Fusarium Root Rot Incidence Research Articles

Morphological and pathogenic characterization of Fusarium species causing common bean root rot in Uganda

Fusarium root rot (FRR) of common bean occurs in Africa, Central and South America, and causes yield losses of up to 86%. Recently, FRR-like wilt symptoms were observed in Uganda’s agroecology zones. To identify the causal pathogen, we conducted surveys in seven agroecology zones to determine the prevalence and incidence of the reported disease. During the surveys, diseased roots were collected for pathogen isolation. Fungal strains were characterized using colony color, mycelial growth rate and microscopic structures such as conidia and microconidia. The pathogenicity of 99 strains on five bean varieties was determined in artificially inoculated soils in the screenhouse. Based on field symptoms, the observed wilting was identified to be Fusarium root rot, the prevalence of which varied across agroecologies, with the highest (95%) in the Karamoja pastoral zone (KP) and the lowest (40%) in West Nile farming system (WN). Similarly, the incidence of FRR was highest (87%) in KP, and lowest (20%) in WN. Fusarium strains differed in growth rate, colony color, shape and size of microscopic structures. All evaluated strains were pathogenic on common bean and caused severities of 0.9 to 98.3%. Further studies are required to identify the isolated strains at the species level using molecular tools.

Agricultural Jiaosu: An Eco-Friendly and Cost-Effective Control Strategy for Suppressing Fusarium Root Rot Disease in Astragalus membranaceus.

Root rot caused by the pathogenic fungi of the Fusarium genus poses a great threat to the yield and quality of medicinal plants. The application of Agricultural Jiaosu (AJ), which contains beneficial microbes and metabolites, represents a promising disease control strategy. However, the action-effect of AJ on Fusarium root rot disease remains unclear. In the present study, we evaluated the characteristics and antifungal activity of AJ fermented using waste leaves and stems of medicinal plants, and elucidated the mechanisms of AJ action by quantitative real-time PCR and redundancy analysis. The effects of AJ and antagonistic microbes isolated from it on disease suppression were further validated through a pot experiment. Our results indicate that the AJ was rich in beneficial microorganisms (Bacillus, Pseudomonas, and Lactobacillus), organic acids (acetic, formic, and butyric acids) and volatile organic compounds (alcohols and esters). It could effectively inhibit Fusarium oxysporum and the half-maximal inhibitory concentration (IC50) was 13.64%. The antifungal contribution rate of the microbial components of AJ reached 46.48%. Notably, the redundancy analysis revealed that the Bacillus and Pseudomonas genera occupied the main niche during the whole inhibition process. Moreover, the abundance of the Bacillus, Pseudomonas, and Lactobacillus genera were positively correlated with the pH-value, lactic, formic and butyric acids. The results showed that the combined effects of beneficial microbes and organic acid metabolites increased the efficacy of the AJ antifungal activity. The isolation and identification of AJ’s antagonistic microbes detected 47 isolates that exhibited antagonistic activities against F. oxysporum in vitro. In particular, Bacillus subtilis and Bacillus velezensis presented the strongest antifungal activity. In the pot experiment, the application of AJ and these two Bacillus species significantly reduced the disease incidence of Fusarium root rot and promoted the growth of Astragalus. The present study provides a cost-effective method to control of Fusarium root rot disease, and establishes a whole-plant recycling pattern to promote the sustainable development of medicinal plant cultivation.

Application of vermicompost and biochar suppresses Fusarium root rot of replanted American ginseng.

Soil sterilization integrated with agronomic measures is an effective method to reduce soilborne replant diseases. However, the effect of vermicompost or biochar application after soil sterilization on soilborne diseases is poorly understood. A pot experiment was conducted in American ginseng to investigate the effects of vermicompost (VF), biochar (BF), and a combination of vermicompost and biochar (VBF) applied after soil sterilization on the incidence of Fusarium root rot using natural recovery (F) as control. After one growing season, the disease index of root rot, the phenolic acids, and the microbial communities of American ginseng rhizosphere soil were analyzed. The disease index of VF, BF, and VBF decreased by 33.32%, 19.03%, and 80.96%, respectively, compared with F. The highest bacterial richness and diversity were observed in the rhizosphere soil of VBF. Besides, VF and VBF significantly increased the relative abundance of beneficial bacteria (Pseudomonas, Lysobacter, and Chryseolinea) in the rhizosphere soil. Higher concentrations of vanillin, one of the phenolic acids in the roots exudates, were recorded in the rhizosphere soils of BF and VBF. The vanillin concentration showed a significant negative correlation with the disease index. To conclude, vermicompost improved the beneficial bacteria of the rhizosphere soil, while biochar regulated the allelopathic effect of the phenolic acids. The study proposes a combined application of biochar and vermicompost to the rhizosphere soil to control Fusarium root rot of replanted American ginseng effectively. KEY POINTS: Vermicompost improves the relative abundance of rhizosphere beneficial bacteria. Biochar inhibits the degradation of phenolic acids by adsorption. The combination of vermicompost and biochar enhances the disease control effect.

The Role of Root Exudates of Barley Colonized by Pseudomonas fluorescens in Enhancing Root Colonization by Fusarium culmorum.

The aim of this study was to find out why after joint inoculation of the substrate with the phytopathogenic fungus Fusarium culmorum and the antagonistic bacterium Pseudomonas fluorescens the amount of the fungus on the root surface in the beginning of the colonization was greater on the roots colonized by the bacterium than on control roots. This phenomenon is especially interesting because joint inoculation with P. fluorescens was always followed by a considerable decrease in the incidence of Fusarium root rot. In two experiments barley was grown in sterile vermiculite inoculated only with F. culmorum, only with P. fluorescens and jointly with the fungus and the bacterium. In the control, vermiculite was not inoculated with any microorganisms. After the removal from the vermiculite, barley plants were transferred into deionized water for the collection of root exudates. The duration of barley growth in the vermiculite and in the water was different in the two experiments. The exudates were tested for their ability to elicit chemotropism in F. culmorum and influence its growth. We did not observe any chemotropism of F. culmorum towards barley root exudates. However, the exudates of the barley colonized by the bacterium stimulated the growth of fungal germ tubes. Using an ultra-performance liquid chromatography system, we found that experimental conditions influenced the quantitative composition of the exudates. The amount of amino acids in the solution of exudates decreased considerably after a prolonged growth of control barley in water, while the presence of P. fluorescens resulted in a considerably increase of the amount of amino acids in the exudates. The exudates of barley colonized by P. fluorescens contained much more glucose, lactic acid and several amino acids than the exudates of control barley. These components are known to be necessary for the growth of F. culmorum. Their presence in the exudates of barley colonized by P. fluorescens seems to be the reason of a more active colonization by the fungus of barley roots colonized by the bacterium.

Interaction between Allelochemicals and <i>Fusarium</i> Root Rot in Asparagus Seedlings Cultured <i>In Vitro</i>

The interaction between Fusarium root rot and 4 allelochemicals in asparagus seedlings was estimated in vitro to clarify the relationship between biotic and abiotic factors in asparagus decline. In in vitro culture of Fusarium oxysporum f. sp. asparagi (Foa) with or without addition of 4 allelochemicals (caffeic acid, ferulic acid, quercetin, malic acid; 0.01%, 0.1%, w/v) using Czapec-Dox media, Foa propagation was suppressed in all the treatments. The degree of suppression became higher in 0.1% than 0.01% among all the allelochemicals. As for the axenic culture of asparagus (Asparagus officinalis L., “Welcome”) seedlings with the 4 allelochemicals, dry weight of both shoots and roots became lower compared to control in 0.1% and 0.01% of caffeic acid, 0.1% ferulic acid, 0.01% quercetin, only dry weight of shoots decreased in 0.1% malic acid. Two weeks after Foa inoculation with Foa-cultured PDA cubes in vitro, incidence of Fusarium root rot reached 100% in most of the plots. The severity of root rot increased in 0.01% and 0.1% caffeic acid, 0.1% ferulic acid, 0.1% malic acid compared to control. From these results, the 4 allelochemicals used in this study are supposed to suppress asparagus growth, and such growth reduction might enhance the disease severity of Fusarium root rot as an indirect effect. In addition, such effect might differ with the allelochemicals and concentrations in asparagus.

Biological control of Meloidogyne incognita and Fusarium solani in dry common bean in the field

Meloidoyne incognita (root-knot nematode) and Fusarium solani (root-rot pathogen) were the common soil-borne pathogens and cause severe damage to bean plants in newly reclaimed sandy soil in Nubaryia district, Behera Governorate, Egypt. The antagonistic effects of Trichoderma album and Trichoderma viride as well as three commercial products namely Rhizo-N® (Bacillus subtilis), Bio-Arc® 6% (Bacillus megaterium) and Bio-Zeid® 2.5% (T. album) were tested against M. incognita and F. solani under naturally infected field conditions. T. album and T. viride highly reduced the frequency (%) population of pathogenic fungi such as Fusarium spp., F. solani and Rhizoctonia spp., than the commercial products. Results indicated that all the tested bio-control agents reduced, significantly, the nematode criteria as evidenced by the number of juvenile (J2) in soil and number of galls and egg masses on roots of common bean and Fusarium root-rot incidence (%). Rhizo-N® highly reduced the number of J2 in soil, while T. album was the best in reducing the number of galls and egg masses in roots. The bio-control agents also increased the plant growth parameters of common bean plants i.e. plant height, plant weight, branch no./plant, pods no./plant, pod weight/plant, pod weight, seeds no./plant, fresh seeds weight/pod, dry seeds weight/pod and dry weight of 100 seeds.

Trichoderma spp. decrease Fusarium root rot in common bean

The effectiveness of six Trichoderma-based commercial products (TCP) in controlling Fusarium root rot (FRR) in common bean was assessed under field conditions. Three TCP, used for seed treatment or applied in the furrow, increased seedling emergence as much as the fungicide fludioxonil. FRR incidence was not affected, but all TCP and fludioxonil reduced the disease severity, compared to control. Application of Trichoderma-based products was as effective as that of fludioxonil in FRR management.

Fusarium root rot incidence and root system architecture in grafted common bean lines

In common bean (Phaseolus vulgaris L.), Fusarium root rot (caused by Fusarium solani f. sp. phaseoli) disease severity is increased by environmental factors that stress the plant. The current study used reciprocal grafting techniques with the resistant cultivar FR266 and the susceptible cultivar Montcalm to determine if the genetic control of resistance is conferred by the rootstock (root genotype) or the scion (shoot genotype) and if root vigor played a role in resistance. The influence of a compacted layer on root and shoot genotype response and root rot resistance was studied. Root rot resistance was found to be controlled by the root genotype, such that on a scale of 1 to 7 (severe disease) the FR266 root had an average score of 2.3 and the Montcalm root had an average score of 4.4. However, when grafted plants were grown in the presence of a compacted layer, the FR266 root and/or shoot genotype in any graft combination with the susceptible Montcalm had reduced root rot (score = 2.4 average) than the Montcalm self graft (score = 4.5). Root mass was shown to be controlled by the root genotype in the absence of compaction such that the FR266 root was 26% larger that the Montcalm root when grafted onto a FR266 shoot or a Montcalm shoot. When a compacted layer was present the root and shoot genotype both contributed to root mass. Average root diameter was controlled by the shoot genotype, as the FR266 shoot grafted to Montcalm or FR266 roots had thicker roots (average diameter 0.455 mm) than the Montcalm shoot (average diameter 0.418 mm). This study shows evidence that root vigor in the presence of Fusarium disease pressure should be evaluated to effectively develop common bean lines resistant to Fusarium root rot across a range of environments.

Incidence of Fusarium Root Rot in Asparagus Seedlings Infected with Arbuscular Mycorrhizal Fungus as Affected by Several Soil Amendments.

Seedlings of asparagus (Asparagus officinalis L., cv. Mary Washington 500 W) were inoculated with arbuscular mycorrhizal (AM) fungus (Glomus sp. R10) and grown in the presence of different soil amendments : carbonized chaff (CC), coconut charcoal (CO) and manure of coffee residue (MC) mixed with the soil in the ratio of 1 : 9 (v/v, 10% plot) or 3 : 7 (30% plot). Nine weeks later, the seedlings were exposed to fusarium root rot, caused by Fusarium oxysporum f. sp. asparagi (Foa) to test their tolerance. When asparagus seedlings were examined 13 weeks after Foa inoculation, incidence of fusarium root rot reached 90-100% in all the AM fungus-noninoculated plants, irrespective of the soil amendments. However, the incidences of root rot were 14.3% in the 30% CO and 20% in the 10% MC plots among the AM fungus-inoculated plants. In the non-AM inoculated plants, the disease indices reached 92.5 in the soil only plot and 48.9 in the 30% CC plot. As for AM-treated plants, the indices attained remarkably low values of 2.9 in the 30% CO and 4.0 in the 10% MC plots. More storage roots developed in the AM-treated plants than in the control, whether they were diseased or healthy. AM fungal infection levels were higher in the root systems of 10% and 30% CO and 10% MC plots than in the other plots ; little difference occurred among 10% and 30% CO and 10% MC plots. Furthermore, the infection area of the AM fungus in a root system was most extensive in the CO plots. These findings suggest that the addition of coconut charcoal or manure of coffee residue to bed soil is effective for increasing the tolerance to fusarium root rot in AM fungus-infected asparagus plants, though the effect differed with the quantity of the soil amendments.

Effect of Arbuscular Mycorrhizal Fungus Infection on the Incidence of Fusarium Root Rot in Asparagus Seedlings.

The incidence of fusarium root rot, caused by Fusarium oxysporum f. sp. asparagi (Foa), was investigated in seedlings of asparagus (Asparagus officinalis L., cv. Mary Washington 500W) by inoculation with three species of arbuscular mycorrhizal (AM) fungi ; Gigaspora margarita (GM), Glomus fasciculatum (GF), and Glomus sp. R10 (GR). Ten weeks after AM fungal inoculation, the inoculated plants were taller ; they produced more shoots and roots and accumulated more dry matter in the shoots and roots than noninoculated ones. The infection levels in a root system differed with fungal species. Six weeks after Foa inoculation, 90% of the noninoculated plants exhibited symptoms of fusarium root rot, whereas 20-50% of the inoculated plants did. The effect was more pronounced in GR, GM, and GF, in that order. As for the disease indices, it was lower in the inoculated plants than in the noninoculated ones. The indices differed among the AM fungal species ; it was significantly low in GR. The number of Foa hyphae invading feeder roots decreased in the inoculated plants, compared with the noninoculated ones. In addition, AM fungal hyphae preferentially elongated into short cells in the exodermis of feeder roots, while the Foa hyphae also elongated into short cells as well as AM fungus. However, no short cells became infected with both AM fungus and Foa. These results reveal that tolerance to fusarium root rot was conditioned by AM fungal infection in asparagus seedlings, although the effect differed with the AM fungal species. It seems that the tolerance to fusarium root rot was partially caused by AM fungal pre-infection in short cells which suppressed invasion by Foa in feeder roots.

Induced resistance of sweetpotato to Fusarium root rot by UV-C hormesis

`Jewel’ sweetpotato storage roots previously treated with a low hormetic dose of ultraviolet light-C (UV-C) were stored for 30 days before inoculated artificially with Fusarium solani. Storage roots showed an increase in resistance to Fusarium root rot, as indicated by a reduction in lesion diameter, depth and weight of rotted tissue following UV-C treatment. The rate of decay development around F. solani inoculum plugs on UV-C treated sweetpotato storage roots progressed slowly, and about 55% failed to develop lesions on wounded UV-C treated, compared to 11% of untreated sweetpotato storage roots, 10 days after inoculation. There was a polynomial curvilinear regression relationship between percent incidence of Fusarium root rot and hormetic UV-C doses. The hormetic dose of UV-C which suppressed decay to the greatest degree was 3.6 kJ m −2. Exposure of sweetpotato storage roots to doses of UV-C promoted phenylalanine ammonia-lyase (PAL) production with the maximum PAL activity occurred to the greatest degree at a UV-C dose of 3.6 kJ m −2. Similarly, a relationship between PAL activity and the incidence of Fusarium root rot was established. Crude extracts from UV-C treated sweetpotato storage roots reduced germination, germ tube elongation, and growth of F. solani compared to extracts obtained from untreated storage roots.

INDUCED RESISTANCE RESPONSE OF SWEETPOTATO TO FUSARIUM ROOT ROT BY UV-HORMESIS

Jewel sweetpotato storage roots previously treated with ultraviolet (UV–C) light and then stored for 30 days before artificial inoculation with Fusarium solani showed increased resistance to Fusarium root rot; as indicated by reduced lesion size, the rate of decay development of rotted tissues. There was a hormetic relationship between the incidence of Fusarium root rot and UV–C doses. The optimum dose of UV which reduced Fusarium root rot was 3.6× 104 ergs/mm2. Exposure of sweetpotato to UV–C doses promoted phenylalanine ammonia–lyase (PAL)4 production with the maximum PAL activity occurring at 3.6×104 ergs/mm2. Crude extracts from UV–C treated sweetpotatoes reduced germination, germ tube elongation and growth of F. solani when compared to untreated extracts.

Effect of Glomus fasciculatum on the Growth of Asparagus and the Incidence of Fusarium Root Rot

Asparagus (Asparagus officinalis L.) seedlings inoculated with the sicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. & Trappe (GF) d Fusarium oxysporum (Schlect.) Snyd. & Hans. (FO) were grown under field and greenhouse conditions. In the fi, shoot volumes of GF-inoculated plants were greater than nonGF plants from the 3rd through the 13th month of growth. By the 14th month, GF-inoculated plants grown in high-P soils had significantly lower disease ratings than nonGF plants grown in low-P soils, and rhizosphere populations of FO were lowest in high-P soils, regardless of VAM status. In greenhouse studies, FO inoculation of VAM-infected asparagus plants reduced GF root colonization levels under well-watered (0 MPa), but not under water stress, conditions (- 1.5 MPa). Well-watered plants inoculated with both FO and GF were less diseased and sustained lower rhizosphere populations of FO than plants inoculated with FO alone. The differences in FO populations and disease ratings in these studies were apparently unrelated to final plant tissue P levels.

Deterioration of Alfalfa Swards in the Hot Humid Subtropics of India1

AbstractAlfalfa (Medicago sativa L.) planted in the humid subtropics of India has not persisted well. To determine the effects of management practices on persistence and production, herbage growth, plant populations, Fusarium incidence on roots, and total available carbohydrates (TAC) were determined.Seven P and K fertilizer regimes and two cutting frequencies were used with ‘Anand—2’ and ‘Sirsa‐9’ alfalfa cultivars sown in the fall of 1975, 1976,. and 1977 on an Antisol soil in the subtropical plains of the eastern region in India.In 1976‐1977 and in 1977‐1978, Sirsa—9 yielded 7.6 and 9.7 metric tons/ha, respectively, while Anand—2 produced 6.9 and 8.3 metric tons/ha, of dry matter, respectively. Major fertilizer yield response was almost linear for 0, 22, and 44 kgha of P. Response to K was minimal and only after plant P needs were satisfied. Response to P was greater in 1977‐1978,Plant populations decreased consistently during the summer to about zero in October 1976 and August 1977, while in 1978 in a better drained area plant populations in July reduced from 70 to 30%.Root weights decreased drastically from 172 days after sowing (DAS) to 263 DAS regardless of management factor in the first two seasons. Fusarium root rot incidence by 203 DAS was severe for all management treatments except for one K treatment. No relationship between incidence and herbage yield was evident, however. Plant density and disease seventy was positively correlated (r = 0.97). Total available carbohydrate concentrations decreased, also, from about 35 at 172 DAS to 18% at 263 DAS. A positive correlation of r = 0.74 was found between disease severity and TAC.Additional work is needed to delineate the effects of Fusarium, and soil and plant factors before alfalfa could be recommended as a perennial in the subtropical regions representative of the experimental area.