Natural Infection Conditions Research Articles

Genome‐Wide Association Mapping and Genomic Prediction of Septoria nodorum Blotch Resistance in Central European Winter Wheat (Triticum aestivum L.)

ABSTRACTSeptoria nodorum blotch (SNB) is a fungal disease of wheat caused by the necrotrophic fungus Parastagonospora nodorum (Berk.), considered as one of the most devastating fungal diseases affecting winter wheat (Triticum aestivum L.). The complex inheritance of resistance to SNB poses significant challenges to breeding programmes. Improving selection precision and identifying novel resistance QTLs are crucial for enhancing SNB resistance. This study investigated strategies for crop genetic improvement, including genome‐wide association mapping (GWAS) and genomic prediction (GP), within a practical breeding programme. A population of 1500 winter wheat breeding lines was phenotyped for SNB resistance over 5 years across 19 geographical locations under natural infection conditions. Despite highly unbalanced breeder's data, medium to high heritabilities for SNB resistance were achieved. GWAS identified 11 significant marker‐trait associations for SNB resistance across Chromosomes 2A, 2B, 4B, 4D, 5D and 7B. GP fivefold cross‐validation analysis revealed a predictive ability of 0.52 for SNB resistance. The resistant wheat genotypes and SNP markers identified in this study will be valuable assets for future breeding efforts to enhance SNB resistance in wheat.

MaAzaR Influences Virulence of Metarhizium acridum against Locusta migratoria manilensis by Affecting Cuticle Penetration.

The entomopathogenic fungus (EPF) Metarhizium acridum is a typical filamentous fungus and has been used to control migratory locusts (Locusta migratoria manilensis). This study examines the impact of the Zn(II)2Cys6 transcription factor, MaAzaR, in the virulence of M. acridum. Disruption of MaAzaR (ΔMaAzaR) diminished the fungus's ability to penetrate the insect cuticle, thereby decreasing its virulence. The median lethal time (LT50) for the ΔMaAzaR strain increased by approximately 1.5 d compared to the wild-type (WT) strain when topically inoculated, simulating natural infection conditions. ΔMaAzaR compromises the formation, turgor pressure, and secretion of extracellular hydrolytic enzymes in appressoria. However, the growth ability of ΔMaAzaR within the hemolymph is not impaired; in fact, it grows better than the WT strain. Moreover, RNA-sequencing (RNA-Seq) analysis of ΔMaAzaR and WT strains grown for 20 h on locust hindwings revealed 87 upregulated and 37 downregulated differentially expressed genes (DEGs) in the mutant strain. Pathogen-host interaction database (PHI) analysis showed that about 40% of the total DEGs were associated with virulence, suggesting that MaAzaR is a crucial transcription factor that directly regulates the expression of downstream genes. This study identifies a new transcription factor involved in EPF cuticle penetration, providing theoretical support and genetic resources for the developing highly virulent strains.

The effect of artificial vs natural infection with Alternaria alternata on tomatoes, in the climate change context

Tomatoes (Solanum lycopersicum L.) are some of the most popular vegetables in the world. The productivity of crops is determined by a detailed knowledge of the natural environment, the correct application of the knowledge related to the specific technology, and the interaction between species and the environment. The environment itself influences the crops and they may be beneficial to the normal development of the plant or may induce different sensitivities to the cultivated plants. The main objective of this article was to identify the most resistant tomato varieties to Alternaria alternata attack, in natural and artificial infection conditions. The biological material used was five varieties of tomatoes with large-fruit: ‘San Marzano’, ‘Marmande’, ‘Romus’ and with cherry-type fruit: ‘Perun’ and ‘Bajaja’. The varieties were chosen due to large scale cultivation, resistance to various stress factors (disease and pest), and different organoleptic qualities. In the present events of climate change, it is necessary to continue testing the genetic material on the resistance and tolerance to the action of pathogens. The aim of the research was to test a group of tomato varieties to A. alternata attack. The pathogens can cause plant populations to evolve into an extremely varied set of immune receptors with differing ways of responding. In the Transylvanian Plain area, Romania, 2021 was a favourable year for this pathogen due to suitable infection conditions. Among the varieties of tomatoes, the cherry-type fruit ‘Perun’ (14.73%), was one of the most resistant to A. alternata. At the same time at the opposite end, the ‘Bajaja’ variety (25.33%) was the most affected cherry-type tomato in case of natural infection in 2022. The differences between the varieties reinforce the fact that climatic conditions significantly impact the dispersion of the pathogen on the field cultivated in both types of infection.

Diallel Analysis of Wheat Resistance to Fusarium Head Blight and Mycotoxin Accumulation under Conditions of Artificial Inoculation and Natural Infection.

Breeding resistant wheat cultivars to Fusarium head blight (FHB), caused by Fusarium spp., is the best method for controlling the disease. The aim of this study was to estimate general combining ability (GCA) and specific combining ability (SCA) for FHB resistance in a set of eight genetically diverse winter wheat cultivars to identify potential donors of FHB resistance for crossing. FHB resistance of parents and F1 crosses produced by the half diallel scheme was evaluated under the conditions of artificial inoculation with F. graminearum and natural infection. Four FHB related traits were assessed: visual rating index (VRI), Fusarium damaged kernels (FDK), and deoxynivalenol and zearalenone content in the harvested grain samples. Significant GCA effects for FHB resistance were observed for the parental cultivars with high FHB resistance for all studied FHB resistance related traits. The significant SCA and mid-parent heterosis effects for FHB resistance were rare under both artificial inoculation and natural infection conditions and involved crosses between parents with low FHB resistance. A significant negative correlation between grain yield under natural conditions and VRI (r = -0.43) and FDK (r = -0.47) under conditions of artificial inoculation was observed in the set of the studied F1 crosses. Some crosses showed high yield and high FHB resistance, indicating that breeding of FHB resistant genotypes could be performed without yield penalty. These crosses involved resistant cultivars with significant GCA effects for FHB resistance indicating that that they could be used as good donors of FHB resistance.

Evaluation of Some Bread Wheat (Triticum aestivum L.) Varieties Reaction to Septoria Tritici Blotch Disease

Septoria tritici blotch (STB), caused by the Zymoseptoria tritici is an important wheat (Triticum aestivum L.) disease in the Türkiye and in many countries in the world. In this study, a total of 92 bread wheat varieties were evaluated for STB in the adult plant stage under natural infection conditions. The field trial was performed at the experimental station at the campus of Akdeniz University, Antalya, Türkiye for two consecutive years with the two replications. Disease evaluations were performed using the double-digit scale (00-99). Based on the disease evaluations, the disease severity ranged from 15 to 80, and 21 to 82 in the growing seasons 2022 and 2023, respectively. In infection types, four disease reactions were determined namely resistant, moderately resistant, moderately susceptible, and susceptible. Overall, while 32.61% and 36.96% of the varieties were resistant and moderately resistant to STB, 17.39% and 13.04% of them showed moderately susceptible and susceptible reactions, respectively. In conclusion, these varieties can be used in resistance breeding programs to STB disease. In further studies, the resistant/susceptible reactions of bread wheat varieties to STB should be identified to carry which resistance gene/genes or not.

Reaction of Selected Citrus Cultivars to Pseudocercospora Leaf and Fruit Spot Disease Under Natural Infection in Northern Uganda

Citrus is an important crop among many resource constrained subsistence farmers living in rural areas of Uganda. Citrus production is affected mainly by drought, declining soil fertility, pests and diseases. Among diseases, citrus leaf and fruit spot disease caused by fungus Pseudocercospora angolensis is currently one of the major constraints to the production of citrus in Uganda where millions of people rely on the crop for nutritional security and household income. The disease can lead to 50-100% fruit yield loss depending on environmental conditions, disease management and weather conditions. In order to identify resistance to P. angolensis, a study was conducted to identify variability for citrus leaf and fruit spot resistance from adapted commercial cultivars as an initial step in developing integrated disease management strategy. Six cultivars were assessed. The screening was under natural infection conditions in disease hot spots in northern Uganda in 2014a and 2014b seasons. The results showed significance difference (p < 0.01) for Area Under Disease Progressive Curve (AUDPC) for number of leaves with P. angolesnis symptoms and number of lesions. Subsequently, the study identified Kuno as resistant and Tangelo as less susceptible to Pseudocercospora leaf and fruit spot infection, and they could be recommended for citrus leaf and fruit spot disease control.

Unveiling the predominance of Saccharum spontaneum alleles for resistance to orange rust in sugarcane using genome-wide association.

Six QTLs of resistance to sugarcane orange rust were identified in modern interspecific hybrids by GWAS. For five of them, the resistance alleles originated from S. spontaneum. Altogether, they efficiently predict disease resistance. Sugarcane orange rust (SOR) is a threatening emerging disease in many sugarcane industries worldwide. Improving the genetic resistance of commercial cultivars remains the most promising solution to control this disease. In this study, an association panel of 568 modern interspecific sugarcane hybrids (Saccharum officinarum x S. spontaneum) from Réunion's breeding program was evaluated for its resistance to SOR under natural conditions of infection. Two genome-wide association studies (GWAS) were conducted between disease reactions and 183,842 single nucleotide polymorphism (SNP) markers obtained by targeted genotyping-by-sequencing. Five resistance quantitative trait loci (QTLs), named Oru1, Oru2, Oru3, Oru4 and Oru5, were identified using a single-locus GWAS (SL-GWAS). These five QTLs all originated from the species S. spontaneum. A multi-locus GWAS (ML-GWAS) uncovered an additional but less significant resistance QTL named Oru6, which originated from S. officinarum. All six QTLs had a moderate to major phenotypic effect on disease resistance. Prediction accuracy estimated with linear regression models based on each of the five QTLs identified by SL-GWAS was between 0.16-0.41. Altogether, these five QTLs provided a relatively high prediction accuracy of 0.60. In comparison, accuracies obtained with six genome-wide prediction models (i.e., GBLUP, Bayes-A, Bayes-B, Bayes-C, Bayesian Lasso and RKHS) reached only 0.65. The good prediction accuracy of disease resistance provided by the QTLs and the predominant S. spontaneum origin of their resistance alleles pave the way for effective marker-assisted breeding strategies.

Phenotypic and genotypic evaluation of Turkish bread wheat (Triticum aestivum L.) varieties to stripe rust (Puccinia striiformis f.sp. tritici)

AbstractWheat stripe rust, which is caused by the basidiomycetes fungal pathogen Puccinia striiformis f.sp. tritici (Pst), is one of the most destructive diseases of wheat in Türkiye and worldwide. In this study, a total of 99 bread wheat varieties were assessed at the adult plant stage under natural infection conditions during the 2021–2022 and 2022–2023 growing seasons. Additionally, specific molecular markers were used to genotype the stripe rust resistance genes Yr26, Yr32, Yr36, Yr44 and YrSP. Disease severity was determined using the modified Cobb scale and infection reactions of each bread wheat varieties were evaluated, and also coefficient of infection value was calculated based on those parameters. To determine whether the wheat varieties had resistance gene(s), specific molecular markers associated with the resistance genes Yr26, Yr32, Yr36, Yr44 and YrSP were used. In the field trials, the majority of the tested varieties showed moderately susceptible and susceptible reactions in both years. According to the molecular results, they were positive for Yr32 in three varieties, Yr36 in 25 varieties, YrSP in two varieties and none of them had Yr26. Furthermore, some varieties carried combinations of these genes, such as Yr32 + Yr36, Yr32 + Yr44, Yr36 + Yr44, Yr36 + YrSP, Yr32 + Yr36 + Yr44 and Yr32 + Yr36 + Yr44 + YrSP. On the other hand, it was not determined these resistance genes in 16 varieties. In the literature, these resistance genes were first identified in Turkish bread wheat varieties. In addition, these findings are valuable for the development of wheat cultivars with effective and more durable resistance to stripe rust in Türkiye.

Artificial infection pathway of largemouth bass LMBV and identification of resistant and susceptible individuals

Identifying disease-resistant and disease-susceptible materials in largemouth bass can provide fundamental analytical information for disease-resistant breeding research on this species. To date, no stable and effective artificial infection pathway has been established against largemouth bass virus (LMBV) in largemouth bass. In this study, using the pathogen at a concentration of 1.60 × 105 TCID50/mL, largemouth bass juveniles were infected using three different methods: muscle injection, feeding, and immersion. A comprehensive comparative study was conducted on parameters such as disease progression, viral load, pathological changes, and electron microscopy. The results revealed that the injection group experienced rapid mortality, with all individuals dying within 6 days after the infection. The feeding group showed minimal mortality, with an overall mortality rate of 28.57%. The immersion group reached its peak mortality on the 9th day after infection, with an accumulated mortality rate of 63.24%. Viral gene quantification results showed that while in the injection group muscles had the highest viral load followed by the liver and spleen, the other infection methods led to the highest viral loads in the liver and spleen. Tissue pathology and electron microscopy observations revealed that the liver and spleen exhibited the most significant pathological changes and were the easiest organs to detect viral particles, indicating that the liver and spleen are the primary target organs of LMBV in largemouth bass. In conclusion, this study suggests that immersing largemouth bass in LMBV at a concentration of 1.99 × 103 c/mL (diluted 80 times) closely mimics the natural infection rate, allowing for a clear differentiation between causes of death and survival, making it an almost non-invasive artificial infection method that closely resembles natural infection conditions. These findings can provide crucial support for the accurate identification of disease-resistant and disease-susceptible materials in largemouth bass and the breeding of disease-resistant varieties.

Artificial infection with Fusarium solani f.sp. passiflorae in plants of passion fruit under controlled conditions

Controlled infection systems constitute a valuable tool in the study of pathosystems, as they enable the observation and measurement of specific characteristics with greater precision and ease compared to natural conditions. Additionally, they are useful for exploring and identifying sources of resistance in host populations. However, the plant's response to infection can vary depending on the inoculation method; invasive methods can damage plant parts, thus facilitating pathogen entry even in the presence of certain resistance mechanisms. The purpose of this study was to evaluate the reproducibility of an artificial infection protocol and an assessment scale for primary symptoms at the stem base/root collar, as well as secondary symptoms in leaves and roots of two Passiflora species. We evaluated the effects of inoculating planting substrates of sweet granadilla and purple passion fruit plants with three concentrations of F. solani f. sp. passiflorae (0.5 × 106, 1 × 106, and 2 × 106 conidia gram-1 of substrate), using non-inoculated plants as controls under controlled conditions. These treatments were tested in two separate experiments performed in 2017 and 2020. The study included symptom development readings integrated in a disease severity index (SI) for collar rot. Both experiments showed severity indices greater that 56%, indicating a high level of efficacy of the inoculation system for replicating disease symptoms in greenhouse settings. Our inoculation method reflects the conditions of natural infection of F. solani in sweet granadilla and purple passion fruit plants; it could be suitable for epidemiological and disease control studies, as well as for routine germplasm screening to identify sources of resistance.

Virulence of Dothistroma septosporum and D. pini on Pinus nigra and P. mugo under conditions of natural infection

AbstractDothistroma needle blight (DNB) is a severe needle disease of pines worldwide, caused by two closely related species, Dothistroma septosporum and D. pini. The two fungal species are similar not only in their morphological characteristics, but also cause very similar symptoms in their hosts, and have a similar ecology. The aim of this study was to compare the virulence of the two Dothistroma species in natural infection experiments on 2-year-old seedlings of two DNB susceptible pine species, Pinus nigra and P. mugo, in two seedling stands for each pathogen species. The virulence of the pathogens and presence of symptoms (symptomatic needles, red bands and acervuli) were assessed after 2 years of exposure to inoculum. The incidence of seedlings with DNB symptoms was 65% and 76% for P. nigra and P. mugo, respectively. No difference was found between D. septosporum and D. pini in any of the three DNB symptoms evaluated on seedlings of P. mugo. However, symptoms of disease differed between the two Dothistroma species on P. nigra. Variables that reflect the intensity of disease development, the number of red bands and acervuli per needle, showed a difference in virulence between D. septosporum and D. pini, but only in the case of the host species P. nigra. The results suggest that the virulence of the two Dothistroma species could be affected by host pine species and that there are differences in the susceptibility of individual pine species to D. septosporum and D. pini. Further factors could affect the virulence of these pathogens, including isolate origin, climatic or environmental factors.

Evaluation of different populations of some tulip species for resistance to Botrytis blight disease (Botrytis tulipae) under natural infection conditions

Botrytis tulipae’nin neden olduğu Botrytis yanıklığı hastalığı lalenin en önemli hastalıklarından bir tanesidir. Hastalığa karşı mücadelede dayanıklı çeşit kullanmak en etkili yollardan bir tanesidir. Bu çalışmada Türkiye’nin farklı illerinden toplanmış olan 12 türe ait 68 lale popülasyonunun Samsun ilinde doğal enfeksiyon koşullarında Botrytis yanıklığına karşı dayanıklılık durumları araştırılmıştır. Çalışma, 2015-2016 yetiştirme sezonunda dört tekerrürlü olacak şekilde gerçekleştirilmiştir. Hastalık belirtileri 0-4 skalası kullanılarak değerlendirilmiştir. Çalışma sonucunda popülasyonlar arasında hastalığa dayanıklılık açısından önemli varyasyonlar belirlenmiştir. Tulipa orphanidea türüne ait dört, T. sylvestris türüne ait iki, T. agenensis türüne ait ise bir popülasyon hastalığa karşı yüksek derecede dayanıklı olarak belirlenirken, T. foliosa türüne ait üç, T. orphanidea türüne ait sekiz ve T. julia türüne ait bir popülasyon ise dayanıklı olarak belirlenmiştir. Çalışmada 25 lale popülasyonunun ise hastalığa karşı hassas olduğu ortaya konulmuştur. Dayanıklı olarak belirlenen popülasyonlar lale ıslah çalışmalarında Botrytis yanıklığına dayanıklılık açısından ebeveyn olarak kullanılma potansiyeline sahiptir. Bu çalışma Türkiye’de lale türlerinin B. tulipae’ye karşı dayanıklılık durumlarının incelendiği ilk çalışmadır.

Performance efficiency of some biocontrol agents on controlling Cercospora leaf spot disease of sugar beet plants under organic agriculture system

This investigation was carried out on commercial organic field in the Fayoum Governorate of Egypt under conditions of natural infection, 2020/2021 and 2021/2022 to evaluate the effectiveness of four commercial biocides—Blight Stop (Trichoderma harzianum), Bio Zeid (T. album), Root Guard (Bacillus subtilis), and Bio ARC (B. megaterium)—as well as, four biocontrol agents (T. harzianum, T. album, B. subtilis, and B. megaterium) in controling Cercospora beticola Sacc, the main causal of Cercospra leaf spot (CLS) disease on sugar beet in an organic farming systems. All biocontrol agents and commercial biocides sprayed at the recommended dose in a two spray regime with 15 days between sprays, were significantly reduced Cercospora beticola, total amino acid and juice impurities (K, Na and α-a N %) in comparison to control treatment. All bioagents and biocides put to the test resulted in a significant rise in phenolic compound values, total chlorophyll, sucrose (%), purity (%), root, top and sugar yield quality of sugar beet during both seasons. Spraying Blight Stop was the most effective treatment followed by T. harzianum. B. megaterium was the least effective biocide treatment compared with the control treatment during the two growing seasons.

Survey of Xylella fastidiosa Infection in Prunus Germplasm in Gainesville, FL, USA

The pathogen Xylella fastidiosa is a xylem-restricted, gram-negative bacterium that is known to cause diseases of many cultivated plant species. Recent outbreaks of X. fastidiosa diseases in Europe have brought attention to the impact of this pathogen, especially to perennial crops. Among the Prunus genus, X. fastidiosa is known to have a wide range of hosts, including plum, almond, peach, cherry, and apricot. Infected trees have reduced fruit quality, possibly resulting in unmarketable fruits, as well as reduced lifespan. There are no curative management options for X. fastidiosa diseases in Prunus; therefore, development of resistant or tolerant cultivars through breeding represents an efficient option to reduce the impact of this pathogen. In this context, the main objective of this study was to determine the occurrence of X. fastidiosa in germplasm of the Stone Fruit Breeding Program at the University of Florida located in Gainesville, FL, USA, under natural infection conditions. A total of 43 individuals representing 10 different genotypic groups within the Prunus genus were tested for the presence of X. fastidiosa. Additionally, we report a novel and easy sampling method using sawdust collected from tree trunks for the detection of this pathogen in Prunus and the development of an endogenous control for improving the diagnosis of this pathogen using real-time polymerase chain reactions. Our results showed a high incidence of X. fastidiosa in the germplasm tested, with more than 65% of the samples positive for the presence of the bacterial pathogen. However, X. fastidiosa was not detected in most of the P. mume samples tested, whereas almost all the P. mume × P. armeniaca hybrids were positive. Negative individuals were also identified in P. avium, P. campanulata, P. umbellata, and P. salicina × P. ceracifera. These trees have been planted in the field, exposed to natural infection for 4 to 11 years, and are considered to show field resistance. Finally, primers and probes based on the Prunus COX gene developed in this study can be used as an internal amplification control to enhance the interpretation of results of X. fastidiosa detection assays using sawdust samples.

Comparative Analysis of Phenotypic and Molecular Data on Response to Main Pear Diseases and Pest Attack in a Germplasm Collection

The pear is an important fruit tree in temperate areas, but due to its sensitivity, fruit yield and quality are often affected by disease and pest attacks. Pear genotypes from a germplasm collection comprising 13 Pyrus species, 17 Romanian varieties, and 50 non-Romanian varieties from a worldwide assortment were investigated in this study. Throughout four years, response to attack of the principal pathogens and pests was investigated phenotypically under natural conditions of infection and infestation. SSR markers were used to analyze the genetic diversity of the genotypes. A standardized method for the evaluation of responses to biotic stressors was proposed, which highlighted significant differences between genotypes. The species and varieties with the lowest degrees of attack (DA%), calculated based on the frequency and intensity of attack, were identified for pear scab (Venturia pyrina), septoria (Septoria pyricola), fire blight (Erwinia amylovora), and psyllids (Psylla sp.). These accessions could provide valuable sources of genes of interest to develop resistant varieties in new pear breeding programs. By combining phenotypic and molecular analyses, significant information was obtained that can be exploited to generate high variability for selection through artificial hybridization by harnessing accessions with complementary molecular fingerprints and high genetic distances.

Time effect of experimental infection on Rainbow trout (Oncorhynchus mykiss) by immersion with Aeromonas salmonicida subsp. salmonicida

Furunculosis caused by Aeromonas salmonicida subsp salmonicida (Ass) is a medically and economically important bacterial disease in salmonid farms that requires therapeutic measures to prevent and control the disease. Evaluation of the effectiveness of traditional measures such as antibiotics or vaccines usually requires infecting fish experimentally. The objective of this study is to develop a method of infectious challenge of large (250-g) Rainbow trout by immersion close to natural infection conditions. We compare mortality, morbidity and anti-Ass antibody production of Rainbow trout following different bathing times (2, 4, 8 and 24 h) at a final bacterial concentration of 106 CFU/mL. One hundred sixty fish divided in five groups corresponding to the 4 bathing times and the non-challenged group were studied. The 24 h contact duration resulted in the infection of all fish, with a mortality rate of 53.25%. The challenged fish developed acute infection with symptoms and lesions (inappetance, altering of swimming behaviour, presence of boils) similar to those observed in furunculosis, and produced antibodies against the bacterium at 4 weeks after challenging, in contrast with the non-challenged group.

Spatiotemporal dynamics of bacterial wilt in Eucalyptus

AbstractBacterial wilt (caused by Ralstonia spp.) is one of the most damaging diseases of Eucalyptus species, and is responsible for substantial losses to producers. For efficient, scientifically‐based management of this disease, it is necessary to understand the various factors involved in its development, including greater knowledge of the epidemiology of the pathogen on Eucalyptus spp. This study aimed to determine the spatialtemporal dynamics of bacterial wilt in Eucalyptus under natural infection conditions. An experiment was conducted in a commercial plantation in the municipality of Itinga, state of Maranhão, Brazil, using the clone FGCA0385 (Eucalyptus urophylla var. platyphylla). The study comprised of four plots composed of 450 plants each, subdivided into nine rows with 50 plants per row with a spacing of 3 × 3 m. Disease incidence was quantified over 1 year. The spatial dynamics of the disease was determined using the dispersion index, a modified Taylor law, and the analysis of the dynamics and structure of foci. For temporal dynamics, the curve of the disease incidence progress was plotted, and the data were analysed by simple linear regression analysis fitted to three empirical models: logistic, monomolecular, and Gompertz. The distribution pattern of Eucalyptus bacterial wilt was random, as confirmed by the Index of dispersion. Analysis of the dynamics and structure of the foci, showed that 69 disease foci occurred, 44 of which were unitary, with an average number of plants per focus of 1.63. Foci had greater length in the direction of the planting line. The epidemics were best described by the monomolecular model, with an estimated incidence of Eucalyptus bacterial wilt of 27.77% in the fourth year of the study. According to the spatiotemporal dynamics of this work, management strategies such as eliminating symptomatic plants and crop renovation can be used based on economic viability.

An overview of the studies on resistance to downy mildew (Plasmopara viticola) on grapevines in Türkiye

Downy mildew caused by oomycete Plasmopara viticola, is one of the most damaging grapevine diseases. This disease can be found in all parts of the grapevines (Vitis vinifera L.) and causes quality and yield losses. Intensive spraying has been done in the vineyards against this disease for many years and the effectiveness of the fungucides used against this disease is gradually decreasing. For this reason, studies on the determination of disease-resistant Vitis species have increased in Türkiye as in the whole world. In this context, 1006 genotypes (59 Vitis vinifera, 47 V. labrusca, 1 V. rotundifolia, 899 interspecific crosses) were evaluated for their resistance to downy mildew disease. 20 genotypes (V. vinifera) among them were tested only under natural infection conditions, while 67 (21 V. vinifera, 34 V. labrusca, and 12 interspecific crosses) were tested both under natural infection and by artificial inoculation. The resistance of 919 genotypes (18 V. vinifera, 13 V. labrusca, 1 V. rotundifolia, 887 interspecific crosses) was determined by artificial inoculation only. In this review, the resistance tests of genotypes performed by different researchers in Türkiye are summarized by considering the inoculation conditions of Vitis spp and the pathogen. The changes in phenolic compounds of different genotypes before and after the disease were also included in the study. At the same time, this study will make important contributions to researchers who will conduct research on resistance to downy mildew in grapevines.

Specific preadaptations of Rhodococcus equi cooperate with its Virulence-associated protein A during macrophage infection.

Gram-positive Rhodococcus equi (Prescotella equi) is a lung pathogen of foals and immunocompromised humans. Intra-macrophage multiplication requires production of the bacterial Virulence-associated protein A (VapA) which is released into the phagosome lumen. VapA pH-neutralizes intracellular compartments allowing R. equi to multiply in an atypical macrophage phagolysosome. Here, we show that VapA does not support intra-macrophage growth of several other bacterial species demonstrating that only few bacteria have the specific preadaptations needed to profit from VapA. We show that the closest relative of R. equi, environmental Rhodococcus defluvii (Prescotella defluvii), does not multiply in macrophages at 37°C even when VapA is present because of its thermosensitivity but it does so once the infection temperature is lowered providing rare experimental evidence for 'thermal restriction'. Using growth experiments with isolated macrophage lysosomes and modified infection schemes we provide evidence that R. equi resists the attack by phagolysosome contents at low pH for several hours. During this time, R. equi produces and secretes VapA which enables it to grow at the expense of lysosome constituents. We present arguments that, under natural infection conditions, R. equi is VapA-less during the initial encounter with the host. This has important implications for vaccine development.

Влияние метеорологических условий на формирование хозяйственно-полезных признаков яровой пшеницы в условиях ЦРНЗ

This article presents the results of the study of the meteorological effect of vegetation on the formation of economic traits of spring wheat in 2021–2022. Fifteen varieties, developed in the different ecological conditions, were selected as study material, among them Zlata was used as a standard. The research work was carried out at the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy (evaluation of field trials during vegetation, analysis of yield and its structure) and at the Department of Remote Hybridization of the N.V. Tsitsin’s Botanical Garden of the Russian Academy of Science (laboratory evaluation of grain quality). The crops studied were grown at the Field Experiment Station of the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy. The soil types were sod-podzolic, sandy loam, loamy, structureless. The plot size is 1 m2, three replications, randomized arrangement. Methods of field evaluation according to the methodology of the State Variety Testing as well as generally accepted laboratory evaluations were used. The meteorological conditions during the summer growing season varied greatly in terms of the sum of active temperatures and humidity conditions. The first half of the growing season in 2021 was favorable for wheat plant development. The period from flowering to the grain maturity was characterized by severe drought. In 2022, growing conditions were generally favorable. Simbirtsit (481 g/m2), Obskaya 2 (484 g/m2), Tobol’skaya (512 g/m2), Margarita (603 g/m2), Favorit (505 g/m2), Granni (484 g/m2) were the most productive varieties. The meteorological conditions of the Central Non-Chernozem region in 2021–2022 had an insignificant effect on the yields of most spring wheat varieties due to compensating mechanisms. Only the varieties Margarita, Uchitel’ and Iren’ were found to respond to the additional moisture. The varieties Saratovskaya 74, Simbirtsit, Tyumenskaya 29, Obskaya 2, and Tobol’skaya are characterized by high resistance to local strains of brown rust under natural infection conditions (7 points). The varieties Favorit and Simbirtsit are immune to powdery mildew (9 points). The varieties Simbirtsit, Obskaya 2, Tobol’skaya, Margarita, Favorit and Trizo are highly resistant to septoriosis (7 points). They can be used as source material for breeding spring wheat varieties. The meteorological effect is tracked for tillering productivity, number and weight of grains per ear, weight of 1000 grains and vitreousness. Drought during the grain formation and filling phase reduced the values of all indicators. Grain unit is the most stable indicator of grain physical properties. The earliest ripening varieties are Zlata and Iren’ (the duration of vegetation is 79–81 and 76–79, respectively). The latest ripening varieties are Tobol’skaya, Favorit and Trizo (8, 10 and 16 days after the standard, respectively). High grain content per ear was observed in the varieties Agata, Margarita, Uchitel’, Favorit, Granni (33–39pcs) in the conditions of the Central Non-Chernozem region. The indicator of grain weight per ear can be used as a morphological marker for selection of high-yielding genotypes of spring wheat in the Central Non-Chernozem region.