Incidence Of Soil-borne Diseases Research Articles

Effects of Rootstock and Location on Open Field ‘BHN 589’ and ‘Nebraska Wedding’ Grafted Tomato Yield

Grafted tomato (Solanum lycopersicum) production is popular, particularly in high tunnels, because grafted plants can mitigate soilborne disease incidence in highly infested soils and increase water and nutrient use efficiency and crop yield and quality. However, these potential benefits are not as well documented in open field production systems with less disease pressure. The objective of this study was to quantify the effect of tomato grafting on fruit yield, number, and size across 2 years (2018 and 2019) and three diverse open-field production environments in Nebraska (Lincoln, North Platte, and Dwight). At each location, a scion from one of two determinant fresh market tomatoes, ‘Nebraska Wedding’ (heirloom) or ‘BHN 589’ (commercial hybrid), were grafted onto one of two rootstocks, ‘Estamino’ and ‘Maxifort,’ and the nongrafted scion cultivars were controls. In year 2, a fertilizer treatment was introduced (0 and 50 kg·ha−1 N). Ripe tomatoes were harvested weekly, sorted as marketable or cull, counted, and weighed fresh. No marketable or total yield benefits of grafting were observed in 2018 for any scion by rootstock combination across locations. Marketable yield of grafted plants was reduced by 32% in Lincoln. However, grafted ‘Nebraska Wedding’ plants (regardless of rootstock) in North Platte (with coarse-textured, lower organic matter soil) increased fruit number (but not yield) by 50% to 63%. In 2019, grafting ‘BHN 589’ to ‘Maxifort’ increased total tomato yield by 24% across all locations. The heirloom variety Nebraska Wedding did not benefit from grafting in 2019. ‘Estamino’ rootstock did not increase tomato yield, number, or size for either scion variety in either year. Nitrogen fertilizer increased yield as expected in 2019, but grafted plants did not perform better than nongrafted under reduced nitrogen fertility. Results from this study suggest that grafting is not consistently beneficial to ‘BHN 589’ and ‘Nebraska Wedding’ in open field production systems in Nebraska, particularly if there are no known soilborne disease issues.

Long-term effects of liming on crop yield, plant diseases, soil structure and risk of phosphorus leaching

This study examined the long-term effects of applying structure lime (mixture of ~80% CaCO3 and 20% Ca(OH)2) and ground limestone (CaCO3) on soil aggregate stability and risk of phosphorus (P) losses 5–7 years after liming, incidence of soil-borne diseases and yield in winter wheat (Tritium aestivum), oilseed rape (Brassica napus) and sugar beet (Beta vulgaris). Lime was applied in 13 field trials in Sweden 2013–2015 and soil characteristics and crop yield were monitored until 2021. Seedbed (0–4 cm depth) aggregate (2–5 mm size) stability was improved to the same extent with both lime treatments compared to the untreated control, sampled 5–7 years after liming. Analyses and estimations of different P fractions (total P, PO4-P, and particulate P) in leachate following simulated rainfall events on undisturbed topsoil cores sampled 6–8 years after liming revealed lower total P and particulate P concentrations in both lime treatments compared to the untreated control. Two sugar beet trial sites with soil pH ≤7.2 before liming showed an increase in sugar yield for structure lime and ground limestone as an effect of increased concentration of soil potassium (K-AL) and/or lower Aphanomyces root rot potential compared to the untreated control. The yield of winter wheat was not affected by the application of either type of lime at sites with pH >7.2 but the yield of oilseed rape decreased after the application of structure lime.

Effects of exogenous strigolactone on growth, dry matter accumulation, and yield of tissue-cultured ginger

ABSTRACT Ginger tissue culture seedlings can reduce the incidence of soil-borne diseases. However, they have several branches, small ginger bulbs, and slow seed recovery. Strigolactone can inhibit the growth of lateral buds, adjust plant types, and increase crop yield. This study used exogenous strigolactone to treat tissue-cultured ginger and assess its effects on growth, dry matter accumulation, and yield. The results showed that the number of branches and ginger bulbs per plant decreased significantly with the application of exogenous GR24 (Synthetic analog of strigolactone, rac-GR24), and higher concentrations led to a greater decrease. Plant height, stem diameter, root, rhizome, stem sheath, leaf and plant dry matter accumulation, average ginger bulb weight, and yield increased significantly, increasing initially and then decreasing with increasing concentration. Depending on the concentrations, exogenous strigolactone can inhibit the branching of tissue-cultured ginger, reduce the number of branches, increase plant height and stem diameter, optimize the aboveground plant type, increase dry matter accumulation and root-shoot ratio, decrease the number of ginger bulbs per plant, increase the average ginger ball weight, and increase yield. When the GR24 concentration was further increased, the number of branches, the plant height, stem diameter, dry matter accumulation, root shoot ratio, ginger bulbs per plant, average weight of ginger bulbs, and ginger yield decreased. Treatment with 7.5 um L−1 of exogenous GR24 could optimize the plant type of tissue-cultured ginger and increase yield.

The effects and interrelationships of intercropping on Cotton Verticillium wilt and soil microbial communities

BackgroundCotton Verticillium wilt, causing by Verticillium dahliae, has seriously affected the yield and quality of cotton. The incidence of Verticillium wilt in cotton fields has been on the rise for many years, especially after straw has been returned to the fields. Intercropping can reduce the incidence of soil borne diseases and is often used to control crop diseases, but the relationship between the effects of intercropping on microbial communities and the occurrence of plant diseases is unclear. This research explored the relationship between soil microbial community structure and Cotton Verticillium wilt in interplanting of cotton-onion, cotton-garlic, cotton-wheat and cotton monocultures. Amplicon sequencing applied to the profile of bacterial and fungal communities.ResultsThe results showed that the disease index of Cotton Verticillium wilt was significantly reduced after intercropping with cotton-garlic and cotton-onion. Chao1 and Sobs indices were not significantly different in the rhizosphere soil and pre-plant soils of the four planting patterns, but the pre-plant fungal shannon index was significantly lower in the cotton-onion intercropping plot than in the other three plots. PCoA analysis showed that the soil microbial communities changed to a certain extent after intercropping, with large differences in the microbial communities under different cropping patterns. The abundance of Chaetomium was highest in the cotton-garlic intercropping before planting; the abundance of Penicillium was significantly higher in the cotton-wheat intercropping than in the other three systems.ConclusionCotton-garlic and cotton-onion interplanting can control Cotton Verticillium wilt by affecting the soil microbial community. Fungi of the genera Chaetomium and Penicillium may be associated with plant disease resistance.

Effects of Chloropicrin, Dimethyl Disulfide and Metham Sodium Applied Simultaneously on Soil-Born Bacteria and Fungi

The area used to grow high-value crops is currently decreasing because production in the same soil for many years increases soil-borne diseases that reduce crop yield and quality as well as farmer income. Soil-borne disease is effectively controlled by soil fumigation prior to planting. In this study, the five different types of soils that had been used to grow tomatoes, watermelon, cucumber, ginseng and ginger were collected from field plots with high incidence of soil-borne diseases. This experiment adopts the indoor fumigation method to conduct triple fumigation of chloropicrin(PIC), metham sodium(MS) and dimethyl disulfide(DMDS) on different soil collected to examine changes in the soil microbial community, including pathogenic fungi and bacteria and beneficial microorganisms in order to clarify the impact on the overall structure of soil microbial community while controlling complex and multiple pathogens. High-throughput gene sequencing was used to detect bacterial and fungal taxonomic changes in the treated soils. Triple fumigation significantly reduced the abundance of at least five kinds of pathogenic fungi, Fusarium oxysporum, Mortierella, Neocosmospora, Nitrospira Alternaria and significantly increased the abundance of two kinds of beneficial species, Bacillus and Trichoderma. The research result observed increases and decreases in the biodiversity and richness of beneficial and pathogenic bacteria and fungi in response to triple fumigation of soil that had been used to grow tomatoes, watermelon, cucumber, ginseng and ginger. The most significant effect was observed in the experimental field of Panax notoginseng in Wenshan, Yunnan. Triple fumigation showed good potential to decrease pathogenic bacteria and fungi in soils and improve the disease resistance of soils, and that it has a good application prospect in the field of soil disinfestation.

Effect of marigold (Tagetes erecta L.) on soil microbial communities in continuously cropped tobacco fields

Root-knot nematode disease is a catastrophic soil-borne disease in tobacco production. The regulation of natural microbial communities is considered a good disease management approach to suppress the incidence of soilborne diseases. In this study, the effects of tobacco (Nicotiana tabacum L.)-marigold (Tagetes erecta L.) rotation on the diversity and structure of soil microbial communities in continuously cropped tobacco fields were analyzed to manage this devastating pathogen. The results showed that the soil bacterial OTUs increased after marigold rotation and that the bacterial Shannon, ACE, Chao1 index, and fungal Shannon index were higher in the tobacco-marigold rotation fields than in the continuously cropped tobacco fields by 3.98%, 10.37%, 5.46%, and 3.43%, respectively. After marigold rotation, the relative abundances of Actinobacteria, Acidobacteria, and Ascomycota increased by 28.62%, 107.50%, and 57.44%, respectively, and the proportion of beneficial bacterial genera such as Nocardioides, Gemmatimonas, and Bradyrhizobium increased. In addition, our results also showed that rotation of marigold could effectively reduce the incidence of root-knot nematodes in the next crop of tobacco. These results indicate that marigold rotation had a positive effect on the soil microecological environment of continuously cropped tobacco fields, reducing the obstacles to continuous cropping of tobacco.

Crop Rotation with Marigold Promotes Soil Bacterial Structure to Assist in Mitigating Clubroot Incidence in Chinese Cabbage.

Clubroot caused by Plasmodiophora brassicae is an economically important soilborne disease of Chinese cabbage worldwide. Integrated biological control through crop rotation is considered a good disease management approach to suppress the incidence of soilborne diseases. In this study, we evaluated the effect of a marigold plant (root exudates, crude extract, and powder) on the germination and death of resting spores of P. brassicae in vitro assays. Additionally, we also performed 16S high throughput sequencing, to investigate the impact of marigold–Chinese cabbage crop rotation on soil bacterial community composition, to manage this devastating pathogen. This study revealed that the marigold root exudates, crude extract, and powder significantly promoted the germination and death of P. brassicae resting spores. Under field conditions, marigold–Chinese cabbage crop rotation with an empty period of at least 15 days enhanced the germination of P. brassicae resting spores, shifted the rhizosphere bacterial community composition, and suppressed the incidence of clubroot by up to 63.35%. Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, and Verrucomicrobia were the most dominant phyla and were present at high relative levels in the rhizosphere soil of Chinese cabbage. We concluded that crop rotation of Chinese cabbage with marigold can significantly reduce the incidence of clubroot disease in the next crop. To our knowledge, this is the first comprehensive study on the prevention and control of clubroot disease in Chinese cabbage through crop rotation with marigold.

Characterization of the belowground microbial community and co-occurrence networks of tobacco plants infected with bacterial wilt disease.

Characterizing the microbial communities associated with soil-borne disease incidence is a key approach in understanding the potential role of microbes in protecting crops from pathogens. In this study, we compared the soil properties and microbial composition of the rhizosphere soil and roots of healthy and bacterial wilt-infected tobacco plants to assess their potential influence on plant health. Our results revealed that the relative abundance of pathogens was higher in diseased plants than in healthy plants. Moreover, compared with healthy plants, there was a significantly higher microbial alpha diversity in the roots and rhizosphere soil of diseased plants. In addition, we detected a lower abundance of certain plant microbiota, including species in the genera Penicillium, Trichoderma, and Burkholderia in the rhizosphere of diseased plants, which were found to be significantly negatively associated with the relative abundance of Ralstonia. Indeed, compared with healthy plants, the co-occurrence networks of diseased plants included a larger number of associations linked to plant health. Furthermore, structural equation modeling revealed that these specific microbes were correlated with disease suppression, thereby implying that they may play important roles in maintaining plant health. In conclusion, our findings provide important insights into the relationships between soil-borne disease incidence and changes in the belowground microbial community. These findings will serve as a basis for further research investigating the use of specific plant-associated genera to inhibit soil-borne diseases.

Assessment of postharvest soil fungal population with special reference to Trichoderma in eggplants

The research work was done to assess the postharvest soil fungal population and to find out the relation between population dynamics of Trichoderma and soil borne disease of 41 eggplant cultivars. Soil samples collected from IPM lab germplasm maintenance field at post-harvest stage were analyzed for microbes in dilution plate technique. Fungal colonies appeared in each plate were counted and made their average. Incidence and severity of Fusarium wilt and Sclerotium collar rot in the plot of 41 eggplant varieties were recorded at flowering-fruiting stage. The highest total soil fungal population was estimated from the plot soil of eggplant var. Singnath S (IPM- 42) that was 40.75×104. The var. Bijoy had the lowest fungal population that was 7.5×104. A comparison between Trichoderma population and other fungal population was made. Different eggplant cultivars had variation in the population of two important soil fungi- Trichoderma and Fusarium. The total populations of Trichoderma and Fusarium in the plot soil of 41 eggplant varieties were 129.75 and 348.75 × 104 per gram of soil, respectively. The average number of colonies of Trichoderma varied with the range (1-8.25) per plate. Fusarium varied with the range from (2-22.50). In 20 important eggplant varieties out of 41, both Fusarium wilt and Sclerotium collar rot incidence ranged between 0.00 to 40.00%. The variety Puta begun had the highest incidence of Fusarium wilt with the highest soil population of Fusarium oxysporum against the absence of Trichoderma harzianum. The disease incidence at flowering-fruiting stage was negatively correlated with the population of Trichoderma. Disease severity decreased with the increase in Trichoderma population. Increase of Trichoderma population, decreased the population of other fungi (Fusarium oxysporum and Sclerotium rolfsii). These results are clearly indicating that Trichoderma might have the antagonistic potential and might contribute to the reduction of incidence of soil-borne diseases.
 Progressive Agriculture 32 (1): 31-42, 2021

Rotation length, crop rotation, anaerobic soil disinfestation and mustard seed meal affect organic strawberry yield and soil-borne disease incidence in California

ISHS IX International Strawberry Symposium Rotation length, crop rotation, anaerobic soil disinfestation and mustard seed meal affect organic strawberry yield and soil-borne disease incidence in California

Palmitic acid mediated change of rhizosphere and alleviation of Fusarium wilt disease in watermelon.

Palmitic acid (PA) in root exudates or decaying residues can reduce the incidence of soil-borne diseases and promote the growth of some crop plants. However, the effects of PA on soil-borne pathogens and microbial communities are poorly understood. Here, we investigate the effects of PA on overall watermelon microbial communities and the populations of Fusarium oxysporum f.sp. niveum (Fon). The effects of PA on the mycelial growth and spore production of Fon were tested in vitro, while its effects on Fon, total bacteria and total fungi populations, and microbial communities were evaluated in a pot experiment. The results revealed that all test concentrations of PA inhibited Fon mycelia growth and spore production. The pot experiment showed that 0.5 mM and 1 mM PA reduced Fon but increased total bacteria populations, and 0.5 mM and 1 mM PA 0.5 mM and 1 mM PA promoted the change to a soil type of bacteria soil. Meanwhile, 0.5 mM PA and 1 mM PA altered the community composition of the rhizosphere microorganisms and reduced the relative abundance of two bacterial operational taxonomic units (OTUs) and the two fungal OTUs that were significantly (p < 0.01) related with disease severity and increased that of four bacterial OTUs and the two fungal that were highly significantly (p < 0.01) negatively correlated with the disease severity. These results suggest that application of PA decreased the populations of Fon, changed the rhizosphere microbial composition, reduced the disease severity of Fusarium wilt, and promoted the growth of watermelon.

Disease-Suppressive Soils-Beyond Food Production: a Critical Review.

In the pursuit of higher food production and economic growth and increasing population, we have often jeopardized natural resources such as soil, water, vegetation, and biodiversity at an alarming rate. In this process, wider adoption of intensive farming practices, namely changes in land use, imbalanced fertilizer application, minimum addition of organic residue/manure, and non-adoption of site-specific conservation measures, has led to declining in soil health and land degradation in an irreversible manner. In addition, increasing use of pesticides, coupled with soil and water pollution, has led the researchers to search for an environmental-friendly and cost-effective alternatives to controlling soil-borne diseases that are difficult to control, and which significantly limit agricultural productivity. Since the 1960s, disease-suppressive soils (DSS) have been identified and studied around the world.Soil disease suppression is the reduction in the incidence of soil-borne diseases even in the presence of a host plant and inoculum in the soil. The disease-suppressive capacity is mainly attributed to diverse microbial communities present in the soil that could act against soil-borne pathogens in multifaceted ways. The beneficial microorganisms employ some specific functions such as antibiosis, parasitism, competition for resources, and predation. However, there has been increasing evidence on the role of soil abiotic factors that largely influence the disease suppression. The intricate interactions of the soil, plant, and environmental components in a disease triangle make this process complex yet crucial to study to reduce disease incidence. Increasing resistance of the pathogen to presently available chemicals has led to the shift from culturable microbes to unexplored and unculturable microbes. Agricultural management practices such as tillage, fertilization, manures, irrigation, and amendment applications significantly alter the soil physicochemical environment and influence the growth and behaviour of antagonistic microbes. Plant factors such as age, type of crop, and root behaviour of the plant could stimulate or limit the diversity and structure of soil microorganisms in the rhizosphere. Further, identification and in-depth of disease-suppressive soils could lead to the discovery of more beneficial microorganisms with novel anti-microbial and plant promoting traits. To date, several microbial species have been isolated and proposed as key contributors in disease suppression, but the complexities as well as the mechanisms of the microbial and abiotic interactions remain elusive for most of the disease-suppressive soils. Thus, this review critically explores disease-suppressive attributes in soils, mechanisms involved, and biotic and abiotic factors affecting DSS and also briefly reviewing soil microbiome for anti-microbial drugs, in fact, a consequence of DSS phenomenon.

The Effects of Earthworms on Fungal Diversity and Community Structure in Farmland Soil With Returned Straw.

BackgroundTo promote the decomposition of returned straw, reduce the incidence of soil-borne diseases caused by returned straw, and accelerate the conversion of straw carbon into soil carbon, we inoculated earthworms into fields with returned straw. The earthworms accelerated straw degradation and promoted carbon conversion. However, the impact of externally inoculated earthworms on the farmland soil ecosystem, especially the structure and the function of its microbial community, remains unclear.MethodsWe analyzed the effects of straw return and earthworms on the diversity of fungal populations and the community structure of dominant fungal taxa in soil by quantifying fungal population size and community composition via PCR amplification of internal transcribed spacer genes and 18S rRNA gene sequencing.ResultsThe results showed that earthworm inoculation significantly accelerated the degradation of rice straw and promoted the conversion of straw carbon to soil carbon. Both fungal abundance and α-diversity (Sobs and Shannon indices) were higher in the plots with surface straw but without earthworms than in those inoculated with earthworms and in the CK. Principal component analysis indicated that straw return increased the diversity and the abundance of the fungal community, whereas earthworms inhibited this expansion of the fungal community caused by straw return. Interestingly, the overall differences in fungal community composition were smallest in plots with straw return, while the dominant fungal community features in plots inoculated with earthworms were closer to those of the CK.ConclusionGenerally, straw return stimulated unclassified_K_fungi, Pseudeurotium, and Fusarium with strong cellulolytic ability. In contrast, the abundances of Stachybotrys, unclassified_c_Sordariomycetes, unclassified_f_Lasiosphaeriaceae, and Schizothecium were higher in the plots inoculated with earthworms and in the CK. Furthermore, evolutionary analysis showed that the evolution of soil fungal communities tended to diverge after straw return, and the evolutionary directions of fungal species in the plots inoculated with earthworms were similar to those in the CK.

Effect of chemical alternatives to methyl bromide on soil-borne disease incidence and fungal populations in Spanish strawberry nurseries: A long-term study.

Chloropicrin (PIC) mixtures of 1,3-dichloropropene and chloropicrin (DD:PIC), dazomet, and metam sodium (MS) have been applied as chemical alternatives to methyl bromide (MB) in Spanish strawberry nurseries since MB was banned as a soil fumigant in 2005. These chemical alternatives were applied to soil in two Spanish strawberry nurseries between 2003 and 2017 to test their efficacy against the main crown and root disease and soil fungal populations in comparison with the use of MB and PIC (MB:PIC). These chemicals were applied at several doses with different application methods under plastic films. Crown and root disease incidence was calculated as the percentage of plants with symptoms caused by soil-borne pathogens. Soil fungal populations were estimated as colony forming units per gram of dry soil. All chemicals significantly reduced soil-borne fungal disease incidence and fungal population in both nurseries over the years. Phytophthora cactorum and Fusarium spp. were the main pathogens causing soil-borne diseases, followed by Verticillium spp. MB:PIC remained the treatment that best controlled P. cactorum. MS and DD:PIC controlled Fusarium disease to a lesser extent than MB:PIC and dazomet in both nurseries. MB:PIC and PIC were the two treatments that most reduced Verticillium spp. The population of Verticillium spp. declined and the presence of other species such as Colletotrichum spp. and Rhizoctonia spp. was minimal during the study. Chemicals are necessary to obtain healthy strawberry plants. The use of chemical alternatives to MB has resulted in changes in the incidence of soil-borne diseases and soil fungal populations in strawberry nurseries. Dazomet was an effective alternative to MB as a soil-borne disease control, except against Verticillium spp. MB alternatives in strawberry nursery soils have caused Fusarium spp. to displace Verticillium spp.

Analysis of the structure of bacterial and fungal communities in disease suppressive and disease conducive tobacco-planting soils in China

To clarify the differences between microbial communities resident in disease suppressive soil (DSS) and disease conducive soil (DCS) in tobacco cultivation, representative soil samples were collected from tobacco plantations in Shengjiaba, China, and the structure and diversity of the resident bacterial and fungal communities were analysed using high-throughput sequencing technology. Our results showed a greater number of operational taxonomic units associated with bacteria and fungi in DSS than in DCS. At the phylum level, abundances of Chloroflexi, Saccharibacteria, Firmicutes, and Planctomycetes in DSS were lower than in DCS, but abundance of Gemmatimonadetes was significantly higher. Abundances of Zygomycota and Chytridiomycota were higher in DSS than DCS, but abundance of Rozellomycota was significantly lower. At the genus level, abundances of 18 bacterial and nine fungal genera varied significantly between DSS and DCS. Relative abundances of Acidothermus, Microbacterium, Curtobacterium, and Colletotrichum were higher in DCS than DSS. The Shannon and Chao1 indices of DSS microbial communities were higher than those of DCS communities. High microbial diversity reduces the incidence of soil-borne diseases in tobacco plantations and promotes the formation of DSSs.

Soilborne Inoculum Density and Environmental Parameters Influence the Development of Pythium Stunt Caused by Pythium tracheiphilum in Head Lettuce Crops.

In Quebec muck soils, Pythium stunt (Pythium tracheiphilum Matta) is responsible for important yield losses in head lettuce crops each year, which can reach up to 50% in certain cases. Despite the significance of the disease, factors influencing its development remain poorly documented, and no disease risk indicators are available, which makes the development of management strategies difficult. Hence, growers systematically use chemical fungicides throughout the growing season to reduce crop losses. However, it is known that soilborne disease incidence or severity may be influenced by soil inoculum density and environmental parameters. Therefore, the objectives of this study were to investigate the influence of inoculum density on lettuce growth under controlled conditions and evaluate the influence of soil inoculum density, air temperature, relative humidity, and rainfall on disease incidence under field conditions. In particular, this study aims to develop accurate predictors for Pythium stunt incidence. Results showed that, under controlled environment, thresholds of inoculum density of 97 and 46 propagules per gram of dry soil were needed to reduce lettuce dry weight by one-half for cultivars Estival and Prestige, respectively. These results were confirmed under field conditions, where a soil inoculum density >132 propagules per gram of dry soil combined with air temperatures <18°C for the first 2 weeks and rain accumulation >64 mm for the first 3 weeks after transplanting accurately predicted disease incidence 79% of the time. These relationships improve understanding of seasonal Pythium stunt development and will provide useful tools to develop sustainable management strategies.

Management of peanut (Arachis hypogaea L.) diseases through nutrient supplements

Crop responses to mineral nutrients may be conducive or adverse to diseases, depending on disease type, severity, crop species, and cultivars. Therefore, an experiment was conducted to measure the effect of nutrient doses on to peanut diseases. The treatments were quite effective to manage the peanut diseases in kharif (Kh) as well as in rabi-summer (RS). All the treatments, applied however significantly reduced the soil borne as well as foliar fungal disease in comparison to control (without any external supply of nutrients). In kharif severity of ELS, LLS and Rust was (6.9) (4.4) and (6.2), respectively while it was highest in control (T7) and the per cent disease incidence of soil borne disease viz. aflaroot, collar rot and stem rot observed (2.5, 3.9 and 13.2 respectively) in T1 while it was (4.5, 5.7 and 16.8 respectively) in control (T7). In rabi stem rot incidence (21.3%) was recorded in control while it was lowest (9.7%) in the treatment T3 (25:50:0 NPK + 500 kg gypsum ha-1 + 2.5 kg zinc ha-1). The pod and haulm yield was recorded for effectiveness of different treatment on yield and found that the treatment T1 (25:50:0 NPK + 500 kg Gypsum+ 2.5 kg zinc+ 1 kg Boron) significantly increased the yield up to 40.5%. In both season T1 (25:50:0 NPK + 500 kg Gypsum+ 2.5 kg zinc + 1 kg Boron) reduces the disease severity significantly.

The effect of crop rotation and fungicide seed treatment on take-all in winter cereals in Lithuania

Agricultural production is increasingly based on monoculture farming in Lithuania, which inevitably exacerbates the problems caused by a rising incidence of soil borne diseases. Take-all (Gaeumannomyces graminis), formerly a minor disease, has become common causing substantial damage to winter wheat and winter barley. The aim of the present study was to analyze the influence of different rotation sequences on take-all occurrence and to investigate disease control options with seed treatment fungicides fluquinconazole and silthiofam during the 2014–2015 growing seasons. The total amount of Gaeumannomyces graminis var. tritici (Ggt) and G. graminis var. avenae (Gga) DNA in the roots of winter wheat seedlings grown in the soil collected from different rotations was measured. Significantly higher DNA concentrations of Ggt/Gga were detected in the roots of seedlings grown in the soil of winter barley monoculture, compared to the winter wheat monoculture. Comparable amount of Ggt/Gga DNA in winter wheat seedlings was determined in the soil of winter wheat monoculture and winter wheat after oil seed rape (OSR) in both seasons, while in the second winter wheat it was considerably lower. Higher take-all incidence and disease index were established in winter barley than in winter wheat monoculture. Nevertheless in the rotation with one-year OSR, take-all incidence and disease index were significantly reduced compared to the monoculture and second winter wheat. The highest grain yield of winter wheat in both years was achieved in the rotation with OSR. The tested seed treatment fungicides fluquinconazole and silthiofam resulted in a significant reduction in take-all occurrence and a slight increase in grain yield. The findings of this study demonstrate that the OSR was the most valuable tool for management of take-all in wheat.

Survey on incidence of soil borne diseases of coriander (Coriandrum sativum L.) in major districts of Andhra Pradesh

Survey on incidence of soil borne diseases of coriander (Coriandrum sativum L.) in major districts of Andhra Pradesh

Variability of Effective Micro-organisms (EM) in bokashi and soil and effects on soil-borne plant pathogens

The microbial inoculant ‘Effective Microorganisms’ (EM) has been used to promote soil fertility and plant growth in agriculture. We tested effects of commercial EM products on suppression of soil-borne diseases, microbial activity and bacterial composition in organically managed sandy soils. EM was supplied as microbial stock suspension and fermented organic matter (EM-bokashi). Bioassays for soil-borne disease incidence were conducted with a naturally infested soil and inoculated disease-free organically managed nonamended soils or the same soils amended with EM-bokashi or sterilized EM-bokashi. Soil respiration analysis and denaturing gradient gel electrophoresis (DGGE) were performed to determine microbial activity, and bacterial composition and diversity. Disease incidence of cucumber plants was not affected by EM-bokashi but reduced by sterilized bokashi compared to the control in naturally infested soil. Pythium ultimum damping-off of cucumber in inoculated soil was enhanced by EM-bokashi and sterilized bokashi compared to the control. In one of three soils, infection of carrot by Rhizoctonia solani was reduced by EM-bokashi compared with sterilized bokashi. Soil respiration increased one week after soil amendment with EM-bokashi and sterilized EM-bokashi compared to the control, but not seven weeks later. DGGE showed that two batches of EM products had different microbial communities and soil amendment with EM-bokashi or sterilized EM-bokashi did not change the bacterial community and diversity in two soils. The added microorganisms in EM were possibly outcompeted and did not affect the existing bacterial community. We conclude that EM did not consistently suppress soil-borne diseases or change microbial activity and bacterial composition and diversity.