Toxicology,biosynthesis,bio-control of aflatoxin and new methods of detection

Mycotoxins and their derivatives since their discoveries and until the present time are behind unspecified economic and medical damages.Aflatoxins are classified according to their physical–chemical and toxicological characters in the most dangerous row of the mycotoxins.These aflatoxins are in part responsible,of irreversible medical disasters that are not easily manageable such as cancer of the liver and kidneys,and in the other part,of losses in the stored cereal products.Based on these crucial findings,monitoring of this toxin became imperative in post-harvest food products,during storage,during transformation chain and even during the long phases of conservation.Vigilance of this toxin is delivered by detection methods using very advanced technologies to respond in the shortest possible times.In addition,the knowledge of factors supporting the biosynthesis of aflatoxins such as the temperature,moisture content,concentration of nitrogen and carbon,and the molecules responsible for the genetic control of the synthesis will be reflected later in the choice of bio-control techniques.This control is currently based on new strategies using the bioactives substances of the plants,the lactic bacteria and some strains of actinomycetes that have good inhibiting activity against aflatoxins with fewer side effects on Man.On the other hand,this brief review summarizes the results of new studies demonstrating the toxicity of the toxin,new detection methods and bio-control.

Chemical Composition of the Neochetina eichhorniae and Neochetina bruchi and Their Potential for Use as Livestock Feed

Neochetina eichhorniae and Neochetina bruchi have been used for over four decades as Eichhorniae crassipes classical biological control agents globally. Despite the success of bio-control against the water hyacinth globally at different levels and environmental sustainability, biological control against water hyacinth seems to have overlooked the socio-economic sustainability in assisting the ravaged communities, gain resilience and adapt to the challenges of the invasive alien species. This manuscript evaluates the potential to draw out more from biological control of the water hyacinth by evaluating the potential to utilize Neochetina eichhorniae and Neochetina bruchi as feed. The live insects of the two species were collected from the water hyacinth marts in the nearby L. Victoria in Siaya county, Kenya. Where they were then transferred for semi-cultivation in localized ponds for reproduction and closer monitoring. The ponds having been set up in completely randomized design while in the open within the same climatic region mimicked the water quality and most abiotic conditions of the lake necessary for the insects’ and host plant acclimatization and reproduction. The samples for proximate analysis were collected from these ponds as per the research and experimental design. The chemical compositions of the Neochetina bruchi, N. eichhorniae and their larvae composite, satisfactorily compared to basic fish feed requirements, specifically as a protein source having crude protein (CP) percentage per DM of 55.0350 ± 0.025, 54.4350 ± 0.035 and 62.2750 ± 0.025 respectively.

Combined application of Trichoderma harzianum SH2303 and difenoconazole-propiconazolein controlling Southern corn leaf blight disease caused by Cochliobolus heterostrophus in maize

Southern corn leaf blight(SCLB)disease caused by Cochliobolus heterostrophus is one of the major threats to corn production worldwide.The synergistic application of low toxic chemical fungicide and biocontrol agents could improve biocontrol stability and efficiency against plant diseases,which ultimately reduce use of chemical fungicide.Trichoderma spp.,well-known biocontrol fungi have been used to control some foliar diseases.However,few works have been reported on synergistic application of chemical fungicide and Trichoderma against foliar diseases.This study was aimed to investigate the control effect on the synergistic application of Trichoderma harzianum SH2303 and difenoconazole-propiconazole(DP)against SCLB.Results showed that the synergistic application of DP and SH2303 reduced the leaf spot area compared to the control.The efficacy of synergistic application of DP+SH2303 against SCLB could last for 15–20 d in pot trial under the greenhouse condition.Under the natural field condition,maize treated with DP+DP and DP+SH2303 showed 60%control,which was higher than that of SH2303+DP(45%)and SH2303+SH2303(35%).All these treatments induced the synthesis of defense-related enzymes(phenylalanine ammonia lyase(PAL),catalase(CAT),and superoxide dismutase(SOD))and the defence-related gene expression of SA pathway(PR1).Taken together the in-vitro leaf test and field trial,the control of SCLB by synergistic application of DP+SH2303 was similar to that of DP+DP.Among synergistic application,the sequential application of DP+SH2303 showed better control than the sequential application of SH2303+DP.It was concluded that the synergistic application of chemical fungicide(DP)and biocontrol agent(T.harzianum SH2303)could be used to reduce the chemical fungicide and to reduce the SCLB diseases in maize,which provided alternative approach to realize an eco-friendly controlling of the foliar disease.

Laboratory efficacy of mycoparasitic fungi(Aspergillus tubingensis and Trichoderma harzianum) against tropical bed bugs(Cimex hemipterus)(Hemiptera:Cimicidae)

Objective: To test the effectiveness of conidial spore formulations [Aspergillus tubingensis(A.tubingensis) and Trichoderma harzianum(T.harzianum)] against tropical bed bugs, Cimex hemipterus.Methods: Spore formulations were made from two fungal strains, T.harzianum and A.tubingensis.The bed bugs were exposed to the conidial spores placed soaked onto a fabric cloth for 1 h and the mortality counts were recorded daily until 14 days.Results: Mean survival times based on Kaplan–Meier survival analysis showed no significant differences between all the concentrations in both the fungal isolates:T.harzianum and A.tubingensis.However, the evaluation of both the isolates in terms of virulence resulted in low lethal hours in all the concentrations except for the high concentration of A.tubingensis(LT_(50)= 44.629 h) at the conidial exposure of 1 × 10~6 spores/mL.Rapid mortality of the bed bugs was observed from Day 6 to Day 12, ranging from 13% to 90% in all three concentrations of A.tubingensis.With reference to the T.harzianum exposure, the concentration of 1 × 10~4 spores/mL displayed a gradual increase in the percentage mortality of 90 on Day 14.Conclusions: Approaches to the bed bugs treatment should be explored in-depth using a natural biological agent like fungus especially A.tubingensis to reduce this pest population, in order to replace chemical methods.

Effect of Plant Extracts on Seed Borne Fungi of Jute

The aim of this study was to determine the prevalence of seed-borne fungal pathogens of jute and their control with plant extract. The experiment was carried out in seed pathology centre, Bangladesh Agricultural University to obtain relevant information about the health of jute seeds and find out the efficacy of extracts as seed-treater. Two varieties viz., Deshipat (Corchorus capsularis) and Tossapat (Corchorus olitorius) were selected for this study and jute seeds were collected from two different locations of Bangladesh. The major predominant identified fungi were Colletotrichum corchori, Macrophomina phaseolina, Fusarium spp., and Botryodiplodia theobromae. Least seed-borne fungi were found in the variety of Tossapat. Low germination of seeds was found related to high prevalence of seed-borne fungal infections. Highest seed-borne infection was obtained in the variety of Deshipat. In this study, we evaluated some major plant extracts such as garlic clove (Allium sativum), neem leaves (Azadirachta indica), allamanda leaves (Allamanda cathartica L.) and marigold leaves (Tagetes spp.) for observing the action of these plant extracts on seed borne fungi of Jute. The study revealed that the extract of Garlic (Allium sativum), and Biskatali (Polygonum hydropiper) increased the germination of seeds and garlic?(Allium sativum) extract was also found to be most effective in controlling the seed-borne infection among all the treatments. Although the inhibiting capacity of the extracts of Allamanda (Allamanda cathartica L.) and Biskatali (Polygonum hydropiper) was found to be similar and Biskatali extract was found to have the second position among all the treated plant extracts in inhibiting the growth of isolated fungal pathogens.

The Predatory Function of Three Spiders to Two Insect Pests in Rice Within a Multi-species Co-existence System

The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica) for brown plant hopper (X4-Nilaparvata lugens) and rice spittle bug (X5-Cal-litettix versicolor) was investigated, as well as how interference between and within species occurred, by using a quadratic regression rotational composite design. Six predation models derived from the analysis of interactions among and within predators and preys were developed. The total predatory capacity of spiders on rice insect pests after coexistence for one day can be expressed as follows: Y3 = 32.795 + 2.25X1 + 1.083X2 + 0.5X3 + 10.167X4 + 3.167X5 - 1.67X12 - 2.42X22 - 3.295X32 - 0.045X42 + 0.455X52 - 3.125X1X2 + 0.375X1X3 -0.625X1X4 - 0.375X1X5 + 0.375X2X3 - 0.875X2X4 + 0.125X2X5 + 0.375X3X4 - 0.375X3X5 + 0.125X4X5. The principal efficiency analysis using this model indicated that increases in insect pest density significantly increased predation by predators; this was much greater than the effect of any single predator. X4 had a greater effect than X5; however, X4 and X5 demonstrated little interspecific interference and even promoted each other and increased predation rates as the densities of the two pests increased. Among the three predators, an increase in the density of X, had the greatest effect on the increase in predation, X3 had the second, X2 the third greatest effect. As predator density increased inter- and intra-species interference occurred, which were largely related to the size, activity, niche breadth, niche overlap and searching efficiency of the predators. X2 produced the greatest interference between different individuals and between any other predator species. X3 had the second greatest, which reduced predation levels at high predator densities. Because of these factors, the highest predation rate was obtained at a prey density of 120 per 4 rice-hills. The optimal proportion of the three predators in the multi-predator prey system was X1: X2: X3 = 5.6:1.3:4.1.

Evaluation of 0.3% Agricultural Antibiotic 702 AS against Three Pathogenic Fungi of Rice

Abstractsolution （AS） against Rhizocto- nia solani, Magnaporthe grisea and Ustilaginoidea virens. [ Method] The toxicity effect of 0.3% agricultural antibiotic 702 AS against R., solani, M. grisea and U. virens were studied by mycelial growth rate method and mycelial wet weight method. [ Result ] The EC50 and EC50 values of agricultural antibiotics 702 AS to R. solani, M. grisea and U. virens in vitro condition were 4.16 and 16.17 mg/L, 16.05 and 41.85 mg/L, 111.2 and 389.0 mg/L, respectively. Agricultural antibi- otics 702 AS had good inhibition effect against R. solani and M. grisea and could basically achieve the effects of commercially available Jinggangmycin and kaanga- mycin, but the inhibition effect against U. v/rens was relatively weak. The preventive activity of aqueous solution was obviously higher than treatment activity. [Conclusion] 0.3% Agricultural antibiotic 702 AS is considered to be a potential biological control agent against R. solani, M. grisea and U. virens, and can be used as the potential alternative pesticide of Jinggangmycin.

First Report of Pseudopestalotiopsis theae Causing Aloe vera Leaf Spot Disease in Bangladesh

Aloe vera (L.) Burm.f. is one of the important medicinal plants, has been commercially cultivated in the Northern part of Bangladesh. An experiment was conducted to detect A. vera leaf disease collected from Natore district, Bangladesh. Fungal leaf spot disease caused by Pseudopestalotiopsis theae (Sawada) Maharachch., K.D. Hyde & Crous was identified through morphological features and sequencing of internal transcribed spacer region of ribosomal DNA. After submitting nucleotide sequences to NCBI, we received an accession number MH333081.1: Pseudopestalotiopsis theae. The growth pattern of the isolated fungal pathogen was evaluated on different solid culture media, at different temperature and light conditions. The results showed the maximum mycelial growth of the fungus on the Richard Agar medium under the complete dark condition at 25°C. We evaluated fungal antagonists against the isolated pathogenic fungus, in which Trichoderma asperellum showed optimistic results. Synthetic fungicides—Tilt 250EC and Ridomil Gold completely inhibited the studied fungus’s vegetative growth. Pseudopestalotiopsis theae causing A. vera leaf spot disease in Bangladesh is a new record to the best of our knowledge.

Penetration and Post-infection Development of Meloidogyne Incognita on Tobacco as Treated by Rhizobacteria Pseudomonas Fluorescens Strain P-72-10

The bio-control potential of rhizospere bacteria Pseudomonas fluorescens against plant-parasite nematode had been demonstrated. P. fluorescens had shown the effect to enhance tobacco resistance to root-knot nematode Meloidogyne incognita. Inoculation with P. fluorescens in tobacco could lead to significant reductions in the number of juveniles that penetrated tobacco root and further life stage development of the juveniles. The number of juveniles penetrated into tobacco root in treatment with P. fluorescens is significantly different from CK at 2DAI,6DAI,8DAI and 10 DAI. Significant reduction and delayed development of juveniles that penetrated into tobacco root and treated were observed in treatment at14 DAI,21DAI,28 DAI and 35 DAI. In addition,P. fluorescens treatment leads to a significant reduction in the number of eggs per egg-mass at 35 DAI. The results show P. fluorescens induced a continuously suppression on root-knot nematode M. incognita throughout their entire early infection phase of root penetration,subsequent life stage development and reproduction.

Visual reaction effects induced and stimulated by different lights on phototactic bio-behaviors in Locusta migratoria manilensis

Control of locusts traditionally relies on chemical insecticides.However,chemical control had led to serious environment problems,while light trap techniques based on manipulating insect phototactic responses,are proposed to use for plague locusts control.The key to high efficiency of the trap is to decide the photoelectric reaction intensities on the positive phototaxis of insects.The study compared the visual reaction effects of locusts with their phototactic photosensitivity through the use of spectrometry and behavior investigations,to obtain the influences of the visual spectrum characteristics on locusts positive phototaxis.The results showed that the visual absorption of photons of mixed spectral light and the visual glimmer reaction of the locusts with migratory spectrum characteristics of the peak wavelength of LED lights,reflected the degree of the visual photosensitivity to light photons absorbed by the eye.The visual photosensitive response intensity and the phototactic aggregation effect stimulated by violet light were the most effective,showing that violet light of locusts visual trending sensitivity was consistent with the short sensitive spectrum light of insects visual electrophysiology,whereas the timeliness of the visual photosensitivity reaction and the induction effect was superior under orange light,showing that the biological behavior of locusts visual physiology reaction caused by orange light regulating locusts light rhythm was complicated.Moreover,weak light resulted in stronger visuospatial orientation in terms of the phototaxis of locusts and stronger light resulted in the better visual orientation towards the light source.The results indicated that optical wave properties could affect the visual absorption of spectral light photons,which resulted in different visual responses to different optical frequency energies and restricted the visual bio-photosensitive induction activity of locusts.The study provides new understanding of positive and negative phototaxis of locusts and useful data for the further development of photoelectric induction techniques for the control of locusts.