Showing papers on "Rhizoctonia solani published in 2019"

Natural variation in ZmFBL41 confers banded leaf and sheath blight resistance in maize

Abstract: Rhizoctonia solani is a widely distributed phytopathogen that causes banded leaf and sheath blight in maize and sheath blight in rice. Here, we identified an F-box protein (ZmFBL41) that confers resistance to banded leaf and sheath blight through a genome-wide association study in maize. Rice overexpressing ZmFBL41 showed elevated susceptibility to R. solani. Two amino acid substitutions in this allele prevent its interaction with ZmCAD, which encodes the final enzyme in the monolignol biosynthetic pathway, resulting in the inhibition of ZmCAD degradation and, consequently, the accumulation of lignin and restriction of lesion expansion. Knocking out the ZmCAD-homologous gene OsCAD8B in rice enhanced susceptibility to R. solani. The results reveal a susceptibility mechanism in which R. solani targets the host proteasome to modify the secondary metabolism of the plant cell wall for its invasion. More importantly, it provides an opportunity to generate R. solani-resistant varieties of different plant species.

Extreme Diversity of Mycoviruses Present in Isolates of Rhizoctonia solani AG2-2 LP From Zoysia japonica From Brazil

Abstract: Zoysia japonica, in Brazil, is commonly infected by Rhizoctonia solani (R. solani) in humid and cool weather conditions. Eight isolates of R. solani, previously identified as belonging to the AG2-2 LP anastomosis group, isolated from samples from large path symptoms, were collected from three counties in Sao Paulo state (Brazil) and investigated for the presence of mycoviruses. After detection of double-strand RNA (dsRNA) in all samples, RNA_Seq analysis of ribosomal RNA-depleted total RNA from in vitro cultivated mycelia was performed. Forty-seven partial or complete viral unique RNA dependent-RNA polymerase (RdRp) sequences were obtained with a high prevalence of positive sense ssRNA viruses. Sequences were sufficiently different from the first match in BLAST searches suggesting that they all qualify as possible new viral species, except for one sequence showing an almost complete match with Rhizoctonia solani dsRNA virus 2, an alphapartitivirus. Surprisingly four large contigs of putative viral RNA could not be assigned to any existing clade of viruses present in the databases, but no DNA was detected corresponding to these fragments confirming their viral replicative nature. This is the first report on the occurrence of mycoviruses in R. solani AG2-2 LP in South America.

Characterization and complete genome analysis of the surfactin-producing, plant-protecting bacterium Bacillus velezensis 9D-6

Abstract: Bacillus velezensis is an endospore-forming, free-living soil bacterium with potential as a biopesticide against a broad spectrum of microbial pathogens of plants. Its potential for commercial development is enhanced by rapid replication and resistance to adverse environmental conditions, typical of Bacillus species. However, the use of beneficial microbes against phytopathogens has not gained dominance due to limitations that may be overcome with new biopesticidal strains and/or new biological knowledge. Here, we isolated B. velezensis strain 9D-6 and showed that it inhibits the in vitro growth of prokaryotic and eukaryotic pathogens, including the bacteria , Clavibacter michiganensis, Pantoea agglomerans, Ralstonia solanacearum, Xanthomonas campestris, and Xanthomonas euvesicatoria; and the fungi Alternaria solani, Cochliobolus carbonum, Fusarium oxysporum, Fusarium solani, Gibberella pulicaris, Gibberella zeae, Monilinia fructicola, Pyrenochaeta terrestris and Rhizoctonia solani. Antimicrobial compounds with activity against Clavibacter michiganensis were isolated from B. velezensis 9D-6 and characterized by high resolution LC-MS/MS, yielding formulae of C52H91N7O13 and C53H93N7O13, which correspond to [Leu7] surfactins C14 and C15 (also called surfactin B and surfactin C), respectively. We further sequenced the B. velezensis 9D-6 genome which consists of a single circular chromosome and revealed 13 gene clusters expected to participate in antimicrobial metabolite production, including surfactin and two metabolites that have not typically been found in this species - ladderane and lantipeptide. Despite being unable to inhibit the growth of Pseudomonas syringae DC3000 in an in vitro plate assay, B. velezensis 9D-6 significantly reduced root colonization by DC3000, suggesting that 9D-6 uses methods other than antimicrobials to control phytopathogens in the environment. Finally, using in silico DNA-DNA hybridization (isDDH), we confirm previous findings that many strains currently classified as B. amyloliquefaciens are actually B. velezensis. The data presented here suggest B. velezensis 9D-6 as a candidate plant growth promoting bacterium (PGPB) and biopesticide, which uses a unique complement of antimicrobials, as well as other mechanisms, to protect plants against phytopathogens. Our results may contribute to future utilization of this strain, and will contribute to a knowledge base that will help to advance the field of microbial biocontrol.

Mycosilver Nanoparticles: Synthesis, Characterization and its Efficacy against Plant Pathogenic Fungi

Abstract: The fungicides used to control plant pathogenic fungi not only kill the fungi but also affect other flora and fauna in the field. To preserve beneficial flora, novel strategies and alternative approaches should be identified. Bio-pesticides are used as an alternative to chemical fungicides. The development of nanotechnology-based fungicides and pesticides are considered as promising alternatives to preserve the biota. At the global level, researchers are working on nanoemulsion and nanofungicides to control plant pathogenic fungi; however, farmers are unaware about these nano-based fungicides. Metal nanoparticles can act as potential fungicides when compared to the conventional chemical fungicides. Hence, our current study is based on utilization of the myco-nanoparticles synthesized from endophytic fungi isolated from Solanum nigrum. The mycosilver nanoparticles are characterized by SEM, TEM and EDAX analysis. The results of the study exhibited the silver nanoparticles were of different morphological shapes including spherical, cylindrical and loosely agglomerated with an average size of 2–50 nm. Further, the plant pathogenic fungi including Fusarium graminearum, Fusarium udum, Rhizoctonia solani and Aspergillus niger were treated with mycosilver nanoparticles to test the efficacy to control plant pathogens, and showed broad spectrum antifungal activity against the phytopathogens by inhibiting the radial growth.

Antifungal and Antibacterial Activities of Musa paradisiaca L. Peel Extract: HPLC Analysis of Phenolic and Flavonoid Contents

Abstract: In the present study, Melia azedarach wood samples that were treated with the methanolic extract of Musa paradisiaca L. peels were evaluated for their antibacterial and antifungal activities against Agrobacterium tumefaciens, Dickeya solani, Erwinia amylovora, Pseudomonas cichorii, Serratia pylmuthica, Fusarium culmorum, and Rhizoctonia solani. The strongest antibacterial activity was only found against A. tumefaciens (inhibition zone 90 mm), while the other bacterial strains showed resistance to wood that was treated with the extract. Potential antifungal activity against F. culmorum and R. solani was observed; the mycelial growth inhibition percentages reached 68.88% and 94.07%, respectively, in wood samples that were treated with the 3% methanolic extract of M. paradisiaca peel. HPLC analysis demonstrated the presence of seven phenolic compounds and three flavonoid compounds, as their peaks were matched with the standard compounds in a HPLC analysis. The major constituents of phenolic and flavonoid compounds in mg/100 g dry extract (DE) were ellagic acid (16.19), gallic acid (7.73), rutin (973.08), myricetin (11.52), and naringenin (8.47). The results demonstrated the potential effects of banana peel extract as a natural compound that can protect wood from molds while in use.

GhABP19, a Novel Germin-Like Protein From Gossypium hirsutum, Plays an Important Role in the Regulation of Resistance to Verticillium and Fusarium Wilt Pathogens

Abstract: Germin-like proteins (GLPs) are water-soluble plant glycoproteins belonging to the cupin superfamily. The important role of GLPs in plant responses against various abiotic and biotic stresses, especially pathogens, is well validated. However, little is known about cotton GLPs in relation to fungal pathogens. Here, a novel GLP gene was isolated from Gossypium hirsutum and designated as GhABP19. The expression of GhABP19 was upregulated in cotton plants inoculated with Verticillium dahliae and Fusarium oxysporum and in response to treatment with jasmonic acid (JA) but was suppressed in response to salicylic acid treatment. A relatively small transient increase in GhABP19 was seen in H2O2 treated samples. The three-dimensional structure prediction of the GhABP19 protein indicated that the protein has three histidine and one glutamate residues responsible for metal ion binding and superoxide dismutase (SOD) activity. Purified recombinant GhABP19 exhibits SOD activity and could inhibit growth of V. dahliae, F. oxysporum, Rhizoctonia solani, Botrytis cinerea, and Valsa mali in vitro. To further verify the role of GhABP19 in fungal resistance, GhABP19-overexpressing Arabidopsis plants and GhABP19-silenced cotton plants were developed. GhABP19-transgenic Arabidopsis lines showed much stronger resistance to V. dahliae and F. oxysporum infection than control (empty vector) plants did. On the contrary, silencing of GhABP19 in cotton conferred enhanced susceptibility to fungal pathogens, which resulted in necrosis and wilt on leaves and vascular discoloration in GhABP19-silenced cotton plants. The H2O2 content and endogenous SOD activity were affected by GhABP19 expression levels in Arabidopsis and cotton plants after inoculation with V. dahliae and F. oxysporum, respectively. Furthermore, GhABP19 overexpression or silencing resulted in activation or suppression of JA-mediated signaling, respectively. Thus, GhABP19 plays important roles in the regulation of resistance to verticillium and fusarium wilt in plants. These modulatory roles were exerted by its SOD activity and ability to activate the JA pathway. All results suggest that GhABP19 was involved in plant disease resistance.

Beneficial Endophytic Bacteria-Serendipita indica Interaction for Crop Enhancement and Resistance to Phytopathogens.

Abstract: Serendipita (=Piriformospora) indica is a fungal endophytic symbiont with the capabilities to enhance plant growth and confer resistance to different stresses. However, the application of this fungus in the field has led to inconsistent results, perhaps due to antagonism with other microbes. Here, we studied the impact of individual bacterial isolates from the endophytic bacterial community on the in vitro growth of S. indica. We further analyzed how combinations of bacteria and S. indica influence plant growth and protection against the phytopathogens Fusarium oxysporum and Rhizoctonia solani. Bacterial strains of the genera Bacillus, Enterobacter and Burkholderia negatively affected S. indica growth on plates, whereas Mycolicibacterium, Rhizobium, Paenibacillus strains and several other bacteria from different taxa stimulated fungal growth. To further explore the potential of bacteria positively interacting with S. indica, four of the most promising strains belonging to the genus Mycolicibacterium were selected for further experiments. Some dual inoculations of S. indica and Mycolicibacterium strains boosted the beneficial effects triggered by S. indica, further enhancing the growth of tomato plants, and alleviating the symptoms caused by the phytopathogens F. oxysporum and R. solani. However, some combinations of S. indica and bacteria were less effective than individual inoculations. By analyzing the genomes of the Mycolicibacterium strains, we revealed that these bacteria encode several genes predicted to be involved in the stimulation of S. indica growth, plant development and tolerance to abiotic and biotic stresses. Particularly, a high number of genes related to vitamin and nitrogen metabolism were detected. Taking into consideration multiple interactions on and inside plants, we showed in this study that some bacterial strains may induce beneficial effects on S. indica and could have an outstanding influence on the plant-fungus symbiosis.

Expression of pathogenesis-related proteins in transplastomic tobacco plants confers resistance to filamentous pathogens under field trials

Abstract: Plants are continuously challenged by pathogens, affecting most staple crops compromising food security. They have evolved different mechanisms to counterattack pathogen infection, including the accumulation of pathogenesis-related (PR) proteins. These proteins have been implicated in active defense, and their overexpression has led to enhanced resistance in nuclear transgenic plants, although in many cases constitutive expression resulted in lesion-mimic phenotypes. We decided to evaluate plastid transformation as an alternative to overcome limitations observed for nuclear transgenic technologies. The advantages include the possibilities to express polycistronic RNAs, to obtain higher protein expression levels, and the impeded gene flow due to the maternal inheritance of the plastome. We transformed Nicotiana tabacum plastids to co-express the tobacco PR proteins AP24 and β-1,3-glucanase. Transplastomic tobacco lines were characterized and subsequently challenged with Rhizoctonia solani, Peronospora hyoscyami f.sp. tabacina and Phytophthora nicotianae. Results showed that transplastomic plants expressing AP24 and β-1,3-glucanase are resistant to R. solani in greenhouse conditions and, furthermore, they are protected against P.hyoscyami f.sp. tabacina and P. nicotianae in field conditions under high inoculum pressure. Our results suggest that plastid co- expression of PR proteins AP24 and β-1,3-glucanase resulted in enhanced resistance against filamentous pathogens.

Viruses Infecting the Plant Pathogenic Fungus Rhizoctonia solani

Abstract: The cosmopolitan fungus Rhizoctonia solani has a wide host range and is the causal agent of numerous crop diseases, leading to significant economic losses. To date, no cultivars showing complete resistance to R. solani have been identified and it is imperative to develop a strategy to control the spread of the disease. Fungal viruses, or mycoviruses, are widespread in all major groups of fungi and next-generation sequencing (NGS) is currently the most efficient approach for their identification. An increasing number of novel mycoviruses are being reported, including double-stranded (ds) RNA, circular single-stranded (ss) DNA, negative sense (-)ssRNA, and positive sense (+)ssRNA viruses. The majority of mycovirus infections are cryptic with no obvious symptoms on the hosts; however, some mycoviruses may alter fungal host pathogenicity resulting in hypervirulence or hypovirulence and are therefore potential biological control agents that could be used to combat fungal diseases. R. solani harbors a range of dsRNA and ssRNA viruses, either belonging to established families, such as Endornaviridae, Tymoviridae, Partitiviridae, and Narnaviridae, or unclassified, and some of them have been associated with hypervirulence or hypovirulence. Here we discuss in depth the molecular features of known viruses infecting R. solani and their potential as biological control agents.

Genotypes and Genomic Regions Associated With Rhizoctonia solani Resistance in Common Bean.

Abstract: Rhizoctonia solani Kuhn (teleomorph Thanatephorus cucumeris) is an important root rot pathogen of common bean (Phaseolus vulgaris L) To uncover genetic factors associated with resistance to the pathogen, the Andean (ADP; n=273) and Middle American (MDP; n=279) diversity panels, which represent much of the genetic diversity known in cultivated common bean, were screened in the greenhouse using R solani anastomosis group 2-2 Repeatability of the assay was confirmed by the response of five control genotypes The phenotypic data for both panels were normally distributed The resistance responses of ~10% of the ADP (n=28) and ~6% of the MDP (n=18) genotypes were similar or higher than that of the resistant control line VAX 3 A genome-wide association study (GWAS) was performed using ~200k single nucleotide polymorphisms (SNPs) to discover genomic regions associated with resistance in each panel, For GWAS, the raw phenotypic score, and polynomial and binary transformation of the scores, were individually used as the input data A major QTL peak was observed on Pv02 in the ADP, while a major QTL was observed on Pv01 with the MDP These regions were associated with clusters of TIR-NB_ARC-LRR (TNL) gene models encoding proteins similar to known disease resistance genes Other QTL, unique to each panel, were mapped within or adjacent to a gene model or cluster of related genes associated with disease resistance This is a first case study that provides evidence for major as well as minor genes involved in resistance to R solani in common bean This information will be useful to integrate more durable root rot resistance in common bean breeding programs and to study the genetic mechanisms associated with root diseases in this important societal legume

Decoding Wheat Endosphere–Rhizosphere Microbiomes in Rhizoctonia solani–Infested Soils Challenged by Streptomyces Biocontrol Agents

Abstract: The endosphere and the rhizosphere are pertinent milieus with microbial communities that perturb the agronomic traits of crop plants through beneficial or detrimental interactions. In this study, we challenged these communities by adding Streptomyces biocontrol strains to wheat seeds in soils with severe Rhizoctonia solani infestation. Wheat plants were grown in a glasshouse standardized system, and the bacterial and fungal microbiomes of 233 samples of wheat roots (endosphere) and rhizosphere soils were monitored for 20 weeks, from seed to mature plant stage. The results showed highly dynamic and diverse microbial communities that changed over time, with Sphingomonas bacteria and Aspergillus, Dipodascus, and Trichoderma fungi increasing over time. Application of biocontrol Streptomyces strains promoted plant growth and maturation of wheat heads and modulated the root microbiome, decreasing Paenibacillus and increasing other bacterial and fungal OTUs. The soils with the highest levels of R. solani had increased reads of Thanatephorus (Rhizoctonia anamorph) and increased root disease levels and increased Balneimonas, Massilia, Pseudomonas, and unclassified Micrococcaceae. As we enter the era of biologically sustainable agriculture, it may be possible to reduce and limit the effects of serious fungal infestations by promoting a beneficial microbiome through the application of biocontrol agents during different periods of plant development.

A LysM effector protein from the basidiomycete Rhizoctonia solani contributes to virulence through suppression of chitin-triggered immunity

Abstract: Rhizoctonia solani is a fungal species that belongs to the fungal division Basidiomycota. It is a soil-borne pathogen that attacks a broad range of plant species and crops. Disease symptoms are commonly seen as damping off of seedlings and root rot, although it can infect plants at any developmental stage. Despite the severity of this disease, many aspects in R. solani infection biology remain unclear. Here we investigated the role of a LysM effector, previously predicted from the genome of a R. solani AG2-2IIIB strain that has sugar beet as a host. Gene expression analysis showed that RsLysM was highly induced upon sugar beet infection. When RsLysM was heterologously expressed in Cercospora beticola, necrotic lesion size and fungal colonization ability were increased, indicating a role in virulence. RsLysM displayed chitin-binding affinity and suppression of chitin-triggered immunity but could not protect hyphae from hydrolysis. Overall, this study is the first characterization of a LysM effector from Basidiomycota, suggesting that this necrotrophic fungal species relies on perturbation of chitin-triggered immunity to establish a successful infection.

Biocontrol of Rhizoctonia solani via Induction of the Defense Mechanism and Antimicrobial Compounds Produced by Bacillus subtilis SL-44 on Pepper (Capsicum annuum L.).

Abstract: Pepper seedling wilt disease is the main cause of crop yield reduction. Biocontrol agents are widely used to control plant diseases caused by pathogenic fungi and activate plant defense systems. Our preliminary work showed that Bacillus subtilis SL-44 played a significant role in the reduction of wilt disease severity on pepper plants. To evaluate biological control mechanism of B. subtilis SL-44 on wilt disease caused by Rhizoctonia solani, the activities of the related enzymes were detected in the pepper seedling with different treatment in this study. Fluorescence microscopy combined with different dyes showed that B. subtilis SL-44 induced a large amount of active oxygen and callose accumulation in pepper leaves. The defense-related enzyme activities in pepper were improved significantly when treated with B. subtilis SL-44, including peroxidase, catalase, superoxide dismutase, polyphenol oxidase, and phenylalanine ammonia lyase. The activity of chitinase and β-1,3-glucanase in B. subtilis SL-44-treated pepper was also enhanced. Furthermore, the expression level of pepper-resistance gene CaPIN II was significantly increased in B. subtilis SL-44 treatment. Besides, B. subtilis SL-44 filtrate led to the death of the pathogenic fungus by fracturing the mycelia and leaking of the cell contents. Surfactin, iturin, and fengycin were found in B. subtilis SL-44 crude extracts, which could be effective antifungal compounds against R. solani. The results suggest that B. subtilis SL-44 could not only activate induced systemic resistance of pepper seedling against wilt disease caused by R. solani by jasmonic acid-dependent signaling pathway but also produce antifungal compounds to inhibit or even damage the mycelium growth of R. solani. The findings of this study provide novel guidance in plant protection development.

Molecular Characterization of a Novel Endornavirus Conferring Hypovirulence in Rice Sheath Blight Fungus Rhizoctonia solani AG-1 IA Strain GD-2

Abstract: The complete sequence and genome organization of a novel Endornavirus from the hypovirulent strain GD-2 of Rhizoctonia solani AG-1 IA, the causal agent of rice sheath blight, were identified using a deep sequencing approach and it was tentatively named as Rhizoctonia solani endornavirus 1 (RsEV1). It was composed of only one segment that was 19,936 bp in length and was found to be the longest endornavirus genome that has been reported so far. The RsEV1 genome contained two open reading frames (ORFs): ORF1 and ORF2. ORF1 contained a glycosyltransferase 1 domain and a conserved RNA-dependent RNA polymerase domain, whereas ORF2 encoded a conserved hypothetical protein. Phylogenetic analysis revealed that RsEV1 was phylogenetically a new endogenous RNA virus. A horizontal transmission experiment indicated that RsEV1 could be transmitted from the host fungal strain GD-2 to a virulent strain GD-118P and resulted in hypovirulence in the derivative isogenic strain GD-118P-V1. Metabolomic analysis showed that 32 metabolites were differentially expressed between GD-118P and its isogenic hypovirulent strain GD-118P-V1. The differential metabolites were mainly classified as organic acids, amino acids, carbohydrates, and the intermediate products of energy metabolism. Pathway annotation revealed that these 32 metabolites were mainly involved in pentose and glucuronate interconversions and glyoxylate, dicarboxylate, starch, and sucrose metabolism, and so on. Taken together, our results showed that RsEV1 is a novel Endornavirus, and the infection of virulent strain GD-118P by RsEV1 caused metabolic disorders and resulted in hypovirulence. The results of this study lay a foundation for the biocontrol of rice sheath blight caused by R. solani AG1-IA.

Biological control of black pepper and ginger pathogens, Fusarium oxysporum, Rhizoctonia solani and Phytophthora capsici, using Trichoderma spp

Abstract: Target specific fungal biocontrol agents are considered ideal for plant pathogen management strategies in crop protection and it offsets the negative environmental impact of chemical pesticides. The present study was conducted to develop novel microbial biocontrol agents for the effective management of black pepper and ginger pathogens in an eco-friendly and sustainable manner. Several Trichoderma species were isolated from the forest rhizosphere soil of Palakkad and Idukki districts of Kerala during pre-monsoon season. After preliminary screening, four isolates were identified by biochemical and molecular characterization, and later, they were studied for their anti-fungal activity. The novel isolates, T. asperellum strain AFP, T. asperellum strain MC1, T. brevicompactum MF1 and T. harzianum strain CH1 were tested for their efficacy in managing various soil-borne phytopathogens such as F. oxysporum, R. solani and P. capsici. The results of antimycotic activity of these isolates showed that T. harzianum exhibited maximum of mycelial growth inhibition over Fusarium oxysporum (78.3%) and Phytophthora capsici (65.3%) than T. asperellum (Strain AFP and MC1) and T. brevicompactum (MF1). Dual culture test results over mycelial growth of Rhizoctonia solani was found to be maximum in T. asperellum strain AFP (62.3%) followed by T. asperellum strain MC1 (56%), T. brevicompactum strain MF1 (49%) and T. harzianum strain CH1 (45.3%). The analyses of growth inhibition assay of all the four Trichoderma isolates were suggestive of their use as effective microbial biocontrol agents.

Inhibition of Fusarium culmorum, Penicillium chrysogenum and Rhizoctonia solani by n-hexane extracts of three plant species as a wood-treated oil fungicide

Abstract: Aims Wood as a packing tool is used for packaging and transportation of fruits and vegetables for a time period varying from hours to days. During transportation, fruits and vegetables can be affected by moulds with significant postharvest problems. The present study describes the possibility of using wood-treated oil fungicide of n-hexane extracts from Eucalyptus camaldulensis (aerial parts), Vitex agenus-castus (leaves) and Matricaria chamomilla (flowers) against the infestation of Fusarium culmorum, Rhizoctonia solani and Penicillium chrysogenum. Methods and results Air-dried wood samples of Melia azedarach were prepared with the dimensions of 0·5 × 1 × 2 cm and treated with the oily extracts at the concentrations of 0, 1, 2 and 3%. Oils extracted with n-hexane from E. camaldulensis and V. agenus-castus showed promising antifungal activities against the isolated and molecularly identified three fungi F. culmorum, R. solani and P. chrysogenum, while M. chamomilla observed the lowest activity against the studied fungi. GC/MS analysis of oils reported that the major components in E. camaldulensis were β-fenchol (25·51%), Cyclobuta[1,2:3,4]dicyclooctene-1,7(2H,6bH)-dione,dodecahydro,(6αβ,6βα,12αα,12ββ)- (17·05), 1,8-cineole (eucalyptol) (12·01%) and sabinene (9·45%); in V. agenus-castus were eucalyptol (22·17%), (E)-β-caryophyllene (18·39%), and β-sitosterol (12·44%); while in M. chamomilla were bisabolol oxide A (27·87%), (Z)-β-farnesene (16·11%), D-limonene (14·18%) and chamazulene (11·27%). Conclusions The results suggest using n-hexane oily extracts from E. camaldulensis and V. agenus-castus as a biofungicide for wood protection. Significance and impact of the study This study highlights the importance of using bio-friendly fungicide agents to protect wood against most common moulds occurring during handling of food packaging.

The rice CYP78A gene BSR2 confers resistance to Rhizoctonia solani and affects seed size and growth in Arabidopsis and rice

Abstract: The fungal pathogen Rhizoctonia solani causes devastating diseases in hundreds of plant species. Among these, R. solani causes sheath blight, one of the three major diseases in rice. To date, few genes have been reported that confer resistance to R. solani. Here, rice-FOX Arabidopsis lines identified as having resistance to a bacterial pathogen, Pseudomonas syringae pv. tomato DC3000, and a fungal pathogen, Colletotrichum higginsianum were screened for disease resistance to R. solani. BROAD-SPECTRUM RESISTANCE2 (BSR2), a gene encoding an uncharacterized cytochrome P450 protein belonging to the CYP78A family, conferred resistance to R. solani in Arabidopsis. When overexpressed in rice, BSR2 also conferred resistance to two R. solani anastomosis groups. Both Arabidopsis and rice plants overexpressing BSR2 had slower growth and produced longer seeds than wild-type control plants. In contrast, BSR2-knockdown rice plants were more susceptible to R. solani and displayed faster growth and shorter seeds in comparison with the control. These results indicate that BSR2 is associated with disease resistance, growth rate and seed size in rice and suggest that its function is evolutionarily conserved in both monocot rice and dicot Arabidopsis.

The Effector AGLIP1 in Rhizoctonia solani AG1 IA Triggers Cell Death in Plants and Promotes Disease Development Through Inhibiting PAMP-Triggered Immunity in Arabidopsis thaliana.

Abstract: Rhizoctonia solani, one of the most detrimental necrotrophic pathogens, causes rice sheath blight and poses a severe threat to production. Focus on the function of effectors secreted by necrotrophic pathogens during infection has grown rapidly in recent years. However, little is known about the virulence and mechanisms of these proteins. In this study, we performed functional studies on putative effectors in R. solani and revealed that AGLIP1 out of 13 putative effectors induced cell death in Nicotiana benthamiana. AGLIP1 was also demonstrated to trigger cell death in rice protoplasts. The predicted lipase active sites and signal peptide of this protein were required for the cell death-inducing ability. AGLIP1 was greatly induced during R. solani infection in rice sheath. The AGLIP1's virulence function was further demonstrated by transgenic technology. The pathogenesis-related genes induced by pathogen-associated molecular pattern and bacteria were remarkably inhibited in AGLIP1-expressing transgenic Arabidopsis lines. Ectopic expression of AGLIP1 strongly facilitated disease progression in Arabidopsis caused by the type III secretion system-defective mutant from Pseudomonas syringae pv. tomato DC3000. Collectively, these results indicate that AGLIP1 is a possible effector that plays a significant role in pathogen virulence through inhibiting basal defenses and promoting disease development in plants.

Phenazine and 1-Undecene Producing Pseudomonas chlororaphis subsp. aurantiaca Strain KNU17Pc1 for Growth Promotion and Disease Suppression in Korean Maize Cultivars.

Abstract: In this study, strain KNU17Pc1 was tested for its antifungal activity against Rhizoctonia solani AG-1(IA), which causes banded leaf and sheath blight (BLSB) of maize. KNU17Pc1 was tested further for its broad-spectrum antifungal activity and in vitro plant growth promoting (PGP) traits. In addition, the in vivo effects of KNU17Pc1 on reduction of BLSB severity and seedling growth promotion of two maize cultivars under greenhouse conditions were investigated. On the basis of multilocus sequence analysis (MLSA), KNU17Pc1 was confirmed as P. chlororaphis subsp. aurantiaca. The study revealed that KNU17Pc1 had strong in vitro antifungal activity and was effective toward all in vitro PGP traits except phosphate solubilization. In this study, for the first time, a strain of P. chlororaphis against Colletotrichum dematium, Colletotrichum gloeosporioides, Fusarium oxysporum f.sp. melonis, Fusarium subglutinans and Stemphylium lycopersici has been reported. Further biochemical studies showed that KNU17Pc1 was able to produce both types of phenazine derivatives, PCA and 2-OH-PCA. In addition, solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis identified 13 volatile organic compounds (VOCs) in the TSB culture of KNU17Pc1, 1-undecene being the most abundant volatile. Moreover, for the first time, Octamethylcyclotetrasiloxan (D4), dimethyl disulfide, 2-methyl-1,3-butadiene and 1-undecene were detected in P. chlororaphis. Furthermore, this study reported for the first time the effectiveness of P. chlororaphis to control BLSB of maize. Hence, further studies are necessary to test the effectiveness of KNU17Pc1 under different environmental conditions so that it can be exploited further for biocontrol and plant growth promotion.

Pectin induced transcriptome of a Rhizoctonia solani strain causing sheath blight disease in rice reveals insights on key genes and RNAi machinery for development of pathogen derived resistance.

Abstract: Key message RNAi mediated silencing of pectin degrading enzyme of R. solani gives a high level of resistance against sheath blight disease of rice.

Effect of Trichoderma velutinum and Rhizoctonia solani on the Metabolome of Bean Plants (Phaseolus vulgaris L.)

Abstract: The common bean (Phaseolus vulgaris L.) is one of the most important food legume crops worldwide that is affected by phytopathogenic fungi such as Rhizoctonia solani. Biological control represents an effective alternative method for the use of conventional synthetic chemical pesticides for crop protection. Trichoderma spp. have been successfully used in agriculture both to control fungal diseases and to promote plant growth. The response of the plant to the invasion of fungi activates defensive resistance responses by inducing the expression of genes and producing secondary metabolites. The purpose of this work was to analyze the changes in the bean metabolome that occur during its interaction with pathogenic (R. solani) and antagonistic (T. velutinum) fungi. In this work, 216 compounds were characterized by liquid chromatography mass spectrometry (LC-MS) analysis but only 36 were noted as significantly different in the interaction in comparison to control plants and they were tentatively characterized. These compounds were classified as: two amino acids, three peptides, one carbohydrate, one glycoside, one fatty acid, two lipids, 17 flavonoids, four phenols and four terpenes. This work is the first attempt to determine how the presence of T. velutinum and/or R. solani affect the defense response of bean plants using untargeted metabolomics analysis.

Antagonistic and plant-growth promoting novel Bacillus species from long-term organic farming soils from Sikkim, India.

Abstract: Three bacteria namely Bacillus luciferensis K2, Bacillus amyloliquefaciens K12 and Bacillus subtilis BioCWB possessing plant growth promotion and biocontrol potential against phytopathogens and rice leaf folder were identified from organic soils of Sikkim, India. The results revealed significant higher production of phytohormones IAA (97.1 μg mL−1) and GA3 (10.6 μg mL−1) was found in K2, whereas BioCWB had higher phosphate solubilization (570.0 μg mL−1) efficacy and also possessed nitrogen fixation ability (5.34 log copy number mL−1 culture). All these bacteria had higher antagonistic activities against phytopathogens viz. Rhizoctonia solani, Fusarium proliferatum, Athelia rolfsii and Colletotrichum gloeosporioides and also had higher larvicidal activity against rice leaf folder Cnaphalocrocis medinalis (Guenne) under in vitro conditions. Molecular insights into the antagonistic mechanisms of Bacillus strains deciphered the presence of several antimicrobial peptides (ericin, subtilin, surfactin, iturin, bacilysin, subtilosin, fengycin and bacillomycin), volatiles (dimethyl disulphide, methyl-Furan, acetic acid, Z-1,3-pentadiene and 3-hexyn-2-ol) and soluble metabolites (9-octadecenamide, E-15-heptadecenal, E-3-eicosene and 5-octadecene). Furthermore, liquid microbial inoculum prepared using the bacterial strains (K2, K12 and BioCWB) were evaluated under glass house (rice) and field condition (capsicum), which significantly enhanced plant growth in rice and yield in capsicum compared to control. The present study revealed the combination of Bacillus spp. (K2, K12 and BioCWB) can be used as bio-inoculants for improving agricultural production in Sikkim. Moreover, for the first time, we demonstrated plant growth promoting (PGP) traits, antifungal and insecticidal properties of B. luciferensis.

Activity of Plant Extracts/Essential Oils Against Three Plant Pathogenic Fungi and Mosquito Larvae: GC/MS Analysis of Bioactive Compounds

Abstract: Certain natural products extracted from different parts of medicinal and aromatic plants were examined for their antifungal activity against three plant pathogenic fungi, Fusarium oxysporum, Rhizoctonia solani, and Alternaria solani, and insecticidal activity against mosquito larvae (Culex pipiens). Acetone extract of Tectona grandis showed the highest antifungal activity against R. solani and A. solani with EC50 values of 118 and 294 μg/mL, respectively. The highest larvicidal activity was displayed by the essential oils of Ocimum basilicum and Eucalyptus gomphocephala with LC50 value of 22, and 30 mg/L, respectively. By gas chromatography–mass spectrometry (GC/MS) analysis 3-allylguaiacol (65.8%) and eugenol acetate (46.6%) were the main compounds in Syzygium aromaticum methanolic extract and essential oil, respectively. The main compound in T. grandis acetone extract was cyclohexylpentyl oxalate (8.7%); its water extract contained (E)-4,4-dimethyl-2-pentene (51.1%); E. gomphocephala branch oil contained p-cymene (28.8%); Euphorbia paralias leaf extract contained 1βH-romneine (26.3%); the seed extract contained α-linolenic acid, TMS (15.2%); Punica granatum extract contained furfural (32.1%); and O. basilicum essential oil contained estragole (65.9%). Thus, extracts from the tested plants can be used as natural biofungicides to manage diseases caused by F. oxysporum, R. solani, and A. solani. Additionally, these extracts show potential la rvicide activities against mosquito larvae.

Anastomosis Groups of Rhizoctonia solani associated with tomato foot rot in Pothohar Region of Pakistan

Abstract: Rhizoctonia solani Kuhn (teleomorph = Thanatephorus cucumeris (Frank) Donk) is one of the important soil-borne fungal pathogen, which infects tomato with typical symptoms of seedling damping-off and foot rot. During surveys (2014 and 2015 crop season) of nine tomato growing areas in Pothohar region of Pakistan, symptoms of foot rot were noted on approximately 33.4% of the plants observed at soil line level of the stem. Lesions on infected plant stems were irregular in shape, water-soaked, brown in colour manifesting sunken appearance. Fungal colonies isolated from stem portions of the diseased plants on malt extract agar medium were light grey to brown in colour with abundant mycelial growth and branched hyphae. A septum was always present in the branch of hyphae near the originating point with a slight constriction at the branch. No conidia or conidiophores were observed. All isolates were multinucleate when subjected to DAPI (4′,6-diamidino-2-phenylindole) stain. Based on morphological characteristics of fungal hyphae, isolates were identified as R. solani. Restriction analysis of PCR-amplified ribosomal DNA with four discriminant enzymes (MseI, AvaII, HincII, and MunI) and hyphal interactions with known tester strains confirmed these isolates belong to AG-3-PT (64.2%), AG-2-1 (14.2%), AG-2-2 (9.5%), AG-5 (7.1%) and AG-4-HGI (4.7%). AG-3-PT was widely distributed to major tomato growing areas while other groups were confined to distinct locations. Internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced which had 99–100% identity with the corresponding gene sequences of respective R. solani AGs. To confirm Koch’s postulates, four week old tomato plants were transplanted into 1.5 L plastic pots containing sterilized potting mixture i.e. sand: clay: farmyard manure, at the rate of 1:1:1. Soil inoculum containing 10 g of barley grains colonized with each isolate of R. solani for 14 days was mixed in the upper 2 cm layer of soil (Taheri and Tarighi, 2012). A set of uninoculated plants was used as a control. Ambient conditions were provided under the greenhouse. 21 days after inoculation, water-soaked greyish to brown lesions similar to the symptoms of the previous infection were observed on stem portions of all inoculated plants while control plants remained symptomless. Fungus re-isolated from infections was confirmed as R. solani by microscopic appearance of the hyphae. Present study is the first report of AG composition of R. solani infecting tomato in Pakistan which will be useful to breeding programs working on varietal evaluation.