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.

Bacterial signal C10-HSL stimulates spore germination of Galactomyces geotrichum by transboundary interaction

The coevolution and coexistence of bacterial–fungal consortium have been widely reported in various natural ecosystems. The transboundary communication mediated by bacterial acyl–homoserine lactone signals probably is the driving force of fungal spore germination. This study aimed to report a functional bacterial signal molecule, C10-acyl homoserine lactone, which could be sensed by Galactomyces geotrichum. The spore germination rates of G. geotrichum increased by 22%. Meanwhile, carbohydrate production improved by 1.0-to 2.5-fold. G. geotrichum signaled to C10-HSL through receptor gene Rho1and made a response in cell wall assembly and carbohydrate biosynthesis by the upregulated expression(above 1-fold) of functional genes, such as Smi1, Utr2, and Chs2. It contributed to spore germination and morphology transformation together. This study provides a novel perspective for understating the transboundary cooperation between fungi and bacteria by cell-to-cell communication.

Inhibition of Ageratina adenophora on Spore Germination and Gametophyte Development of Macrothelypteris torresiana

Allelopathy of Ageratina adenophora plays an important role in its invasion. However, we have little knowledge of its allelpathic effects on ferns. In Petri dish bioassays, the inhibitory potential of aqueous leachates from roots, stems and leaves of A. adenophora was studied on the spore germination and gametophyte development of Macrothelypteris torresiana. All leachatss inhibited the spore germination and growth of the first rhizoid of M. torresiana and inhibitory effects increased with increasing leachate concentrations. Root leachates proved most inhibitory. Gametophyte rhizoids of M. torresiana treated with stem and leaf leachates of A. adenophora were erect, which was similar to those of the control. However, gametophyte rhizoids of M. torresiana treated with root leachates of A. adenophora were erect, but also curving or swollen. Moreover, curving and swollen rhizoids increased with increasing concentrations. As time went by, rhizoids treated with root leachates were not so curved and the swelling almost disappeared. Possible causes are discussed in the present study. The increasing concentrations of leaf leachates also delayed the stages of gametophyte development. With the treatment of root leachates, the delay was more obvious. Thus A. adenophora inhibited the spore germination and gametophyte development of M. torresiana and the root leachates were most inhibitory.

Characteristics of spore germination and protonemal development in Hypnum pacleseens

The spore germination,protonemal development,and gametophyte differentiation of Hypnum pacleseens were observed in cultivation.Photomicrographs showed that spore germination of Hypnum pacleseens occured within the exospore.Its protonema is massive with filamentous chloronema formed inside.The terminal part of the chloronema differentiated into filamentous caulonema and its rhizoid was derived from the apical cell of the filamentous chloronema.The initial cell of gametophyte differentiated from chloronema and caulonema.Sporeling-type of Hypnum pacleseens is developmentally similar to Glyphmitrium-type.

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%.

Positive effects of biochar application and Rhizophagus irregularis inoculation on mycorrhizal colonization,rice seedlings and phosphorus cycling in paddy soils

Phosphorus(P)is an essential element for plant growth but is often limiting in ecosystems;therefore,improving the P fertilizer use efficiency is important.Biochar and arbuscular mycorrhizal fungi(AMF)may enhance P cycling in paddy soils that contain high content of total P but low content of available P(AP).In this study,the effects of biochar addition and Rhizophagus irregularis inoculation on the organic and inorganic P contents and phosphatase activities in paddy soils,rice seedling growth,and AMF colonization were investigated.Compared with no biochar addition,biochar addition enhanced the percentage of spore germination at day 7,hyphal length,most probable number,and mycorrhizal colonization rate of R.irregularis by 32%,662%,70%,and 28%on average,respectively.Biochar and R.irregularis altered soil P cycling and availability.Biochar and R.irregularis,either individually or in combination,increased soil AP content by 2%–48%.Rice seedlings treated with biochar and R.irregularis produced greater biomass,improved root morphology,and increased nutrient uptake compared with those of the control without biochar and R.irregularis.The results suggest that combined application of biochar and R.irregularis is beneficial to rice cultivation in paddy soils with high content of total P but low content of AP.

Whole lifecycle observation of single‐spore germinated Streptomyces using a nanogap‐stabilized microfluidic chip

Streptomyces is a model bacterium to study multicellular differentiation and the major reservoir for antibiotics discovery.However,the cellular‐level lifecycle of Streptomyces has not been well studied due to its complexity and lack of research tools that can mimic their natural conditions.In this study,we developed a simple microfluidic chip for the cultivation and observation of the entire lifecycle of Streptomyces development from the single‐cell perspective.The chip consists of channels for loading samples and supplying nutrients,microwell arrays for the seeding and growth of single spores,and air chambers beside the microwells that facilitate the development of aerial hyphae and spores.A unique feature of this chip is that each microwell is surrounded by a 1.5µm nanogap connected to an air chamber,which provides a stabilized water–air interface.We used this chip to observe the lifecycle development of Streptomyces coelicolor and Streptomyces griseus germinated from single spores,which revealed differentiation of aerial hyphae with progeny spores at micron‐scale water–air interfaces and air chambers.Finally,we demonstrated the applicability of this chip in phenotypic assays by showing that the microbial hormone A‐Factor is involved in the regulatory pathways of aerial hyphae and spore formation.The microfluidic chip could become a robust tool for studying multicellular differentiation,single‐spore heterogeneity,and secondary metabolism of single‐spore germinated Streptomyces.

Red Light-Induced Phytochrome Relocation into the Nucleus in Adiantum capillus-veneris

Phytochromes in seed plants are known to move into nuclei in a red light-dependent manner with or without interacting factors. Here, we show phytochrome relocation to the nuclear region in phytochrome-dependent Adiantum capillus-veneris spore germination by partial spore-irradiation experiments. The nuclear or non-nuclear region of imbibed spores was irradiated with a microbeam of red and/or far-red light and the localization of phytochrome involved in spore germination was estimated from the germination rate. The phytochrome for spore germination existed throughout whole spore under darkness after imbibition, but gradually migrated to the nuclear region following red light irradiation. In- tracellular distribution of PHY-GUS fusion proteins expressed in germinated spores by particle bombardment showed the migration of Acphy2, but not Acphyl, into nucleus in a red light-dependent manner, suggesting that Acphy2 is the photoreceptor for fern spore germination.