Antifungal activity of some plant extracts on some pathogenic fungi

The inhibitory activity of five plant extracts viz. Artemisia absinthium L., Rumex obtusifolius L., Taraxacum officinale Weber ex Wiggers, Plantago lanceolata L. and Malva sylvestris L. were evaluated against the mycelial growth of three fungi Alternaria alternata (Fr.) Keissler, Penicillium expansum Link ex Thom. and Mucor piriformis Fisher that cause rot diseases in fruits and vegetables resulting in low yield and quality of fruits and vegetables. Results revealed that all the concentrations of plant extracts brought about significant inhibition in the mycelial growth of these pathogenic fungi. However, the highest concentration caused maximum inhibition in the mycelial growth followed by lower concentrations of plant extracts. The extract of A. absinthium leaves at highest concentration (S) proved highly effective in inhibiting the mycelial growth of all these pathogenic fungi followed by other plant extracts. These plants thus may have potential as the new natural fungicide for management of fungal rot diseases.     

Post-harvest diseases of tomato in india

Summary A systematic account of nine fungal diseases of tomatoes caused byAlternaria tenuis, Colletotrichum dematium, Cladosporium fulvum, Fusarium roseum, Malustela aeria, Myrothecium roridum, Oospora lactis f. parasitica, Phoma sp. andRhizopus nigricans during storage has been given. Except Oospora rot the other diseases included in the present paper have not been recorded previously from India. Post-harvest decay of tomatoes due toMalustela aeria has not been described from any part of the world and is new to science.     

Facultative parasites and host respiration. I. Healthy tissue adjacent to the site of infection

Summary The respiration, as measured by oxygen uptake, was higher for healthy tissue adjacent to soft rots of apple (var. Bramley) caused byPenicillium expansum Link andThom. andBotrytis cinerea Fr. and of potato tuber (var. Arran Banner) caused byErwinia aroideae Townsend, than tissue at a more distant site. The respiration of tissue adjacent to a physiological rot caused by bruising was not affected. It was concluded that there is diffusion of a substance(s) from the site of infection which causes an increase in the rate of respiration of the adjacent tissue.This work formed part of a Ph. D. thesis submitted to the University of London, July 1961.     

Studies on the fungi associated with tomato fruit rots and effects of environment on storage

Seven fungi associated with fruit rot of tomato were isolated includingFusarium equiseti, F. chlamydosporum, Alternaria solani, Geotrichum candidum, Acremonium recifei, Aspergillus flavus andA. niger. They were all pathogenic on tomato fruits, most pathogenic beingGeotrichum candidum followed byA. niger. Least rot was caused byAlternaria solani. The optimum temperature for maximum rotting caused byG. candidum, A. niger andA. flavus was 30°C. The relative humidity for maximum rot ranged from 70–90%. Tomato fruits stored well at 0–10°C and rather poorly at 20–30°C. Fruits stored at 35°C showed blemishes. The best RH for storage ranged between 60 and 90%.     

Effects of Exin on the development of microbial infection and ethylene release in plants

Effects of Exin on infection of tomato, potato, and cabbage plants withPseudomonas solanacearum andErwinia carotovora and a fungusSclervtium rolfsii were studied. The treatment of infected plants with Exin caused no significant effect on the development of the disease. Treatment with streptomycin as a standard for comparison completely inhibited the growth of these microorganisms. Pretreatment with Exin for one to eight days before infection inhibited the development of diseases. The numbers of tomato and potato plants damaged among those infected withP. solanacearum were lower by 10 and 35% respectively. In field experiments (350 plants per variant), treatment with Exin decreased the development of wilt caused byS. rolfsii andP. solanacearum and rot caused byE. carotovora. Treatment with Exin activated the release of ethylene for not less than 30 days. Possible mechanisms of the effects of Exin are discussed.     

Studies on Biological Control of Postharvest Rot in Yams (Dioscorea spp.) using Trichoderma viride

From in vitro and in vivo screening tests for antagonism by isolates of Trichoderma against postharvest pathogens of yams (Dioscorea spp.), an isolate of Trichoderma viride Pers. ex S.F. Gray was selected as the most promising candidate for the biocontrol of postharvest rot of yams. Inoculation of white yam (Dioscorea rotundata Poir.) with conidiaspores of T. viride and subsequent storage of the tubers under the ambient environment conditions of a traditional yam barn, resulted in a drastic reduction in the frequency of occurrence of the normal tuber surface mycoflora over a 4‐month (December‐April) storage period. Trichoderma viride on the other hand, maintained a high frequency of occurrence during the same period. Furthermore, whereas up to 52.0%) rot was found among groups of tubers that were artificially inoculated with the postharvest pathogens of yams, Aspergillus niger Van Tiegh., Botryodiplodia theobromae Pat. or Penicillium oxalicum Currie and Thom, and also the group that was not inoculated with any organism (control), among groups of tubers that were inoculated with T. viride the rot was either totally suppressed or only a low percentage of rot occurred. The significance of the findings is discussed in relation to yam storage especially by farmers with limited resources.     

Infection and disintegration of vascular tissues of non-suberized roots of spruce byHeterobasidion annosum and use of antibodies for characterizing infection

Vascular disintegration mainly of medulla rays of spruce roots is of major significance in root rot disease of spruce caused byH. annosum. Using seedling roots as an experimental model, the possible routes and initial host reactions preceding invasion of vascular tissues was investigated. Transmission electron microscopy showed that penetration through the endodermis was an obvious route but not without host resistance. Using antibodies againstH. annosum hyphal materials, some labelling of vascular tissues remote from sites of fungal colonization suggest the release of fungal secretory products partly active in tissue disintegration. Similarly, intense labelling was also observed in severely colonized host tissues at late stages of infection. Strong labelling recorded at 3 d p.i. mainly on fungal hyphae and scant gold particles on invaded host tissues could imply that induction of host antifungal metabolites may have been a late event. A correlation was found between total antigenic material in root homogenates measured by ELISA, density of tissue labelling by immunocytochemistry and severity of disease symptoms. The importance of this in relation to diagnosis of biotic root rot diseases in the field is discussed.     

A taxonomic study of the Penicillium chrysogenum series

The taxonomy of the Penicillium chrysogenum series is reconsidered. On account of the observations of the available type strains and numerous isolates mainly obtained from food products, Penicillium notatum Westling, P. meleagrinum Biourge and P. cyaneofulvum Biourge are placed in synonymy with P. chrysogenum Thom. Synonymy and variability of the species are discussed.     

Biological control of onion neck rot (Botrytis aclada): Protection of wounds made by leaf topping

The efficacy of fungal antagonists in protecting onions from neck rot caused by Botrytis aclada was investigated. Leaf wounds made by topping of onions during harvest, which are considered as important entrance sites for B. aclada, were treated with conidial suspensions (5 × 10⁷ conidia ml^‐1) of antagonists. In field experiments with artificial inoculation with conidia of B. aclada, applications of Trichoderma viride during harvest reduced the incidence of neck rot, assessed after three months’ storage of the onions at 9° C, from 35% to 24% in 1989 and from 28% to 18% in 1990, when onions initially had been stored under favourable conditions for fungal development. Comparable results were obtained with T. hamatum and Gliocladium roseum. A bioassay based on wound treatment of detached onion leaves was developed to select further antagonists. From 40 candidate antagonists tested, 20 strains gave similar or better control than the strain of T. viride applied in the field experiments. Effective antagonists could be found amongst strains of Trichoderma spp. Gliocladium spp. and Penicillium spp. as well as amongst fungi such as Aureobasidium pullulans and yeasts isolated from green leaves of onion or rye.     

On four British hyphomycetes

Summary

Dreschlera cactivora isolated from an imported collection of Cactaceae is described. A blossum rot of Hedyscype canterburgense caused by Penicillium lavendulum and a root-rot of Rhododendron root-stocks are noted. A leaf-spot of Arum neglectum caused by Ramularia ari is recorded.     

Production of the Tremorgenic Mycotoxins Verruculogen and Fumitremorgin B by Penicillium piscarium Westling

The tremorgenic mycotoxins verruculogen and fumitremorgin B were isolated from Penicillium piscarium Westling. The coexistence of these tremorgens in culture has previously been reported for one other unrelated fungal species, Aspergillus caespitosus Raper and Thom, and lends further support to the suggestion that the tremorgens have a common biosynthetic origin.     

Precipitation and kinetics of fungal cellulases

Summary The cellulases of two mould fungi namely Penicillium oxalicum Curie et Thom and Helminthosporium cyclops Drechsler were precipitated either by organic solvents or inorganic salts. Acetone seems to be the most suitable precipitant for these enzymes. The action of some factors including temperature, p_H value, enzyme concentration and reaction time on the enzymatic activity was also investigated.     

Effect of organic amendments on root rot of gram (Cicer arietinum L.) and their influence on plant growth

Summary Rhizoctonia root rot of gram caused byR. bataticola was significantly controlled by the amendment of soil with wheat straw, maize straw and sorghum straws. Amendment of soil with sarson straw was almost ineffective. Organic amendments with urd, mung and Trifolium straws increased the disease. It appears that perhaps a comparatively high C/N ratio of the organic amendment controls the root rot disease of gram. Evidence is also presented which suggests that certain organic amendments increase growth of gram.     

Studies on the PR toxin of penicillium roqueforti

A mycotoxin, confirmed by chemical, physical and spectroscopic data as the PR toxin described by Ru-Dong Wei and coll. (15) has been isolated from culture filtrates of Penicillium roqueforti Thom. Factors affecting the toxin and mycelium production, acute and chronic toxicity in experimental animals and the frequency of toxinogenesis of 21 isolates of P. roqueforti (including a brown mutant) isolated from different materials, foods especially, were also studied. An hypothesis on the absence of PR toxin in cheeses fermented with P. roqueforti is also advanced.     

Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994,Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes,Alternaria alternata, Rhizopus stolonifer andA. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory againstA. alternata, A. niger andR. stolonifer. At 10 and 100 µg ml^–1, neither of the fungicide caused a noticeable inhibition ofAlternaria rot. At 1000 µg ml^–1 benlate, rovral and sumisclex completely preventedAlternaria andAspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused byA. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 µg ml^–1). Sodium hypochlorite has good curative properties against fruit rots especially those caused byA. alternata andA. niger.     

Endophytic fungi promote plant growth and mitigate the adverse effects of stem rot: an example of Penicillium citrinum and Aspergillus terreus

Disease resistance is a highly desirable crop trait in the sustainable agricultural industry. Endophytic fungi with gibberellins-secreting potential are now widely known for their ability to stimulate plant growth, but their role in promoting disease resistance in plants has rarely been reported. We have studied the role of Penicillium citrinum LWL4 and Aspergillus terreus LWL5 in time-dependent manner on sunflower (Helianthus annuus L.) growth, disease resistance and their capacity for the regulation of hormone signaling networks involved in plant defense against the stem rot caused by Sclerotium rolfsii for 3, 6 and 12 days after treatment (DAT). Our results show that plant growth characteristics (i.e. shoot length, shoot diameter, shoot fresh/dry weight, transpiration, stomatal conductance, photosynthesis and chlorophyll content) were promoted in fungi-treated plants with or without the disease caused by Sclerotium rolfsii as compared to their respective controls in 3, 6 and 12 DAT. The negative impacts of stem rot in endophyte-treated diseased plants were greatly reduced in comparison to control diseased plants shown by low disease severity in 3, 6 and 12 DAT. Similarly, fungal endophytes in diseased plants relieved the biotic stress in time-dependent manner (3, 6 and 12 DAT) as shown by low level of endogenous salicylic acid and jasmonic acid contents and were significantly higher in control diseased plants. Furthermore, we observed that the Penicillium citrinum LWL4 association had a greater positive effect on sunflower plants than Aspergillus terreus LWL5. It was concluded that inoculation with fungal endophytes reprogramed plant growth during disease incidence by regulating responses associated with host plant defense. Management strategies involving endophytic symbiosis can help achieve sustainability in agriculture in an eco-friendly manner by reducing excessive fungicide use.     

Fungal volatiles associated with moldy grain in ventilated and non-ventilated bin-stored wheat

The fungal odor compounds 3-methyl-l-butanol, l-octen-3-ol and 3-octanone were monitored in nine experimental bins in Winnipeg, Manitoba containing a hard red spring wheat during the autumn, winter and summer seasons of 1984–85. Quality changes were associated with seed-borne microflora and moisture content in both ventilated and non-ventilated bins containing wheat of 15.6 and 18.2% initial moisture content. All three odor compounds occurred in considerably greater amounts in bulk wheat in non-ventilated than in ventilated bins, particularly in those with wheat having 18.2% moisture content. The presence of these compounds usually coincided with infection of the seeds by the fungi Alternaria alternata (Fr.) Keissler, Aspergillus repens DeBarry, A. versicolor (Vuill.) Tiraboschi, Penicillium crustosum Thom, P. oxalicum Currie and Thom, P. aurantiogriseum Dierckx, and P. citrinum Thom. High production of all three odor compounds in damp wheat stored in non-ventilated bins was associated with heavy fungal infection of the seeds and reduction in seed germinability. High initial moisture content of the harvested grain accelerated the production of all three fungal volatiles in non-ventilated bins.     

Biological control of the root rot and wilt diseases ofLens culinaris medic

Summary Biological control visualizes a control of disease with the help of living organisms. In case of root disease, organisms occur in soil which suppress the activity of disease fungi. In the present investigation antagonists have been isolated and used in the control of root rot and wilt disease ofLens culinaris caused byS. rolfsii andF. oxysporum respectively.Isolation of antagonistic micro-organisms were done from the rhizosphere soil of Bombay 20 and local varieties and from field soil. Antagonists were screened against certain test organisms and pathogens. The selected antagonists were used for the control of the diseases of lentil crop by inoculating the antagonists in the soil and thereby to see the effect of decreased plant disease in sterilized and unsterilized soil.Amendments in the form of different organic materials were also given to control the diseases in natural soil.The most effective results were obtained withT. viride, Streptomyces gougeroti Streptomyces species 12 and 13, bacterial isolates no. 16 and 18 in case ofF. oxysporum f.lentis inoculated pots, where there was no disease. In case ofS. rolfsii inoculated pots not a single antagonist was able to eradicate the disease completely.Portion of the Ph. D. thesis accepted by the University of Saugor, Sagar, India.     

花魔芋软腐病原真菌分离鉴定

魔芋软腐病是魔芋生产过程中的重要病害,也是限制魔芋产业发展的主要因素。目前,已有报道魔芋软腐病主要由细菌引起,鲜有真菌引起魔芋球茎软腐发病的报道。为明确云南曲靖市花魔芋(Amorphophallus konjac)软腐病的病原种类和侵染特征,该研究通过组织分离法,对采集自云南曲靖市的花魔芋病样进行了真菌的分离,通过形态学结合基于ITS与LSU序列分析的分子鉴定方法对分离真菌进行鉴定,并根据柯赫氏法则进行致病性测定,并对鉴定出的病原真菌同魔芋软腐病原细菌进行了双回接试验分析。结果表明:(1)从形态学和分子水平鉴定了轮纹镰刀菌(Fusarium concentricum)、尖孢镰刀菌(F. oxysporum)和F. ambrosium 3种镰刀菌,1种毛霉属真菌(Mucor sp.),1种根霉属真菌(Rhizopus sp.),1种青霉属真菌(Penicillium sp.)和1种粉红螺旋聚孢霉属真菌(Clonostachys sp.)。(2)统计分析发现,轮纹镰刀菌的相对丰度最高,为45.45%。(3)柯赫氏法则检测发现轮纹镰刀菌具有致病性。(4)轮纹镰刀菌和病原细菌胡萝卜果胶杆菌(Pectobacterium aroidearum)双接种魔芋球茎发现软腐病发病更快,病变组织重量显著高于单接种轮纹镰刀菌或果胶杆菌处理。综上表明,魔芋软腐病可能是由真菌和细菌复合侵染引发。该研究结果为魔芋软腐病的防治提供了理论依据。     

Pythium aphanidermatum root rot of pawpaw (Carica papaya L.) in Nigeria

Root rot of pawpaw (Carica papaya L.) reported in Nigeria is caused byPythium aphanidermatum which was consistently isolated from diseased plant parts and highly pothogenic. Out of 16 different media tested, it grew best on corn-meal-agar (CMA) and CMA supplemented with cellulose and sucrose. The highest number of oospores/ml was on CMA with average diameter of 19.9±0.1 µm. The symptom is characterized by dark brown rot of roots, absence of secondary roots and disintegration of internal tissue of the main root. These cause the progressive decline of the aerial parts of the tree untill it dies.