Root Rot Fungus Research Articles

Managing the root rot disease of sunflower with endophytic fluorescent Pseudomonas associated with healthy plants

Use of pesticides is an effective way to control plant diseases but their excessive or misuse of chemical pesticides can cause environmental pollution. Whereas, biological control of plant diseases with saprophytic bacteria and fungi still giving inconsistent results, utilization of endophytic bacteria in plant disease management has been appeared as a new hope. In current study, 40 isolates of endophytic fluorescent Pseudomonas (EFP) were isolated from 20 healthy plants grown in experimental field of Karachi University and agricultural fields of Karachi and its suburb and identified according to Bergey's manual. Identification of ten potential isolates was also confirmed using genus-specific primer set i.e. PA-GS-R F 5′-CACTGGTGTT- CCTTCCTATA-3′ and PA-GS-F 5′-GACGGGTGAGTAATGCCTA-3’. Phylogenetic reconstruction associated the fluorescent Pseudomonas as a descendent of P. monteilii and P. aeruginosa. Out of 40 isolates, 10 caused growth inhibition of all 4 test root rotting fungi Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and F. oxysporum in vitro. Most of them were found to produce hydrogen cyanide, volatile antifungal metabolites, ammonia and indole acetic acid besides solubilizing phosphate. In field plot experiments five selected isolates of EFP were applied as soil drench, significantly suppressed root rotting fungi of sunflower. EFP-121 was found highly effective in improving plant height and fresh shoot weight, than other isolates and carbendazim, a fungicide. Endophytic fluorescent Pseudomonas associated with healthy plants are seems to be an effective alternate to chemical fungicides.

Interactive effect of Meloidogyne incognita and Macrophomina phaseolina on the development of root–rot disease complex in relation to growth and physiological attributes of chickpea

Summary The interactive relationship between the root–knot nematode Meloidogyne incognita and the root-rot fungus Macrophomina phaseolina in a root–rot disease complex of chickpea (Cicer arietinum var. avrodhi) was studied in a net house. The present study was carried out in such a manner so that the pathogenic potential of M. incognita and M. phaseolina individually, simultaneously and sequentially could be monitored. The pathogens singly as well as in combination led to significant reduction in growth, yield, nutrient and biochemical parameters. Gaseous exchange parameters like photosynthetic rate, transpiration rate and stomatal conductance were also reduced following infection of plants by the pathogens. However, maximum reduction was noticed in simultaneous inoculation with both pathogens. Sequential inoculation, where M. incognita preceded M. phaseolina by 15 days, was more damaging to the crop in comparison to that where M. phaseolina preceded M. incognita inoculation by 15 days. Infection by M. phaseolina caused a considerable reduction in the number of galls, egg–masses and nematode multiplication, with the highest reduction observed in plants simultaneously inoculated with the pathogens. Those plants also showed the highest disease severity in terms of percent root–rot. Thus, a manifold action plan to reduce the impact of the root-rot disease complex on chickpea crops has to be formulated.

Growth of broadleaved species on post-agricultural lands introduced during the process of stand conversion with a use of artificial gaps

Abstract This paper presents results on the restoration of Scots pine stands established on post-agricultural lands undergoing conversion into mixed stands. Sessile oak (Quercus petraea), common beech (Fagus sylvatica) and small-leaved lime (Tilia cordata) seedlings were planted in artificially created gaps (0.02 ha to 0.05 ha each) cut in six experimental plots (Forest Districts: Bielsk, Krynki, Sobibór, Dobieszyn, Skrwilno and Łupawa) located in 20–25-years-old pine stands. The experimental plots were spread across northern, central and eastern Poland and affected by root-rot fungus (Heterobasidion annosum). Nine years after planting, the number of individual trees and shrub species, their height sum and average height were calculated for fenced artificial gaps (LSO) as well as non-fenced artificial gaps (LSN) and compared to natural gaps (LN) and non-disturbed neighboring stands (D). Results were calculated separately for the planted species (oak, lime and beech) but combined for all other species. The results indicate satisfactory restoration in all of the investigated plots except in Krynki, which is located in a relatively poor site. Significant differences appeared between height sum as well as average height of planted species in fenced compared to non-fenced gaps. Furthermore, in both, natural and artificial gaps, the species composition of the young generation was enriched with natural regeneration of pioneer species, mainly silver birch (Betula pendula), rowan (Sorbus aucuparia) and aspen (Populus tremula).

Efficacy of soil solarization on black root rot disease and speculation on its leverage on nematodes and weeds of strawberry in Egypt

BackgroundStrawberry (Fragaria ananassa Duch.) is an economically important crop in Egypt. Yet complex black root rot disease of strawberry caused by Fusarium solani, Rhizoctonia solani, and Pythium sp. can cause considerable yield losses. Therefore, this study aimed at evaluating different aspects of soil solarization against this disease. Such an evaluation would better be viewed in the context of other beneficial effects of soil solarization on nematodes and weeds.Materials/methodsGrowth agar disks, growth suspension, and resting stages of strawberry black root rot fungi were evaluated at different temperatures and exposure times using digital hot water bath. Cloth bags artificially infested with single fungal species were buried into the soil before soil solarization at soil depths of 1–10, 11–20, and 21–30 cm at three spots of each plot for each of the abovementioned fungi for 3, 6, or 9 weeks. The disease incidence and severity in solarized and un-solarized soil was compared with the application of the fungicide Actamyl. Effects of soil solarization on nematodes and weeds were also consulted.ResultsThe lethal temperature to F. solani, Pythium sp., and R. solani was 58, 58, and 56 °C, respectively when exposure time was 1 min. Chlamydospores were killed at 62 °C while sclerotia were killed at 58 °C in hot water for 1 min. Maximum soil temperature in solarized soil was raised by 15, 14, and 12 °C at depths of 1–10, 11–20, and 21–30 cm as compared with non-solarized soil. Solarization for 3, 6, and 9 weeks significantly reduced the disease incidence and severity and increased the strawberry yield. Complete reduction in total count of all tested fungi was obtained after 9 weeks at all tested depths. A review of collective soil pest and pathogen control via solarization documented its beneficial application.ConclusionThe study may exploit hot months in Egypt for soil solarization against the serious root rot disease either singly or in an integrated pest management program.

Estimation of losses caused by root rotting fungi and root knot nematodes infecting some important crops in lower Sindh and Hub, Balochistan of Pakistan

Estimation of losses caused by root rotting fungi and root knot nematodes infecting some important crops in lower Sindh and Hub, Balochistan of Pakistan

Management of root rot fungi by Grewia asiatica L. leaves and on the growth of crop plants

Management of root rot fungi by Grewia asiatica L. leaves and on the growth of crop plants

Toothpick method to evaluate soil antagonism against the white root rot fungus, Rosellinia necatrix

A method was developed to evaluate soil antagonism against the white root rot fungus, Rosellinia necatrix. Toothpicks colonized by the fungus were immersed into hot water to produce an extinction zone (EZ) of the fungus and then inserted into soil from different orchards. The EZ differed to various extents in unsterile soils; however, when soil was sterilized, the EZ disappeared. Using this method, we investigated the mechanism of the hot water drip irrigation method devised to control white root rot. The results showed the involvement of synergism between hot water and soil antagonists in the control measure against R. necatrix.

A NEW WAY TO ELIMINATE THE ROOT ROT FUNGI IN GREEN FODDER UNDER THE HYDROPONIC CONDITIONS

This study was done to indicate the activity of secondary metabolites of cyanophyta algal extracts for Anabaena Azolla which live in Azolla plant in Egypt and to study the effective of secondary metabolites in An.Azolla extracts (cold water and methanol extracts) to inhibition species of fungi (Fusarium oxysporum, penicillium expansum, Aspergillus niger and candida albicans) also used of HPLC analysis to detected some of active secondary metabolites was done only for methanol extracts also to preliminary statements that used of two extracts of blue green alga Anabaena Azolla. The role of An.Azolla extracts to inhibition growth of these fungi was detected through measured diameter of inhibition zone diameters were, 16.58, 11.42, 11.0 & 11.0 mm in case of Fusarium oxysporum, Penicillium expansum, Aspergillus niger and candida albicans respectively, but aqueous extract give inhibition zone were 18.15, 14.13, 14.0 & 13.0mm respectively. and the results showed these extracts had high correlation ratio and fungi shows high sensitivity to these extract. The mode of mechanism action to inhibition was on fungi cell wall by inhibition active enzymes, excelled treatment for cold water extract . The most important active compounds had been detected in HPLC were phenolic compounds and flavonoids compounds these all compounds detected specially in methanol extract of An .Azolla. The experiment has been conducted under temperature and artificial illumination at growth room of Soilless Culture Laboratory, Sadat city University, Egypt. The results showed that green fodder can be produced in 8 days using hydroponic technique. Trays treated with Azolla gave more green fresh yield (11.8 kg/tray) than untreated ones (7.2 kg/tray). Adding Azolla increased protein content and the percentages of N, P, K by 28.7% and 0.98, 0.82, 0.70 %, respectively, as compared to no addition of Azolla. Zero disease incidences were achieved with treated by Azolla as compared to 26.0 % with those untreated by Azolla. It could be concluded from this study that adding Azolla to hydroponic barley forage production improved green forage yield and its chemical analysis and free from root rot fungi.

RESPONSE OF BARLEY FORAGE PRODUCTION AND CHEMICAL ANALYSIS TO ADDING AZOLLA UNDER HYDROPOIC SYSTEM

Barley (Hordeum vulgare L.) matures faster and more evenly under a hydroponic system than a conventional soil based system. Supplemented Azolla (Azolla Pinnata) to hydroponic system as an aquatic free floating fern provides protein with all essential amino acid which is required for animal nutrition. So, this investigation aimed to evaluate green fodder production and inhibition of root rot fungi under hydroponic conditions for barley. The experiment has been conducted under temperature and artificial illumination at growth room of Soilless Culture Laboratory, Sadat city University, Egypt. The results showed that green fodder can be produced in 8 days using hydroponic technique. Trays treated with Azolla gave more green fresh yield (11.8 kg/tray) than untreated ones (7.2 kg/tray). Adding Azolla increased of protein, N, P and K content percentages by 28.7, 0.98, 0.82 and 0.70 %, respectively, as compared to no addition of Azolla. There is no disease incidences were achieved with treated by Azolla as compared to 26.0 % with those untreated by Azolla. It could be concluded from this study that adding Azolla to hydroponic barley forage production improved green forage yield and its chemical analysis

Growth of Phlebiopsis gigantea in wood of seven conifer species

AbstractHeterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.

ICTV Virus Taxonomy Profile: Megabirnaviridae.

Megabirnaviridae is a family of non-enveloped spherical viruses with dsRNA genomes of two linear segments, each of 7.2-8.9 kbp, comprising 16.1 kbp in total. The genus Megabirnavirus includes the species Rosellinia necatrix megabirnavirus 1, the exemplar isolate of which infects the white root rot fungus (Rosellinia necatrix) to which it confers hypovirulence. Megabirnaviruses are characterized by their bisegmented genome with large 5'-untranslated regions (1.6 kb) upstream of both 5'-proximal coding strand ORFs, and large protrusions on the particle surface. This is a summary of the ICTV Report on the family Megabirnaviridae, which is available at ictv.global/report/megabirnaviridae.This Profile is dedicated to the memory of our valued colleague Professor Said A. Ghabrial.

Colonization of Pinus radiata D. Don Seedling Roots by Biocontrol Bacteria Erwinia billingiae and Bacillus simplex

Erwinia billingiae S31R1 and Bacillus simplex S11R41, isolated from the rhizosphere of a healthy tree located in a Pinus radiata D. Don plantation with high presence of fungal pathogens, are antagonists of pine root rot fungi Heterobasidion annosum and Armillaria mellea in vitro and in young trees. For effective biocontrol of these pathogens, the bacteria must stably colonize P. radiata roots following their application. To determine root colonization patterns, the bacteria were transformed with stable plasmids encoding green fluorescent protein (GFP). Transformed E. billingiae was visualized on roots 24 days after soil inoculation by confocal and epifluorescence microscopy, and GFP was detected by ELISA 31 days after inoculation. The presence of E. billingiae microcolonies, in some cases in root intercellular spaces, suggests that bacterial growth was active and localized. Fluorescence of B. simplex S11R41 was visualized on P. radiata roots 31 days after inoculation and its colonization pattern changed from scattered cells to localized microcolonies. Although the populations decreased over time, microcolony formation and localization in specific regions of roots indicated that E. billingiae, normally considered to be an epiphyte, and B. simplex can stably colonize roots of P. radiata.

Alphapartitiviruses of Heterobasidion Wood Decay Fungi Affect Each Other's Transmission and Host Growth.

Heterobasidion spp. root rot fungi are highly destructive forest pathogens of the northern boreal forests, and are known to host a diverse community of partitiviruses. The transmission of these mycoviruses occurs horizontally among host strains via mycelial anastomoses. We revealed using dual cultures that virus transmission rates are affected by pre-existing virus infections among two strains of H. annosum. The transmission efficacy of mycovirus HetPV15-pa1 to a pre-infected host was elevated from zero to 50% by the presence of HetPV13-an1, and a double infection of these viruses in the donor resulted in an overall transmission rate of 90% to a partitivirus-free recipient. On contrary, pre-existing virus infections of two closely related strains of HetPV11 hindered each other's transmission, but had unexpectedly dissimilar effects on the transmission of more distantly related viruses. The co-infection of HetPV13-an1 and HetPV15-pa1 significantly reduced host growth, whereas double infections including HetPV11 strains had variable effects. Moreover, the results showed that RdRp transcripts are generally more abundant than capsid protein (CP) transcripts and the four different virus strains express unique transcripts ratios of RdRp and CP. Taken together, the results show that the interplay between co-infecting viruses and their host is extremely complex and highly unpredictable.

Confirmation of Fusarium root rot resistance QTL Fsp-Ps 2.1 of pea under controlled conditions

BackgroundDry pea production has increased substantially in North America over the last few decades. With this expansion, significant yield losses have been attributed to an escalation in Fusarium root rots in pea fields. Among the most significant rot rotting pathogenic fungal species, Fusarium solani fsp. pisi (Fsp) is one of the main causal agents of root rot of pea. High levels of partial resistance to Fsp has been identified in plant genetic resources. Genetic resistance offers one of the best solutions to control this root rotting fungus. A recombinant inbred population segregating for high levels of partial resistance, previously single nucleotide polymorphism (SNP) genotyped using genotyping-by-sequencing, was phenotyped for disease reaction in replicated and repeated greenhouse trials. Composite interval mapping was deployed to identify resistance-associated quantitative trait loci (QTL).ResultsThree QTL were identified using three disease reaction criteria: root disease severity, ratios of diseased vs. healthy shoot heights and dry plant weights under controlled conditions using pure cultures of Fusarium solani fsp. pisi. One QTL Fsp-Ps 2.1 explains 44.4–53.4% of the variance with a narrow confidence interval of 1.2 cM. The second and third QTL Fsp-Ps3.2 and Fsp-Ps3.3 are closely linked and explain only 3.6–4.6% of the variance. All of the alleles are contributed by the resistant parent PI 180693.ConclusionWith the confirmation of Fsp-Ps 2.1 now in two RIL populations, SNPs associated with this region make a good target for marker-assisted selection in pea breeding programs to obtain high levels of partial resistance to Fusarium root rot caused by Fusarium solani fsp. pisi.

Assessment of presence and distribution of Armillaria and Heterobasidion root rot fungi in the forest of Vallombrosa (Apennines Mountains, Italy) after severe windstorm damage

Abstract: One of the main problems for the management and conservation of silver fir stands has long been pathogens causing root rot, in particular Armillaria spp. and Heterobasidion annosum s.l. These opportunistic pathogens are especially threatening now that climate change related stress is increasing tree susceptibility to disease and vulnerability to windstorms. The northern Apennines Mountains (central Italy) are forecast to be one of the areas with the highest temperature increase in the next future. However, no systematic assessment exists of the risk posed by the disturbance due to secondary pathogens in the Apennine forests. In the Nature Reserve of Vallombrosa (northern Apennines), where silver fir forests have been managed and conserved for centuries since the Middle Ages, making it an ideal site for studying these parasites, the high presence of H. annosum was reported already in 1990, while only sporadic observations are available on Armillaria species. The aim of this work was to examine the occurrence of both pathogens, since detailed knowledge about their distribution may assist forest management planning and decision-making. Systematic sampling was undertaken at the intersection of 52 grid points covering the whole forest. Different fungal species from soil and fungal samples (fruiting bodies or rhizomorphs) were identified by combining morphological descriptions with molecular methods. The analyses confirmed the presence of H. abietinum in about 70% of the investigated points. The fungus was detected at two new localities above 1000 metres suggesting a possible expansion of the parasite at upward elevation, which might be associated with climate change. Armillaria was widespread: almost 90% of the samples resulted positive, and four different Armillaria species were successfully identified. The most frequent species were A. cepistipes, whose rhizomorphs were especially abundant, and A. ostoyae, which was often detected just in soil samples. At sites where A. cepistipes was found to coexist with A. gallica, these two species might specialize themselves to necrotrophic and saprotrophic lifestyle, respectively. Besides, there were unexpected findings of A. mellea, supposed to be a residual from the previous rotation of broadleaves.

Management of root rotting fungi and root knot nematode with endophytic fluorescent Pseudomonas associated with Salvadora species

Management of root rotting fungi and root knot nematode with endophytic fluorescent Pseudomonas associated with Salvadora species

Low Water Availability Increases Necrosis in Picea abies after Artificial Inoculation with Fungal Root Rot Pathogens Heterobasidion parviporum and Heterobasidion annosum

Research Highlights: Dedicated experiments to investigate how disturbances will affect Heterobasidion sp.—Norway spruce pathosystems are important, in order to develop different strategies to limit the spread of Heterobasidion annosum s.l. under the predicted climate change. Here, we report on a greenhouse experiment to evaluate the effects of water availability on the infection severity of Heterobasidion parviporum or Heterobasidion annosum, respectively, on Picea abies saplings. Background and Objectives: Changes in climatic conditions and intense logging will continue to promote H. annosum s.l. in conifer forests, increasing annual economic losses. Thus, our aim was to test if disease severity in Norway spruce was greater after infection with H. parviporum or H. annosum in low water availability conditions, compared to seedlings with high water availability. Materials and Methods: We performed inoculation studies of three-year-old saplings in a greenhouse. Saplings were treated as high (+) or low (−) water groups: High water group received double the water amount than the low water group. The necrosis observed after pathogen inoculation was measured and analyzed. Results: The seedling growth was negatively influenced in the lower water group. In addition, the water availability enhanced the necrosis length of H. parviporum in phloem and sapwood (vertical length) in the low water group. H. annosum benefited only in horizontal length in the phloem. Conclusions: Disturbances related to water availability, especially low water conditions, can have negative effects on the tree host and benefit the infection ability of the pathogens in the host.

Role of Rhizobia in Suppressing the Root Diseases of Soybean Under Soil Amendment

ABSTRACT: Rhizobia are soil bacteria, characterized by their unique ability to colonize the roots of leguminous crops, where they form nitrogen fixing nodules. Considerable evidence has been accumulated to identify the benefits associated with use of rhizobia as biocontrol agents against soil-borne pathogens, in addition to biological nitrogen fixation. In this study, out of four rhizobial isolates tested, Bradyrhizobium sp. inhibited the radial growth of all the test fungi viz: Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and F. oxysporum, while other 3 rhizobial isolates inhibited the growth of at least three fungi. Cell free culture filtrates of rhizobia also showed nematicidal activity by killing second-stage juveniles of Meloidogyne javanica at varying degrees. Application of rhizobial isolates alone or in mustard cake amended soil significantly (p<0.05) by suppression of root rotting fungi and root knot nematode on soybean roots. Rhizobia-treated plants showed less penetration of nematodes in roots than untreated control plants. Efficacy of rhizobia was found to increase against nematodes in mustard cake at 1% amended soil. Rhizobia also improved soybean growth by producing taller plants although plants showed poor nodulation. The tallest plant was found in some nitrogen fixing bacteria (NFB) + mustard cake (1%) treatment, but in most cases, the combined application did not offer any added advantage.

First report of Aphanomyces cochlioides causing root rot of sugar beet in Turkey

Turkey produces c. 16 million tonnes of sugar beet annually, making it the fifth largest producer in the world, and around a third is grown in the province of Konya (FAO, 2014). Fungal root rots of sugar beet (Beta vulgaris) have been…

Estimating the Fitness Effect of Deleterious Mutations During the Two Phases of the Life Cycle: A New Method Applied to the Root-Rot Fungus Heterobasidion parviporum.

Many eukaryote species, including taxa such as fungi or algae, have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance-a measure that accounts for these two effects-should be close to 0.5 in these species. It also predicts that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring, and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum-a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons, and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.