Bean Seedlings Research Articles

Uptake and transport of antibiotic kasugamycin in castor bean (Ricinus communis L.) seedlings.

Kasugamycin (KSM), an aminoglycoside antibiotic, has been widely used for the management of plant diseases, especially for the control of rice blast in Asia. However, its uptake mechanism and transport in plants are still obscure. The castor bean (Ricinus communis L.) seeding, a model plant for phloem transport, was used to study the mechanism of uptake and transport of KSM. Results showed that cotyledon-applied KSM could transport into the phloem and distributed in root and shoot of plant. The temperature, concentration, and pH had significant effects on the uptake of KSM, indicating that the uptake of KSM was mediated by an active carrier system. Compared with the control, competitive inhibitors of sugar transporters D-glucose, D-chiro-inositol, and phloridzin inhibited 71.03%, 67.95%, and 61.73% uptake of KSM, respectively. Energy inhibitor dinitrophenol (DNP) and carbonyl cyanide chlorophenylhydrazone (CCCP) also affected the uptake of KSM, and the inhibition rates were 34.23% and 48.06%. All the results showed that the uptake of KSM was mediated by a sugar transporter, and it could transport from shoot to root in plants via the phloem. The study preliminary elucidated the plant–microbe interactions in the context of the transport of microbial secondary metabolites in plants. It has certain significance for scientific application of antibiotics and biological control of plant diseases and provides theoretical basis for the development of bidirectional transport pesticides.

First report of the hibiscus strain of citrus leprosis virus C2 infecting passionfruit (Passiflora edulis).

In Hawaii, passionfruit (Passiflora edulis; Passifloraceae) is grown primarily in residential properties and community gardens (CG). In 2019, passionfruit plants displaying chlorotic spots on young leaves, and green spots in senescing leaves were observed at two CG in Honolulu. Symptoms resembled those of passionfruit green spot virus (PfGSV) infection in Passiflora spp. (Ramos-González et al. 2020) and of the hibiscus strain of citrus leprosis virus C2 (CiLV-C2H) infection in hibiscus in Hawaii (Melzer et al. 2013). Both viruses belong to the genus Cilevirus, family Kitaviridae. Total RNA was extracted from two sample pools comprised of 40 symptomatic leaves collected from both the CG following a CTAB-based procedure (Li et al. 2008). To identify the virus associated with the P. edulis infection, reverse transcription (RT)-polymerase chain reaction (PCR) was performed using CiLV-C2 (Olmedo-Velarde et al. 2021) and PfGSV specific primers (Ramos-González et al. 2020). RT-PCR assay amplified the CiLV-C2 amplicon but failed to produce the PfGSV amplicon from infected leaves. Amplicon sequencing followed by a BLASTn search showed the nucleotide sequence had >99% identity with the CiLV-C2H-RNA1 (KC626783). A ribo-depleted RNA library created using the TruSeq Stranded Total RNA Library Prep kit (Illumina) underwent high throughput sequencing (HTS) on a NextSeq550 Illumina platform (2x75 cycles). The 6.5 million raw reads obtained were trimmed, filtered, and de novo assembled using Metaviral SPAdes v. 3.15.02 (Antipov et al. 2020). The resulting contigs were searched against an in-house database generated from GenBank virus and viroid sequences using BLASTn. This identified 12 and 3 contigs corresponding to CiLV-C2H and watermelon mosaic virus, respectively, with the latter being previously reported in passionfruit (Watanabe et al. 2016). RNA1 contigs covered 80.17% of the CiLV-C2H genome, whereas RNA2 contigs covered 94.5% with an average coverage depth of 31.660 and 57.121, respectively. To obtain the near complete genome of CiLV-C2H, gaps from the assembled HTS data were filled by overlapping RT-PCR followed by Sanger sequencing. RNA1 (8,536 nt, Acc. No. MW413437) and RNA2 (4,878 nt, MW413438) genome sequences shared 99.2% and 97.0% identity with CiLV-C2H-RNA1 (KC626783) and -RNA2 (KC626784). To further confirm the presence of CiLV-C2H in symptomatic P. edulis plants, 40 symptomatic leaf samples were individually tested by RT-PCR, and 30 samples were positive. Brevipalpus mites collected from CiLV-C2H-positive P. edulis leaves were transferred to common bean (Phaseolus vulgaris) seedlings (Garita et al. 2013). At 15-30 days post-transfer, RNA extracted from lesions observed in recipient plants tested positive for CiLV-C2H by RT-PCR. Total RNA from individual Brevipalpus mites was isolated, and cDNA was prepared to tentatively identify the mite species involved in CiLV-C2H transmission in passionfruit (Druciarek et al 2019, Olmedo-Velarde et al. 2021). CiLV-C2H was detected in individual mites, and the 28S ribosomal mite RNA sequence (MZ478051) shared 99-100% nucleotide identity with B. yothersi (MK293678 and MT812697), a vector of CiLV-C2 (Roy et al. 2013). CiLV-C2 currently has a host range limited to the families Malvaceae, Araceae, and Rutaceae (Roy et al. 2015). CiLV-C2H infects hibiscus alone and citrus in mixed infection with CiLV-C2 (Roy et al; 2018) which is responsible for causing citrus leprosis disease. Detection of CiLV-C2H in passionfruit expands the number of host families of CiLV-C2H.

Genome-Wide Transcriptomic Analysis of the Effects of Infection with the Hemibiotrophic Fungus Colletotrichum lindemuthianum on Common Bean.

Bean anthracnose caused by the hemibiotrophic fungus Colletotrichum lindemuthianum is one of the most important diseases of common bean (Phaseolus vulgaris) in the world. In the present study, the whole transcriptome of common bean infected with C. lindemuthianum during compatible and incompatible interactions was characterized at 48 and 72 hpi, corresponding to the biotrophy phase of the infection cycle. Our results highlight the prominent role of pathogenesis-related (PR) genes from the PR10/Bet vI family as well as a complex interplay of different plant hormone pathways including Ethylene, Salicylic acid (SA) and Jasmonic acid pathways. Gene Ontology enrichment analysis reveals that infected common bean seedlings responded by down-regulation of photosynthesis, ubiquitination-mediated proteolysis and cell wall modifications. In infected common bean, SA biosynthesis seems to be based on the PAL pathway instead of the ICS pathway, contrarily to what is described in Arabidopsis. Interestingly, ~30 NLR were up-regulated in both contexts. Overall, our results suggest that the difference between the compatible and incompatible reaction is more a question of timing and strength, than a massive difference in differentially expressed genes between these two contexts. Finally, we used RT-qPCR to validate the expression patterns of several genes, and the results showed an excellent agreement with deep sequencing.

Pathogenic variability of the fungus Colletotrichum lindemuthianum on dry bean in South Africa

Dry bean (Phaseolus vulgaris L) anthracnose is an economically important seed-borne fungal disease caused by the fungus Colletotrichum lindemuthianum. The pathogenic variability of C. lindemuthianum was evaluated in a glasshouse study. A total of 32 isolates were collected in three provinces, namely KwaZulu-Natal, Mpumalanga and North-West. The isolates were collected from different fields of dry bean at research stations and also from small-scale farmers’ fields. Inoculum developed from the different isolates was sprayed onto 12 CIAT differential dry bean cultivars that were used to identify pathogen races. The inoculation was carried out during the trifoliate developmental stage of the dry bean seedlings raised in pots 14 days post-sowing. Using the CIAT binomial system, eight pathogenic races of C. lindemuthianum were identified, namely, 3, 6, 7, 81, 83, 89, 263 and 323 out of the 32 isolates evaluated. Only pathogenic races 7, 81, 83 and 89 were found in the more humid locations of the province of KwaZulu-Natal. Races 7, 81 and 89 are internationally recognized and show characteristics reported of races in Brazil. Race 6 was identified in Mpumalanga and North west provinces and this was important as it has been reported in other Southern African countries. The races populations were distinct between locations as they infected both the Andean and the Meso-American bean landraces. The most important dry bean landraces were AB 136, G 2333, Kaboon, TU and PI 207262 as they showed complete resistance from the isolates. The study findings suggests that these six landraces can be successfully used to improve anthracnose resistance, especially G 2333 because of its horizontal resistance that can be used to improve the current cultivars used for the control of anthracnose in South Africa. Additionally, Cornell 49242 was one of the landraces of importance, as it showed glimpses of anthracnose that faded overtime under controlled suitable environmental conditions. Use of these landraces will ensure stability in the long-term control of dry bean anthracnose since the pathogen C. lindemuthianum is highly variable and widely distributed in South Africa. Key words: Anthracnose, Colletotrichum lindemuthianum, dry bean, disease, pathogenic races, seed, differential cultivars, resistance

Phytotoxicity assessment study of gold nanocluster on broad bean (Vicia Faba L.) seedling

ABSTRACT In this study, we investigated the phytotoxicity of gold nanoclusters (AuNCs) on seed germination capacity, physiological response to stress and uptake, and the transport of gold nanomaterials in broad beans. Although similar findings were observed for AuNCs on broad bean root tip cells between micronucleus assays and traditional phytotoxicity experiments, the former was more sensitive and rapid. At experimental concentrations of 0–200 mg/L, the toxicity performance of broad bean seedlings showed an overall positive correlation with the concentration of AuNCs. AuNCs posed a potential risk to the environment at a concentration of 20 mg/L. Moreover, studies on the uptake and transport of gold nanomaterials showed that the smaller the particles entering the bean, the higher the transport coefficient, while materials not entering the bean were mainly adsorbed on the root surface of the bean seedlings by competition with potassium ions.

Clue of zinc oxide and copper oxide nanoparticles in the remediation of cadmium toxicity in Phaseolus vulgaris L. via the modulation of antioxidant and redox systems.

The present study represents new evidence of the successful use of metal oxide nanoparticles in the remediation of heavy metals. Zinc oxide nanoparticles (ZnO NP) and copper oxide nanoparticles (CuO NP) were assessed to alleviate cadmium (Cd) toxicity in Phaseolus vulgaris L. seedlings and plants. Monitoring physiological and metabolic parameters allowed to elucidate Cd mechanism and process whereby it exerts phytotoxic effects on bean. The response of P. vulgaris seedlings is NP dose-dependent (10 mg/L, 50 mg/L, 100 mg/L, and 200 mg/L). Similarly, applied concentrations triggered a differential response of growing plants in terms of length and biomass. Our physiological data allowed to select 100 mg/L as the most appropriate concentration to apply, in order to avoid any risk of phytotoxicity. The regulatory mechanisms by which ZnO NP and CuO NP act are for the first time compared in the embryonic axes of bean seedlings under Cd stress. Both NP were able to reduce the hypergeneration of hydrogen peroxide (H2O2). They also acted via enhancing ROS scavenging enzymatic capacity, and activity of antioxidant enzymes CAT, APX, GPOX, GPX, and GR, and inhibited the activity of ROS producing enzymes such as GOX and NOX. Another mechanistic effect of NP consisted of the modulation of redox enzymes Trx, NTR, Fd, and FNR evolved in cellular homeostasis and maintaining reduced status in cells. Taken together, ZnO NP triggered more significant metabolic regulations allowing to mitigate the oxidative damage caused by Cd.

Hormesis and other non-monotonic growth responses in mung bean (Vigna radiata) seedlings treated with seaweed liquid extracts

Hormesis and other non-monotonic growth responses in mung bean (Vigna radiata) seedlings treated with seaweed liquid extracts

Mung Bean (Vigna radiata) Treated with Magnesium Nanoparticles and Its Impact on Soilborne Fusarium solani and Fusarium oxysporum in Clay Soil.

The nanotechnology revolution is developing daily all over the world. Soil-borne fungi cause a significant yield loss in mung beans. Our study was performed to identify the impact of different concentrations of MgO nanoparticles (MgONPs) and to assess the prevalence of Fusarium solani (F. solani) and Fusarium oxysporum (F. oxysporum) in mung bean plants under in vivo conditions and, subsequently, the remaining impacts on soil health. In vitro studies revealed that MgONPs could inhibit fungal growth. Mung bean plants treated with MgONPs showed a promotion in growth. The obtained MgONPs were applied to the roots of 14-day-old mung bean plants at a concentration of 100 µg/mL. The application of MgONPs at a concentration of 100 µg/mL caused an increase in mung bean seedlings. Compared to the control treated with water, plants exposed to MgONPs at 100 µg/mL showed improvements (p < 0.05) in shoot fresh weight (28.62%), shoot dry weight (85.18%), shoot length (45.83%), root fresh weight (38.88%), root dry weight (33.33%), root length (98.46%), and root nodule (70.75%). In the greenhouse, the severity of disease caused by F. solani decreased from approximately 44% to 25% and that by F. oxysporum from 39% to 11.4%, respectively. The results of this study confirm that the temporal growth of the soil microbial biomass was partially reduced or boosted following the nanoparticle drenching addition and/or plant infections at higher concentrations of 50 and 100 µg/mL while there was no significant decrease at the lowest concentration (25 µg/mL). The current research helps us to better understand how nanoparticles might be used to prevent a variety of fungal diseases in agricultural fields while avoiding the creation of environmental hazards to soil health.

Screening of Indanoyl-Type Compounds as Elicitors of Isoflavonoid Phytoalexins in Colombian Common Bean Cultivars.

Eleven indanoyl derivatives were synthesized and, along with methyl jasmonate, evaluated as isoflavonoid-phytoalexin elicitors in two cultivars of common bean (Phaseolus vulgaris L. cvs. ICA-Cerinza and Uribe Rosado, tolerant and susceptible to anthracnose, respectively). Indanoyl derivatives (an ester, two amides, and eight indanoyl-amino acid conjugates) were obtained from 1-oxo-indane-4-carboxylic acid. In general, the accumulation of isoflavonoid-type phytoalexins, such as isoflavones (genistein, daidzein, and 2′-hydroxygenistein), isoflavanones (dalbergioidin and kievitone), isoflavan (phaseollinisoflavan), coumestrol, and pterocarpans (phaseollidin and phaseollin), was dependent on the common bean cultivar, the post-induction time, and the elicitor structure. Isoflavones, dalbergioidin, and coumestrol reached their highest amounts during the first 48 to 72 h, whereas kievitone, phaseollinisoflavano, and the pterocarpans reached maximum levels between 72 and 96 h. The 1-oxo-indanoyl-L-isoleucine methyl ester elicited the highest levels of phytoalexins (similar to those elicited by the methyl jasmonate) and showed no significant phytotoxic effects on common bean seedlings. The indanoyl-type synthetic elicitor, 1-oxo-indanoyl-L-isoleucine methyl ester, may represent a promising agronomic alternative for disease control in common bean by enhancing the accumulation of antimicrobial isoflavonoid phytoalexins.

Folic Acid Confers Tolerance against Salt Stress-Induced Oxidative Damages in Snap Beans through Regulation Growth, Metabolites, Antioxidant Machinery and Gene Expression.

Although the effect of folic acid (FA) and its derivatives (folates) have been extensively studied in humans and animals, their effects are still unclear in most plant species, specifically under various abiotic stress conditions. Here, the impact of FA as a foliar application at 0, 0.1, and 0.2 mM was studied on snap bean seedlings grown under non-saline and salinity stress (50 mM NaCl) conditions. The results indicated that under salinity stress, FA-treated plants revealed a significant (p ≤ 0.05) increase in growth parameters (fresh and dry weight of shoot and root). A similar trend was observed in chlorophyll (Chl b), total chlorophyll, carotenoids, leaf relative water content (RWC), proline, free amino acids (FAA), soluble sugars, cell membrane stability index (CMSI), and K, Ca, and K/Na ratio compared to the untreated plants. In contrast, a significant decrease was observed in Na and salinity-induced oxidative damage as indicated by reduced H2O2 production (using biochemical and histochemical detection methods) and rate of lipid peroxidation (malondialdehyde; MDA). This enhancement was correlated by increasing the activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POX), and ascorbate peroxidase (APX). Gene expression analyses conducted using qRT-PCR demonstrated that genes coding for the Na+/H+ antiporter protein Salt Overly Sensitive 1 (SOS1), the tonoplast-localized Na+/H+ antiporter protein (NHX1), and the multifunctional osmotic protective protein (Osmotin) were significantly up-regulated in the FA-treated plants under both saline and non-saline treatments. Generally, treatment with 0.2 mM FA was more potent than 0.1 mM and can be recommended to improve snap bean tolerance to salinity stress.

Efficacy of a multi-dentate Schiff base and its vanadyl complex on various morphological and biochemical parameters of Vigna radiata L.

A N2O2 donor Schiff base polydentate ligand was synthesized by the condensation of benzidine and benzil in ethanolic medium. The formed ligand was condensed further with VOSO4.xH2O to get the corresponding vanadyl complex. Both the ligand and the complex were characterized by spectroscopic and elemental analyses. Mung bean (Vigna radiata L.) was selected as a plant material. Various morphological and biochemical parameters, e.g. leaf senescence assay, chlorophyll content, and different reactive oxygen species (ROS) were estimated and were compared to those with ammonium vanadate. Outcomes of the experiments revealed that the Schiff base complex has less toxic effects than ammonium vanadate on mung bean seedlings and provide better tolerance to vanadium toxicity. Though different stress marker and ROS accumulation were less and minimum pigment damage was noticed in the Schiff base complex-treated seedlings but the optimum positive impact largely depends on the dose. Beyond certain concentration, the complex may show inhibitory effects on the plants. Therefore, the present study revealed that heavy metal Schiff base complexes can be used as potential supplement to meet up micronutrient deficiency and at the same time such complexes can minimize the toxicity generated by application of different heavy metals.

Common bean seedlings show increased tolerance to cool temperatures when treated with progesterone, β-oestradiol, abscisic acid, and salicylic acid

Common bean seedlings show increased tolerance to cool temperatures when treated with progesterone, β-oestradiol, abscisic acid, and salicylic acid

Plant Growth Promoting Activity of Paenibacillus alvei WW001 and its antagonistic effects against Phytopathogenic Bacteria

A bacterium strain with nebular growth pattern was isolated from a rice field and was identified as Paenibacillus alvei WW001. The isolate exhibited several plant-growth promoting activities including solubilization of tri-calcium phosphate at 1,152.9 μg/ml after 6 days of cultivation and production of indole acetic acid (IAA) which reached the maximum concentration of 5.1 μg/ml after 4 days of cultivation in nitrogen free medium supplemented with L-tryptophan. In addition, high production of ammonia and siderophore was detected on day 7 of cultivation (1.7 μmol/ml and 60% siderophore units respectively). Gibberellic acid production from a dayold culture in LB broth was quantified to be 79.6 μg/ml. Strain WW001 also displayed an ACC deaminase activity, albeit at a low level. Its cell-free culture supernatant (CFCS) showed antimicrobial activity against bacterial phytopathogen; Pectobacterium carotovorum DoA 263, Xanthomonas campestris DoA 1869 and X. axonopodis at 40, 1280 and 1280 Arbitrary Unit (AU)/ml respectively. Tricine SDSPAGE analysis revealed a 3-kDa peptide associated with the observed inhibitory effect. Treating mung bean seedlings (n=30) with strain WW001 only or mixture of strain WW001 and X. campestris resulted in longer roots and higher total dry weights. Collectively, both in vitro and in vivo results attested that P. alvei WW001 is an efficient plant growth promoting rhizobacterium (PGPR) with a potent activity against bacterial phytopathogen.

Comparative transcriptome analysis of cold-tolerant and -sensitive asparagus bean under chilling stress and recovery.

BackgroundLow temperature is a type of abiotic stress that threatens the growth and yield of asparagus bean. However, the key genes and regulatory pathways involved in low temperature response in this legume are still poorly understood. Methodology. The present study analyzed the transcriptome of seedlings from two asparagus bean cultivars—Dubai bean and Ningjiang 3—using Illumina RNA sequencing (RNA-seq). Correlations between samples were determined by calculating Pearson correlation coefficients (PCC) and principal component analysis (PCA). Differentially expressed genes (DEGs) between two samples were identified using the DESeq package. Transcription factors (TF) prediction, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs were also performed.ResultsPhenotypes and physiological indices indicated that Ningjiang 3 seedlings tolerated cold better than Dubai bean seedlings, in contrast to adult stage. The transcriptome dynamics of the two cultivars were closely compared using Illumina RNA-seq following 0, 3, 12, and 24 h of cold stress at 5 °C and recovery for 3 h at 25 °C room temperature. Global gene expression patterns displayed relatively high correlation between the two cultivars (>0.88), decreasing to 0.79 and 0.81, respectively, at 12 and 24 h of recovery, consistent with the results of principal component analysis. The major transcription factor families identified from differentially expressed genes between the two cultivars included bHLH, NAC, C2H2, MYB, WRKY, and AP2/ERF. The representative GO enrichment terms were protein phosphorylation, photosynthesis, oxidation-reduction process, and cellular glucan metabolic process. Moreover, KEGG analysis of DEGs within each cultivar revealed 36 transcription factors enriched in Dubai bean and Ningjiang 3 seedlings under cold stress.ConclusionsThese results reveal new information that will improve our understanding of the molecular mechanisms underlying the cold stress response of asparagus bean and provide genetic resources for breeding cold-tolerant asparagus bean cultivars.

Attenuation of salt stress by lycopene on common bean seeds

Salinity is a major abiotic stress that adversely affects several physiological and biochemical aspects of plants. Antioxidants can be used as a potential remediation mechanism to promote plant resilience. Therefore, the objective of the present study was to evaluate increasing doses of the antioxidant lycopene on the germination and initial growth of common bean seedlings under conditions of salt stress. Seeds were treated with the following lycopene concentrations: 0.018; 0.036; 0.072; 0.144; and 0.288 g L-1 and two controls (negative and positive) and evaluated under two growth conditions (without and with salt stress) for physiological quality and pigment content. Data were analyzed by completely randomized design, in 2 x 7 factorial (two growth conditions, with paper towel moistened with water or salt solution x seven treatments, including five lycopene doses and two controls), in four replicates of 50 seeds by concentration. With the results of the analysis of variance, growth conditions (without and with salt stress) were compared by the Tukey test (5%), and the effects of lycopene doses were analyzed by polynomial regression. Lycopene promoted tolerance of bean seeds to salt stress and had a positive influence on the attenuation of salt harmful effects to the initial growth of seedlings, mainly at the doses of 0.072 g L-1 and 0.144 g L-1.

Integrated lipidomic and transcriptomic analysis reveals triacylglycerol accumulation in castor bean seedlings under heat stress

Heat stress is one of the most challenging environmental factors for plants, which have evolved various mechanisms to cope with it. However, the role of lipid remodeling caused by heat stress is not yet fully understood. Here, we integrated UPLC-QTOF/MS-based lipidomic and transcriptomic analyzes to uncover the molecular basis of lipid remodeling under heat stress in castor bean (Ricinus communis), an important non-edible oil crop. We detected 297 lipid compounds in castor bean seedlings, of which 54 displayed altered abundances under heat stress. In particular, polyunsaturated triacylglycerols (TAGs) (e.g., TAG54:6, TAG54:7, TAG54:8, and TAG54:9) and diacylglycerols (DAGs) (DAG36:6) significantly increased, while polyunsaturated monogalactosyldiacylglycerols (MGDGs) (MGDG34:3) markedly decreased. When heat stress was subsequently relieved, these lipid molecules recovered to their normal levels. We found that heat-induced TAGs primarily accumulate in the cytosol. Transcriptomic analysis indicated that polyunsaturated fatty acids (FAs) used for TAGs are not derived from de novo synthesis, but likely from the lipids remodeling via lipase activity, and are subsequently esterified into TAGs via diacylglycerol acyltransferase (DGAT). Our results suggest that TAGs may act as intermediates in lipid turnover and provide one mechanism by which plants respond to heat stress, broadening our understanding of how lipid remodeling functions in plant adaptation to heat stress.

First Report of Collar and Root Rot of Faba Bean Caused by Rhizoctonia solani AG-2-2 IIIB in Bangladesh.

Faba bean (Vicia faba L.) is an underutilized promising grain legume commercially grown in central and northern part of Bangladesh (Yasmin et al. 2020). In January 2021, faba bean plants exhibiting symptoms of collar and root rot and yellowing of leaves were observed in thirty plots of an experimental field at the Bangladesh Agricultural University (24.75° N, 90.50° E), Mymensingh, Bangladesh. Infected plants had dark brown to black lesions on the roots, extending above the collar region. An average disease incidence and severity was 7.16% and 6.91%, respectively. Eight diseased plants were collected from the field by uprooting one plant from each of eight randomly selected experimental plots and surface disinfected with sodium hypochlorite (0.2%) for 3 min followed by 1 min in ethanol (70%), and then rinsed three times with distilled water and dried on sterile paper towels. Collar and root pieces (5×5 mm) of symptomatic tissues were placed on Potato Dextrose Agar (PDA). Plates were incubated at 25°C for three days and isolates were purified from single-tip culture. The isolates produced brown colored mycelia often with brown sclerotia. Under microscope, fungal colonies exhibited right-angled branching with constriction at the base of hyphal branches and a septum near the originating point of hyphal branch consistent with the description of Rhizoctonia solani Kuhn (Sneh et al. 1991). The isolates grew at 35°C on PDA (5 mm/24). Molecular identification of the isolates BTRFB1 and BTRFB7 was determined by sequencing the rDNA internal transcribed spacer (ITS) region using primers ITS1 and ITS4 (White et al. 1990). A BLAST search showed that the sequences (GenBank Accession nos. MZ158299.1 and MZ158298.1) had 99.28% similarity with R. solani isolates Y1063 and SX-RSD1 (GenBank Accession nos. JX913811.1 and KC413984.1, respectively). Phylogenetic analysis revealed that the present isolates grouped with R. solani anastomosis group AG-2-2 IIIB. To confirm pathogenicity, both isolates were grown individually on sterile wheat kernels at 28°C for 6 days (D'aes et al. 2011). Faba bean seedlings were grown in plastic pots containing sterile potting mix (field soil/composted manure/sand 2:2:1 [v/v]). Two-week-old plants were inoculated by placing five infested wheat seeds adjacent to the roots. Control pots were inoculated with sterile wheat kernels using the same procedure. Plants were placed in a growth room with a 16 h/8 h light/dark photoperiod at 25 ± 2°C after inoculation. Fifteen days after inoculation, typical collar and root rot symptoms were developed on inoculated plants, similar to symptoms observed in the field. Control plants remained non-symptomatic. Finally, six isolates of R. solani were isolated from the symptomatic plants and identified by morphological and molecular analysis. Rhizoctonia solani is the causal agent of seed and root rot, hypocotyl canker, and seedling damping-off diseases of faba bean in many other countries (Rashid and Bernier 1993; Assunção et al. 2011). To our knowledge, this is the first confirmed report of Rhizoctonia solani causing collar and root rot of faba bean in Bangladesh. This finding will be helpful for the development of management strategies to control this disease and to expand the production of faba bean in Bangladesh.

Culturable Bacterial Endophytes Associated With Shrubs Growing Along the Draw-Down Zone of Lake Bogoria, Kenya: Assessment of Antifungal Potential Against Fusarium solani and Induction of Bean Root Rot Protection.

Vascular shrubs growing along the draw-down zones of saline lakes must develop adaptive mechanisms to cope with high salinity, erratic environmental conditions, and other biotic and abiotic stresses. Microbial endophytes from plants growing in these unique environments harbor diverse metabolic and genetic profiles that play an important role in plant growth, health, and survival under stressful conditions. A variety of bacterial endophytes have been isolated from salt tolerant plants but their potential applications in agriculture have not been fully explored. To further address this gap, the present study sought to isolate culturable bacterial endophytes from shrubs growing along the draw-down zone of Lake Bogoria, a saline alkaline lake, and examined their functional characteristics and potential in the biocontrol of the bean root rot pathogen, Fusarium solani. We collected shrubs growing within 5 m distance from the shoreline of Lake Bogoria and isolated 69 bacterial endophytes. The endophytic bacteria were affiliated to three different phyla (Firmicutes, Proteobacteria, and Actinobacteria) with a bias in the genera, Bacillus, and they showed no tissue or plant specificity. All selected isolates were positive for catalase enzyme grown in 1.5 M NaCl; three isolates (B23, B19, and B53) produced indole acetic acid (IAA) and only one isolate, B23 did not solubilize phosphate on Pikovskaya agar. Isolates, B19 and B53 exhibited more than 50% of mycelial inhibition in the dual culture assay and completely inhibited the germination of F. solani spores in co-culture assays while two isolates, B07 and B39 had delayed fungal spore germination after an overnight incubation. All isolates were able to establish endophytic association in the roots, stems, and leaves of been seedlings in both seed soaking and drenching methods. Colonization of bean seedlings by the bacterial endophytes, B19 and B53 resulted in the biocontrol of F. solani in planta, reduced disease severity and incidence, and significantly increased both root and shoot biomass compared to the control. Taxonomic identification using 16S rRNA revealed that the two isolates belong to Enterobacter hormaechei subsp., Xiangfangensis and Bacillus megaterium. Our results demonstrate the potential use of these two isolates in the biocontrol of the bean root rot pathogen, F. solani and plant growth promotion.

Acaricidal and Antioxidant Activities of Anise Oil (Pimpinella anisum) and the Oil’s Effect on Protease and Acetylcholinesterase in the Two-Spotted Spider Mite (Tetranychus urticae Koch)

The two-spotted spider mite, Tetranychus urticae, also known as the red spider, is one of the most harmful pests in agriculture and causes large losses of many crops. These mites have rapidly developed a resistance to many chemical pesticides in recent years. In this study, the essential oil of seeds of the anise plant (Pimpinella anisum) was extracted by hydrodistillation, and the chemical composition of the oil was analyzed. The antioxidant activity of the volatile oil was determined by the DPPH radical scavenging assay. The acaricidal activity of the anise oil, a natural acaricide, was evaluated for its ability to protect green bean plants from mite injury. The two-spotted spiders were spread on green bean seedlings for 1 week; then, different plants were sprayed with different concentrations of anise oil (10, 20, 30, or 40 µL/L). Our results revealed that anethole was the major component of anise oil, at 53.23%. The acaricidal effect of the various concentrations on T. urticae was recorded after 24, 48, and 72 h of treatment. Our findings suggest that anise oil showed significant acaricidal activity against T. urticae in a dose- and time-dependent manner. Anise oil at a concentration of 40 µL/L killed 96.0% of the red spiders after 72 h. Also, all concentrations of anise oil inhibited acetylcholinesterase, and the spiders’ protease activity declined when the plants were treated with 30 or 40 µL/L of anise oil. The concentrations of 10 and 20 µL/L did not significantly affect the protease activity of T. urticae mites. We can conclude that anise oil exhibited acaricidal activity against T. urticae and that this was highly correlated with the inhibition of acetylcholinesterase and protease activities in the mites.

First report of Fusarium oxysporum causing damping-off of tree bean (Parkia timoriana) seedlings in Northeastern India

Tree bean (Parkia timoriana), is an important multipurpose leguminous tropical deciduous tree species widely grown in the Northeastern states of India. The occurrence of the high incidence of damping-off (86.19%) disease was observed in tree bean nursery grown in Umiam, Meghalaya, a state in Northeastern India. Therefore, a systematic study was undertaken to record the symptoms and characterize the morphological features, the taxonomy of pathogen causing damping-off disease of P. timoriana and confirm it by pathogenicity assay. The infected seeds exhibited typical symptoms of covering with whitish mycelium and cotyledons were completely rotten in later stages of infection and emitted foul odour. Infected seedlings exhibited the symptoms of root rot followed by wilting, dried stem, and complete mortality of the seedlings. The pathogen isolated from the rotten seeds and wilted seedlings consistently showed the association of Fusarium oxysporum and its identity was confirmed based on morphological characteristics and sequences of ITS-rDNA and TEF genomic regions. Five representative isolates (TBSR 1 to 5) exhibited high similarity (>98%) to the known authentic gene sequence of F. oxysporum. The pathogenicity test produced similar to natural symptoms of wilt at 30 days after inoculation, confirming the etiological association of Fusarium oxysporum. To the best of our knowledge, this is the first to report on F. oxysporum causing damping-off disease of P. timoriana in India and worldwide.