Sclerospora Graminicola Research Articles

Fungicides and Bioagents Are Used to Manage Downy Mildew on Pearl Millet

Pennisetum glaucum (L.), pearl millet Known by most as bajra, it is a significant warm-season grain that is mostly farmed in India under rainfed circumstances. In India, downy mildew caused by Sclerospora graminicola (Sacc.) Schroet is the most common and deadly disease affecting pearl millet. Two weeks after seeding, the illness was visible as chlorotic stripes on the leaf surface advanced from the base to the top. Most infected plants were unable to develop typical, healthy earheads. The bioagents that were examined as seed dressers were Trichoderma harzianum (6 g/kg seed), Pseudomonas fluorescens (8 g/kg seed), Trichoderma viride (6 g/kg seed), and neem oil and water. The downy mildew disease incidence was significantly reduced (2.83%) by the fungicides Mancozeb at 0.2%, Neem oil, Metalaxyl at 0.25%, and Carbendazim at 0.25%, as compared to the control, which had a documented disease incidence of 40.33%. Neem oil considerably outperformed all evaluated bioagent seed dressings for downy mildew prevention, including the seed dressing containing Pseudomonas fluorescens seed treatment at 8 g/kg seed was statistically comparable to Trichoderma harzianum seed treatment at 6 g/kg seed and Metalaxyl application at 0.25%. The downy mildew was also greatly reduced by foliar application of Mancozeb at 0.2 % and seed treatment with Metalaxyl (6 g/kg seed) + spray of Propiconazole at 25% EC at 0.25%; these two methods outperformed the seed dressing with all evaluated bioagents. The positive outcome of using neem oil topically suggests that, when it comes to managing downy mildew in pearl millet in an environmentally benign manner, it might replace fungicides.

QTL mapping of downy mildew resistance in foxtail millet by SLAF‑seq and BSR-seq analysis.

Key message Three major QTLs for resistance to downy mildew were located within an 0.78 Mb interval on chromosome 8 in foxtail millet. Downy mildew, a disease caused by Sclerospora graminicola, is a serious problem that jeopardizes the yield and quality of foxtail millet. Breeding resistant varieties represents one of the most economical and effective solutions, yet there is a lack of molecular markers related to the resistance. Here, a mapping population comprising of 158 F6:7 recombinant inbred lines (RILs) was constructed from the crossing of G1 and JG21. Based on the specific locus amplified fragment sequencing results, a high-density linkage map of foxtail millet with 1031 bin markers, spanning 1041.66 cM was constructed. Based on the high-density linkage map and the phenotype data in four environments, a total of nine quantitative trait loci (QTL) associated with resistance to downy mildew were identified. Further BSR-seq confirmed the genomic regions containing the potential candidate genes related to downy mildew resistance. Interestingly, a 0.78-Mb interval between C8M257 and C8M268 on chromosome 8 was highlighted because of its presence in three major QTL, qDM8_1, qDM8_2, and qDM8_4, which contains 10 NBS-LRR genes. Haplotype analysis in RILs and natural population suggest that 9 SNP loci on Seita8G.199800, Seita8G.195900, Seita8G.198300, and Seita.8G199300 genes were significantly correlated with disease resistance. Furthermore, we found that those genes were taxon-specific by collinearity analysis of pearl millet and foxtail millet genomes. The identification of these new resistance QTL and the prediction of resistance genes against downy mildew will be useful in breeding for resistant varieties and the study of genetic mechanisms of downy mildew disease resistance in foxtail millet.

Identification of candidate RXLR effectors from downy mildew of foxtail millet pathogen Sclerospora graminicola and functional analysis of SG_RXLR41

AbstractDowny mildew caused by Sclerospora graminicola is a systemic disease that affects the yield and quality of foxtail millet. This obligate biotrophic oomycete manipulates host physiology and immune processes through numerous effectors. A thorough comprehension of effector biology is crucial to unravel disease mechanisms and understand host plant resistance. In this study, bioinformatic analyses revealed 498 potentially secreted proteins in S. graminicola, of which 62 were identified as RXLR effectors; 46 RXLR‐encoding genes exhibited upregulated expression during the early stages of infection. To elucidate the functions of these secreted proteins, a heterogeneous expression system was developed using Nicotiana benthamiana. Twenty‐one RXLR effectors secreted by S. graminicola were transiently expressed in N. benthamiana, of which four could suppress INF1‐triggered cell death. Various defence responses in N. benthamiana were attenuated, including inhibition of defence gene expression, reduction of reactive oxygen species (ROS) accumulation and diminished callose deposition. The expression of SG_RXLR41 also enhanced the growth of Phytophthora capsici on N. benthamiana leaves. These findings indicate that S. graminicola facilitates infection and expansion through the secretion of multiple RXLR effectors, and SG_RXLR41 is an important virulence‐related effector that is involved in manipulating plant immunity by suppressing cell death.

Diseases prevalent in Kharif crops grown in Barmer district of Rajasthan, India

In the Kharif season, pearl millet (Pennisetum glaucum) is the predominant crop of the Barmer district followed by cluster bean (Cyamopsis tetragonoloba) and moth bean (Vigna aconitifolia). Sesame (Sesamum indicum) and green gram (Vigna radiata) are other important Kharif oilseed and pulse crops, respectively. A survey was conducted to determine the status of major diseases of Kharif crops grown in the Barmer district of the Marwar region of Rajasthan, India. Five blocks and three villages in each block were surveyed through a random field survey method during the collection of diseased samples every Sunday for the practical classes of agricultural students of the College of Agriculture, Baytu; in August and September 2023. Per cent disease incidence was recorded on randomly selected plants in a particular field of selected location. The incidence of diseases was observed based on typical field symptoms and later the association was confirmed through microscopic examinations in the laboratory. In survey, yellow mosaic (virus), leaf crinkle/ curl (virus), bacterial leaf spot/ blight (Xanthomonas phaseoli) of green gram;green ear/ downy mildew (Sclerospora graminicola), rust (Puccinia substriata) and blast (Pyricularia grisea) of pearl millet; Phytophthora stem blight (Phytophthora parasitica var. sesame) and phyllody (Phytoplasma) of sesame; yellow mosaic (virus)and bacterial leaf spot/ blight (Xanthomonas axonopodis pv. cyamopsidis) of cluster beanwere recorded with >50% incidence. However; charcoal rot (Macrophomina phaseolina), web blight (Rhizoctonia solani), Cercospora leaf spot (Cercospora canescens) and anthracnose (Colletotrichum lindemuthianum) of green gram; Alternaria blight/ leaf spot (Alternaria sesame) of sesame,sorghum rust (Puccinia purpurea) and Alternaria blight/ leaf spot (Alternaria cyamopsidis) of cluster beanwere noticed with 10 to 50% incidence.

Underlying Mechanisms of the Hedgehog-Like Panicle and Filamentous Leaf Tissue Symptoms Caused by Sclerospora graminicola in Foxtail Millet.

Downy mildew caused by Sclerospora graminicola is a systemic infectious disease affecting foxtail millet production in Africa and Asia. S. graminicola-infected leaves could be decomposed to a state where only the veins remain, resulting in a filamentous leaf tissue symptom. The aim of the present study was to investigate how S. graminicola influences the formation of the filamentous leaf tissue symptoms in hosts at the morphological and molecular levels. We discovered that vegetative hyphae expanded rapidly, with high biomass accumulated at the early stages of S. graminicola infection. In addition, S. graminicola could affect spikelet morphological development at the panicle branch differentiation stage to the pistil and stamen differentiation stage by interfering with hormones and nutrient metabolism in the host, resulting in hedgehog-like panicle symptoms. S. graminicola could acquire high amounts of nutrients from host tissues through secretion of β-glucosidase, endoglucanase, and pectic enzyme, and destroyed host mesophyll cells by mechanical pressure caused by rapid expansion of hyphae. At the later stages, S. graminicola could rapidly complete sexual reproduction through tryptophan, fatty acid, starch, and sucrose metabolism and subsequently produce numerous oospores. Oospore proliferation and development further damage host leaves via mechanical pressure, resulting in a large number of degraded and extinct mesophyll cells and, subsequently, malformed leaves with only veins left, that is, "filamentous leaf tissue." Our study revealed the S. graminicola expansion characteristics from its asexual to sexual development stages, and the potential mechanisms via which the destructive effects of S. graminicola on hosts occur at different growth stages.

Transcriptome analysis of foxtail millet inflorescence tissue in response to Sclerospora graminicola infection

Floral reversion caused by Sclerospora graminicola infection seriously affects development and grain formation of floral organs in foxtail millet. Herein, we observed morphological changes to infected panicles from stamen and pistil differentiation to flowering stages, and used RNA sequencing and weighted correlation network analysis (WGCNA) to analyse the key genes and pathways involved in interactions between foxtail millet and S. graminicola. All floral organs of infected panicles, including glume, lemma and palea, transformed into leaf-like structures, leading to malformed inflorescence. Transcriptome analysis showed that S. graminicola infection regulated host physiology and hormone metabolism, and differentially expressed genes (DEGs) were mainly enriched in disease resistance responses involving plant hormone metabolism, peroxidase activity and flavonoid biosynthesis pathways. Subsequently, 8 % of identified DEGs were predicted to be transcription factors, including bHLH and WRKY members related to biotic stress. Plant physiological measurements showed that infection and stress caused by S. graminicola led to changes in antioxidant enzymes superoxide dismutase and peroxidase, and defence hormones jasmonic acid, salicylic acid and 1-aminocyclopropane-1-carboxylic acid in foxtail millet. WGCNA identified 17 hub genes in four key modules (black, magenta, green and turquoise) including a MYB domain protein (Si2g07390), an ethylene-responsive transcription factor ERF094 (Si8g10010) and an NAC domain protein (Si5g40460). The results indicate that transcriptional expression, hormones and oxidation-reduction participate in inflorescence reversion in foxtail millet caused by S. graminicola.

Screening of Pearl Millet Lines against Downy Mildew Incited by Sclerospora graminicola (Sacc.) J. Schrot in Madhya Pradesh, India

Pearl millet (Pennisetum glaucum L.) is the oldest cultivated crop prone to attack by many pathogens viz., Sclerospora graminicola, Moesziomyces penicillariae and Puccinia substriata. The present investigation is on the management of the downy mildew pathogen by exploiting the resistance mechanism of the host. Out of 163 lines and two checks were tested against downy mildew disease. The germplasms were screened in the downy mildew sick plot. The finding exposes that 40 lines were never present of downy mildew and another 68 lines showed < 5% and > 10% downy mildew incidence was recorded in 23 lines and remaining 33 lines were recorded in the category of 5-10% incidence, while a maximum of 83.27 and 97.05% downy mildew incidence was noted in 7042-S at 30 and 60 days after sowing. When compared to all the test lines, the susceptible check 7042-S showed considerably greater incidence of downy mildew at 30 and 60 days. The present investigation suggests that the resistance in the Pearl millet germplasms can be exploited for the management of the pathogens and is an effective management practice with less use of inputs.

Efficacy of biocontrol agents against Sclerospora graminicola causing downy mildew in fodder pearl millet

Downy mildew incited by Sclerospora graminicola is the main hurdle in the successful cultivation of pearl millet and is capable of causing more than 60% losses in terms of grain and fodder yields. The disease could be managed by fungicide applications but due to several associated environmental and health-related issues, there was a necessity to formulate some eco-friendly measures for downy mildew management. Thus attempts were made to find out the usefulness of three biocontrol agents (Bacillus subtilis, Pseudomonas fluorescens and Trichoderma viride) and two fungicides (mancozeb 64% + metalaxyl 4% and metalaxyl) under field conditions for three seasons (2017-2019) against downy mildew. The least downy mildew incidence (14.37%) was observed with seed treatment + foliar spray of B. subtilis as compared to untreated control (31.30%) with 54.10% disease reduction followed by seed treatment + foliar spray of P. fluorescens (17.58% disease incidence) with 43.82% disease control. The same treatments were significantly superior over others in increasing the green fodder yield by 56.59 and 40.79% respectively. Another treatment proven effective was seed treatment + two foliar sprays of T. viride which provided more than 43% reduction in downy mildew incidence as compared to chemical check which provided 30% disease control and increase in green fodder yield. These findings advocated the potential use of biocontrol agents against downy mildew of pearl millet in an eco-friendly manner.

Elucidating the role of effector protein as biomarker for enhanced resistance against pearl millet downy mildew disease

A variety of secreted effectors are used by fungal pathogens to evade, disrupt, or modify crucial elements of transcription, defense signaling, and metabolic processes to induce resistance against biotic stress in host plant. Induced resistance is a crucial component of managing downy mildew disease in Pennisetum glaucum. However, the underlying mechanisms of effectors and their host targets in biotrophic fungal infections are mainly unknown. In the current study, the effector protein 35983_g from Sclerospora graminicola was treated against the Pennisetum glaucum callus and seedlings of resistant and susceptible variety to downy mildew and compared with the control. Hypersensitivity response (HR), protein-cell wall cross-linking, lignin deposition, hydrogen peroxide (H2O2), phenylalanine-ammonia lyase (PAL) and peroxidase (POX) were evaluated in the both the varieties of Pennisetum glaucum. Experimental data demonstrated that effector protein induced HR, boosted the activity of the enzymes PAL and POX. Additionally, a histochemical examination showed that downy mildew resistant variety treated with effector protein had thicker cell walls due to lignin deposition than untreated cultivar. The identified oomycetes effector protein in this study can be used as a biomarker in breeding programmes to screen pearl millet downy mildew resistant lines across the globe.

Pearl Millet (Pennisetumglaucum L.) Research in India: A scientometric journey through the last two decades (2000-2022)

Pearl millet (Pennisetum glaucum L.), a member of the Poaceae family, is a widely cultivated cereal crop and considered to be one of the most important millet crops globally due to its remarkable drought tolerance, adaptability to marginal environments, and high nutritional value. This scientometric study aims to identify the most relevant sources of information in the field of pearl millet research in India during 2000-2022. A total of 844 documents from 181 sources were identified, indicating a moderate level of research activity. The average citations per document were 13.42, suggesting that the research landscape in India has received a reasonable level of attention in the scientific community. The highest number of articles published were in 2021 (55) followed by 2020 (51) and 2018 (44). The data showed that the Indian Journal of Agricultural Sciences was the most prolific and the other journals maintained a relatively stable production over time. The most frequent topics were downy mildew, Sclerospora graminicola, and sorghum. The results suggest that India has established collaborative relationships with various countries worldwide to produce scientific papers.

Genome-Wide Characterization of Effector Protein-Encoding Genes in Sclerospora graminicola and Its Validation in Response to Pearl Millet Downy Mildew Disease Stress.

Pearl millet [Pennisetum glaucum (L.) R. Br.] is the essential food crop for over ninety million people living in drier parts of India and South Africa. Pearl millet crop production is harshly hindered by numerous biotic stresses. Sclerospora graminicola causes downy mildew disease in pearl millet. Effectors are the proteins secreted by several fungi and bacteria that manipulate the host cell structure and function. This current study aims to identify genes encoding effector proteins from the S. graminicola genome and validate them through molecular techniques. In silico analyses were employed for candidate effector prediction. A total of 845 secretory transmembrane proteins were predicted, out of which 35 proteins carrying LxLFLAK (Leucine-any amino acid-Phenylalanine-Leucine-Alanine-Lysine) motif were crinkler, 52 RxLR (Arginine, any amino acid, Leucine, Arginine), and 17 RxLR-dEER putative effector proteins. Gene validation analysis of 17 RxLR-dEER effector protein-producing genes was carried out, of which 5genes were amplified on the gel. These novel gene sequences were submitted to NCBI. This study is the first report on the identification and characterization of effector genes in Sclerospora graminicola. This dataset will aid in the integration of effector classes that act independently, paving the way to investigate how pearl millet responds to effector protein interactions. These results will assist in identifying functional effector proteins involving the omic approach using newer bioinformatics tools to protect pearl millet plants against downy mildew stress. Considered together, the identified effector protein-encoding functional genes can be utilized in screening oomycetes downy mildew diseases in other crops across the globe.

Biodegradable hybrid biopolymer film based on carboxy methyl cellulose and selenium nanoparticles with antifungal properties to enhance grapes shelf life

In the current study, cellulose was extracted from sugarcane bagasse and further converted into carboxy methyl cellulose. The morphological, chemical, and structural characterization of synthesizeed carboxy methyl cellulose was performed. Further, the biopolymer was fabricated with mycogenic selenium nanoparticles and used to develop the biopolymer films. The developed biopolymer films were examined for the fruit shelf life stability, antifungal activity, and biodegradation potential. The results revealed that grapes wrapped with biofilms showed enhanced shelf life of fruit at all storage time intervals. The study also witnesses the antifungal activity of biopolymer films with a remarkable inhibitory action on the spores of Fusarium oxysporum and Sclerospora graminicola phytopathogens. Lastly, the biopolymer films were significantly degradable in the soil within two weeks of incubation. Thus, the developed biopolymer films exhibit multifaceted properties that can be used as an alternative to synthetic plastics for fruit packaging and also helps in protecting against fungal contaminants during storage with naturally degradable potential.

Comparative transcriptome profiling of resistant and susceptible foxtail millet responses to Sclerospora graminicola infection

BackgroundDowny mildew of foxtail millet, which is caused by the biotrophic oomycete Sclerospora graminicola (Sacc.) Schroeter, is one of the most disruptive diseases. The foxtail millet-S. graminicola interaction is largely unexplored. Transcriptome sequencing technology can help to reveal the interaction mechanism between foxtail millet and its pathogens.ResultsTransmission electron microscopy observations of leaves infected with S. graminicola showed that the structures of organelles in the host cells gradually became deformed and damaged, or even disappeared from the 3- to 7-leaf stages. However, organelles in the leaves of resistant variety were rarely damaged. Moreover, the activities of seven cell wall degrading enzymes in resistant and susceptible varieties were also quite different after pathogen induction and most of enzymes activities were significantly higher in the susceptible variety JG21 than in the resistant variety G1 at all stages. Subsequently, we compared the transcriptional profiles between the G1 and JG21 in response to S. graminicola infection at 3-, 5-, and 7-leaf stages using RNA-Seq technology. A total of 473 and 1433 differentially expressed genes (DEGs) were identified in the resistant and susceptible varieties, respectively. The pathway analysis of the DEGs showed that the highly enriched categories were related to glutathione metabolism, plant hormone signalling, phenylalanine metabolism, and cutin, suberin and wax biosynthesis. Some defence-related genes were also revealed in the DEGs, including leucine-rich protein kinase, Ser/Thr protein kinase, peroxidase, cell wall degrading enzymes, laccases and auxin response genes. Our results also confirmed the linkage of transcriptomic data with qRT-PCR data. In particular, LRR protein kinase encoded by Seita.8G131800, Ser/Thr protein kinase encoded by Seita.2G024900 and Seita. 2G024800, which have played an essential resistant role during the infection by S. graminicola.ConclusionsTranscriptome sequencing revealed that host resistance to S. graminicola was likely due to the activation of defence-related genes, such as leucine-rich protein kinase and Ser/Thr protein kinase. Our study identified pathways and genes that contribute to the understanding of the interaction between foxtail millet and S. graminicola at the transcriptomic level. The results will help us better understand the resistance mechanism of foxtail millet against S. graminicola.

Sclerospora graminicola Suppresses Plant Defense Responses by Disrupting Chlorophyll Biosynthesis and Photosynthesis in Foxtail Millet.

Downy mildew of foxtail millet is an important oomycete disease caused by Sclerospora graminicola, affecting the yield and quality of the crop. Foxtail millet infected with S. graminicola exhibit symptoms of leaf yellowing and leaf cracking. To uncover the pathogenic mechanism of this disease, we explored the effects on chlorophyll synthesis and photosynthesis of foxtail millet leaves infected by S. graminicola. An elite foxtail millet variety, JG21, susceptible to S. graminicola, was used as for this study. S. graminicola inhibited chlorophyll synthesis and caused loose mesophyll cell arrangement. In addition, some cells were severely vacuolated in S. graminicola-infected foxtail millet leaves at the early stages of infection. S. graminicola could invade the mesophyll cells through haustoria which destroyed the chloroplast structure at the middle stages of infection causing significant accumulation of osmiophilic particles (OPs) and disintegrated chloroplast grana lamellae. Furthermore, foxtail millet leaves split longitudinally at the later stages of infection. Chlorophyll and carotenoid contents in infected leaves decreased significantly compared with those in the control. Net photosynthetic rate (Pn) of leaves and stomatal conductance showed a downward trend, and intercellular carbon dioxide concentrations increased significantly following the infection with S. graminicola. A total of 1,618 differentially expressed genes (DEGs) were detected between the control group and the treatment groups using RNA sequencing (RNA-Seq) among S1–S5 stages. DEGs associated with “photosynthesis” and “light reaction” were enriched. Gene expression patterns showed that 91.3% of 23 genes related to chlorophyll synthesis and photosynthesis, were significantly down-regulated than the control during S1–S5 stages. Based on the gene expression dataset, weighed gene co-expression network analysis (WGCNA) with 19 gene co-expression modules related to photosynthesis revealed six hub genes related to chlorophyll synthesis, which were suppressed during infection. The results suggest that infection of S. graminicola led to weak chlorophyll synthesis and rapid chloroplasts disappearance in foxtail millet. The defense responses and resistance of foxtail millet to S. graminicola were inhibited because chloroplast structure and function were destroyed in leaves, and the sexual reproduction in S. graminicola could be completed rapidly.

Determination of heterosis for downy mildew (Sclerospora graminicola (Sacc.) Schroet) tolerance in pearl millet (Pennisetum glaucum L. R. Br.)

Downy mildew (Sclerospora graminicola (Sacc.) Schroet) is the most important disease of pearl millet (Pennisetum glaucum L. R. Br.) in many countries of the world including Nigeria. The study was conducted at the Usmanu Danfodiyo University Dry land farm, Sokoto State and Bui village in Arewa local government area of Kebbi State both in Nigeria to determine heterosis for downy mildew in some pearl millet crosses. Twelve parents and thirty hybrids were evaluated for their reaction to the disease. The genotypes were sown in the field in randomized complete block design with two replications. They were inoculated by spraying them with sporangia suspension at seedling stage. Data were collected on downy mildew disease incidence, severity score and some agronomic traits. Analysis of variance for combine location depicts significant (P < 0.05) difference among the genotypes for all the characters except plant height (PHT), number of panicles harvested (NPH) and panicle weight (PWT). Heterosis over high parent and mid parent recorded positive and negative heterotic values in desired direction for grain yield (kg/ha), downy mildew incidence and severity across the locations.

Exogenous salicylic acid enhanced resistance of Foxtail Millet (Setaria italica) to Sclerospora graminicola

To ward off pathogens, plants establish innate immunity system in which salicylic acid (SA) plays an important role. The downy mildew of foxtail millet (Setaria italica) is an oomycete disease caused by biotrophic pathogen Sclerospora graminicola, which seriously affects the yield and quality of foxtail millet. However, it is not clear how SA regulating the defense responses of foxtail millet. In this study, we found that spraying exogenous SA of low concentration (1 mM and 3 mM) had good effect on enhancing the resistance while high concentration (6 mM and 9 mM) did not significantly affect the defense of foxtail millet. Excess SA inhibited the growth and development of plants and we found spraying exogenous SA reduced the plant height, fresh weight and dry weight of foxtail millet. The low concentration of exogenous SA promoted the accumulation of Chlorophyll, soluble sugar and proline, promoted the activity of Phenylalanine Ammonia-Lyase and suppressed the accumulation of Malondialdehyde. After the treatment with 1 mM or 3 mM of SA, the expressions of genes related to disease resistance were increased at the early stage after treatment. The results indicated exogenous SA could enhance the resistance of foxtail millet against the pathogen and provided a basis for improving the control methods of downy mildew.

Sexual Compatibility Types in F1 Progenies of Sclerospora graminicola, the Causal Agent of Pearl Millet Downy Mildew.

Sclerospora graminicola is primarily heterothallic in nature with two distinct mating types (G1 and G2); however, homothallism does exist in the pathogen populations. In this study, a cross was made between two self-sterile isolates (Sg 019, Mat-2, G2 × Sg 445-1, Mat-1, G1) of S. graminicola and a total of 39 F1 progenies were established. The study on sexual compatibility types in F1 progenies was conducted by crossing each F1 progeny with both the parents (Sg 445-1, Mat-1, G1; and Sg 019, Mat-2, G2). The results revealed the presence of four sexual compatibility types, viz. G1, G2, G1G2 and G0 (neuter) in the progenies. The G1G2 progenies that produced oospores with both the parents were found as self-fertile (homothallic) and self-sterile (heterothallic) types. Similarly, self-fertile parental type G1 and G2 progenies were designated as secondary homothallic, whereas self-sterile parental type G1 and G2 progenies were of heterothallic type. The result of the present study revealed Mendelian segregation of mating type locus in S. graminicola which indicates that sexual reproduction plays an important role in the evolution of new genetic recombinants in the pathogen. The study also helps in understanding the genetic structure of S. graminicola populations and potential for possible evolution of new virulences in the pathogen.

Identification of sugar transporter gene family <italic>SiSTPs</italic> in foxtail millet and its participation in stress response

<p id="C3">Sugar transporter proteins (STPs), a class of monosaccharide transporters that mainly transport hexose, play an important role in the growth, development, and stress resistance of crops. Foxtail millet is the main cultivated crop in green dryland agriculture, and also is the model plant for C₄ photosynthesis mechanism and stress resistance gene mining of Gramineae crops. However, no systematical study of <italic>SiSTPs</italic> gene has been performed in foxtail millet. In this study, we identified the whole genome of six Gramineae crops including foxtail millet by bioinformatics method, and focused on the physicochemical properties, the chromosomal localization, the systematic evolution, gene structure, and the conserved domain. Moreover, the relative expression level of <italic>SiSTPs </italic>gene and its resistance to the infection of <italic>Sclerospora graminicola</italic> under drought stress and low phosphate stress in foxtail millet were investigated. The results showed that a total of 24, 26, 23, 22, 33, and 27 STP gene family members were individually identified in <italic>Setaria italica</italic>, <italic>Setaria viridis</italic>,<italic> Sorghum bicolor</italic>,<italic> Zea mays</italic>,<italic> Triticum aestivum</italic>, and <italic>Oryza sativa</italic>, which were divided into four clades by phylogenetic analysis. The 24 SiSTP genes were distributed unevenly on 7 chromosomes, and the size of the encoded amino acids ranged from 499 aa to 581 aa. The SiSTP all had the Sugar_tr (PF00083) conserved domain. The <italic>cis</italic>-acting elements included a large number of light-responsive elements and stress-responsive elements. These <italic>SiSTPs</italic> was subjected to strong purification and selection pressure during the evolutionary process of foxtail millet, and had obvious tissue expression specificity and photoinduced phenomena. Different <italic>SiSTPs</italic> showed different temporal and spatial expression and response to the drought stress, the low phosphate stress, and <italic>Sclerospora graminicola</italic> infection. Our results provide a theoretical basis for elucidating the function and response mechanism to stress of SiSTP.

Immunity elicitors for induced resistance against the downy mildew pathogen in pearl millet

Pearl millet (Pennisetum glaucum (L.) R. Br.) is a globally important cereal whose production is severely constrained by downy mildew caused by Sclerospora graminicola (Sacc.). In this study, immunity eliciting properties of 3,5-dichloroanthranilic acid (DCA), Cell Wall Glucan (CWG), Lipopolysaccharide (LPS), and Glycinebetaine (GB) was deciphered through enzymatic and protein studies based on elicitor treatment activated defense mechanisms. Glycinebetaine, LPS, CWS and DCA elicited enzyme activities and gene expression of the defense enzymes, such as β-1,3-glucanase, phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO), lipoxygenase (LOX) and defense protein hydroxyproline-rich glycoproteins (HRGPs). However, the speed and the extent of elicitation differed. High levels of enzyme activities and gene expression in elicitor-treated P. glaucum positively correlated with the increased downy mildew resistance. A very rapid and large changes in elicitor-treated seedlings, in contrast to the delayed, smaller changes in the untreated susceptible control seedlings suggests that the rate and magnitude of defense gene expression are important for effective manifestation of defense against pathogen. As compared to other elicitors and control, GB promoted increase in enzyme activities and gene expression, implicating that GB is a promising elicitor of downy mildew resistance in P. glaucum.

A jacalin-like lectin domain-containing protein of Sclerospora graminicola acts as an apoplastic virulence effector in plant-oomycete interactions.

The plant extracellular space, including the apoplast and plasma membrane, is the initial site of plant–pathogen interactions. Pathogens deliver numerous secreted proteins, called effectors, into this region to suppress plant immunity and establish infection. Downy mildew caused by the oomycete pathogen Sclerospora graminicola (Sg) is an economically important disease of Poaceae crops including foxtail millet (Setaria italica). We previously reported the genome sequence of Sg and showed that the jacalin‐related lectin (JRL) gene family has significantly expanded in this lineage. However, the biological functions of JRL proteins remained unknown. Here, we show that JRL from Sg (SgJRL) functions as an apoplastic virulence effector. We identified eight SgJRLs by protein mass spectrometry analysis of extracellular fluid from Sg‐inoculated foxtail millet leaves. SgJRLs consist of a jacalin‐like lectin domain and an N‐terminal putative secretion signal; SgJRL expression is induced by Sg infection. Heterologous expression of three SgJRLs with N‐terminal secretion signal peptides in Nicotiana benthamiana enhanced the virulence of the pathogen Phytophthora palmivora inoculated onto the same leaves. Of the three SgJRLs, SG06536 fused with green fluorescent protein (GFP) localized to the apoplastic space in N. benthamiana leaves. INF1‐mediated induction of defence‐related genes was suppressed by co‐expression of SG06536‐GFP. These findings suggest that JRLs are novel apoplastic effectors that contribute to pathogenicity by suppressing plant defence responses.