SARS-CoV-2 spike glycoprotein mediates receptor binding and subsequent membrane fusion. It exists in a range of conformations, including a closed state unable to bind the ACE2 receptor, and an open state that does so but displays more exposed antigenic surface. Spikes of variants of concern (VOCs) acquired amino acid changes linked to increased virulence and immune evasion. Here, using HDX-MS, we identified changes in spike dynamics that we associate with the transition from closed to open conformations, to ACE2 binding, and to specific mutations in VOCs. We show that the RBD-associated subdomain plays a role in spike opening, whereas the NTD acts as a hotspot of conformational divergence of VOC spikes driving immune evasion. Alpha, beta and delta spikes assume predominantly open conformations and ACE2 binding increases the dynamics of their core helices, priming spikes for fusion. Conversely, substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies. At the same time, its core helices show characteristics of being pre-primed for fusion even in the absence of ACE2. These data inform on SARS-CoV-2 evolution and omicron variant emergence.

During 120 years of Polish breeding of oats (Avena sativa L.), dozens of new varieties have been developed. This study was undertaken to investigate the diversity and population structure of 72 Polish oat cultivars released since 1893. The analysis was based on pedigree data as well as ISSR and REMAP marker polymorphisms. The ancestry of common oat cultivars was traced back to 124 cultivars, breeding lines, and landraces. The five most common progenitors were ‘Markische Landsorte’, ‘selection from Ligowo oat’, ‘Fransk Svarthavre’, ‘Blanche de Siberie’, and ‘selection from Schleswig-Holstein landrace’. We found that at least one of them was present in 78% of analysed objects. The studied cultivars were assigned to four groups according to the period of their breeding (before 1945, 1945–1969, 1970–2000, and after 2000) and six groups according to the breeding company (Strzelce Plant Breeding Company, DANKO Plant Breeding, Station of Plant Breeding in Rogaczewo, Małopolska Plant Breeding Company, Station of Plant Breeding in Borów, and other). A decrease in observed heterozygosity within the groups was observed only in the postwar period (1945–1969). As a result of breeders' efforts and extensive crosses with foreign materials initiated in 1970 and 1980, new alleles were provided to the oat gene pool. The highest number of new varieties came from the Strzelce and DANKO breeding companies. There were no significant differences between modern cultivars derived from different breeding companies. However, very early breeding centres functioning before 1945 had significantly different materials from the modern ones. The population genetic structure of the studied group of cultivars appeared to be quite simple. It was shown that their genetic makeup consisted of two or three distinct gene pools, depending on the method of polymorphism assessment. The performed research proved that Polish oat breeding using traditional breeding methods—such as selection or intraspecific and interspecific crosses—although focused on improving yield and tolerance to biotic and abiotic stress, did not significantly narrow the oat gene pool and has been releasing cultivars that are competitive in the European market.

Crown rust, caused by Puccinia coronata f. sp. avenae, is one of the most destructive fungal diseases of oat worldwide. Growing disease-resistant oat cultivars is the preferred method of preventing the spread of rust and potential epidemics. The object of the study was Pc50-5, a race-specific seedling crown rust resistant gene, highly effective at all growth stages, selected from the differential line Pc50 (Avena sterilis L. CW 486-1 × Pendek). A comparison of crown rust reaction as well as an allelism test showed the distinctiveness of Pc50-5, whereas the proportions of phenotypes in segregating populations derived from a cross with two crown rust-susceptible Polish oat cultivars, Kasztan × Pc50-5 and Bingo × Pc50-5, confirmed monogenic inheritance of the gene, indicating its usefulness in oat breeding programs. Effective gene introgression depends on reliable gene identification in the early stages of plant development; thus, the aim of the study was to develop molecular markers that are tightly linked to Pc50-5. Segregating populations of Kasztan × Pc50-5 were genotyped using DArTseq technology based on next-generation Illumina short-read sequencing. Markers associated with Pc50-5 were located on chromosome 6A of the current version of the oat reference genome (Avena sativa OT3098 v2, PepsiCo) in the region between 434,234,214 and 440,149,046 bp and subsequently converted to PCR-based SCAR (sequence-characterized amplified region) markers. Furthermore, 5426978_SCAR and 24031809_SCAR co-segregated with the Pc50-5 resistance allele and were mapped to the partial linkage group at 0.6 and 4.0 cM, respectively. The co-dominant 58163643_SCAR marker was the best diagnostic and it was located closest to Pc50-5 at 0.1 cM. The newly discovered, very strong monogenic crown rust resistance may be useful for oat improvement. DArTseq sequences converted into specific PCR markers will be a valuable tool for marker-assisted selection in breeding programs.