Effect of Soil Amendments on Soil Borne Pathogens of French Bean （Phaseolus vulgaris L,） in Organic Farming System in Manipur

The rationale behind the use of soil amendments by traditional marginal farmers against soil borne pathogen is an area of interest. The present work ascertain the effect of certain soil amendments against pre emergent and post emergent rot of French bean in the agro climatic condition of Manipur, Four soil amendments： cow dung （COD）, sawdust （SD） ＋ paddy husk （PH）, decomposed floating phytomat （DFP） was tried in field conditions in four different combinations. These have been often used by the traditional farmers. A locally available commonly cultivated pole type of French bean has been used for the study. Disease incidences in plots treated with these amendments were then compared with that of control plots where no amendments were made. The plots with a combined treatment of the soil amendments showed maximum seed germination and least post emergent rot against sclerotinia rot. But DFP showed effectiveness against rhizoctonia rot with maximum seed germination while saw dust showed maximum decrease in post emergent rot against rhizoctonia rot. The plots treated with organic soil amendments showed statistically significant positive effect against the pathogens as compared with untreated control plots.

Fungal community structure analysis of peanut pod rot in soil in Hebei Province,China

In recent years,peanut yield and quality are more seriously affected by pod rot disease in China.However,managing this disease has proven challenging due to the wide host range of its pathogens.In this study,four soil samples were collected from fields with pod rot disease in Hebei Province,and 454 pyrosequencing was used to analyze the fungal communities structure within them.All 38490 ITS high-quality sequences were grouped into 1203 operational taxonomic units,the fungal community diversity of four soil samples was evaluated and compared using Shannon index and Simpson index.The results showed that members of Ascomycota were dominant,followed by Basidiomycota.According to the BLAST results at the species level,Guehomyces had the highest abundance,accounting for about 7.27%,followed by Alternaria,Fusarium,and Davidiella.The relative abundance of Fusarium oxysporum isolated from rotting peanuts in soil with peanut rot was higher than that in the control,indicating that Fusarium oxysporum might be one of the main pathogenic fungus of peanut rot in this area.This study delved into the broader fungal community associated with peanut pod rot,providing a theoretical foundation for preventing and treating this disease in agriculture.

Identification of candidate soil microbes responsible for small-scale heterogeneity in strawberry plant vigour

Studies were conducted to identify candidate soil microbes responsible for observed differences in strawberry vigour at a small spatial scale, which was not associated with visual disease symptoms. Samples were obtained from the soils close to the rhizosphere of ‘big＇ and ‘small＇ plants from small plots which exhibited large local heterogeneity in plant vigour. A metabarcoding approach was used to profile bacterial and fungal compositions, using two primer pairs for 16 S ribosomal RNA genes（16S r DNA） and one for the fungal internal transcribed spacer（ITS） region. Of the two 16 S r DNA primer sets, the 341F/805 R resulted in sequences of better quality. A total 28 operational taxonomic units（OTUs） had differential relative abundance between samples from ‘big＇ and ‘small＇ plants. However, plausible biological explanation was only possible for three fungal OTUs. Two were possible phytopathogens： Verticillium spp. and Alternaria alternata although the latter has never been considered as a main pathogen of strawberry in the UK. For samples from ‘small＇ plants, the abundance of these OTUs was much greater than from ‘big＇ plants. The opposite was true for a mycorrhizal OTU. These results suggest that soil microbes related to crop production can be identified using metabarcoding technique. Further research is needed to assess whether A. alternata and Verticillium spp. could affect strawberry growth in the field.

The negative effects of soil microorganisms on plant growth only extend to the first weeks

Soil biotic communities can strongly impact plant performance.In this paper,we ask the question:how longlasting the effect of the soil microbial community on plant growth is.We examined the plant growth rates at three stages:early,mid and late growth.We performed two growth experiments with Jacobaea vulgaris,which lasted 49 and 63 days in sterilized soil or live soil.In a third experiment,we examined the effect of the timing of soil inoculation prior to planting on the relative growth rate of J.vulgaris with four different timing treatments.In all experiments,differences in biomass of plants grown in sterilized soil and live soil increased throughout the experiment.Also,the relative growth rate of plants in the sterilized soil was only significantly higher than that of plants in the live soil in the first two to three weeks.In the third experiment,plant biomass decreased with increasing time between inoculation and planting.Overall,our results showed that plants of J.vulgaris grew less well in live soil than in sterilized soil.The negative effects of soil inoculation on plant mass appeared to extend over the whole growth period but arise from the negative effects on relative growth rates that occurred in the first weeks.

Soil nitrogen availability intensifies negative density-dependent effects in a subtropical forest

Aims The importance of density-dependent mortality in maintaining tree species diversity is widely accepted.However,density-dependent effects may vary in magnitude and direction with different abiotic conditions in forests.Theoretical predictions surmise that density-dependent effects may vary with soil available nitrogen(AN),but this still needs to be tested.Methods We analyzed the density-dependent effects on survival of newly germinated seedlings for 18 common species based on a long-term seedling census across environmental gradients in a subtropical forest.We also conducted a root lesion detection experiment for five species to investigate the potential effects of pathogens on variation in density-dependent disease between rich and poor AN environments.Important Findings The seedling dynamics analysis revealed that the strength of density-dependent effects increased with AN,shifting from neutral or positive with low AN to negative with high AN.Three of the five tree species had stronger density-dependent effects on root lesions in rich AN environments than in poor AN environments,which is consistent with the results of a long-term seedling dynamics analysis.We also found higher species diversity in rich AN environments,which may be promoted by the stronger negative density-dependent effects.Both the seedling dynamic analysis and root lesion detection experiment revealed stronger negative density-dependent effects in higher AN environment,resulting from stronger disease pressure by soil pathogens.Our study emphasized the importance of considering context dependence when testing the density dependence hypotheses.