Most cultivated potato (Solanum tuberosum) varieties are highly susceptible to common scab (Streptomyces scabei). The disease is widespread in all major potato production areas and leads to high economic losses and food waste. Varietal resistance is seen as the most viable and sustainable long-term management strategy. However, resistant potato varieties are scarce, and their genetic architecture and resistance mechanisms are poorly understood. Moreover, diploid potato relatives to commercial potatoes remain to be fully explored. In the current study, a panel of 384 ethyl methane sulfonate (EMS)-mutagenized diploid potato clones were evaluated for common scab coverage, severity, and incidence traits under field conditions, and genome-wide association studies (GWASs) were conducted to dissect the genetic architecture of their traits. Using the GAPIT-MLM and RTM-GWAS statistical models, and Mann–Whitney non-parametric U-tests, we show that 58 QTNs/QTLs distributed on all 12 potato chromosomes were associated with common scab resistance, 52 of which had significant allelic effects on the three traits. In total, 38 of the 52 favorable QTNs/QTLs were found to be pleiotropic on at least two of the traits, while 14 were unique to a single trait and were found distributed over 3 chromosomes. The identified QTNs/QTLs showed low to high effects, highlighting the quantitative and multigenic inheritance of common scab resistance. The QTLs/QTNs associated with the three common scab traits were found to be co-located in genomic regions carrying 79 candidate genes playing roles in plant defense, cell wall component biosynthesis and modification, plant–pathogen interactions, and hormone signaling. A total of 61 potato clones were found to be tolerant or resistant to common scab. Taken together, the data show that the studied germplasm panel, the identified QTNs/QTLs, and the candidate genes are prime genetic resources for breeders and biologists in breeding and targeted gene editing.

Cultivated potato (Solanum tuberosum) is known to be highly susceptible to drought. With climate change and its frequent episodes of drought, potato growers will face increased challenges to achieving their yield goals. Currently, a high proportion of untapped potato germplasm remains within the diploid potato relatives, and the genetic architecture of the drought tolerance and maturity traits of diploid potatoes is still unknown. As such, a panel of 384 ethyl methanesulfonate-mutagenized diploid potato clones were evaluated for drought tolerance and plant maturity under field conditions. Genome-wide association studies (GWAS) were conducted to dissect the genetic architecture of the traits. The results obtained from the genetic structure analysis of the panel showed five main groups and seven subgroups. Using the Genome Association and Prediction Integrated Tool–mixed linear model GWAS statistical model, 34 and 17 significant quantitative trait nucleotides (QTNs) were found associated with maturity and drought traits, respectively. Chromosome 5 carried most of the QTNs, some of which were also detected by using the restricted two-stage multi-locus multi-allele-GWAS haploblock-based model, and two QTNs were found to be pleiotropic for both maturity and drought traits. Using the non-parametric U-test, one and three QTNs, with 5.13%–7.4% phenotypic variations explained, showed favorable allelic effects that increase the maturity and drought trait values. The quantitaive trait loci (QTLs)/QTNs associated with maturity and drought trait were found co-located in narrow (0.5–1 kb) genomic regions with 56 candidate genes playing roles in plant development and senescence and in abiotic stress responses. A total of 127 potato clones were found to be late maturing and tolerant to drought, while nine were early to moderate–late maturing and tolerant to drought. Taken together, the data show that the studied germplasm panel and the identified candidate genes are prime genetic resources for breeders and biologists in conventional breeding and targeted gene editing as climate adaptation tools.

Late blight caused by Phytophthora infestans is a serious threat to potato production. Currently, solutions to manage late blight in organic systems are scarce. This study was undertaken to evaluate the effect of selenium (Se) on plant emergence from seed pre-treated with Se and the seed decay pathogens Pectobacterium carotovorum ssp. carotovorum and Fusarium sambucinum, and on foliar potato late blight following inoculation with P. infestans and foliar treatment with Se. The potential modes of action of Se were also evaluated. Following inoculation of the seed decay pathogens on potato seed pre-treated with different rates of Se, plant emergence was not affected by Se treatment. By pre-treating potato seed with different Se rates, and applying different foliar Se rates on potato plants subsequently inoculated with the late blight pathogen in a greenhouse setting, we showed that foliar Se application alone or combined with Se seed treatment reduced the severity and incidence of late blight, and activated the production of secondary metabolites in potato leaves and tubers. Further, in vitro studies showed that Se directly inhibited the mycelial growth of P. infestans and other important plant pathogens, including Fusarium graminearum and Sclerotinia sclerotiorum. The data suggest that Se acts as an inducer of plant defences, while also inhibiting fungal growth. The study highlights the potential of Se for managing late blight, and suggests that its application could contribute to improving plant health in greenhouse production systems by helping to control diseases caused by P. infestans, F. graminearum and S. sclerotiorum.

Common scab disease in potato has become a widespread issue in major potato production areas, leading to increasing economic losses. Varietal resistance is seen as a viable and long-term scab management strategy. However, the genes and mechanisms of varietal resistance are unknown. In the current study, a comparative RNA transcriptome sequencing and differential gene signaling and priming sensitization studies were conducted in two potato cultivars that differ by their response to common scab (Streptomyces scabies), for unraveling the genes and pathways potentially involved in resistance within this pathosystem. We report on a consistent and contrasted gene expression pattern from 1,064 annotated genes differentiating a resistant (Hindenburg) and a susceptible (Green Mountain) cultivars, and identified a set of 273 co-regulated differentially expressed genes in 34 pathways that more likely reflect the genetic differences of the cultivars and metabolic mechanisms involved in the scab pathogenesis and resistance. The data suggest that comparative transcriptomic phenotyping can be used to predict scab lesion phenotype in breeding lines using mature potato tuber. The study also showed that the resistant cultivar, Hindenburg, has developed and maintained a capacity to sense and prime itself for persistent response to scab disease over time, and suggests an immune priming reaction as a mechanism for induced-resistance in scab resistant potato cultivars. The set of genes identified, described, and discussed in the study paves the foundation for detailed characterizations towards tailoring and designing procedures for targeted gene knockout through gene editing and phenotypic evaluation.

Steroidal glycoalkaloids (SGAs) can be toxic to humans at more than 100 mg/100 g dry weight of potato tubers. The objective of the current study was to characterize phenotypically and genotypically a subset of 1750 ethyl methane sulfonate (EMS)-mutagenized diploid potato clones previously reported in our group for altered SGA production. The study reports on a wide range of SGA profiles in 246 EMS-mutant lines, of which 14% showed lower SGA content than the wild types and commercial varieties. An Ampliseq gene panel sequencing of 9 key SGA biosynthetic genes from 87 EMS-treated lines showing varied SGA profiles revealed 61 unique functional SNP mutations in 56 unique EMS-treated individual lines. Mutational frequencies in the target genes ranged from 1/16 kb (SGT2) to 1/341 kb (GAME7), with an average of 1/47 kb. Among these mutations, mutations were detected in GAME7, GAME6, GAME11, GAME4CH6, GAME4CH12, and SGT3 genes of low SGA EMS-treated lines, genes deemed essential for steroidal aglycone hydroxylation, oxidation, and solanidine glycosylation. Subsequent comparative transcriptomic analysis of a low SGA mutant line and a high SGA wild type line showed significant downregulation of UDP-glycosyltransferases and cytochrome P450s expression in the low SGA EMS-mutant line. Using EMS-mutagenesis, this study is the first to show evidence of an effective alteration of SGA production in diploid potato tubers and paves the way for more functional analysis of this mutant population as well as diploid mutant potato cultivar development.

Mutations are the key drivers for evolution and diversification in plants. In varietal selection, sources for variation are always sought as starting breeding materials. Thus, in the absence of desired natural variations in breeding populations, targeted or random mutagenesis is applied to induce variations. Cultivated potato (Solanum tuberosum L.) is autotetraploid crop species with a narrow and highly heterozygous genetic base, and the complexity of its genome makes its genetic studies more difficult. In the current study, induced mutagenesis was performed in diploid potato using ethyl methane sulfonate (EMS) to enlarge the genetic variability for its use as pre-breeding materials in both polyploid and diploid potato breeding. As starting materials, true potato seeds were treated with 1.2% EMS for 4–6 h along with untreated seeds as controls. A large variation in terms of germination rate, plant, flower, and tuber phenotype was observed in EMS-treated plants compared with their untreated counterparts. In particular, abnormal phenotypes including twisted stem, partial and (or) completely chlorotic leaves and stems, variations in stem colour and weak-stemmed plants with lateral growth habit as well as plants with determinate growth habit were observed along with normal plant characteristics. Moreover, variations in flower colour and tuber colour, shape, and size, as well as yield potential, were observed in EMS-treated lines. The reported phenotypic characterization of EMS mutagenized diploid potato collection is to our knowledge the first in its kind and represents a premium genetic resource for potato breeding programs and plant biologists for genes functional characterization in potato.

Flax secoisolariciresinol (SECO) diglucoside (SDG) lignan is an emerging natural product purported to prevent chronic diseases in humans. SECO, the aglycone form of SDG, has shown higher intestinal cell absorption but it is not accumulated naturally in planta. Recently, we have identified and characterized a UDP-glucosyltransferase gene, UGT74S1, that glucosylates SECO into its monoglucoside (SMG) and SDG forms when expressed in yeast. However, whether this gene is unique in controlling SECO glucosylation into SDG in planta is unclear. Here, we report on the use of UGT74S1 in reverse and forward genetics to characterize an ethyl methane sulfonate (EMS) mutagenized flax population from cultivar CDC Bethune and consisting of 1996 M2 families. EMS mutagenesis generated 73 SNP variants causing 79 mutational events in the UGT74S1 exonic regions of 93 M2 families. The mutation frequency in the exonic regions was determined to be one per 28 Kb. Of these mutations, 13 homozygous missense mutations and two homozygous nonsense mutations were observed and all were transmitted into the M3 and M4 generations. Forward genetics screening of the population showed homozygous nonsense mutants completely lacking SDG biosynthesis while the production of SMG was observed only in a subset of the M4 lines. Heterozygous or homozygous M4 missense mutants displayed a wide range of SDG levels, some being greater than those of CDC Bethune. No additional deleterious mutations were detected in these mutant lines using a panel of 10 other genes potentially involved in the lignan biosynthesis. This study provides further evidence that UGT74S1 is unique in controlling SDG formation from SECO and this is the first report of non-transgenic flax germplasm with simultaneous knockout of SDG and presence of SMG in planta.