An In Vitro Study of The Spore Densities Effect of Trichoderma spp. as Biocontrol Agent for Fusarium Wilt in Cayenne Pepper (Capsicum sp.)

Root disease controlling has been a challenge in increasing plant productivity. The soil-borne pathogens become the main concern which mostly infects the root surface. One of the most common soil-borne pathogens is Fusarium oxysporum (Fo). Cayenne pepper (Capsicum sp.) is one of the most abundant commodities and contributes significantly to the economy. This plant is also susceptible to Fusarium wilt infection. The use of endophytic fungi as biocontrol agents is an alternative against soil-borne pathogens, one of which is Trichoderma spp. fungi. This study aims to determine the effectiveness of various spore densities of Trichoderma spp. against the pathogen Fo. The research was conducted through an in vitro study by antagonistic testing between spore suspensions of Trichoderma spp. (103, 105, and 107 spores/mL) with Fo. The results showed the density of 107 spores/mL gave the highest percentage of inhibition (54.59%) compared to spore density of 103 (35.27%) and 105 spores/mL (44.44%). The spore density of 107 spores/mL gave a significant difference in response to the density of other spores according to the BNT test at a significance level of 5% and was able to inhibit the growth of Fo more than 50%. The results of this study are expected to be a reference for the formulation of Trichoderma spp. which is ideal for controlling Fo pathogens in the fields.

Mycorrhizal Status of Natural Stands of Pterocarpus erinaceus Poir. (Fabaceae) in Sudanian and Guinean Zones of West Africa

Background and Aims: The sylviculture of Pterocarpus erinaceus is still in its infancy due to lack of information on its biology. The aim of this study is to investigate its mycorrhizal status in order to better address its sylviculture. Place and Duration of Study: The study was performed on the field from May 2019 to December 2020 and data were analyzed at the laboratory from January to March 2021. Methodology: The frequency and intensity of mycorrhization were determined under a microscope after staining with trypan blue of fine roots collected at a depth of 20 cm under adult plants at 5 sites, 3 in the Guinean zone and 2 in the Sudanian zone in Togo. The spore density was obtained on soil samples taken at the same depth under the same trees. Results: Results indicate, without significant differences (P value = 0.166) among sites, and show that P. erinaceus is frequently mycorrhized (88% to 94%). However, there were significant differences (P value = 0.001) in spore densities between sites located in the Sudanian zone (16.53 ± 1.25 and 10.66 ± 0.71 spores per gram of soil – SPGS – respectively for the Fazao-Malfakassa and Oti-Kéran-Mandouri) and those located in the Guinean zone (4.54 ± 0.3, 2.93 ± 0.43 and 3.76 ± 1.01 SPGS respectively at Abdoulaye, Hahomegbe and Togodo). There are significant differences between mycorrhization intensities Togodo which has a mycorhization intensity of 33.52 ± 2.54 and other sites. The redundancy analysis carried out by taking into account substrates’ chemical characteristics shows that spore density remains low when phosphorus and nitrogen are important in the rhizosphere whereas the intensity of mycorhizations is low when PHKCl is high. Conclusion: This study provided evidence of mycorrhizal symbiosis in Pterocarpus erinaceus whether in the Sudanian or Guinean zone. Chemical quality of the growing substrate has an influence on parameters of mychorization. Further studies should therefore allow an assessment of the degree of dependence of this species with respect to the possible benefits associated with this symbiosis.

Dynamics of arbuscular mycorrhizal fungi in relation to root colonization, spore density, and soil properties among different spreading stages of the exotic plant threeflower beggarweed (Desmodium triflorum) in a Zoysia tenuifolia lawn

Weed invasion is a prevailing problem in modestly managed lawns. Less attention has been given to the exploration of the role of arbuscular mycorrhizal fungi (AMF) under different invasion pressures from lawn weeds. We conducted a four-season investigation into a Zoysia tenuifolia Willd. ex Thiele (native turfgrass)–threeflower beggarweed [Desmodium triflorum (L.) DC.] (invasive weed) co-occurring lawn. The root mycorrhizal colonizations of the two plants, the soil AM fungal communities and the spore densities under five different coverage levels of D. triflorum were investigated. Desmodium triflorum showed significantly higher root hyphal and vesicular colonizations than those of Z. tenuifolia, while the root colonizations of both species varied significantly among seasons. The increased coverage of D. triflorum resulted in the following effects: (1) the spore density initially correlated with mycorrhizal colonizations of Z. tenuifolia but gradually correlated with those of D. triflorum. (2) Correlations among soil properties, spore densities, and mycorrhizal colonizations were more pronounced in the higher coverage levels. (3) Soil AMF community compositions and relative abundances of AMF operational taxonomic units changed markedly in response to the increased invasion pressure. The results provide strong evidence that D. triflorum possessed a more intense AMF infection than Z. tenuifolia, thus giving rise to the altered host contributions to sporulation, soil AMF communities, relations of soil properties, spore densities, and root colonizations of the two plants, all of which are pivotal for the successful invasion of D. triflorum in lawns.

Spore Density and Arbuscular Mycorrhizal Colonization in Sunflower Grown in Campo Verde (Brazil)

The objective of this study was to evaluate the number of spores and the mycorrhizal root colonization in a Cerrado soil (Red-Yellow Latosol) cultivated with different sunflower genotypes. The sampling of the rhizospheric soil was performed at three growth stages: Sowing, flowering, and harvest. The experimental design was in completely randomized blocks with four replications. Three different sunflower hybrids were tested in the 2009 and 2010 cropping seasons. The collected data comprised the total number of spores per 50 g of soil at the three growth stages, along with arbuscular mycorrhizal fungi (AMF) colonization. It was verified that the mycorrhizal colonization was not influenced by the sunflower genotypes, and the mean spore densities were equivalent to 4.94 and 4.64 g soil-1 in 2009 and 2010, respectively. More importantly, AMF colonization was enhanced by lower soil phosphorus levels. The maximum spore production was obtained at flowering, with mycorrhizal colonization rates ranging from 21 to 28% and from 28 to 48% in 2009 and 2010, respectively. The number of spores also varied from 153 to 342 and from 147 to 320 in 2009 and 2010, respectively.

Endophytic Fungal Root Colonization of Eragrostis tef in Eroded Croplands of the Ethiopian Highlands is Limited by Low Spore Density and Fertilisation

Eragrostis tef (teff) is a (sub-)tropical cereal crop and a staple food in Eastern Africa. As soil erosion has become increasingly worse in the Ethiopian highlands, we test the hypotheses that 1) eroded soils possess low arbuscular mycorrhizal fungi (AMF) spore densities, 2) teff growth is limited by low endophytic fungal root colonization rates and 3) colonization rates and spore densities are additionally reduced by fertilization. A pot experiment was set up to study the effect of cropland soil inoculation using pristine fungal communities (from adjacent forests) or fertilization. AMF spore densities in soil with and without teff and root colonization by AMF and dark septate endophytes (DSE) were related to straw and grain yields. AMF and DSE colonization rates were higher after inoculation, which provides evidence that a low spore density limits teff root colonization in eroded soils. However, teff yields were significantly increased after fertilisation but not inoculation. N-P fertilization further lowered root colonization rates and spore density. We conclude that forest soils serve as a refugium for soil biota in the degraded landscape of the Ethiopian highlands. As both increased AMF and DSE increase the stress resistance of plants, their inoculation potential should be considered when developing sustainable management methods for teff.

Potensi Beauveria bassiana sebagai Agens Hayati Spodoptera litura Fabr. pada Tanaman Kedelai

ABSTRACTThe Potency of Beauveria bassiana as a biological control agent of Spodoptera lituraThe attack of Spodoptera litura can result in the decrease of soybean yield, so that the soybean production cannot fulfill the demand of soybean. The objective of the study was to examine the potency of Beauveria bassiana as a biological control agent of Spodoptera litura. The research was conducted at the Pest Laboratory, Departement of Agrotechnology, UIN Sunan Gunung Djati Bandung from January to March 2017. The research was carried out using Completely Randomized Design (RBD) with six treatments of B. bassiana spore density and four replications. The treatments were spore densities of 100 (control), 102, 104, 106, 108, and 1010/ml aquades that applied to the instar II of S. litura larvae. The advanced test used was Duncan's advanced test of 5%. The results showed that the B. bassiana density spore of 1010/ml aquades caused the highest S. litura larvae mortality of 82.50% and the lowest weight of food eaten by S. litura larvae of 0.79 g.Keywords: Biocontrol Agent, Beauveria bassiana, Spodoptera litura, SoybeanABSTRAKSerangan Spodoptera litura dapat menurunkan hasil tanaman kedelai, sehingga produksi tanaman kedelai belum bisa memenuhi permintaan kedelai di Indonesia. Tujuan penelitian ini untuk menguji patogenitas Beauveria bassiana sebagai agens hayati pengendali Spodoptera litura. Penelitian dilaksanakan di Laboratorium Hama Jurusan Agroteknologi, UIN Sunan Gunung Djati Bandung dari Januari sampai Maret 2017, menggunakan Rancangan Acak Lengkap (RAL) dengan enam perlakuan kerapatan spora B. bassiana dan empat ulangan. Perlakuan tersebut adalah kerapatan spora 100 (kontrol), 102, 104, 106, 108, dan 1010/ml aquades yang diaplikasikan pada larva S. litura instar II. Uji lanjut yang digunakan adalah Uji lanjut Duncan taraf 5%. Hasil penelitian menunjukkan bahwa kerapatan spora B. bassiana 1010 /ml aquades menyebabkan mortalitas larva S. litura sebesar 82,50% dan bobot pakan yang dimakan oleh larva S. litura paling rendah sebesar 0,79 g.Kata Kunci: Agens hayati, Beauveria bassiana, Spodoptera litura, Kedelai

Cooperation among germinating spores facilitates the growth of the fungus, Neurospora crassa

Fusions between individuals are a common feature of organisms with modular, indeterminate life forms, including plants, marine invertebrates and fungi. The consequences of fusion for an individual fungus are poorly understood. We used wild-type and fusion mutant strains of the genetic model Neurospora crassa to chronicle the fitness in two different laboratory habitats, and in each experiment started colonies from multiple different densities of asexual spores. On round Petri dishes, fusion enabled wild-type colonies to grow larger than mutant ( soft ) colonies; but in linear ‘race tubes’, the soft mutant always grew more quickly than the wild-type. Starting a colony with more spores always provided an advantage to a wild-type colony, but was more often neutral or a cost to the soft mutant. The ability to fuse does not provide a consistent advantage to wild-type colonies; net benefits are shaped by both habitat and initial spore densities.

Biofilm formation by zygomycetes: quantification, structure and matrix composition

Most studies on fungal biofilms have focused on Candida in yeasts and Aspergillus in mycelial fungi. To the authors’ knowledge, biofilm formation by zygomycetes has not been reported previously. In this study, the biofilm-forming capacity of Rhizopus oryzae, Lichtheimia corymbifera, Rhizomucor pusillus and Apophysomyces elegans was evaluated. At appropriate seeding spore densities, Rhp . oryzae (105 c.f.u. ml−1), L. corymbifera (104 c.f.u. ml−1) and Rhm. pusillus (104 c.f.u. ml−1) produced highly intertwined, adherent structures on flat-bottomed polystyrene microtitre plates after 24 h at 37 °C. The adhered fungal hyphae were encased in an extracellular matrix, as confirmed by phase-contrast and confocal microscopy. The thickness of Rhp. oryzae, L. corymbifera and Rhm. pusillus biofilms was 109.67±10.02, 242±23.07 and 197±9.0 µm (mean±sd), respectively. Biochemical characterization of the biofilm matrix indicated the presence of glucosamine, constituting 74.54–82.22 % of its dry weight, N-acetylglucosamine, glucose and proteins. Adherence and biofilm formation were not observed in A. elegans. Although A. elegans spores germinated at all three seeding densities tested (1×107, 1×106 and 1×105 c.f.u. ml−1), no significant difference was observed (P>0.05) between the A 490 of wells inoculated with A. elegans and the cut-off A 490 for biofilm detection. This study highlights the potential for biofilm formation by at least three medically important species of zygomycetes.

Effects of Pathogen Density, Soil Moisture, and Soil pH on Biological Control of Clubroot in Chinese Cabbage by Heteroconium chaetospira

The effects of soil moisture and pH, and pathogen resting spore density, on the effectiveness of the biological control of clubroot by the fungal endophyte Heteroconium chaetospira was evaluated in greenhouse and field experiments. Conditions favoring disease development included low pH (5.5) and high soil moisture content (80%), with significant reductions in the disease being observed at a higher pH (6.3 and 7.2) and lower soil moisture content (40 and 60%). In greenhouse tests, H. chaetospira effectively controlled clubroot (reducing the disease by 90 to 100%) at pathogen resting spore densities of 104 and 105 spores/g of soil at all soil pHs tested (5.5, 6.3, and 7.2). However, when the resting spore density was 106 spores/g of soil, plants were severely diseased, regardless of treatment, and H. chaetospira had no effect on disease. At a soil moisture content of 40%, disease occurrence was low, regardless of pathogen spore density, but disease was significantly lower in H. chaetospira-treated plants at pathogen spore density of 105 spores/g of soil. At 60% soil moisture content, H. chaetospira significantly could affect at pathogen spore densities of 104 and 105 but not 104/g of soil. At 80% soil moisture content, there was no effect of H. chaetospira at pathogen density. In situ, the soil moisture contents were constantly adjusted to relatively low to moderate (pF 2.2 to 2.4 and pF 2.0 to 2.2) and high (pF 1.6 to 1.8). Other environmental conditions, such as resting spore density and soil pH, were maintained at constant levels. Control plants (not treated with H. chaetospira) showed uniformly high disease levels and proportions of diseased plants across all three moisture treatments (disease index = 72 to 80, proportion of diseased plants 85 to 97%). In the field, H. chaetospira-treated plants at low soil moisture (pF 2.2 to 2.4, plot 1) had 68% disease reduction compared with untreated controls and 49% reduction at moderate moisture pF (pF 2.0 to 2.2, plot 2). There was no effect on disease by H. chaetospira at high soil moisture (pF 1.6 to 1.8, plot 3). Based on our results, H. chaetospira is an effective biocontrol agent against clubroot in Chinese cabbage at a low to moderate soil moisture range and a pathogen resting spore density of 105 (or lower resting spores per gram of soil in situ.