Inhibitory Effects of Sixteen Fungicides on Mycelial Growth and Spore Germination of Monilinia fructicola

[Objective]The paper was to compare the indoor toxicities of sixteen fungicides on mycelial growth and spore germination of Monilinia fructicola,to screen out effective fungicides and to discuss use characteristics of various types of fungicides.[Method]The inhibitory activities of 16 fungicides on mycelial growth and spore germination were determined by mycelial growth rate method and spore germination method.[Result]The EC50 values of 16 fungicides against mycelial growth ranged from 0.0184 to 61.5305 mg/L.Prochloraz,tetramycin,fenbuconazole and fludioxonil had strong inhibitory activities on mycelial growth,and their EC50 values were 0.0184,0.0456,0.0531 and 0.0814 mg/L,respectively,significantly lower than those of other 12 fungicides.The EC50 values of 16 fungicides against spore germination ranged from 0.0084 to 189.3938 mg/L.Tetramycin and chlorothalonil had strong inhibitory activities on mycelial growth,and their EC50 values were 0.0084 and 0.0378 mg/L,respectively,significantly lower than those of other 14 fungicides.[Conclusion]The 16 fungicides had great value in preventing and controlling peach brown rot.Benzimidazoles,diformimides and ergosterol inhibitors had good inhibitory activities on mycelial growth.Strobilurins,succinate dehydrogenase inhibitors and multiple-site protective fungicides had good inhibitory activities on spore germination.The agricultural antibiotics tetramycin,phenazine-1-carboxylic acid and pyrrole fungicide fludioxonil had good inhibitory activities on mycelial growth and spore germination.

Molecular Identification of Alternaria alternate (Fr.) Keissl. from the Leaf Blight Disease of Centella asiatica L.

Centella asiatica (L.), frequently known as Thankuni, is an important ethnobotanical plant in Bangladesh. This study was conducted to evaluate the morphological characteristics, cultural factors and molecular identification of the causal agent of Alternaria leaf blight disease of C. asiatica. The potato dextrose agar (PDA) medium recorded the maximum mycelial growth (69 mm), followed by the yeast extract agar (YEA) medium, while the honey peptone agar (HPA) medium recorded the lowest growth (27 mm). The optimal pH and temperature for mycelial growth of Alternaria alternata were 6 and 30°C, respectively. Internal transcribed spacer (ITS) region of Alternaria alternata PCR products measured 558 bp and blast search showed 99% sequence similarity with Alternaria alternata species complex. To the best of our knowledge, Alternaria leaf blight disease caused by Alternaria alternata is the first record in Bangladesh.

Activity of Azoxystrobin and SHAM to Four Phytopathogens

The study was conducted to make clear the activity of azoxystrobin to 4 plant pathogens and the synergistic effects of salicylhydroxamic acid （SHAM）, which acted on the alternative oxidase. It was also conducted to be aware of the mechanism of azoxystrobin in inhibition on mycelial respiration and the influence of SHAM. The activity test of azoxystrobin and SHAM was carried out with a mycelial linear growth test and spore germination test. Other related biological properties were also observed. Inhibition of azoxystrobin and SHAM on 4 pathogens was determined by using SP-II oxygraph system. Azoxystrobin inhibited mycelial growth in Colletotrichum capsici, Botrytis cinerea, Rhizoctonia solani, and Magnaporthe grisea, respectively; it also inhibited conidia germination, and conidia production in C. capsici, B. cinerea M. grisea, and sclerotia formation in R. solani. Moreover, it created stayed pigment biosynthesis in C. capsici and M. grisea somehow. Salicylhydroxamic acid enhanced inhibition by azoxystrobin. An oxygen consuming test of the mycelia showed that azoxystrobin inhibited all the 4 fungi＇s respiration in the early stages. With the concentration rising up, the effectiveness increased. However, as time went on, the respiration of the mycelia treated with fungicides recovered and SHAM could not inhibit the oxygen consuming. This reaction between the mycelia and the fungicides appeared not to initiate alternative respiration but rather the other mechanism created a lack of efficacy.

Antifungal Activity of Corydalis Chloroform Extract against Several Kinds of Pathogenic Fungi of Corn and Soybean

In order to better control common diseases of corn and soybean in Sanjiang plain,the in vitro antifungal activity of corydalis chloroform extract against several common fungal diseases of corn and soybeans was tested using mycelial growth rate method. The test result of mycelial growth rate showed that the inhibition rate of corydalis chloroform extract against Cercosporidium sofinum（ Hara） Liu ＆ Guo and Rhizoctonia solani Kuhn were all above 80%,and EC50 values were52. 98- 58. 98 mg /L. The test result of spore germination showed that the inhibition rates against spore germination of all pathogenic fungi were high,in which the inhibition rates against spore germination of C. sofinum and Bipolaris maydis reached 100%. Biological control test showed that the control effects against other diseases were below 60% except that against R. solani reaching 61. 46%.

Biological Characteristics of the Pathogen Phyllosticta capitalensis Causing Banana Freckle Disease in Hainan Province

[Objectives]This study was conducted to clarify the biological characteristics of the pathogen Phyllosticta capitalensis,the causal agent of freckle disease on Cavendish banana in Hainan Province,China.[Methods]The impact of various nutritional and environmental factors,including media,carbon sources,nitrogen sources,temperature,pH and light on the growth and sporulation of P.capitalensis was assessed using two distinct methods:mycelium growth rate and blood counting chamber.[Results]The mycelial growth and sporulation of P.capitalensis on different media exhibited notable differences.The use of banana leaf extract dextrose agar(BLEAD)and carrot agar(CA)was observed to facilitate rapid mycelial growth.The potato dextrose agar(PDA)and potato sucrose agar(PSA)were conducive to the production of conidia.The utilization of distinct carbon and nitrogen sources exerted a pronounced influence on the growth of P.capitalensis.Maltose,dextrose,fructose,and casein acid hydrolysate were the preferred substrates for mycelial growth.The tested carbon and nitrogen sources did not significantly stimulate conidial production,whereas dextrose and NaNO 3 were found to favor sporulation.The optimal temperature for mycelial growth and conidial production was determined to be 28 and 32℃,respectively.No mycelial growth was observed at 5℃.Active mycelial growth was observed at pH 6-10,with pH 6-7 being particularly conducive to sporulation.Complete darkness was conducive to mycelial growth and sporulation.[Conclusions]It is recommended that BLEDA and PDA should be incubated at 28℃for 14 d in the dark for the purpose of mycelial growth and sporulation of P.capitalensis,respectively.

Optimizing bio-physical conditions and pre-treatment options for breaking lignin barrier of maize stover feed using white rot fungi

The greatest limitation to utilization of maize stover by ruminants as a feed is the high concentration of lignin, which limits fibre digestibility. However, ruminants can effectively utilize maize stover if its nutritive value is improved using white rot fungal species. This study was designed to determine optimal biophysical conditions for mycelial growth and select the most ideal fungal species and pre-treatment options for improving nutritive value of maize stover. Four popular edible Pleurotus fungal species(viz.Pleurotus florida,Pleurotus ostreatus, Pleurotus sajor caju and Pleurotus pulmonarius) were subjected to varying temperatures, pH levels, hydrogen peroxide(H_2 O_2) concentration and illumination to establish the extent of mycelial growth rate.Inclusion of H_2 O_2 was used to determine optimal levels for preservation and prevention of contamination from other indigenous microbiota. Effects of pre-treatment options on chemical composition and nutritive value of maize stover were also examined. Mycelial growth rate of Pleurotus species on potato dextrose agar(PDA) varied(P < 0.05) with temperature, pH level and H_2 O_2 concentration following a quadratic trend. Optimal temperature, pH and H_2 O_2 concentration for mycelial growth on PDA were 25 ℃,5 and 0.01 mL/L, respectively. Under the different bio-physical conditions,P. sajor caju had the highest mycelia density and growth rate. Chemical composition of solid-state fermented maize stover differed(P < 0.05) among the Pleurotus species. Maize stover fermented with P. sajor caju had the highest crude protein(CP) of 86.6 g/kg DM, in-vitro dry matter digestibility(IVDMD) of 731 g/kg DM, in-vitro organic matter digestibility(IVOMD) of 670.4 g/kg DM and metabolizable energy(ME) of10.0 MJ/kg DM but with the lowest lignin(sa) of 50 g/kg DM. At 25℃, P. sajor caju had the highest mycelial growth rate on PDA and highest lignin(sa) breakdown in the maize stover substrate. It was, therefore,selected as the most ideal fungal species for improving nutritive value of maize stover. Pre-treatment of maize stover with Lactobacillus plantarum and molasses under anaerobic condition for 7 days before inoculation with P. sajor caju resulted into a substrate with the highest(P< 0.05) CP(96.6 g/kg DM), IVDMD(752.3 g/kg DM), IVOMD(687.2 g/kg DM) and ME(10.2 MJ/kg DM). However, neutral detergent fiber exclusive of residual ash(NDFom) and lignin(sa) fractions decreased(P < 0.05) as a result of subjecting maize stover to pre-treatment with L. plantarum and molasses prior to fermentation with P. sajor caju.Therefore, pre-treatment of maize stover with L. plantarum and molasses for 7 days prior to fermentation with P. sajorcaju for 14 days in darkness at 25℃ offered the greatest potential for breaking the lignin barrier.

Effect of temperature on the morphological characteristics of Botrytis cinerea and its correlated with the genetic variability

Objective:To study the effect of temperature on the morphological characteristics of Botrytiscinerea(B.cinerea)and its correlated with the genetic variability.B.cinerea is a plant-pathogenic fungus that produces the disease known as grey mould in a wide variety of agriculturally important hosts in many countries.Methods:Six strains from different host collected have been isolated and characterized by several methods as mycelial growth,fungicide resistance,pathogenicity and the effects of the temperature.Also was analyzed by PCR and distinguished by the presence or absence of transposable elements.Results:Results showed that clear morphological differences exist between strains at the temperature of 4,12 and 28℃.All strains analyzed molecularly were classified as Group II(transposa-type).Demonstrating a negative correlation between mycelial growth and other characteristics as the fungicide resistance and pathogenicity.Lastly,it is difficult to establish relationships phenotypic and genotypic between strains of B.cinerea.Conclusions:The results indicated that the mycelial growth,resistance at fungicide and pathogenicity are independent of the characteristics molecular,however,are dependent of a factor such as temperature.