Bipolaris Sorokiniana Research Articles

Potential biocontrol mechanisms of Bacillus sp. TSO2 against Bipolaris sorokiniana, spot blotch in wheat

<p class="Default"><em>Bipolaris sorokiniana </em>is a pathogen of cereals such as wheat and barley, causing root rot, leaf blight, seedling blight, and spot blotch. This phytopathogen causes a considerable reduction in cereal yield of up to 85%. Thus, sustainable alternatives to the application of synthetic fungicides are determinants for the control of phytopathogens, such as the application of biological control agents. This study aims to identify the potential biocontrol mechanisms of the bacterial strain TSO2 by sequencing, annotation, and mining its genome. The draft genome of strain TSO2 was sequenced through the Illumina Miseq platform and presented 4,242,212 bp, 43.9% G+C content, 300,069 bp N50, 5 L50, 47 contigs, 96 RNAs, and 4,432 predicted coding DNA sequences. Besides, the presence of 86 CDS of agricultural importance involved in virulence, disease, defense, iron acquisition, and secondary and phosphate metabolisms was detected. On the other hand, seven putative secondary metabolite gene clusters involved in biocontrol activity were identified in the genome of strain TSO2. <em>Bacillus </em>sp. TSO2 contains a great number of biosynthetic gene clusters which supports its biocontrol activity against phytopathogenic fungi. Thus, this strain needs to be further studied as a potential bioactive ingredient for the biopesticide formulation due to its high potential as a biological control agent.</p>

Enzyme activity and population genetic structure analysis in wheat associated with resistance to Bipolaris sorokiniana-common root rot diseases

Common root rot disease (CRR) caused by Bipolaris sorokiniana (Sacc.) (Pleosporaceae), is an important fungal disease of wheat, Triticum aestivum (Poaceae), causing considerable yield losses globally. Incorporating genetic resistance in cultivated crops is considered the most efficient and sustainable solution to counter root rot diseases. Moreover, resistance to CCR is quantitative in nature, and thus the mechanism is poorly understood. To this aim, we analyzed the activities of defense-related enzymes; peroxidase (POX), superoxide dismutase (SOD), polyphenol oxidase (PPO), catalase (CAT), phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU) and chitinase (CHI), as well as total phenol content (TPC) to CRR on the three known resistant wheat ‘Alvand’ and ‘Bam’, ‘Mehregan’ at different time points (wpi) following CRR pathogen, B. sorokiniana inoculation. Of which, were selected out of 33 wheat cultivars previously screened for resistance to CRR. We also analyzed the genetic variability of the entire germplasm, 33 wheat cultivars using seven simple sequence repeat (SSR) primer pairs. The activity of antioxidant enzymes was increased in the related resistant genotypes. Of which, ‘Bam’ had the highest increase in PPO, and GLU activities, followed by ‘Alvand’ in SOD, PAL, and CHI significantly. Whereas, ‘Mehregan’ showed the highest level of TPC, POX, and CAT activities. In addition, five out of seven used SSR primers produced a total of 20 polymorphic bands, of which the number of alleles in each gene locus varied within 3–7 bands. The polymorphism information content (PIC) value also ranged from 0.44 to 0.81, with the mean of 0.65, Shannon Information Index (I) between 0.29 and 0.63 with an average of 0.47 per locus, and Nei's gene diversity (h) value varied from 0.16 to 0.44 with an average of 0.32. The average number of effective alleles was 1.52, ranging between 1.21 and 1.8. The gene locus Xgwm 140 showed the highest diversity in the population genetic structure, which explains the ability of the primers to resolve the assayed germplasm. Thus, resistance to CRR in wheat was mainly related to the enhancement of antioxidant enzymes, although the specific metabolic pathways require further study. This study presents new insights for understanding resistance mechanisms of the selected wheat cultivars to CRR, thus improving wheat yield in the future.

Role of Melanin Production by pecies on HelminthosporiumsPathogenicity in Graminaceous Hosts

Fifty foliar blight diseased samples collected from wheat, barley and oat growing areas of north-western India revealed that Bipolaris sorokiniana Phalaris minor, Drechslera avenae was present in all the isolates collected from barley, wheat and while was associated with isolates from oats. All the test isolates were pathogenic on their susceptible check PL426 (barley), HD-2329 (wheat), OL-9 (oats) and viz., Phalaris minor. Minimum incubation period (2 days), maximum no. of lesions per leaf (9.29), maximum size of lesions (9.30 mm ) and highest 2terminal disease severity score (89) were recorded with isolate Bsb1 from barley, followed by Bsw32 from wheat. The highest melanin production was recorded in isolate Bsb1 (2.58 µg g ) followed by 2.52 µg g and 2.49 µg g in isolate Bsp43 and Bsw32, respectively. -1 -1 -1 Comparison of melanin production and pathogenic behaviour of different isolates revealed that more aggressive isolates on their respective hosts also produced higher melanin as compared to other isolates and strong positive correlation (r=0.749) existed between the pathogenicity and melanin production in different isolates of .

First Report of Brown Leaf Spot of Rice (Oryza sativa) Caused by Bipolaris sorokiniana in Pakistan.

Brown leaf spot of rice is one of the major seed-borne diseases and can diminish grain production up to 52% (Barnwal et al. 2013). In 2018, infected leaf samples showing the typical symptoms of brown spots were collected from the vicinity of the University of Agriculture, Faisalabad (31°26'10.3"N 73°03'35.1"E). The symptoms were brown-dark spots, with gray-light gray or brown centers surrounded by dark margins and with chlorotic halos and of oval or cylindrical shapes (5 to 9 mm in diameter). Disease incidence averaged 61% across the seven fields observed. Leaves were collected from the seven infected fields and symptomatic leaf tissues of 5 mm2 were excised from representative necrotic spots in each. These tissues were surface disinfected with 70% ethanol, rinsed with sterile distilled water (SDW), dried by blotting on paper, and placed on potato dextrose agar medium. For pathogen growth, the plates were placed at 25oC (±2oC) with a 12-hour photoperiod for 5 days. Five samples from each of the infected fields were taken for pathogen isolation and among them ten isolates were sub-cultured and purified by using the single spore method. The resulting fungal colonies were fluffy and ranged in color from grayish black/black to light brown. Fifteen conidia were measured that are olivaceous-brown to dark brown in color, elliptical to oblong with narrow (tapered) ends, with 3-10 septa and 35.6-65.4 µm in length x 13.1-25.7 µm in width. Conidiophores were yellowish-brown, geniculate, and solitary (Pratt 2003). For molecular studies, rDNA of the internal transcribed spacer (ITS) region, translation elongation factor (tef), RNA polymerase II second largest subunit (rpb2) and glyceraldehyde-3-phosphate dehydrogenase (gpd) gene were amplified by using the primers ITS1F/ITS4R (White et al. 1990), EF1-983F/EF1-2218R (Rehner and Buckley 2005), 5F2/7CR (O'Donnell et al. 2007), and GPD1/GPD2 (Berbee et al. 1999) respectively. The sequence of all the amplified gene regions of one SUL-1 isolate was deposited into GenBank with accession numbers MN314844 (ITS), MN326866 (tef), MN990457 (rpb2) and MN990456 (gpd). BLASTn queries of the obtained sequences (ITS, tef, rpb2 and gpd) showed 99-100% homology with the corresponding nucleotide sequences of B. sorokiniana (GenBank accession nos. GU480767, MF490855, LT715652 and MK558818 respectively). To fulfill the Koch's postulates, twenty rice plants (cv. Basmati-385) were sprayed at 2 to 3 leaf stages by using the two representative isolates with a spore suspension of 105 spores/ml. SDW was sprayed on ten control plants. The plants were covered with polyethylene bags to keep the moisture contents and incubated at 25oC (±2oC) for 7 days. After a week, same symptoms as those described above were observed. In the repeated experiment, B. sorokiniana was re-isolated from the infected rice leaves and confirmed morphologically; fulfill the Koch's postulates. With grave worry, the other species of the genus Bipolaris (B. oryzae, and B. victoriae) have also been found to the cause brown leaf spot of rice (Motlagh and Kaviani 2008). To our knowledge, this is the first report of Bipolaris sorokiniana causing brown leaf spot of rice in Pakistan. Because rice is highly consumable grain in Pakistan, so the rapid spread of this disease in the rice farming areas is of a serious concern.

Genomic selection for spot blotch in bread wheat breeding panels, full-sibs and half-sibs and index-based selection for spot blotch, heading and plant height

Key messageGenomic selection is a promising tool to select for spot blotch resistance and index-based selection can simultaneously select for spot blotch resistance, heading and plant height.A major biotic stress challenging bread wheat production in regions characterized by humid and warm weather is spot blotch caused by the fungus Bipolaris sorokiniana. Since genomic selection (GS) is a promising selection tool, we evaluated its potential for spot blotch in seven breeding panels comprising 6736 advanced lines from the International Maize and Wheat Improvement Center. Our results indicated moderately high mean genomic prediction accuracies of 0.53 and 0.40 within and across breeding panels, respectively which were on average 177.6% and 60.4% higher than the mean accuracies from fixed effects models using selected spot blotch loci. Genomic prediction was also evaluated in full-sibs and half-sibs panels and sibs were predicted with the highest mean accuracy (0.63) from a composite training population with random full-sibs and half-sibs. The mean accuracies when full-sibs were predicted from other full-sibs within families and when full-sibs panels were predicted from other half-sibs panels were 0.47 and 0.44, respectively. Comparison of GS with phenotypic selection (PS) of the top 10% of resistant lines suggested that GS could be an ideal tool to discard susceptible lines, as greater than 90% of the susceptible lines discarded by PS were also discarded by GS. We have also reported the evaluation of selection indices to simultaneously select non-late and non-tall genotypes with low spot blotch phenotypic values and genomic-estimated breeding values. Overall, this study demonstrates the potential of integrating GS and index-based selection for improving spot blotch resistance in bread wheat.

Parasitization of Bipolaris sorokiniana Sacc. Shoem. in the organ system of spring wheat varieties in the northern forest-steppe of Priobye region

The work aimed was to identify the effect of varieties on the parasitic activity of Bipolaris sorokiniana Sacc. Shoem. in the system of underground and aboveground organs of spring wheat. The research was carried out in 2020-2021 in the northern forest-steppe of Priobye region. The tasks of the study were to investigate the development of root rot and the etiology of the disease on the underground organs of a number of spring wheat varieties of different geographical origin; determine the role of varieties in the manifestation of dark brown leaf spot and black germ of spring wheat grain; establish the presence or absence of relationships between forms of helminthosporium; identify the effect of varieties on the intensity of reproduction B. Sorokiniana on root leaves and the number of conidia of the phytopathogen in the rhizosphere soil The authors used a collection of 15 varieties of spring wheat. The study did not identify any varieties whose underground organs showed resistance to fusarium-helminthosporium rot. Root rot development averaged over the organs to reach 3.8 units of Economic Threshold of Harmfulness (ETH) in 2020, and in 2021 - 4.4 units of ETH. The effect of the “variety” factor on the incidence of root rot in spring wheat was 31.8% and the “year” factor 30.3%. The authors presented the etiology of root rot of spring wheat cultivars by Bipolaris sorokiniana Sacc. Shoem. and fungi of the genus Fusarium Link. The ratio of phytopathogenes on underground organs was determined by conditions of the year and phytosanitary state of soil; the ratio varied from 1:1 to 11:1 with predominance of fungi of genus Fusarium. The prevalence of brown spot disease reached 1.9 units to 5 units ETH in the lactic maturity phase of the cultivars. The correlation coefficient between the development of root rot and the prevalence of dark brown spot was 0.526±251 and was statistically reliable. Variety differences in the prevalence of grain black spot reached 11.4 times, 3 varieties (Sibirskaya 17, Novosibirskaya 15, Ruslada) were affected at the threshold level; 4 varieties were affected to a moderate degree; 7 varieties were severely affected. Коэффициент корреляции распространенности темно-бурой пятнистости и черноты зародыша составил 0,521±232 и был статистически достоверным на 1%-м уровне значимости. The authors used Ward’s hierarchical clustering method to divide the plants into two groups according to the sporulation dynamics of B. sorokiniana on the root leaves of spring wheat. The first group of spring wheat was with a uniform rate. The second group were varieties of wheat with an exponential jump in sporulation intensity. The varieties Jin Chun 2 (China) and K-65834 (Tajikistan) were the most active sources of B. sorokiniana reproduction in both study years. The size of the soil population of the phytopathogen reflected the intensity

4-Nitropyrazolin-5-ones as Readily Available Fungicides of the Novel Structural Type for Crop Protection: Atom-Efficient Scalable Synthesis and Key Structural Features Responsible for Activity.

The development of new types of fungicides for agriculture and medicine is highly desirable due to the uprising fungal resistance against commonly used compounds. Herein, 4-substituted-4-nitropyrazolin-5-ones (nitropyrazolones) were proposed as highly active fungicides of the novel structural type. The first scalable and practical method for the nitropyrazolone synthesis was proposed, which is atom-efficient, is applicable for the multigram scale synthesis, and allows for production of a wide variety of nitropyrazolones with high yields and purity. The synthesized compounds demonstrated high fungicidal activity against the broad spectrum of phytopathogenic fungi (Venturia inaequalis, Rhizoctonia solani, Fusarium oxysporum, Fusarium moniliforme, Bipolaris sorokiniana, and Sclerotinia sclerotiorum). Their mycelium growth inhibiting activity was comparable or superior to that of kresoxim-methyl. In vitro activity against Staphyloccocus aureus, Candida albicans, and Aspergillus niger revealed that nitropyrazolones are promising candidates against human pathogens. The key factors for the manifestation of high fungicidal activity were established to be an aromatic substituent on the N1 atom and small substituents, such as methyl, at the C3 and C4 positions of the pyrazolone ring.

SNP Discovery Using BSR-Seq Approach for Spot Blotch Resistance in Wheat (Triticum aestivum L.), an Essential Crop for Food Security.

The pathogenic fungus, Bipolaris sorokiniana, that causes spot blotch (SB) disease of wheat, is a major production constraint in the Eastern Gangetic Plains of South Asia and other warm, humid regions of the world. A recombinant inbred line population was developed and phenotyped at three SB-prone locations in India. The single nucleotide polymorphism (SNP) for SB resistance was identified using a bulked segregant RNA-Seq-based approach, referred to as “BSR-Seq.” Transcriptome sequencing of the resistant parent (YS#24), the susceptible parent (YS#58), and their resistant and susceptible bulks yielded a total of 429.67 million raw reads. The bulk frequency ratio (BFR) of SNPs between the resistant and susceptible bulks was estimated, and selection of SNPs linked to resistance was done using sixfold enrichments in the corresponding bulks (BFR >6). With additional filtering criteria, the number of transcripts was further reduced to 506 with 1055 putative polymorphic SNPs distributed on 21 chromosomes of wheat. Based on SNP enrichment on chromosomal loci, five transcripts were found to be associated with SB resistance. Among the five SB resistance-associated transcripts, four were distributed on the 5B chromosome with putative 52 SNPs, whereas one transcript with eight SNPs was present on chromosome 3B. The SNPs linked to the trait were exposed to a tetra-primer ARMS-PCR assay, and an SNP-based allele-specific marker was identified for SB resistance. The in silico study of these five transcripts showed homology with pathogenesis-related genes; the metabolic pathway also exhibits similar results, suggesting their role in the plant defense mechanism.

Influence of a finely dispersed suspension based on a metal/carbon nanocomposite of copper on growth processes and seeds infection of spring wheat

The article presents the results of laboratory studies on the treatment of spring wheat seeds of the Svecha variety with a fine suspension based on a metal/carbon nanocomposite of copper (MeC NC Cu). The aim of the research is to identify the fungicidal action and stimulate the growth processes of plants at the initial stage of organogenesis. The experimental results showed that the effect of copper nanocomposite on plants is ambiguous and in some cases contradictory. This nanomaterial at a concentration of 0.1% had a toxic effect on the seeds of Triticum aestivum. The drug at a concentration of 0.005% (by 15.7%) had a weak stimulating, but insignificant, effect on root development. It was revealed that an increase in the concentration of MeC NC Cu has an inhibitory effect on plants: the immune system weakens and the resistance to pathogens of seed infection decreases. Development of Bipolaris sorokiniana Syn. increases by 2.90-3.31%, Alternaria sp. - by 1.94%. With an increase in the concentration of NC to 1.00%, the indicators deteriorate in comparison with the control to 3.06%. Infection of seeds with a fungus of the genus Fusarium was observed in the following variants: MeC NC Cu 0.05% by 54.5%, MeC NC Cu 1.0% by 6.90% with the least significant difference (95%) 1.36. Other fungi are noted in descending order; the degree of damage varied from 4.65% to 7.83% with an increase in the concentration of MeC NC Cu (the least significant difference (95%) = 0.67).

Silicon, biological seed treatment and cutting reduce the intensity of leaf spot diseases affecting Lolium multiflorum

AbstractItalian ryegrass is a major pasture crop cultivated mainly for feeding cattle in southern Brazil. The choice of crop is based on nutritional quality and the shortage of pastures that occur during the winter in the southernmost part of Brazil. In this region, the production of biomass and seeds are threatened by diseases, in particular fungal diseases that affect the foliage. In this study we identified and monitored the natural occurrence of a complex of leaf spotting diseases and evaluated the effects of combined management practices to reduce the intensity of foliar diseases: seed treatment with Trichoderma atroviride, soil amendment with silicon and cutting frequency (none, one or two cuts). Three diseases were present in a two‐season experiment: grey leaf spot (Pyricularia oryzae), brown leaf spot (Bipolaris sorokiniana) and parrot's eye leaf spot (Cercospora sp.). Grey leaf spot had the highest severity, regardless of treatment, during the first season, and was the only disease present in the following season. Grey leaf spot dominated, and plants receiving only one cut were more prone to P. oryzae infection. The treatments with silicon or T. atroviride reduced the relative disease by 40% to 80%, in relation to untreated and uncut regimes. This study showed the main leaf spot diseases associated with L. multiflorum. Moreover, it demonstrates for the first time in the region the effectiveness of reducing leaf spot via the application of silicon in the soil, inoculation of seeds with T. atroviride and managing the cutting regime.

Efficacy of Fungicides against Bipolaris sorokiniana under in vitro and in vivo Conditions

Spot blotch of wheat caused by Bipolaris sorokiniana could be effectively and economically controlled by two foliar sprays of either Propiconazole or Hexaconazole @ 0.1 per cent at fifteen days interval but on the basis of cost- benefit ratio Hexaconazole had an edge over Propiconazole. The harmful effects of fungicides to human and environment, there have been proved useful and economical in the control of spot blotch. Non systemic and systemic foliar fungicides belonging to the dithiocarbamate and Triazoles are found to be effective. Foliar applications of systemic fungicides between heading and grain filling stages, are cost effective. Propiconazole, Hexaconazole and Difenaconazole + Propiconazole at 250 ppm completely inhibited the mycelial growth of B. sorokiniana. Carbendazim and Copper oxychloride also causes and complete inhibition but at 500 and 1000 ppm, respectively but Mancozeb could not give complete inhibition even at 1000 ppm.

Effect of Date of Sowing and Nitrogen Levels on Spot Blotch Disease of Wheat Caused by Bipolaris sorokiniana

In India, wheat is grown in the Rabi season mostly under irrigated condition. The main constraints responsible for less yield of wheat in comparison to other country seem to non-availability of seeds of improved high yielding varieties to farmers, poor fertility, unirrigated land and other inputs. Experimental findings clearly indicates that yield loss due to spot blotch varied between 7 to 30 per cent and loss in 1000-grain weight between 3 to 23 per cent, depending upon the levels of disease. Delayed sowing favored incidence of spot blotch irrespective of nitrogen level and more disease developed at higher nitrogen level in all the three date of sowing. Higher levels of nitrogen at all the three date of sowing increased yield and 1000-grain weight and with delay in sowing, yield and 1000-grain weight decreased significantly at all the three nitrogen level.

UPLC-Q-TOF-MS/MS Analysis of Seco-Sativene Sesquiterpenoids to Detect New and Bioactive Analogues From Plant Pathogen Bipolaris sorokiniana.

Seco-sativene sesquiterpenoids are an important member of phytotoxins and plant growth regulators isolated from a narrow spectrum of fungi. In this report, eight seco-sativene sesquiterpenoids (1–8) were first analyzed using the UPLC-Q-TOF-MS/MS technique in positive mode, from which their mass fragmentation pathways were suggested. McLafferty rearrangement, 1,3-rearrangement, and neutral losses were considered to be the main fragmentation patterns for the [M+1]+ ions of 1–8. According to the structural features (of different substitutes at C-1, C-2, and C-13) in compounds 1–8, five subtypes (A–E) of seco-sativene were suggested, from which subtypes A, B/D, and E possessed the diagnostic daughter ions at m/z 175, 189, and 203, respectively, whereas subtype C had the characteristic daughter ion at m/z 187 in the UPLC-Q-TOF-MS/MS profiles. Based on the fragmentation patterns of 1–8, several known compounds (1–8) and two new analogues (9 and 10) were detected in the extract of plant pathogen fungus Bipolaris sorokiniana based on UPLC-Q-TOF-MS/MS analysis, of which 1, 2, 9, and 10 were then isolated and elucidated by NMR spectra. The UPLC-Q-TOF-MS/MS spectra of these two new compounds (9 and 10) were consistent with the fragmentation mechanisms of 1–8. Compound 1 displayed moderate antioxidant activities with IC50 of 0.90 and 1.97 mM for DPPH and ABTS+ scavenging capacity, respectively. The results demonstrated that seco-sativene sesquiterpenoids with the same subtypes possessed the same diagnostic daughter ions in the UPLC-Q-TOF-MS/MS profiles, which could contribute to structural characterization of seco-sativene sesquiterpenoids. Our results also further supported that UPLC-Q-TOF-MS/MS is a powerful and sensitive tool for dereplication and detection of new analogues from crude extracts of different biological origins.

Root disease and fungal populations in organic crops under different tillage–cropping systems

AbstractThere has been a steady expansion in organic production in the Canadian Prairies because of higher consumer demand. Thus, increasing the sustainability of organic systems would be important. An organic trial was conducted in the semi‐arid Prairies (2010–2015) with two tillage intensities (low vs. high) in a simplified [spring wheat (Triticum aestivum L.)–forage pea (Pisum sativum L.) green manure (GM)] and a diversified (spring wheat–oilseed–pulse–GM) rotation. In 2013–2015, the impact of these systems on root rot was examined on spring wheat, pulses, and GM crops. Several Fusarium spp. were more abundant in GM and pulses than spring wheat, suggesting that they could be a source of inoculum, especially of F. avenaceum (Fr.:Fr.) Sacc. (teleomorph Gibberella avenacea Cook), for Fusarium diseases in cereals including Fusarium head blight. Under different environments, tillage–rotation systems had an impact on root disease and fungal populations, some of which have biocontrol capabilities. There was no difference among systems for root rot in forage pea, while the low tillage‐diversified rotation had the lowest root rot in spring wheat but was associated with more Fusarium spp. For all crops, most Fusaria were not associated with root rot severity. Cochliobolus sativus (Ito & Kurib.) Drechs. ex Dast. [anamorph Bipolaris sorokiniana (Sacc.) Shoemaker] accounted the most for root rot in spring wheat and was favored by intensive tillage and simplified rotations. The Shannon diversity index (H') of fungal species in spring wheat was higher in the diversified rotation under both tillage intensities than when spring wheat alternated with GM in the simplified rotation, especially under high tillage. In forage pea, H' was higher than in spring wheat, but did not differ among tillage–rotation systems.

Genome-Wide Association Mapping Indicates Quantitative Genetic Control of Spot Blotch Resistance in Bread Wheat and the Favorable Effects of Some Spot Blotch Loci on Grain Yield.

Spot blotch caused by the fungus Bipolaris sorokiniana poses a serious threat to bread wheat production in warm and humid wheat-growing regions of the world. Hence, the major objective of this study was to identify consistent genotyping-by-sequencing (GBS) markers associated with spot blotch resistance using genome-wide association mapping on a large set of 6,736 advanced bread wheat breeding lines from the International Maize and Wheat Improvement Center. These lines were phenotyped as seven panels at Agua Fria, Mexico between the 2013–2014 and 2019–2020 crop cycles. We identified 214 significant spot blotch associated GBS markers in all the panels, among which only 96 were significant in more than one panel, indicating a strong environmental effect on the trait and highlights the need for multiple phenotypic evaluations to identify lines with stable spot blotch resistance. The 96 consistent GBS markers were on chromosomes 1A, 1B, 1D, 2A, 3B, 4A, 5B, 5D, 6B, 7A, 7B, and 7D, including markers possibly linked to the Lr46, Sb1, Sb2 and Sb3 genes. We also report the association of the 2NS translocation from Aegilops ventricosa with spot blotch resistance in some environments. Moreover, the spot blotch favorable alleles at the 2NS translocation and two markers on chromosome 3BS (3B_2280114 and 3B_5601689) were associated with increased grain yield evaluated at several environments in Mexico and India, implying that selection for favorable alleles at these loci could enable simultaneous improvement for high grain yield and spot blotch resistance. Furthermore, a significant relationship between the percentage of favorable alleles in the lines and their spot blotch response was observed, which taken together with the multiple minor effect loci identified to be associated with spot blotch in this study, indicate quantitative genetic control of resistance. Overall, the results presented here have extended our knowledge on the genetic basis of spot blotch resistance in bread wheat and further efforts to improve genetic resistance to the disease are needed for reducing current and future losses under climate change.

Identification and Pathogenicity of Fungi Associated with Leaf Spot of Muskmelon in Eastern Shandong Province, China.

Leaf spot is a serious disease in the growth and development of muskmelon, which can affect its quality and yield. Over the past years, Malianzhuang Muskmelon Base, the main muskmelon producing area in Shandong Province, China, has been seriously affected by leaf spot. Since 2018, symptomatic leaves were collected from 11 production areas of this base to determine the pathogens of muskmelon foliar diseases. Two-hundred fungal strains were isolated and 10 genera and 17 species were identified based on morphological characteristics and multilocus phylogenetic analysis (ITS, GADPH, RPB2, HIS3, EF-1α, and LSU). The most frequently isolated species from each sampling area was Alternaria tenuissima with 77 strains, followed by A. alternata. Pathogenicity experiments showed that A. alternata, A. tenuissima, Fusarium neocosmosporiellum (formerly Neocosmospora vasinfecta), F. acuminatum, Exserohilum rostratum, Bipolaris sorokiniana, and Stagonosporopsis cucurbitacearum (formerly Didymella bryoniae) could cause symptoms highly similar to those of infected leaves observed under natural conditions in the field. Therefore, these fungal isolates are considered to be the primary pathogens causing muskmelon leaf spot, and A. tenuissima and A. alternata were the most common and virulent pathogens in this study. In addition, this is the first study of F. neocosmosporiellum, F. acuminatum, E. rostratum, and B. sorokiniana as pathogens associated to muskmelon leaf spot in China as well as the world.

The Ability of Bipolaris Sorokiniana Isolated from Spring Barley Leaves to Survive in Plant Residuals of Different Crops

The Ability of <i>Bipolaris Sorokiniana</i> Isolated from Spring Barley Leaves to Survive in Plant Residuals of Different Crops

Pathotype Identification and Virulence Variation in Cochliobolus sativus in China

Spot blotch caused by Cochliobolus sativus has become an important disease in the wheat-growing regions in China that has resulted from changes in the regional climate, agricultural cultivation patterns, and the susceptible wheat varieties that are widely grown. Little information is available about virulence variability and pathogenic specialization of the C. sativus isolates from major wheat-growing regions in China. Here, 12 representative wheat varieties and foundation breeding stocks were selected to characterize the pathotypes of C. sativus isolates from infected wheat plants. Based on the infection phenotypes in the 12 differential genotypes at the seedling stage, 70 Chinese pathotypes were identified from 110 isolates and clustered into three virulence groups. The high virulence isolates were collected from wheat leaves, crowns, and roots, with most (10 of 14) from the Henan province in the Huang-Huai plain. No relationship was evident between virulence variability of C. sativus isolates and their geographic origins or types of diseased wheat tissues. C. sativus showed a significant pathogenic specialization in hosts of wheat and barley. Most of the wheat isolates (50 of 65) were avirulent to all the differential barley genotypes, and a few were virulent only to highly susceptible barley genotypes. These results indicated that C. sativus isolates from the wheat-growing regions in China varied considerably for their virulence in wheat varieties, and showed significant pathogenic specialization to the wheat and barley hosts.

Monitoring of Host Suitability and Defense-Related Genes in Wheat to Bipolaris sorokiniana.

Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat worldwide. This study investigated the aggressiveness of B. sorokiniana isolates from different wheat-growing areas of Bolu province in Turkey on the cultivar Seri-82. Host susceptibility of 55 wheat cultivars was evaluated against the most aggressive isolate. Our results indicated that the cultivars Anafarta and Koç-2015 were the most resistant. A specific and sensitive qPCR assay was developed for detecting the pathogen in plant tissues and evaluating wheat plants with different resistance levels. Three primer sets, BsGAPDHF/BsGAPDHR, BsITSF/BsITSR, and BsSSUF/BsSSUR, were designed based on glyceraldehyde-3-phosphate dehydrogenase, internal transcribed spacers, and 18S rRNA loci of B. sorokiniana with detection limits of 1, 0.1, and 0.1 pg of pathogen DNA, respectively. The qPCR assay was highly sensitive and did not amplify DNA from the other closely related fungal species and host plants. The protocol differentiated wheat plants with varying degrees of resistance. The assay developed a useful tool for the quantification of the pathogen in the early stages of infection and may provide a significant contribution to a more efficient selection of wheat genotypes in breeding studies. In the present study, expression levels of PR proteins, phenylalanine ammonia-lyase, catalase, ascorbate peroxidase, and superoxide dismutase enzymes were upregulated in Anafarta (resistant) and Nenehatun (susceptible) cultivars at different post-infection time points, but more induced in the susceptible cultivar. The results showed considerable variation in the expression levels and timing of defense genes in both cultivars.

Seed Priming Through Fungicides, Biocontrol Agents and Botanicals as Effective Method for Controlling Spot Blotch Pathogen, Bipolaris sorokiniana in Barley

Seed Priming Through Fungicides, Biocontrol Agents and Botanicals as Effective Method for Controlling Spot Blotch Pathogen, Bipolaris sorokiniana in Barley