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.

Aspergillus tubingensis Causes Leaf Spot of Cotton (Gossypium hirsutum L.) in Pakistan

Cotton(Gossypium hirsutum L.)is a key fiber crop of great commercial importance.Numerous phytopathogens decimate crop production by causing various diseases.During July-August 2018,leaf spot symptoms were recurrently observed on cotton leaves in Rahim Yar Khan,Pakistan and adjacent areas.Infected leaf samples were collected and plated on potato dextrose agar(PDA)media.Causal agent of cotton leaf spot was isolated,characterized and identified as Aspergillus tubingensis based on morphological and microscopic observations.Conclusive identification of pathogen was done on the comparative molecular analysis of CaM andβ-tubulin gene sequences.BLAST analysis of both sequenced genes showed 99%similarity with A.tubingensis.Koch’s postulates were followed to confirm the pathogenicity of the isolated fungus.Healthy plants were inoculated with fungus and similar disease symptoms were observed.Fungus was re-isolated and identified to be identical to the inoculated fungus.To our knowledge,this is the first report describing the involvement of A.tubingensis in causing leaf spot disease of cotton in Pakistan and around the world.

柚苷酶高产菌株选育及其产酶在蜜橘果汁脱苦中的应用

为了得到1株高产柚苷酶菌株并探究其工业应用价值,从发霉的柚子皮上筛选出1株塔宾曲霉(Aspergillus tubingensis)MN589840,采用紫外与常压室温等离子体(atmospheric room temperature plasma,ARTP)复合诱变技术,获得突变株UA13,其柚苷酶活力可达41.524 U/mL,是原始菌株的3.06倍。对酶解条件进行探究,其酶解最适温度为40~50℃,最适pH值为5.0。利用突变株UA13发酵产酶脱苦宜昌蜜橘果汁并进行理化指标检测,当酶解约50 min时,果汁中柚皮苷含量低于柚皮苷苦阈值;当酶解时间>75 min,果汁中仅剩下少量柚皮苷。使用高效液相色谱对脱苦结果验证检测,结果显示,突变株UA13产酶可有效水解果汁中的柚皮苷,且能提高果汁风味。因此,突变株UA13具有潜在的工业应用价值,为后续实验研究奠定基础。

Biological silicon nanoparticles improve Phaseolus vulgaris L. yield and minimize its contaminant contents on a heavy metals-contaminated saline soil

The synthesis of biological silicon nano-particles(Bio-Si-NPs)is an eco-friendly and lowcost method.There is no study focusing on the effect of Bio-Si-NPs on the plants grown on saline soil contaminated with heavy metals.In this study,an attempt was made to synthesis Bio-Si-NPs using potassium silica florid substrate,and the identified Aspergillus tubingensis AM11 isolate that separated from distribution systems of the potable water.A twoyear field trial was conducted to compare the protective effects of Bio-Si-NPs(2.5 and 5.0 mmol/L)and potassium silicate(10 mmol/L)as a foliar spray on the antioxidant defense system,physio-biochemical components,and the contaminants contents of Phaseolus vulgaris L.grown on saline soil contaminated with heavy metals.Our findings showed that all treatments of Bio-Si-NPs and potassium silicate significantly improved plant growth and production,chlorophylls,carotenoids,transpiration rate,net photosynthetic rate,stomatal conductance,membrane stability index,relative water content,free proline,total soluble sugars,N,P,K,Ca2+,K+/Na+,and the activities of peroxidase,catalase,ascorbic peroxidase and superoxide oxide dismutase.Application of Bio-Si-NPs and potassium silicate significantly decreased electrolyte leakage,malondialdehyde,H2 O2,O2·-,Na+,Pb,Cd,and Ni in leaves and pods of Phaseolus vulgaris L.compared to control.Bio-Si-NPs were more effective compared to potassium silicate.Application of Bio-Si-NPs at the rate of 5 mmol/L was the recommended treatment to enhance the performance and reduce heavy metals content on plants grown on contaminated saline soils.