Biocomputational Assessment of Natural Compounds as a Potent Inhibitor to Quorum Sensors in Ralstonia solanacearum.

Ralstonia solanacearum is among the most damaging bacterial phytopathogens with a wide number of hosts and a broad geographic distribution worldwide. The pathway of phenotype conversion (Phc) is operated by quorum-sensing signals and modulated through the (R)-methyl 3-hydroxypalmitate (3-OH PAME) in R. solanacearum. However, the molecular structures of the Phc pathway components are not yet established, and the structural consequences of 3-OH PAME on quorum sensing are not well studied. In this study, 3D structures of quorum-sensing proteins of the Phc pathway (PhcA and PhcR) were computationally modeled, followed by the virtual screening of the natural compounds library against the predicted active site residues of PhcA and PhcR proteins that could be employed in limiting signaling through 3-OH PAME. Two of the best scoring common ligands ZINC000014762512 and ZINC000011865192 for PhcA and PhcR were further analyzed utilizing orbital energies such as HOMO and LUMO, followed by molecular dynamics simulations of the complexes for 100 ns to determine the ligands binding stability. The findings indicate that ZINC000014762512 and ZINC000011865192 may be capable of inhibiting both PhcA and PhcR. We believe that, after further validation, these compounds may have the potential to disrupt bacterial quorum sensing and thus control this devastating phytopathogenic bacterial pathogen.

Evaluation of bioefficacy potential of entomopathogenic fungi against the whitefly (Bemisia tabaci Genn.) on cotton under polyhouse and field conditions.

The whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is becoming a serious problem on Bt cotton. It causes enormous crop loss through its direct feeding and as a vector of cotton leaf curl virus. Chemical-dependent management is harming the environment and increased insecticide resistance is often observed in the fields. Identification of most virulent strains of entomopathogenic fungi (EPF) is essential to serve as an important component of an IPM program for management of B. tabaci. Compared to B. tabaci adults, the nymphal stage is reported to be more susceptible to entomopathogens, and targeting nymphs also helps vector management. We evaluated the bioefficacy of EPF and chemical pesticides against nymphs of B. tabaci on Bt cotton under polyhouse and field conditions. The bioefficacy index (BI) was considered as a mechanism to select the most effective EPF strains for field evaluation. The highest nymphal mortality under polyhouse conditions was recorded for Metarhizium anisopliae NA-01299 (86.7%), Beauveria bassiana MT-4511 (85.1%), Cordyceps javanica IT-10498 (81.1%), IT-10499 (81%), and B. bassiana NA-0409 (78.2%) relative to other EPF strains, spiromesifen (69.6%), buprofezin (62.2%) and pyriproxyfen (52.7%) at 7-days-post-spray treatment (DAS). However, among all the EPF, the highest BI was recorded in C. javanica IT-10499 (77%), IT-10495 (75.4%), Fusarium verticillioides IT-10493 (74.6%), and B. bassiana MT-4511 (73.1%). The pooled data of two-year field trials (2017-18 & 2018-19) revealed that the highest nymphal mortality was recorded for MT-4511 (85%), IT-10499 (83.2%), and pyriproxyfen 10% EC (78.6%) at 7-DAS. The BI-based selection of EPF proved to be a useful predictor of field efficacy. A sequential spray of the selected EPF would be a vital approach for resilient and sustainable integrated management of the B. tabaci nymphal population under field conditions.

Dataset on double mutation in PGIP of Glycine max improves defense to PG of Sclerotinia sclerotiorum.

The cell wall of the Glycine max altered by the polygalacturonases (PGs) secreted by the fungus Sclerotinia sclerotiorum, causes disease and quality losses. In soybeans, a resistance protein called polygalacturonases-inhibiting proteins (PGIPs) binds to the PG to block fungal infection. The active site residues of PGIP3, VAL170 and GLN242 are mutated naturally by various amino acids in different types of PGIPs. Therefore, the mutation of VAL170 to GLY is ineffective but the GLN242 amino acid mutation by LYS significantly alters the structure and is crucial for interacting with the PG protein. Docking and Molecular Dynamics simulation provide a comprehensive evaluation of the interactions between gmPGIP and ssPG. By elucidating the structural basis of the interaction between gmPGIP and ssPG, this investigation lays a foundation for the development of targeted strategies in-order to enhance soybean resistance against Sclerotinia sclerotiorum. By leveraging this knowledge, researchers can potentially engineer soybean varieties with improved resistance to the fungus, thereby reducing disease incidence and improving crop yields.

Evaluation of the Bioefficacy and Insecticide Compatibility of Entomopathogens for Management of Whitefly (Hemiptera: Aleyrodidae) on Upland Cotton Under Laboratory and Polyhouse Conditions.

Entomopathogens (EPFs) are potential alternatives to chemical insecticides for managing Bemisia tabaci (Genn.), an invasive pest of the cotton crop. EPFs alone may not always provide enough insect pest control, but combining EPFs with pesticides, provided both components are compatible, can make an integrated pest management program considerably more effective. Hence, the bioefficacy of EPFs against whitefly, their compatibility with pesticides, and the factors responsible for determining compatibility were studied. The highest nymphal mortality was recorded with the Beauveria bassiana strains Bb-4511 (95.1%) and Bb-4565 (89.9%), and Metarhizium anisopliae Ma-1299 (86.7%) at 1 × 106 conidia ml-1. Lower LC50 values were observed for Cordyceps javanica Cj-089 and Bb-4511, 0.2 × 104 and 0.5 × 104 conidia ml-1, respectively. The toxicity index values in insecticide sensitivity assays ranged from 19.4 to 119.6% among all the EPFs. Comparatively, all the EPFs except Bb-4543 and Bb-4565 showed compatible to moderately toxic reactions to neonicotinoids and spinosyns. Organophosphates (ethion) and pyrethrins (bifenthrin) were toxic to very toxic to all the EPFs except Bb-4511, Fv-083, and Ma-1299. Cj-102 and Cj-089 were compatible with 50% of the average recommended dose of bifenthrin and ethion, and the average recommended dose for the field application of neonicotinoids and spinosyns. Principal component analysis showed that spore production and toxicity index values correlate with each other and are responsible for determining the EPF compatibility with insecticides. The EPF spore production and toxicity index are important factors for determining chemical compatibility. Compatible EPFs can be used individually or in combination as promising and compatible biological alternatives to insecticides in the management of whitefly in cotton.

Modulation of plant growth and antioxidative defense system through endophyte biopriming in cotton (Gossypium spp.) and non-host crops.

Seed biopriming is very promising in improving seed health by mitigating various biotic and abiotic stresses. In this study, the effect of biopriming with cotton endophytes on seed germination and other growth parameters in host and non-host crops like wheat, sorghum, cowpea and chick pea was examined. The endophytes were antagonistic to cotton pathogens Corynespora cassiicola and Fusarium solani under in vitro. Among the eight endophytes, CFR-1 and CEL-48 were highly efficient with inhibition rates of 66.16% and 64.24% respectively against C. cassiicola, whereas CFL-34 was efficient against F. solani with more than 50% inhibition. Seed biopriming enhanced seed germination in cotton and non-host crops whereas seed vigor index was highest in bio-primed cotton. Moreover, growth promotion parameters were also enhanced upon endophyte biopriming. Total sugar content ranged from 5.46 to 7.54 mg/g F.W in cotton and highest was found in CFL-34 treated wheat (8.64 mg/g FW). There was an increase of 10-30% soluble protein in bioprimed cotton over control. Interestingly, the antioxidant potential in all the bio-primed crops was improved with increased catalase and peroxidase activity. Specific activity of catalase ranged from 0.42 to 1.90 µmol/min/mg protein in cotton, while highest activity was reported in CEL-48 primed wheat. The findings of this investigation emphasizes seed biopriming with endophytes for sustainable plant health management.

An insight into molecular interaction of PGIP with PG for banana cultivar.

PolyGalacturonase Inhibiting Proteins (PGIPs) are leucine rich repeat pathogenesis-related (PR) cell wall proteins, which interact and inhibit the PolyGalacturonase (PG), an enzyme secreted by the pathogen to degrade pectin. Interaction of PGIP with PG limits the vulnerability of PG by the activation of host defense response against pathogenic attack. Erwinia is gram-negative soft rot bacteria responsible for rhizome rot disease in banana and many other crop plants. The interaction of PG with PGIP is one of the crucial steps for plant-pathogen interaction. To study the molecular mechanism of PR proteins, we employed molecular modelling, protein-protein docking and molecular dynamics simulations of banana PGIP (bPGIP) with Erwinia carotovora PG (ecPG). Further, insilico site-directed mutagenesis was performed in Phaseolus vulgaris PGIP (pvPGIP2) to elucidate the interaction with ecPG. Docking and simulation studies divulge that binding of bPGIP and PvPGIP2 with active site residues of EcPG induces structural changes and thereby inhibit the enzyme. This study provides a unique insight into PG-PGIP interaction, which may help in the development of bacterial soft-rot resistant banana cultivars.

Rapid detection of Tobacco streak virus (TSV) in cotton (Gossypium hirsutum) based on Reverse Transcription Loop Mediated Isothermal Amplification (RT-LAMP).

Tobacco Streak Virus (TSV) belongs to the genus Ilarvirus of the family Bromoviridae an emerging pathogen posing threat to the crop species worldwide. Identification of symptoms due to TSV infection by visual observation of plants often results in misdiagnosis as symptoms produced by this virus can match with those reflecting physiological and nutritional disorders affecting cotton. Development of diagnostic tools with rapidity will have immense role to play in detection and management of the emerging virus. The protocol for rapid diagnosis of TSV infected samples by using Reverse Transcription-Loop Mediated Isothermal Amplification (RT-LAMP) was optimised and this is the first report of its use for diagnosis of TSV on cotton and Soybean. The colorimetric detection for diagnostic simplicity of amplified RT-LAMP product by using different dyes lead to enhanced applicability of this technique. The RT-LAMP diagnostic tool can be utilized not only for laboratory research but also for quarantine and field diagnosis of this important emerging pathogen affecting cotton.

Compatibility of entomopathogenic fungi with insecticides and their efficacy for IPM of Bemisia tabaci in cotton.

Bemisia tabaci, a vector of cotton leaf curl virus disease, is among the most devastating pests causing huge economic losses due to reduced cotton yield and quality. The excessive use of chemical pesticides causes insecticide resistance. Entomopathogenic fungi (EPFs) have a role as mycoinsecticides. The combined use of these insecticides is a promising pest-control option to minimize adverse chemical effects. Thus, we have evaluated 10 EPFs under polyhouse conditions for their virulence against whitefly nymphs and their compatibility with chemical and botanical insecticides. The highest overall biological efficacy index was recorded with Ij-102, followed by Bb-4511, and Ij-089. An in vitro compatibility study was conducted to evaluate the effect of botanical and chemical pesticides on mycelial growth and spore production using the poisoned food technique. The effect of pesticides on the reduction of mycelial growth and conidial production ranged from -169 to 94.1% and -25.6 to 87.6%, respectively. However, Ij-089, Ij-102, Ma-1299, and Bb-4511 were found to be the most compatible with the chemical and botanicals evaluated. Comparatively, spiromesifen, diafenthiuron, buprofezin, pyriproxyfen, and flonicamid were more compatible with EPFs at half doses, as compared to the other chemical pesticides, namely imidacloprid, fipronil, profenophos, and triazophos. These results might provide the basis for future work and indicate that applications of EPFs showing the best virulence and compatibility have the maximum likelihood for the management of B. tabaci in the field in an integrated pest management system.