Disease Incidence Of Seedlings Research Articles

Effect of provenance on seed-borne Mycoflora, germination and seedling disease incidence on Khaya Senegalensis seeds in Ghana

Seed provenance is an important component determining seed quality in forest restorations. Collection of seeds from diseased-free agro-ecological zones for reforestation programs in Ghana is key. To contribute to knowledge, a research was conducted to assess the effect of provenance on seed-borne mycoflora prevalence, germination and initial seedling disease incidence of Khaya Senegalensis seeds in three agro-ecological zones of Ghana. Four seed-borne fungi in three genera namely Aspergillus niger, A. flavus, Colletotrichum sp. and Penicillium sp. were isolated from Khaya Senegalensis seeds collected from the three different provenances namely Deciduous forest, Transitional and Guinea Savannah zones. Total seed-borne mycoflora infections on Khaya Senegalensis varied significantly (p<0.05) between provenances. Transitional and Deciduous zones recorded equal highest incidence of 100.0% total seed-borne mycoflora infections whilst seeds from the Guinea Savannah zone recorded the least total seed-borne mycoflora infection of 58.3%. Significant differences (p<0.05) were observed between provenances with respect to seed germination. Seeds from Guinea Savannah zone recorded the highest (73.7%) whilst the least percentage (16.3%) germination was observed in seeds sourced from the Deciduous forest zone. There were no significant difference (p<0.05) for percent seedling disease incidence amongst provenances. However, the highest (20.0 %) seedling disease incidence was recorded in seeds sourced from Transitional zone whilst the least (12.5%) recorded in seeds from the Deciduous Forest zone. Provenance has significant effect on seed-borne mycoflora prevalence and seed germination. It is recommended that seeds be collected from provenances with low incidence of seed-borne mycoflora to enhance high seed germination for reforestation programs.

Biocontrol of Bacterial Fruit Blotch by Seed Priming with Bacillus Amyloliquefaciens and Pseudomonas Fluorescens

Bacterial fruit blotch (BFB), caused by the seed-transmitted pathogen Acidovorax citrulli, poses a serious threat to cucurbitaceous crops worldwide. In this study, two biocontrol bacteria strains, Bacillus amyloliquefaciens (Ba- 2) and Pseudomonas fluorescens (2P24), with significant antagonistic activity against A. citrulli were and applied by seed priming to control BFB seed transmission. Artificially infested watermelon and melon seeds were treated with the biocontrol strains by liquid or solid matrix seed priming. The seed bio-priming effects were evaluated under greenhouse conditions. Germination percentages were improved by seed priming treatments for melon, and seedling uniformity was higher for seeds primed with Ba-2 than for seeds from the other treatments for watermelon. Seedling disease incidence of untreated seeds were 6.5% for watermelon and 16.0% for melon, and water-priming resulted in similar disease progress curves as the untreated control. Seed priming with Ba-2 and 2P24 significantly reduced seedling BFB incidence for both watermelon and melon. Evaluation with naturally infested watermelon seeds primed with biocontrol strains indicated that 2P24 seed priming was more effective than Ba-2 ( P < 0.05) and 2P24 solid matrix priming, reducing the seedling disease incidence to 1.3%. Seed bio-priming has potential as an effective and eco-friendly approach for suppressing bacterial fruit blotch seed-to-seedling transmission.

Pathogen-Mediated Assembly of Plant-Beneficial Bacteria to Alleviate Fusarium Wilt in Pseudostellaria heterophylla.

Fusarium wilt (FW) is a primary replant disease that affects Pseudostellaria heterophylla (Taizishen) and is caused by Fusarium oxysporum, which occurs widely in China under the continuous monocropping regime. However, the ternary interactions among the soil microbiota, P. heterophylla, and F. oxysporum remain unknown. We investigated the potential interaction relationship by which the pathogen-mediated P. heterophylla regulates the soil and the tuberous root microbiota via high-throughput sequencing. Plant–pathogen interaction assays were conducted to measure the arrival of F. oxysporum and Pseudomonas poae at the tuberous root via qPCR and subsequent seedling disease incidence. A growth assay was used to determine the effect of the tuberous root crude exudate inoculated with the pathogen on P. poae. We observed that pathogen-mediated P. heterophylla altered the diversity and the composition of the microbial communities in its rhizosphere soil and tuberous root. Beneficial microbe P. poae and pathogen F. oxysporum were significantly enriched in rhizosphere soil and within the tuberous root in the FW group with high severity. Correlation analysis showed that, accompanied with FW incidence, P. poae co-occurred with F. oxysporum. The aqueous extract of P. heterophylla tuberous root infected by F. oxysporum substantially promoted the growth of P. poae isolates (H1-3-A7, H2-3-B7, H4-3-C1, and N3-3-C4). These results indicated that the extracts from the tuberous root of P. heterophylla inoculated with F. oxysporum might attract P. poae and promote its growth. Furthermore, the colonization assay found that the gene copies of sucD in the P. poae and F. oxysporum treatment (up to 6.57 × 1010) group was significantly higher than those in the P. poae treatment group (3.29 × 1010), and a pathogen-induced attraction assay found that the relative copies of sucD of P. poae in the F. oxysporum treatment were significantly higher than in the H2O treatment. These results showed that F. oxysporum promoted the colonization of P. poae on the tuberous root via F. oxysporum mediation. In addition, the colonization assay found that the disease severity index in the P. poae and F. oxysporum treatment group was significantly lower than that in the F. oxysporum treatment group, and a pathogen-induced attraction assay found that the disease severity index in the F. oxysporum treatment group was significantly higher than that in the H2O treatment group. Together, these results suggest that pathogen-mediated P. heterophylla promoted and assembled plant-beneficial microbes against plant disease. Therefore, deciphering the beneficial associations between pathogen-mediated P. heterophylla and microbes can provide novel insights into the implementation and design of disease management strategies.

Effects of Probiotic and Organic Manures for Soil Amendments On Seedling Survivability and Leaf Chlorophyll for Crop Improvement In Wheat (Triticum Aestivum L.)

Under this study a total of nine treatments were considered for soil amendments where organic manures, chemical fertilizer and probiotics were used to evaluate the efficiency on growth and yield of wheat. On the basis of seedling disease incidence and chlorophyll presence parameters data were recorded on seedling infection at 14 days, seedling blight at 21 days, and chlorophyll content at 70 days after sowing. In this study the same experiments were conducted up to three years (2016-2019) and data were compiled and analyzed. It was observed that the disease prevalence attributes significantly decreased in T5 (Trichoderma harzianum + vermicompost + green manuring) than other treatment combinations and control (T0). Noteworthy results were found on seedling health, application of probiotic and organic manures which significantly influenced the less infection of wheat. Besides this, chlorophyll content of wheat leaf and plant number with effective tiller enhanced largely under T8 (chemical fertilizer) than T4 (poultry manure + vermicompost + green manuring) and control (T0). The main advantage of this research is to evaluate efficiency for growing healthy wheat plant which reflects on plant growth and yield and ultimately helps for food security. J. Bio-Sci. 29(2): 61-70, 2021 (December)

Endophytic Trichoderma Species Isolated from Persea americana and Cinnamomum verum Roots Reduce Symptoms Caused by Phytophthora cinnamomi in Avocado.

Avocado root rot caused by the oomycete Phytophthora cinnamomi is a severe disease that affects avocado production in Mexico and worldwide. The use of biological control agents such as Trichoderma species isolated from places where the disease is always present, represents an efficient alternative to reduce losses. Thus, the objective of this research was to evaluate the biocontrol ability of 10 endophytic Trichoderma spp. strains against P. cinnamomi tested both in vitro and in the greenhouse. The endophytic Trichoderma spp. were recovered from Persea americana and Cinnamomum verum roots, isolated and purified on potato–dextrose–agar medium. Ten strains were identified by phylogenetic reconstruction of the internal transcribed spacer region of rDNA sequences as T. asperellum (T-AS1, T-AS2, T-AS6, and T-AS7), T. harzianum (T-H3, T-H4, and T-H5), T. hamatum (T-A12), T. koningiopsis (T-K8 and T-K11), and P. cinnamomi (CPO-PCU). In vitro dual-culture assay, the percentage of inhibition of radial growth (PIRG) between Trichoderma spp. and P. cinnamomi strains was measured according to the Bell’s scale. PIRG results indicated that T-AS2 reached the highest value of 78.32%, and T-H5 reached the lowest value of 38.66%. In the greenhouse, the infection was evaluated according to the percentage of disease incidence. Plants with the lowest incidence of dead by avocado root rot were those whose seedlings were inoculated with T-AS2 and T-AS7, resulting in only 5% death by root rot caused by P. cinnamomi. The disease incidence of seedlings with wilt symptoms and death decreased more than 50% in the presence of Trichoderma spp. Relying on the results, we conclude that T. asperellum and T. harzianum contribute to the biocontrol of soil-borne pathogenic oomycete P. cinnamomi.

Serratia marcescens: a key pathogen caused ginger rhizomes soft rot disease

Ginger is an important horticultural crop with high economic and nutritional value. However, it is prone to pathogenic bacterial infection that negatively affects growth, post-harvest quality, and reduced economic profits. The study of pathogenic bacteria associated with ginger disease through its productive life cycle is extremely valuable. In this study, we isolated a key pathogen Serratia marcescens from diseased ginger rhizomes. Koch’s postulates helped verify that S. marcescens provoked disease symptoms in ginger rhizomes and seedlings. Antioxidant enzyme activities of the host were markedly increased following S. marcescens infection rhizomes. Disease incidence of seedlings was 87.3% ± 3.05, and the disease severity index was 27.1 ± 1.2 after 15 days of root filling. Further, we verified that the isolated bacterium could infect rat peripheral nerve cells (RSC96), resulting cell lysis and death. All in all, we isolated a key pathogenic bacteria S. marcescens from rot rhizomes and analyzed its pathogenic features in ginger rhizomes and seedlings and its latent ability to infect mammalian cells. This study provides new information critical to managing ginger diseases caused by bacteria with a cross-kingdom infective cycle.

Ecofriendly Management of Seedling Diseases of Chickpea (Cicer arietinum)

The experiment was carried out in the field of Plant Pathology Department, Bangladesh Agricultural University, Mymensingh, Bangladesh to determine the effect of BARI-biofertilizer and Integrated Pest Management (IPM) biopesticide for controlling foot and root rot diseases of chickpea. It was observed that both BARI-Biofertilizer and IPM biopesticide resulted significantly lower disease incidence of seedlings of the test pulse over the control. Soil treatment with BARI-Biofertilizer resulted the lowest disease incidence of chickpea var. Hyprosola, Binasola-2, Binasola-3 and Binasola-4 at 20 DAS (Days after sowing) that displayed reduction of disease incidence up to 83.77%, 54.48%, 70.76% and 71.45% respectively over control. While at 28 DAS, showedup to 82.82%, 71.92%, 84.72% and 68.39%, respectively, reduction of disease incidence over control. At 35 DAS, exhibited up to 79.91%, 73.18%, 81.32% and 73.44%, respectively, reduction of disease incidence over control. BARI-biofertilizer and IPM biopesticide increased fresh weight of plant, number of nodules per plant and fresh weight of nodules per plant.

Control of Ginseng Damping-Off Disease Using Chitinolytic Bacterial Mixtures

An effective bioformulation of mixtures of chitin-degrading bacteria has been used successfully to control plant diseases and nematodes. In this study, the bioformulation approach was assessed to control dampingoff disease of ginseng. In pot experiments with soils infested with dapming-off pathogens of ginseng, rootdrenchings of Chrobacterium sp. C-61, Lysobacterium enzymogenes C-3, and mixture of two bacterial strains grown in chitin minimal medium were signficantly increased emergence of seeds and reduced dampingoff disease incidence of seedlings. Efficacy of the bioformulated product depended on the dose and timing of application. In two-year-old ginseng field, the high control efficacies were achieved by soil drenching of two times with an undiluted product or three times with a 10-fold diluted product. In a To-jik nursery (self soil nursery), biocontrol efficacy of the undiluted product against damping-off disease were similar to that of a seed dressing with fungicide, Tolclofos-methyl WP. These results suggest that the bioformulated product containing Chromobacterium sp. C-61 and L. enzymogenes C-3 could be an effective approach to control of ginseng damping-off disease.

A seed-recruited microbiome protects developing seedlings from disease by altering homing responses of Pythium aphanidermatum zoospores

We investigated potential mechanisms by which a seed microbiome recruited from vermicomposted dairy manure alters Pythium aphanidermatum zoospore mediated pathogenesis in cucumber. Bioassays were conducted to measure arrival of zoospores at the seed surface via qPCR and subsequent seedling disease incidence. Seed exudates were collected at relevant time points for use in zoospore microscopy assays. Metabolomic analysis was used to characterize seed exudates. Microbes recruited by the germinating seed from a disease suppressive substrate within 8 hours of sowing prevented zoospore arrival at the seed surface, modified seed exudates and reduced disease incidence. In vitro exposure to microbially modified seed exudates altered zoospore homing responses and reduced both encystment and germination compared to control exudates. Combining modified and control exudates failed to restore zoospore attraction to levels observed with control exudates. Observed zoosporolytic activity of the modified exudates was unique to the ethyl acetate fraction and metabolomic analysis revealed several putative zoosporolytic compounds present at higher relative abundance when compared to control exudates. The observed disease suppression was likely due to the production of a specific zoosporolytic compound or set of compounds in the spermosphere by one or more members of the seed-recruited vermicompost microbiome.

Cotton seed borne disease in Golestan Province in Northern Iran

Abstract. In order to effect of seed mycroflora to incidence of seedling diseases and verticillium wilt, five thousands of cotton seed were collected from five categories (nucleus, super elite, elite, maternal and certified seed) of Sahel cultivar. Seed were delinted with sulfuric acid and treated by sodium hypochlorite 0.5%.Coat and embryo of seeds separated and placed on Potato Dexterous Agar and Alcol Agar medium and incubated at 18 – 24 0c . After 5 – 15 days fungi that grew on were isolated and diagnosed. Sand (less than 2mm) were collected on sea coast and sterilized for 30 minutes at 30 0c for three times and transfer on flower pot. Fuzzy and delinted seeds and embryo (each 400 number) planted inside them and placed at 17 – 25 0c on green house. Percent of seedling diseases and seed rot after 15 days and vertcillium wilt after 60 days were counted. The results showed that on 63% of coat of seed,43% of embryo that cultured on PDA, fungi were grew on. Frequency of species, Rhizoctonia solani, Aspergillus flavus, Alternaria macrospora &A.alternata and Fusarium spp. , on coat seeds were 13.3,0,25 andv21.4 and on embryo of seeds were 0,4,32.14 and 33.3 respectively. Percent of healthy seedling, diseased seedling and seed rot that planted on sterilized sand in delinted seeds were 75.5, 3.76 and 12, in fuzzy seeds 67.25, 18.25 and 14.5 and in embryo 74.75, 2.75 and 20.5 respectively. Aspergillus flavus (6.6%), Alternaria macrospora &A.alternata (66.6%) and Fusarium spp.(26.6%) were isolated and diagnosed on diseased seedling and rotted seed . Verticillium dahliae the casual agent of wilt have not on fungi that isolated and symptom of wilt was not found on plant that planted on flower pot after 60 days.

Evaluation of transgenic cotton varieties and a glyphosate application on seedling disease incidence

Evaluation of transgenic cotton varieties and a glyphosate application on seedling disease incidence

Effect of Seed Cleaning, Washing and Seed Treatment on Seedling Disease Incidence and Yield of Rice

Effect of Seed Cleaning, Washing and Seed Treatment on Seedling Disease Incidence and Yield of Rice