selection

Evaluation of pea genotype PI180693 partial resistance towards aphanomyces root rot in commercial pea breeding

The cultivation of vining pea (Pisum sativum) faces a major constraint with root rot diseases, caused by a complex of soil-borne pathogens including the oomycetes Aphanomyces euteiches and Phytophtora pisi. Disease resistant commercial varieties are lacking but the landrace PI180693 is used as a source of partial resistance in ongoing pea breeding programs. In this study, the level of resistance and their interaction with A. euteiches virulence levels of six new back-crossed pea breeding lines, deriving from the cross between the susceptible commercial cultivar Linnea and PI180693, were evaluated for their resistance towards aphanomyces root rot in growth chamber and green house tests. Resistance towards mixed infections by A. euteiches and P. pisi and commercial production traits were evaluated in field trials. In growth chamber trials, pathogen virulence levels had a significant effect on plant resistance, as resistance was more consistent against A. euteiches strains exhibiting high or intermediate virulence compared with lowly virulent strains. In fact, line Z1701-1 showed to be significantly more resistant than both parents when inoculated with a lowly virulent strain. In two separate field trials in 2020, all six breeding lines performed equally well as the resistant parent PI180693 at sites only containing A. euteiches, as there were no differences in disease index. In mixed infections, PI180693 exhibited significantly lower disease index scores than Linnea. However, breeding lines displayed higher disease index scores compared with PI180693, indicating higher susceptibility towards P. pisi. Data on seedling emergence from the same field trials suggested that PI180693 was particularly sensitive towards seed decay/damping off disease caused by P. pisi. Furthermore, the breeding lines performed equally well as Linnea in traits important for green pea production, again emphasizing the commercial potential. In summary, we show that the resistance from PI180693 interacts with virulence levels of the pathogen A. euteiches and is less effective towards root rot caused by P. pisi. Our results show the potential use of combining PI180693 partial resistance against aphanomyces root rot with commercially favorable breeding traits in commercial breeding programs

Genetic diversity of the pea root pathogen Aphanomyces euteiches in Europe

The oomycete pathogen Aphanomyces euteiches causes root rot in various legume species. In this study we focused on A. euteiches causing root rot in pea (Pisum sativum), thereby being responsible for severe yield losses in pea production. We aimed to understand the genetic diversity of A. euteiches in Europe, covering a north-to-south gradient spanning from Sweden, Norway and Finland to the UK, France and Italy. A collection of 85 European A. euteiches strains was obtained, all isolated from infected pea roots from commercial vining pea cultivation fields. The strains were genotyped using 22 simple-sequence repeat markers. Multilocus genotypes were compiled and the genetic diversity between individual strains and population structure between countries was analysed. The population comprising strains from Italy was genetically different and did not share ancestry with any other population. Also, strains originating from Finland and the eastern parts of Sweden were found to be significantly different from the other populations, while strains from the rest of Europe were more closely related. A subset of 10 A. euteiches strains from four countries was further phenotyped on two susceptible pea genotypes, as well as on one genotype with partial resistance towards A. euteiches. All strains were pathogenic on all pea genotypes, but with varying levels of disease severity. No correlation between the genetic relatedness of strains and virulence levels was found. In summary, our study identified three genetically distinct groups of A. euteiches in Europe along a north-to-south gradient, indicating local pathogen differentiation

A LOW-COST METHOD FOR THE DETECTION OF DUPLICATE HOLDINGS AMONG GENEBANK ACCESSIONS

A set of 185 pairs of accessions with the same name from the Russian and Nordic collections of barley were grown in the field in Pushkin and were scored by the same person using a set of morphological descriptors. No differences were detected in the majority of the pairs (63%).In four out of six pairs no differences were detected for any of the agro-botanical characters. The accessions are most likely duplicates. In 13% of the pairs, the accessions were probably distinct and another 24% fell in-between these categories and required further investigation. Simple screening can reduce the number of duplicates. [The work is dedicated to Sergey M. Alexanian, Vice Director for Foreign Relations of VIR, who passed away in 2014]

A century of breeding - is genetic erosion a reality?

Barley (Hordeum vulgare L. ssp. vulgare) is an important crop in the Nordic and Baltic countries, where it is mainly used for feed and malt. Commercial breeding of barley has been carried out in this region for more than a century, and landraces have been completely replaced by pure line cultivars. There is a concern that plant breeding might lead to a severe reduction of genetic diversity, so-called genetic erosion, since commercial breeding was initially based only on a few successful selections from landraces. The consequences of such erosion would affect plasticity of the crop, which might reduce its ability to adapt to future agriculture and consumption demands and increase the vulnerability to epidemics. The aim of this study was to evaluate the degree of putative genetic erosion and relationships in Nordic and Baltic barley material. A large collection representing landraces and cultivars from the end of the 19th century up to modern material were analysed by isozymes and DNA markers. In addition, field trials were performed in order to observe changes in the diversity of agronomic traits. General indications of a decrease in diversity were observed. A loss of less common alleles was found in molecular markers and a significant decrease of variability was detected for most agronomic traits. However, the molecular markers failed to prove significant diversity changes in the material as a whole. New alleles, not present in Nordic and Baltic landraces and old cultivars, were found in modern material. Differences in the magnitude of diversity varied depending of country and region (North vs South) of origin and row type of the crop. Some of these diversity changes were also significant in the molecular makers, for example a significant decrease in material from the southern part of the region was observed. The two-rowed and six-rowed cultivars of this region were well differentiated not only by agronomic data, but also by DNA markers. They demonstrated differences at chromosome regions distant from the inflorescence determinating genes. While agronomical data separate modern material from landraces and old cultivars fairly well, DNA markers achieved this for most of the countries only when the material was analysed separately by country. The main conclusion of this study is that breeding in Nordic and Baltic countries has decreased diversity at some traits, but overall diversity of the crop has not changed significantly. However, the landraces and old cultivars of the region should still be considered as valuable diversity sources since some of the loci found there are not present in modern materials

Report of a Working Group on Barley: Seventh meeting, 10-12 May 2011, Nicosia, Cyprus

The seventh meeting of the ECPGR Barley Working Group (WG), organized in collaboration with the Agricultural Research Institute (ARI) of Cyprus, was held from 10 to 12 May 2011 in Nicosia, bringing together 24 members, 3 observers and the ECPGR Coordinator. The meeting covered a wide range of topics: implementation of “A European Genebank Integrated System” (AEGIS) by the Barley WG (approaches and aims for the European Barley Collection; criteria for Most Appropriate Accessions; quality standards criteria; species-specific maintenance protocols for wild Hordeum species as part of the AEGIS Quality System); precise genetic stocks of barley; collection of developmental mutants of barley and their potential use in pre breeding work; Trust multiplication project for cereals and legumes; characterization and evaluation (pre-breeding workshop and activities, ring tests update, breeding for climate change); in situ and on-farm activities in barley (Hordeum wild species in Europe, crop wild relatives of cultivated barley, conservation strategy for wild Hordeum species); documentation and information (the European Barley Database and EURISCO; the International Barley Core Collection); pre-breeding and joint research proposals (development of a disease resistance database; development of phenotype tests for abiotic stress resistance; evaluation of germplasm through ring tests; lobbying for pre-breeding at EU and national level; collaboration for joint project proposals; sharing of information and expertise)

Transcriptomic analysis identifies candidate genes for Aphanomyces root rot disease resistance in pea

Abstract Background Aphanomyces euteiches is a soil-borne oomycete that causes root rot in pea and other legume species. Symptoms of Aphanomyces root rot (ARR) include root discoloration and wilting, leading to significant yield losses in pea production. Resistance to ARR is known to be polygenic but the roles of single genes in the pea immune response are still poorly understood. This study uses transcriptomics to elucidate the immune response of two pea genotypes varying in their levels of resistance to A. euteiches. Results In this study, we inoculated roots of the pea (P. sativum L.) genotypes ‘Linnea’ (susceptible) and ‘PI180693’ (resistant) with two different A. euteiches strains varying in levels of virulence. The roots were harvested at 6 h post-inoculation (hpi), 20 hpi and 48 hpi, followed by differential gene expression analysis. Our results showed a time- and genotype-dependent immune response towards A. euteiches infection, involving several WRKY and MYB-like transcription factors, along with genes associated with jasmonic acid (JA) and abscisic acid (ABA) signaling. By cross-referencing with genes segregating with partial resistance to ARR, we identified 39 candidate disease resistance genes at the later stage of infection. Among the genes solely upregulated in the resistant genotype ‘PI180693’, Psat7g091800.1 was polymorphic between the pea genotypes and encoded a Leucine-rich repeat receptor-like kinase reminiscent of the Arabidopsis thaliana FLAGELLIN-SENSITIVE 2 receptor. Conclusions This study provides new insights into the gene expression dynamics controlling the immune response of resistant and susceptible pea genotypes to A. euteiches infection. We present a set of 39 candidate disease resistance genes for ARR in pea, including the putative immune receptor Psat7g091800.1, for future functional validation