Index Of Plant Diseases Research Articles

Rhizosphere microbial community assembly as influenced by reductive soil disinfestation to resist successive cropping obstacle.

Reductive soil disinfestation (RSD), which involves creating anaerobic conditions and incorporating large amounts of organic materials into the soil, has been identified as a reliable strategy for reducing soilborne diseases in successive cropping systems. However, limited research exists on the connections between soil microorganism composition and plant diseases under various types of organic material applications. This study aimed to evaluate the effects of distinct RSD strategies (control without soil amendment; RSD with 1500 kg ha-1 molasses powder; RSD with 3000 kg ha-1 molasses powder; RSD with 3000 kg ha-1 molasses powder and 37.5-41.3 kg ha-1 microbial agent) on the plant disease index, bacterial community composition and network structure in rhizosphere soil. RSD treatments significantly reduced the occurrence of black shank disease in tobacco and increased soil bacterial diversity. High amounts of molasses powder in RSD treatments further enhanced disease inhibition and reduced fungal abundance and Shannon index. RSD also increased the relative abundance of bacterial phylum Firmicutes and fungal phylum Ascomycota, while decreasing the relative abundance of bacterial phyla Chloroflexi and Acidobacteriota and fungal phylum Basidiomycota in rhizosphere soil. A multiple regression model identified bacterial positive cohesion as the primary factor influencing the plant disease index, with a greater impact than bacterial negative cohesion and community stability. The competition among beneficial bacteria for creating a healthy rhizosphere environment is likely a key factor in the success of RSD in reducing plant disease risk. RSD, especially with higher rates of molasses powder, is a viable strategy for controlling black shank disease in tobacco and promoting soil health by fostering beneficial microbial communities. This study provides guidelines for soil management and plant disease prevention. © 2024 Society of Chemical Industry.

Effect of Magnetic Field and UV-C Radiation on Postharvest Fruit Properties

This review focuses on the recent information on the effect of different types of magnetic fields (MFs) and ultraviolet radiation (UV-C) on the processes that may finally affect fruit quality and its storage potential. Firstly, the biological effect of MFs on every plant’s growth and development level is described. The magnetic field interacts with a plant’s metabolism and changes the permeability of membranes affecting cells’ homeostasis. It also could affect early seedling development, stimulating enzyme activity and protein synthesis, and later on nutrient and water uptake of adult plants. In some cases, it makes plants more resilient, increasing their tolerance to environmental stresses. Also, MF treatment could lower the disease index of plants, thus improving the internal and external fruit quality indices. The second part of this review focuses on interesting perspectives of using UV-C radiation to reduce postharvest fruit diseases, but also to delay fruit ripening and senescence. The application of UV-C light to combat postharvest infections is associated with two mechanisms of action, such as direct elimination of microorganisms located on the fruit surface and indirect triggering of the plant’s defense reaction. Moreover, the use of hormetic doses of UV-C can additionally increase the nutritional properties of fresh fruit, lead to the accumulation of desired phytochemicals such as polyphenols, for example, to increase anthocyanin or resveratrol content, or elevate antioxidant activity.

Core species impact plant health by enhancing soil microbial cooperation and network complexity during community coalescence

Soil microbial communities mix and interact, a widespread phenomenon known as community coalescence. However, in the context of different coalescence degrees, the effects and potential applicability of soil mixing on plant disease resistance have not been studied. Here, we mixed soils from two habitats (healthy and diseased soils) at different mixing ratios for watermelon planting. Rhizosphere soils were collected for amplicon sequencing to study the effects of different degrees of bacterial community coalescence on plant growth and disease resistance, as well as on the characteristics, network complexity and stability of rhizosphere microbial communities. Combined with network and cohesion analyses, we found that mixing in more healthy soil reduced the plant disease index and increased biomass by improving the stability and complexity of the network; positive cohesion, reflecting degree of cooperation, was also negatively correlated with the plant disease index. The rhizosphere from healthy soils enriched the core taxa, Nitrospirillum and Singulisphaera. These core taxa were significantly associated with disease suppression and important for regulating the positive cohesion and modularity of the networks. Overall, these findings revealed that the soil bacterial community coalescence enhanced the stability and complexity of the rhizobacterial network, simultaneously core taxa enhanced microbial potential cooperation and network complexity, ultimately enhancing plant health and biomass. Our results provide insights into the understanding of microbial community coalescence as a potentially effective mechanism for improving plant microbial community function and suggest promising new tools for improving plant fitness via mixing soil microbiota.

Plant resistance to tomato yellow leaf curl virus is enhanced by Bacillus amyloliquefaciens Ba13 through modulation of RNA interference.

Tomato yellow leaf curl virus (TYLCV), which is a typical member of the genus Begomovirus, causes severe crop yield losses worldwide. RNA interference (RNAi) is an important antiviral defense mechanism in plants, but whether plant beneficial microbes used as biocontrol agents would modulate RNAi in defense against TYLCV remains unclear. Here, we employed whole-transcriptome, bisulfite, and small RNA sequencing to decipher the possible role of Bacillus amyloliquefaciens Ba13 as a bacterial biocontrol agent against TYLCV in RNAi modulation. Potted tomato plants were exposed to whiteflies for natural viral infection 14 days after bacterial inoculation. Compared with non-inoculated controls, the abundance of TYLCV gene in the leaves of inoculated plants decreased by 70.1% at 28 days post-infection, which mirrored the pattern observed for plant disease index. The expression of the ARGONAUTE family genes (e.g., AGO3, AGO4, AGO5, and AGO7) involved in antiviral defense markedly increased by 2.44-6.73-fold following bacterial inoculation. The methylation level at CpG site 228 (in the open reading frame region of the RNA interference suppressing gene AV2) and site 461 (in the open reading frame regions of AV1 and AV2) was 183.1 and 63.0% higher in inoculated plants than in non-inoculated controls, respectively. The abundances of 10 small interfering RNAs matched to the TYLCV genome were all reduced in inoculated plants, accompanied by enhancement of photosystem and auxin response pathways. The results indicate that the application of Ba. amyloliquefaciens Ba13 enhances plant resistance to TYLCV through RNAi modulation by upregulating RNAi-related gene expression and enhancing viral genome methylation.

Self-assembled thiophanate-methyl/star polycation complex prevents plant cell-wall penetration and fungal carbon utilization during cotton infection by Verticillium dahliae

No effective fungicides are available for the management of Verticillium dahliae, which causes vascular wilt disease. In this study, a star polycation (SPc)-based nanodelivery system was used for the first time to develop a thiophanate-methyl (TM) nanoagent for the management of V. dahliae. SPc spontaneously assembled with TM through hydrogen bonding and Van der Waals forces to decrease the particle size of TM from 834 to 86 nm. Compared to TM alone, the SPc-loaded TM further reduced the colony diameter of V. dahliae to 1.12 and 0.64 cm, and the spore number to 1.13 × 108 and 0.72 × 108 cfu/mL at the concentrations of 3.77 and 4.71 mg/L, respectively. The TM nanoagents disturbed the expression of various crucial genes in V. dahliae, and contributed to preventing plant cell-wall degradation and carbon utilization by V. dahliae, which mainly impaired the infective interaction between pathogens and plants. TM nanoagents remarkably decreased the plant disease index and the fungal biomass in the root compared to TM alone, and its control efficacy was the best (61.20 %) among the various formulations tested in the field. Furthermore, SPc showed negligible acute toxicity toward cotton seeds. To the best of our knowledge, this study is the first to design a self-assembled nanofungicide that efficiently inhibits V. dahliae growth and protects cotton from the destructive Verticillium wilt.

Variability in Alternaria lini causing leaf blight disease of linseed (Linum usitatissimum L.)

Alternaria blight is an important disease of linseed that hampers its productivity and oil content. The pathogen is geneticallydiverse showing variability in respect of cultural, morphological and pathogenic characters. Variability in seventeen isolates of Alternaria lini was carried out. Studies on cultural variability showed considerable variation among the isolates. The colony diameter varied from 46.67- 71.67 mm after 96 hrs. of incubation and most of the isolates recorded medium growth rate (50-64mm). The isolates Alt-6,Alt-7 Alt-12 showed fast growth habit (>65mm). The colony colour varied from grayish white, grey, dark olive green to grayish black. Sporulation in most of the isolates were late and concentric ring was present only in four isolates (Alt 3, Alt 8, Alt 13, Alt 14) while zonation was completely absent in other isolates. Morphologically different isolates of A. lini revealed variation with respect to mycelium width, size, shape, colour and septation of conidia. Mycelial width of most of the isolates having moderate to long width. Conidial length ranged from 24.87-33.68 mm similarly breadth of conidia ranged from7.54-10.67 mm. Transverse septation were more than longitudinal septation. Variation in beak size ranged from 3.5-6.4 mm while colour of conidia varied from brown to dark brown colour and most of the isolates exhibited obclavate, oval to obclavate shaped conidia while one isolate appeared as oval shaped. Studies on pathogenic variations revealed that the variation observed in accordance with the latent period, lesion size, lesion shape and plant disease index. The latent period of A. lini isolates varied from4.75 to 6.25 days with shortest (4.75 days) latent period recorded by isolates Alt-3 and Alt-11 and longest latent period of 6.25 days was observed in isolates Alt-6, Alt-14, Alt-16. The size of lesion varied from 2.25 to 4.75 mm and maximum lesions size (4.75 mm) was observed in isolate Alt-4 whereas minimum lesion size (2.25 mm) was observed in isolate Alt-5. The lesion produced after inoculation were elongated, oval and irregular in shape. The average number of lesions ranged from 2.75 to 4.00 with maximum number (4.00) of lesion recorded in isolate Alt-13. Plant disease index revealed that Meera and Nagarkot were more severe/virulent compare to Divya and Priyam in all the isolates.

Infection by Endophytic Epichloë sibirica Was Associated with Activation of Defense Hormone Signal Transduction Pathways and Enhanced Pathogen Resistance in the Grass Achnatherum sibiricum.

Epichloë endophytes can improve the resistance of host grasses to pathogenic fungi, but the underlying mechanisms remain largely unknown. Here, we used phytohormone quantifications, gene expression analysis, and pathogenicity experiments to investigate the effect of Epichloë sibirica on the resistance of Achnatherum sibiricum to Curvularia lunata pathogens. Comparison of gene expression patterns between endophyte-infected and endophyte-free leaves revealed that endophyte infection was associated with significant induction of 1,758 and 765 differentially expressed genes in the host before and after pathogen inoculation, respectively. Functional analysis of the differentially expressed genes suggested that endophyte infection could activate the constitutive resistance of the host by increasing photosynthesis, enhancing the ability to scavenge reactive oxygen species, and actively regulating the expression of genes with function related to disease resistance. We found that endophyte infection was associated with induction of the expression of genes involved in the biosynthesis pathways of jasmonic acid, ethylene, and pipecolic acid and amplified the defense response of the jasmonic acid/ethylene co-regulated EIN/ERF1 transduction pathway and Pip-mediated TGA transduction pathway. Phytohormone quantifications showed that endophyte infection was associated with significant accumulation of jasmonic acid, ethylene, and pipecolic acid after pathogen inoculation. Exogenous phytohormone treatments confirmed that the disease index of plants was negatively related to both jasmonic acid and ethylene concentrations. Our results demonstrate that endophyte infection can not only improve the constitutive resistance of the host to phytopathogens before pathogen inoculation but also be associated with enhanced systemic resistance of the host to necrotrophs after C. lunata inoculation.

English

Citrus is known as a major fruit due to its high nutritional value and adaptability in tropical and sub-tropical regions. Among diseases, citrus dieback is one of the most threatening diseases in which overall plant growth is reduced. Major causes are Colletotrichum gloeosporioides and citrus nematode (Tylenchulus semipenetrans) with 15-35% losses all over the world. Plant material was established adopting sanitary measures in earthen pots (12-inch diameter). Fresh culture of C. gloeosporioides and T. semipenetrans was prepared for the inoculation by following the standard procedures. In the first set, rootstocks were inoculated with 200mL of water having spore suspension of C. gloeosporioides while in in the second set, inoculation of T. semipenetrans was done by using 45 mL of water suspension having 2000 freshly hatched juveniles per pot, while at the rate of 1 × 107 spores/mL per plant. In the third set, the interaction of C. gloeosporioides and T. semipenetrans was studied by inoculating selected citrus rootstocks by both pathogens. After four months of inoculation, data were recorded on plant disease index (PDI) along with plant growth parameters (root weight, shoot weight, shoot weight, shoot length and number of leaves). Trifoliate orange and cox mandarin hybrid showed resistance against the development of T. semipenetrans while rough lemon, C-35 Citrange and sour orange were found susceptible. There was a significant difference in plant growth parameters between inoculated and healthy plants. Root weight and shoot weight decreased by 8.98g and 11.53g, while root length and shoot length decreased by 7.29cm and 13.5cm respectively as compared to control treatments in most susceptible rootstocks. Per cent Branch Infection (PBI) and per cent Disease Index (PDI) were maximum (71.52, 37) per cent on rough lemon respectively. Results regarding combined inoculation of C. gloeosporioides and T. semipenetrans showed that there was a significant difference in plant growth parameters between inoculated and healthy plants. In rough lemon, Root weight and shoot weight decreased by 13.86 and 20.57g respectively in diseased and healthy plants. Root length and shoot length decreased by 8.37 and 20.04cm respectively as compared to control treatments in most susceptible rootstocks. Overall results depicted that inoculation of both pathogens reduced plant growth more severely as compared to their individual application.

Identification of new resistant sources against downy mildew disease from a selected set of cucumber germplasm and its wild relatives

This study was undertaken to identify new sources of resistance against downy mildew of cucumber caused by Pseudoperonospora cubensis [(Berk. and Cart.) Rostow]. Pot experiments were conducted with 16 accessions each of Cucumis sativus and C. hardwickii during the years 2017 and 2018 using 12 isolates of P. cubensis representing different agroclimatic zones of India. The accession, IC331627 from Dehradun, Uttarakhand showed plant disease index (PDI) ranging from 5.55-20.35 per cent with an average PDI of 11.56 and 11.87 per cent during the years, 2017 and 2018, respectively. Hence, IC331627 was identified to be resistant against the five isolates of P. cubesis (Pc12, Pc17, Pc19, Pc21 and Pc24) and moderately resistant against one isolate (Pc22). This resistant accession C. hardwickii (IC331627) could be utilized to develop mapping population to map genomic regions conferring the resistance to downy mildew in cucumber.

Predicting Virulence of Fusarium Oxysporum f. sp. Cubense Based on the Production of Mycotoxin Using a Linear Regression Model.

Fusarium wilt caused by Fusarium oxysporum f.sp. cubense (Foc) is one of the most destructive diseases for banana. For their risk assessment and hazard characterization, it is vital to quickly determine the virulence of Foc isolates. However, this usually takes weeks or months using banana plant assays, which demands a better approach to speed up the process with reliable results. Foc produces various mycotoxins, such as fusaric acid (FSA), beauvericin (BEA), and enniatins (ENs) to facilitate their infection. In this study, we developed a linear regression model to predict Foc virulence using the production levels of the three mycotoxins. We collected data of 40 Foc isolates from 20 vegetative compatibility groups (VCGs), including their mycotoxin profiles (LC-MS) and their plant disease index (PDI) values on Pisang Awak plantlets in greenhouse. A linear regression model was trained from the collected data using FSA, BEA and ENs as predictor variables and PDI values as the response variable. Linearity test statistics showed this model meets all linearity assumptions. We used all data to predict PDI with high fitness of the model (coefficient of determination (R2 = 0.906) and adjust coefficient (R2adj = 0.898)) indicating a strong predictive power of the model. In summary, we developed a linear regression model useful for the prediction of Foc virulence on banana plants from the quantification of mycotoxins in Foc strains, which will facilitate quick determination of virulence in newly isolated Foc emerging Fusarium wilt of banana epidemics threatening banana plantations worldwide.

Dual inoculation of alfalfa (Medicago sativa L.) with Funnelliformis mosseae and Sinorhizobium medicae can reduce Fusarium wilt.

This study was designed to evaluate the biocontrol of the arbuscular mycorrhizal fungus (AMF) Funnelliformis mosseae and the rhizobium Sinorhizobium medicae on alfalfa (Medicago sativa) wilt caused by Fusarium oxysporum, a severe soil-borne fungal pathogen. The effects of co-inoculation of F. mosseae and S. medicae on alfalfa growth, nitrogen, phosphorus uptake and wilt caused by F. oxysporum were tested. Plant defence-related chemicals were measured to reveal the biochemical mechanism by which alfalfa responds to pathogen infection and how it is regulated by AMF and rhizobium. Pathogen infection caused typical yellowing of alfalfa leaflets and significantly reduced plant AMF colonization. AMF or rhizobium alone and the co-inoculation reduced the plant disease index by 83·2, 48·4 and 81·8% respectively. Inoculation with AMF or rhizobium alone increased the dry weight of alfalfa by more than 13 and 3 times respectively; it also increased plant chlorophyll content by 65·6 and 16·6% respectively. Co-inoculation of AMF and rhizobium induced the plant to accumulate more disease-related antioxidant enzymes, plant hydrolase and plant hormones, such as superoxide dismutase, β-1,3-glucanase, chitinase, and phenylalanine ammonialyase, abscisic acid, ethylene and H2 O2 , under pathogen stress. Co-inoculation with F. mosseae and S. medicae offered complementarily improved alfalfa nutrient uptake and growth, which increased plant health. The co-inoculation of AMF and rhizobium regulated plant physiological and biochemical processes and induced plants to produce defence-related compounds, thus decreasing the severity of disease. The simultaneous application of F. mosseae and S. medicae is a potential biocontrol strategy to increase the systemic defence responses of alfalfa to Fusarium wilt. This research showed that complex plant-pathogen interactions are affected by rhizobium and AMF, providing insight into plant-microbiome interactions in the rhizosphere as well as the application of the microbiome in agriculture production.

Growth-promotion and disease control effects on chili and eggplant by arbuscular mycorrhizal fungi and plant symbiotic actinomycetes

Arbuscular mycorrhizal fungi (AMF) or plant symbiotic actinomycetes (PSA) play an important role in stimulating plant growth, antagonizing pathogens, tolerating stress, and controlling plant disease. However, whether there is a synergistic effect between AMF and PSA in promoting plant growth and controlling disease is worth exploring. The aim of this study was to evaluate the effects of AMF and PSA on growth-promotion and controlling disease on Solanaceae vegetables and to obtain effective AMF+PSA combinations. Under greenhouse pot conditions, chili (Capsicum annu-um, cultivar: Yangjiaojiao) and eggplant (Solanum melongena, cultivar: Heiguanchangqie) were inoculated with or without AMF Funneliformis mosseae (Fm), Glomus versiforme (Gv), PSA Streptomyces globosus H6-1, Streptomyces rochei S2-2, Streptomyces coralus D11-4 or/and pathogenic fungi Botrytis cinerea. There were a total of 48 treatments. The growth, disease and root symbiont development of plants were determined. The results showed that Fm and PSA could promote each other's colonization, while Gv and PSA inhibited each other. Compared with the control, AMF, PSA and AMF+PSA improved the photosynthetic performance, root activity, and growth of chili and eggplant. Under the condition of inoculation with pathogenic fungi, AMF and/or PSA treatment significantly increased growth and reduced the disease index of plants, with the effects of PSA being greater than that of AMF. Fm+H6-1 combination had the best effect on the growth-promotion and controlling disease of chili plants, with the controlling effect on gray mold reaching 69.1%. Fm+ D11-4 had the best effect on the growth promotion and controlling disease of eggplant, the controlling effect of which on gray mold reached 75.5%. Fm+H6-1 andFm+D11-4 were efficient combinations of chili and eggplant for promoting growth and controlling disease under the conditions of this experiment. Further tests in field are needed.

Magnetic field regulates plant functions, growth and enhances tolerance against environmental stresses.

Global climatic fluctuations and the increasing population have been responsible for the decline in the crop productivity. The chemical fertilizers, pesticides, and suitable genetic resources are commonly used for improving the crop yield. Magnetic field (MF) therapy for plants and animals has been found to be an effective and emerging tool to control diseases and increase tolerance against the adverse environment. Very limited studies have been attempted to determine the role of MF on plant tolerance against various stress conditions. This review aims to highlight the mitigating effect of MF on plants against abiotic and biotic stresses. MF interacts with seeds and plants and accelerates metabolism, which leads to an improved germination. The primary and secondary metabolites, enzyme activities, uptake of nutrient and water are reprogrammed to stimulate the plant growth and yield under favorable conditions. During adverse conditions of abiotic stress such as drought, salt, heavy metal contamination in soil, MF mitigates the stress effects by increasing antioxidants and reducing oxidative stress in plants. The stunted plant growth under different light and temperature conditions can be overcome by the exposure to MF. An MF treatment lowers the disease index of plants due to the modulation of calcium signaling, and proline and polyamines pathways. This review explores the basic and recent information about the impact of MF on plant survival against the adverse environment and emphasizes that thorough research is required to elucidate the mechanism of its interaction to protect the plants from biotic and abiotic stresses.

Incidence of Plant Viral Disease Symptoms and Their Transmission Agents in Dutsin-Ma Metropolis

This work explores the incidence of plant viral disease symptoms as well as their transmission agents in Dutsin-Ma Local Government Area Katsina State, Nigeria. The studied diseased plants were identified while diseases were based on visual inspection using characteristic symptoms. Organisms associated with such symptoms were collected by handpicking, shacking/beating and tissue teasing methods. Identification was done using a standard voucher. Incidence of plants with viral symptoms was determined by plant disease index method. Chi square analysis was used to ascertain significant differences (P≥ 0.05) of plants showing viral symptoms. Results shows that plants with viral symptoms included Amaranthus sp. (Amaranthus), Vigna unguiculata (cowpea), Zea mays (maize), Abelmoschus esculentus (okra), Carica papaya (pawpaw) and Capsicum sp (pepper). Studies also reveal Myzus persicae (aphids), Frankinella occidentalis (thrips), Bemisa tabaci (whitefly), Peregrinus maydis (leafhoppers) and Pseudococcidae (mealy bugs) as organisms associated with diseased plants with viral symptoms. Disease index showed Amaranthus spp. 63%, Vigna unguiculata 84%, Zea mays 73%, Abelmoschus esculentus, Carica papaya and Capsicum spp. 100%. Incidence rate varied significantly (P≥ 0.05) in the various locations surveyed. Further studies need to be carried out to identify the individual viruses.

Field efficacy of different combinations of Trichoderma harzianum, Pseudomonas fluorescens, and arbuscular mycorrhiza fungus against the major diseases of tomato in Uttarakhand (India)

Tomato is one of the major cash crops in the Golapar area of district Nainital in Uttarakhand (India), where farmers are facing the problem of diseases in tomato cultivation. In the present investigation, a survey of tomato fields in the Golapar area of Haldwani block was conducted. The survey revealed the occurrence of late blight, early blight, stem rot, and wilt diseases causing an average loss of 80% to tomato. To counter the above diseases, Trichoderma harzianum (Th43), Pseudomonas fluorescens (Pf173), Jas mycorrhiza (AMF), and the fungicide (Mancozeb) in different combinations applyed through soil application (SA), seedling treatment (ST), and foliar spray (FA) were evaluated for growth promotion and disease control in tomato at experimental and farmers’ fields. The results of the study revealed that in experimental field, the maximum plant height (43.67 cm), highest number of branches (7.33) per plant, highest weight of fruit (47 g), highest number of fruits (39) per plant, minimum plant mortality (4% at 30 DAT and 3.2% at 30–60 DAT), minimum plant disease index (6.85), maximum total yield (256.00 q/ha), and marketable yield (246.67 q/ha) were observed in Th+Pf+JM (SA) + Th+Pf (ST) + Mancozeb (FS). At farmer’s field, minimum plant mortality (7.31%) at 30 days after transplanting (DAT) (5.73%) in 30–60 DAT, minimum plant disease index (11.47), and maximum yield 249.91 q/ha were observed in Th+Pf+JM (SA) + Th+Pf (ST) + Mancozeb (FS) combination. So, it can be concluded that among all the treatments, integrated treatment comprising of soil application of T. harzianum, P. fluorescens, Jas mycorrhiza (AMF) + seedling treatment with T. harzianum and P. fluorescens + three foliar sprays of Mancozeb was found very effective in reducing the plant mortality, promoting the plant growth, and increasing the yield at experimental field as well as at farmers’ fields.

Efficacy and cost study of green fungicide formulated from crude beta-glucosidase

Current agricultural management strategies to control the soil-borne pathogen Macrophomina phaseolina (Tassi) Goid, which causes charcoal rot disease, are insufficiently efficacious. We hypothesized that a natural antagonist of M. phaseolina, Trichoderma harzianum Rifai, could be used to develop a greener fungicide formulation to combat the disease. T. harzianum produces an extracellular β-glucosidase that explicitly hydrolyzes the amorphic β-1, 3-glucan filling material of the chitin cell wall in M. phaseolina during hyperparasitism. Herein, we describe a highly efficient β-glucosidase isolated from T. harzianum T12 as a safer bioactive component for reducing the plant disease index in soybean plants grown in soil inoculated with M. phaseolina. A Box–Behnken design was used to investigate the effects of metal ions, surfactants, enzyme concentration and irrigation in maximizing the efficacy of the enzyme to achieve the lowest PDI under a greenhouse setting. Under optimum conditions (Zn2+, 10 mM; Tween 80, 2% [w/v]; enzyme concentration, 15 mg/L; irrigation, 2 times/week), a minimum plant disease index of 4.32% was obtained (R2 = 0.9676). The bioenzyme-based fungicide was more efficient in lowering the plant disease index as compared with conventional methods using natural antagonists or a chemical fungicide. Our formulation yielded the lowest plant disease index (4.14%; P < 0.05) as compared with the antagonist T. harzianum (26.13%) and the fungicide Carbendazim (32.45%). This formulation was also substantially less expensive, costing US$34/acre as compared with Carbendazim at US$240/acre of soybean. This formulation is eco-friendlier and combines the practicality of an on-demand in situ spraying for rapid control of M. phaseolina infestation.

Growth, Fruit Yield and Disease Index of Carica papaya L. Inoculated with Pseudomonas straita and Inorganic Fertilizers

Experiment was conducted to study the effects of Pseudomonas straita and chemical fertilizers on growth, fruit yield and leaf mosaic virus in Carica papaya var. Sinta F1. The experiment comprised four treatments namely Farmers practices (T0- NP (Nitrogen: Phophorus) 100:50+10 kg FYM (Farm Yard Manure)/plant/year), Phosphorus Solubilizing Bacteria (T1- Pseudomonas straita @20 g culture /plant/year), Recommended fertilizer dose (T2- NPK 300:300:300+FYM 10 kg/plant/year), T3- Pseudomonas straita + NPK (300:300:300NPK+FYM 10 kg + P. straita 20 g /plant/year) in seven replications. The planting density was 2500 ha-1 (2 m × 2 m). The treatment effects found significant (p<0.05) for plant height, leaf number, leaf length, fruit weight, fruit volume and fruit yield while, nonsignificant for trunk girth, inter nodal length and pulp thickness. The treatment T3 plants occurred growth and fruit yield maximum followed with T2. Pseudomonas straita (T1) alone gave poorest result but its combination with NPK (T3) rendered highest number of fruit (48 fruit /plant) with an average weight of 675 g. The plant with T2 showed 18.18% higher leaves, 36.84% higher fruit weight and 41.03% higher yield compared to T0. Trends of Plant Disease Index (PDI) was declining by 50.36% with T1 followed with T3 (27.88%) and T2 (13.40%) compared T0. The treatment effects were positively correlated with plant height (r2=0.78), leaf number (r2=0.81), fruit yield (r2=0.97) and recorded negative for PDI (Plant Disease Index) (r2=0.30).

Induction of a wheat β-1,3-glucanase gene during the defense response toBipolaris sorokiniana

Bipolaris sorokiniana causes spot blotch, an important disease of wheat in Asia and America. To understand the host response to challenge by B. sorokiniana, we calculated the plant disease index (PDI) of twelve popular wheat (Triticum aestivum L.) genotypes and examined the expression levels of PR protein genes and wax synthesizing genes on an inoculation time-course using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Gene expression was studied in a resistant (R) and a highly susceptible (HS) genotype selected from a PDI experiment under glasshouse conditions. A gene (β-1,3-glucanase II) was induced at 24 h post inoculation and to higher levels in the resistant genotype Chiriya-3 (PDI = 1.3) than in the highly susceptible genotype Agra Local (PDI = 40.1). Densitometry analysis showed that expression of an Actin gene was the same at all stages of inoculation due to its constitutive expression in both the resistant and susceptible genotypes, while a 7-fold increase in expressi...

Ｆｕｓａｒｉｕｍ ｏｘｙｓｐｏｒｕｍによるスイートピー株枯病（新称）

A new disease was observed in sweet pea (Lathyrus odoratus L.) growing in greenhouses in Miyazaki Prefecture, Japan, in 2004. A Fusarium sp. that was highly pathogenic to sweet pea was isolated from the bases of sweet pea. On the basis of morphological tests performed using synthetic low-nutrient agar (SNA) and potato dextrose agar (PDA) cultures, the isolate was identified as Fusarium oxysporum. Further, the analysis of partial nucleotide sequences of the mitochondrial small subunit (mtSSU) rDNA and β-tubulin gene of the isolate confirmed the isolate to be F. oxysporum. This disease has not been reported in Japan till date. In foreign countries, F. oxysporum f. sp. vasinfectum can be seen as a pathogen causing sweet pea wilt in the “Index of Plant Diseases in the United States”. However, the details of the disease remain unknown. Therefore, we propose the following common name for this disease: fusarium wilt of sweet pea (“sweet pea kabugare-byo” in Japanese). The isolate were also strongly pathogenic to common bean (Phaseolus vulgaris). The level of sensitivity to the pathogen varies depending on the cultivar of sweet pea.

Evaluation of Daphne Germplasm for Resistance to Daphne Sudden Death Syndrome Caused by the Soil-borne Pathogen Thielaviopsis basicola

Many daphne cultivars are susceptible to fungal root pathogens and require frequent fungicide applications during production. To identify taxon differences to disease susceptibility, we evaluated 32 Daphne species and cultivars for resistance to the soil-borne pathogen, Thielaviopsis basicola (Berk. and Broome) Ferr., by both in vitro- and in vivo-based methods. Disease-free plant roots were inoculated with the pathogen through topical application of a spore suspension and observed weekly for disease development/progression. Significant variation for disease severity among the taxa evaluated was determined using a plant disease index. Plant reactions ranged from highly resistant, e.g., D. tangutica and D. retusa, to highly susceptible, e.g., D. cneorum. In addition, a high correlation was found between the in vitro and in vivo techniques for the seven selected species, indicating that they are comparable. However, the in vitro assay provided results in significantly less time than the in vivo assay.