Optimal Liquid Spawn Conditions and Grain Medium Enhanced Hispidin Production by Phellinus linteus in Solid-State Fermentation

This study aimed to screen a highest hispidin production of strain from 12 strains of Phellinus, and to evaluate the effects of liquid spawn conditions and grain medium on this strain’s hispidin production levels after solid-state fermentation. Results showed that the P. linteus 04 led to the highest hispidin production, this strain was then selected to elucidate the optimal liquid spawn conditions and grain medium for hispidin production. Various liquid spawn conditions were evaluated, and the highest hispidin yield, specific productivity of hispidin, and total content of hispidin were found to be optimal at 1 week of liquid spawn age, cultured with potato dextrose borth, and using 10 % inoculum rate, with each condition resulting to 0.350, 0.325, and 0.328 mg/g dry weight of mycelium, 0.352, 0.251, and 0.249 µg/mg week− 1 specific productivity, 57.90, 60.23, and 61.77 mg/kg dry weight of brown rice medium, respectively. These liquid spawn conditions were then used to determine the appropriate grain medium for hispidin production. The highest hispidin yield and total content of hispidin were observed in pearl barley which resulted in 1.107 mg/g dry weight of mycelium and 199.76 mg/kg dry weight of pearl barley, which led to results that were 4.73-fold and 5.35-fold higher than those of control (brown rice medium). Overall, this study shows that P. linteus hispidin production can be enhanced by solid-state fermentation using optimal liquid spawn conditions and the appropriate grain medium.

Biocontrol of Aflatoxins Using Non-Aflatoxigenic Aspergillus flavus: A Literature Review

Aflatoxins (AFs) are mycotoxins, predominantly produced by Aspergillus flavus, A. parasiticus, A. nomius, and A. pseudotamarii. AFs are carcinogenic compounds causing liver cancer in humans and animals. Physical and biological factors significantly affect AF production during the pre-and post-harvest time. Several methodologies have been developed to control AF contamination, yet; they are usually expensive and unfriendly to the environment. Consequently, interest in using biocontrol agents has increased, as they are convenient, advanced, and friendly to the environment. Using non-aflatoxigenic strains of A. flavus (AF−) as biocontrol agents is the most promising method to control AFs’ contamination in cereal crops. AF− strains cannot produce AFs due to the absence of polyketide synthase genes or genetic mutation. AF− strains competitively exclude the AF+ strains in the field, giving an extra advantage to the stored grains. Several microbiological, molecular, and field-based approaches have been used to select a suitable biocontrol agent. The effectiveness of biocontrol agents in controlling AF contamination could reach up to 99.3%. Optimal inoculum rate and a perfect time of application are critical factors influencing the efficacy of biocontrol agents.

Effect of Arbuscular Mycorrhizal Inoculum Rate on Tomato (Lycopersicum esculenta L.) Seedlings

An experiment on the effect of rate of arbuscular mycorrhiza inoculum in producing tomato seedlings (var. Ratan) were conducted in the seedbed of Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh during rabi season of 2007-08 and 2008-09. Seven rates of AM inoculum viz. 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 kg m-2 were studied on tomato seedlings. Cowdung was used at the rate of 5 kg m-2 as basal. Seeds were sown in 10 cm apart solid lines on 13 November 2007 and 11 November 2008, and the seedlings were thinned down to about 3 cm from seedling to seedling within a week of germination. Ratan was used as the variety of tomato. Biomass yield, seedling height and nutrient uptake by tomato seedlings increased greatly with the use of AM inoculum. Biomass yield of tomato seedlings followed quadratic trend with the increase of AM inoculum rate from 0 to 1.0 kg m-2 in 2007-08 and 0 to 2.0 kg m-2 in 2008-09.Bangladesh J Microbiol, Volume 29, Number 2, Dec 2012, pp 104-108

Effect of rate of arbuscular mycorrhiza inoculum on Tomato (Solanum lycopersicum) seedlings

An experiment on the effect of rate of Arbuscular mycorrhiza (AM) inoculum on tomato seedlings was conducted at Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh for two consecutive years. Seven rates of AM inoculum viz., 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 kg/m2 were tested. Cowdung was used at a rate of 5 kg/m2. Seeds were sown in 10 cm apart lines on 13 November 2007 and 11 November 2008, and the seedlings were thinned out to about 3 cm from seedling to seedling within a week of germination. Roma VF was used as a variety of tomato. Biomass yield, root colonization, spore number, and nutrient uptake by tomato seedlings increased remarkably with the rates of AM inoculum. The biomass yield followed a quadratic trend with the increase of AM inoculum rate from 0 to 2.0 kg/m2 in 2007-08 and 0 to 1.5 kg/m2 in 2008-09. DOI: http://dx.doi.org/10.3329/bjar.v38i3.16974 Bangladesh J. Agril. Res. 38(3): 473-480, September 2013

Seed Treatment Using Pre-infiltration and Biocontrol Agents to Reduce Damping-off of Corn Caused by Species of Pythium and Fusarium

Bioassays were conducted in a greenhouse at 18°C to determine the effectiveness of a seed treatment used in combination with biocontrol agents for the reduction of corn damping-off caused by species of Pythium and Fusarium. Corn seeds were infiltrated with tap water, drained, air-dried, and then coated with biomass of an antagonistic fungus, Gliocladium virens isolate Gl-3, or an antagonistic bacterium, Burkholderia cepacia isolates Bc-B or Bc-1, or a combination of Gl-3 with each of the bacterial isolates. A nonsterile field soil was infested with a combination of pathogens: Pythium ultimum, P. arrhenomanes, and Fusarium graminearum at 2 inoculum rates (1× and 4×). Pre-infiltration enhanced (P ≤ 0.05) disease control with most treatments at both inoculum rates. Treatments with biocontrol agents alone or in combination, as well as the fungicide captan, effectively reduced the disease at a pathogen inoculum rate of 1×, resulting in greater (P ≤ 0.05) seedling stands, plant height, and fresh weight, and lower (P ≤ 0.05) root rot severity compared with untreated seeds in infested soil. At a pathogen inoculum rate of 4×, stands were lower (P ≤ 0.01) and root-rot severity was higher (P ≤ 0.01) compared to those at 1× for all treatments. Nevertheless, coating seeds with all biocontrol agents (alone or in combination), except with Bc-1 alone, reduced disease (P ≤ 0.05) compared to untreated seeds in infested soil. At both inoculum rates of 1× and 4×, coating seeds with Gl-3 + Bc-B was more effective (P ≤ 0.05) in disease control than any other treatment, resulting in stands, growth rate (plant height and fresh weight), and root rot severity similar to plants from untreated seeds in noninfested soil. In addition, when the exudate from a 2-h infiltration of corn seed was added to the seeds during seed coating, seedling stand was often lower and root rot severity was often higher than those from infiltrated seeds (P ≤ 0.05). These results indicated that the infiltration process removed certain exudates, including nutrients and/or stimulants (not detected in this study) that might be utilized by pathogens to initiate seed infection. A thin-layer chromatography (TLC) profile of the exudates showed the presence of eight amino acids and three major carbohydrates.