Estimation of immunity of the winter grain varieties sown in the south of Russia to the pink snow mold pathogen (Microdochium nivale)

The purpose of the current study was to estimate immunity of the winter grain varieties sown in the south of Russia to the pink snow mold pathogen (Microdochium nivale (Fr.) Samuels & I.C. Hallett) in the sprouting phase. For resistance to M. nivale there have been studied 35 winter wheat varieties sown in the south of the Russian Federation, 19 winter barley varieties and 4 variety samples and 13 winter triticale varieties developed in the LLC “Agrostandart”, FSBSI RCG named after P.P. Lukyanenko, FSBSI FRC Kabardino-Balkarian Research Center of the RAS, FSBSI “ARC Donskoy”, FSBSI “North Caucasian FRSC”, FSBSI “FRAC”, NPO “KUBANZERNO”, FSBEI HE “KubSAU”. There has been substantiated a methodological approach to conducting research on immunological estimation of winter grain varieties in the laboratory conditions. The optimal temperature for the cultivation of the pathogen was +10/+15 °C (with a photoperiod of 12 hours). There was found that the required temperature to stimulate sporulation was +5 °C. The optimum temperature for the incubation period was +5 °C at 85% humidity. There has been established that the only winter wheat variety ‘Dolya’ had a very high resistance degree to pink snow mold; the varieties ‘Antonina’ and ‘Brigada’ had a high resistance degree; 21 varieties were classified as resistant. M. nivale resistance was demonstrated by 9 winter barley varieties and 3 variety samples (‘Versal’, ‘Iosif’, ‘KA-12’, ‘KA-5/KA-3’, ‘KA-5/KA-1’, ‘Karrera’, ‘Kondrat’, ‘Kubagro-1’, ‘Lazar’, ‘Master’, ‘Romans’, ‘Sarmat’). Among the studied winter triticale varieties, 4 varieties had a very high resistance degree (‘Argus’, ‘Slon’, ‘Tikhon’, ‘Ullubiy’) and 9 varieties had a high resistance degree to pink snow mold pathogen (‘Aznavur’, ‘Argo’, ‘Arioso’, ‘Valentin 90’, ‘Iliya’, ‘Sotnik’,’ Styuard’, ‘Forte’, ‘Khleborob’).

An Apoplastic Defensin of Wheat Elicits the Production of Extracellular Polysaccharides in Snow Mold

TAD1 (Triticum aestivum defensin 1) is a plant defensin specifically induced by low temperature in winter wheat. In this study, we demonstrated that TAD1 accumulated in the apoplast during cold acclimation and displayed antifungal activity against the pink snow mold fungi Microdochium nivale. When M. nivale was treated with TAD1, Congo red-stainable extracellular polysaccharides (EPS) were produced. The EPS were degradable by cellulase treatment, suggesting the involvement of β-1,4 glucans. Interestingly, when the fungus was treated with FITC-labeled TAD1, fluorescent signals were observed within the EPS layer. Taken together, these results support the hypothesis that the EPS plays a role as a physical barrier against antimicrobial proteins secreted by plants. We anticipate that the findings from our study will have broad impact and will increase our understanding of plant–snow mold interactions under snow.

Rye Snow Mold-Associated Microdochium nivale Strains Inhabiting a Common Area: Variability in Genetics, Morphotype, Extracellular Enzymatic Activities, and Virulence

Snow mold is a severe plant disease caused by psychrophilic or psychrotolerant fungi, of which Microdochium species are the most harmful. A clear understanding of Microdochium biology has many gaps; the pathocomplex and its dynamic are poorly characterized, virulence factors are unknown, genome sequences are not available, and the criteria of plant snow mold resistance are not elucidated. Our study aimed to identify comprehensive characteristics of a local community of snow mold-causing Microdochium species colonizing a particular crop culture. By using the next-generation sequencing (NGS) technique, we characterized fungal and bacterial communities of pink snow mold-affected winter rye (Secale cereale) plants within a given geographical location shortly after snowmelt. Twenty-one strains of M. nivale were isolated, classified on the basis of internal transcribed spacer 2 (ITS2) region, and characterized by morphology, synthesis of extracellular enzymes, and virulence. Several types of extracellular enzymatic activities, the level of which had no correlations with the degree of virulence, were revealed for Microdochium species for the first time. Our study shows that genetically and phenotypically diverse M. nivale strains simultaneously colonize winter rye plants within a common area, and each strain is likely to utilize its own, unique strategy to cause the disease using “a personal” pattern of extracellular enzymes.

Snow mold of winter cereals: a complex disease and a challenge for resistance breeding

Key message Snow mold resistance is a complex quantitative trait highly affected by environmental conditions during winter that must be addressed by resistance breeding. Abstract Snow mold resistance in winter cereals is an important trait for many countries in the Northern Hemisphere. The disease is caused by at least four complexes of soilborne fungi and oomycetes of which Microdochium nivale and M. majus are among the most common pathogens. They have a broad host range covering all winter and spring cereals and can basically affect all plant growth stages and organs. Their attack leads to a low germination rate, and/or pre- and post-emergence death of seedlings after winter and, depending on largely unknown environmental conditions, also to foot rot, leaf blight, and head blight. Resistance in winter wheat and triticale is governed by a multitude of quantitative trait loci (QTL) with mainly additive effects highly affected by genotype × environment interaction. Snow mold resistance interacts with winter hardiness in a complex way leading to a co-localization of resistance QTLs with QTLs/genes for freezing tolerance. In practical breeding, a multistep procedure is necessary with (1) freezing tolerance tests, (2) climate chamber tests for snow mold resistance, and (3) field tests in locations with and without regularly occurring snow cover. In the future, resistance sources should be genetically characterized also in rye by QTL mapping or genome-wide association studies. The development of genomic selection procedures should be prioritized in breeding research.

Evaluating the Effects of Propiconazole on Hard Fescue (Festuca brevipila) via RNA sequencing and Liquid Chromatography–Mass Spectrometry

Propiconazole is often used to remove fungal endophytes from turfgrass to study the effects of Epichloë endophytes. However, besides a fungicidal effect, propiconazole can bind to the genes in the cytochrome P450 family and affect the biosynthesis of brassinosteroids. For this reason, outside of fungicidal application, propiconazole has also been used as plant growth regulator. In this study, we used a combination of RNA sequencing and liquid chromatography–mass spectrometry (LC-MS) to study how hard fescue (Festuca brevipila) responded to the high dose of propiconazole treatment. To test the long-term effect of the heavy use of propiconazole on plants, we inoculated with Microdochium nivale (causal agent of pink snow mold) half year post the last fungicide application. Propiconazole-treated plants showed enhanced pink snow mold resistance. This study suggested that the high dose use of propiconazole fungicide resulted in phenotypic and physiological changes in the plant such as slow growth and change in disease resistance. Genes and pathways affected by propiconazole identified in this study provide turfgrass breeders new information for genetic improvement of hard fescue and also provide turfgrass management new ways to control turfgrass diseases.

Carbohydrate Accumulation and Differential Transcript Expression in Winter Wheat Lines with Different Levels of Snow Mold and Freezing Tolerance after Cold Treatment

Winter wheat (Triticum aestivum L.) undergoes a period of cold acclimation in order to survive the ensuing winter, which can bring freezing temperatures and snow mold infection. Tolerance of these stresses is conferred in part by accumulation of carbohydrates in the crown region. This study investigates the contributions of carbohydrate accumulation during a cold treatment among wheat lines that differ in their snow mold tolerance (SMT) or susceptibility (SMS) and freezing tolerance (FrT) or susceptibility (FrS). Two parent varieties and eight recombinant inbred lines (RILs) were analyzed. The selected RILs represent four combinations of tolerance: SMT/FrT, SMT/FrS, SMS/FrT, and SMS/FrS. It is hypothesized that carbohydrate accumulation and transcript expression will differ between sets of RILs. Liquid chromatography with a refractive index detector was used to quantify carbohydrate content at eight time points over the cold treatment period. Polysaccharide and sucrose content differed between SMT and SMS RILs at various time points, although there were no significant differences in glucose or fructose content. Glucose and fructose content differed between FrT and FrS RILs in this study, but no significant differences in polysaccharide or sucrose content. RNAseq was used to investigate differential transcript expression, followed by modular enrichment analysis, to reveal potential candidates for other mechanisms of tolerance, which included expected pathways such as oxidative stress, chitinase activity, and unexpected transcriptional pathways. These differences in carbohydrate accumulation and differential transcript expression begin to give insight into the differences of wheat lines when exposed to cold temperatures.