Use of Panus tigrinus fungi for production of pressed materials from cotton plant waste

Changes in the chemical composition of cotton plant stems used as a substrate for solid-phase cultivation of the fungus Panus tigrinus were studied as well as the effect of these changes on properties of the pressed materials made of these stems. During the first 3 days of growth, the fungus better consumed cellulose; then, the rate of cellulose consumption was comparable with that of lignin. Intensity and pattern of these changes depended on the age of inoculum. The rate of cotton plant waste biodegradation was higher when a 3-day-old incoculum was used. The pressed materials made of the raw stuff treated with a 3-day-old inoculum of P. tigrinus for 2-3 days displayed better characteristics. Annually, large amounts of lignocellulose stuff is lost while processing of agricultural waste: straw, awn, plant stems, etc. In the countries with developed cotton growing, the annual amount of only guza-paya (dry cotton plant stems) reaches several million tons. To solve this problem, bioconversion of these wastes is studied to manufacture useful products and materials.     

A tripartite culture system for endomycorrhizal inoculation of micropropagated strawberry plantlets in vitro

The objective of the current investigation was to develop a reliable method to obtain vesicular arbuscular mycorrhizae (VAM) in micropropagated plantlets and to determine their influence on growth. An in vitro system for culturing the VA mycorrhizal fungus Glomus intraradices with Ri T-DNA-transformed carrot roots or nontransformed tomato roots was used in this study as a potential active source of inoculum for the colonization of micropropagated plantlets. After root induction, micropropagated plantlets grown on cellulose plugs (sorbarod) were placed in contact with the primary mycorrhizae in growth chambers enriched with 5000 ppm CO₂ and fed with a minimal medium. After 20 days of tripartite culture, all plantlets placed in contact with the primary symbiosis were colonized by the VAM fungus. As inoculum source, 30-day-old VA mycorrhizal transformed carrot roots had a substantially higher infection potential than 5-, 10-or 20-day-old VAM. Colonized plantlets had more extensive root systems and better shoot growth than control plants. The VAM symbiosis reduced the plantlet osmotic potential. This response may be a useful pre-adaptation for plantlets during transfer to the acclimatization stage.     

Infection of potato stems by the gangrene pathogen, Phoma exigua var. foveata

Limited transport of pycnidiospores of Phoma exigua var. foveata within transpiring stems was demonstrated by isolating from cut mature stems placed for 24 h in a spore suspension. Pieces of shoot dipped in spore suspension and subsequently rooted contained the pathogen which was redistributed as the plants grew but without causing symptoms until after desiccation. The fungus was only rarely detected within stems growing from rotted seed tubers suggesting that spore transport in the vascular system was relatively unimportant in these experiments. Stems were readily infected from spore suspensions applied to unwounded epidermis especially when the inoculum was held in cotton wool and secured with wax film. The progressive colonisation of growing stems was demonstrated by isolations made at different positions on the stem and at different times after inoculation. In field experiments in two years stems were inoculated with four spore concentrations on four dates from late June to late August. After desiccation the extent of pycnidial lesions was greatest from the earliest inoculation date and the largest spore concentration and these differences were reflected subsequently in the incidence of gangrene on damaged progeny tubers. Younger stems may be more susceptible and infection in early summer probably results in extensive growth within the stem before desiccation and thus in massive pycnidial production.     

Methods of Inoculation of Faba Bean Plants with Sclerotinia sclerotiorum

Different organic materials colonized by the fungus were applied, as an energy-rich inoculum, on faba bean plants cv. Polycarpe in growth chamber experiments. The organic materials used were colonized pieces of celery stems, faba bean petioles, and carrot root, blocks of cultures on potato dextrose agar and pieces of sclerotia. The inoculum was left attached to the plant stems for 48 h. After removal of the inoculum the plants were scored for disease incidence and severity. It was found that colonized pieces of carrot root produced the most uniform disease incidence and severity.     

Microbial production of gallic acid by modified solid state fermentation

Bioconversion of tannin to gallic acid from powder of teri pod (Caesalpinia digyna) cover was achieved by the locally isolated fungus, Rhizopus oryzae, in a bioreactor with a perforated float for carrying solid substrate and induced inoculum. Modified Czapek-Dox medium, put beneath the perforated float, with 2% tannic acid at pH 4.5, temperature 32°C, 93% relative humidity, incubated for 3 days with 3-day-old inoculum was optimum for the synthesis of tannase vis-à-vis gallic acid production. Conversion of tannin to gallic acid was 90.9%. Diethyl ether was used as the solvent for extraction of gallic acid from the fermented biomass. Received 14 December 1998/ Accepted in revised form 17 June 1999     

Wood Lignin Modification by the Fungus Panus tigrinus

The treatment of sawdust with the fungus Panus tigrinus VKM F-3616 D changed the contents of functional groups in lignin from wood raw material. These changes are accompanied by the release of carboxyl and phenyl hydroxyl groups involved in chemical bond formation between wood particles in pressed materials manufactured from wood wastes.     

Interrelationships of Rotylenchulus reniformis with Rhizoctonia solani on Cotton

The interrelationships between reniform nematode (Rotylenchulus reniformis) and the cotton (Gossypium hirsutum) seedling blight fungus (Rhizoctonia solani) were studied using three isolates of R. solani, two populations of R. reniformis at multiple inoculum levels, and the cotton cultivars Dehapine 90 (DP 90) and Dehapine 41 (DP 41). Colonization of cotton hypocotyl tissue by R. solani resulted in increases (P ≤ 0.05) in nematode population densities in soil and in eggs recovered from the root systems in both 40- and 90-day-duration experiments. Increases in soil population densities resulted mainly from increases in juveniles. Enhanced reproduction of R. reniformis in the presence of R. solani was consistent across isolates (1, 2, and 3) of R. solani and populations (1 and 2) and inoculum levels (0.5, 2, 4, and 8 individuals/g of soil) of R. reniformis, regardless of cotton cultivar (DP 90 or DP 41). Severity of seedling blight was not influenced by the nematode. Rhizoctonia solani caused reductions (P ≤ 0.05) in cotton growth in 40- and 90-day periods. Rotylenchulus reniformis reduced cotton growth at 90 days. The relationship between nematode inoculum levels and plant growth reductions was linear. At 90 days, the combined effects of these pathogens were antagonistic to plant growth.     

Host specificity of Puccinia spegazzinii (Pucciniales: pucciniaceae), a biological control agent for Mikania micrantha (Asteraceae) in Australia

The biology and host specificity of the rust fungus Puccinia spegazzinii, a biological control agent for Mikania micrantha, was studied in a quarantine laboratory in Brisbane, Australia. Nineteen plant species, all from the family Asteraceae were inoculated during host specificity trials. Spore formation occurred only on M. micrantha and no other plant was infected. The first signs of infection (white spots on leaves, petioles and stems) occurred 7 days after exposure to inoculum, becoming yellow by day 11. Mature pustules containing teliospores had developed by 20 days. Results obtained here support testing in other countries showing that P. spegazzinii is host specific to M. micrantha and no that other plant in Australia would be at risk if it were to be released in the environment. Recommendations on assessing pathogens to improve trials were proposed. Counting infected plants, plant parts and pustules formed can demonstrate that all test plants would have been adequately exposed to inoculum and thus increase the confidence in host specificity of pathogens in weed biological control.     

Chilli rhizosphere fungus Aspergillus spp. PPA1 promotes vegetative growth of cucumber (Cucumis sativus) plants upon root colonisation

A rhizosphere fungus was isolated from roots of chilli plants and identified as Aspergillus spp. PPA1. The fungus was tested for its ability to promote the growth of cucumber plants in a pot experiment. Cucumber seeds were sown in sterilised field soil amended with wheat grain inoculum (WGI) of PPA 1 at the rate of 0.5, 1 and 1.5% w/w, and plants were grown for 21 days in a net house. The treatment with PPA1 significantly increased shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, root dry weight, plant length, leaf area and leaf chlorophyll content of cucumber plants compared to non-treated control. The growth promotion rate increased with the increasing concentration of inoculum of PPA1 applied to the soil. The fungus was re-isolated from the roots of cucumber plants at higher frequencies. These results suggest that Aspergillus spp. PPA1 is a root colonising plant-growth promoting fungus for cucumber.     

The role of laccase and peroxidase of <Emphasis Type="Italic">Lentinus (Panus) tigrinus</Emphasis> fungus in biodegradation of high phenol concentrations in liquid medium

The possibility of the usage of Lentinus tigrinus fungus strain VKM F-3616D for biodegradation of high (up to 5%) phenol concentrations in liquid medium and the involvement of laccase and peroxidase in this process have been studied. L. tigrinus fungus was demonstrated to effectively degrade phenol with easy biomass deletion from the liquid. Decrease in phenol concentration was accompanied by increased secretion level and laccase activity at the preliminary stages of biodegradation, while that of peroxidase was at the latest stages of biodegradation. These enzyme secretions in distinct ratios and consequences are necessary for effective phenol biodegradation. An effective approach for phenol concentration decrease in the waste water of smoking shops in meat-processing factories using L. tigrinus fungus was described.     

Soil-Behaviour of Phytophthora clandestina

Investigations were undertaken to study the nature and behaviour of P. clandestina in soil. The pathogen was recovered only from soil sievings 250–499 μm and 500 μm–0.99 mm, containing small root fragments. In soil the introduced inoculum of the fungus was incapable of saprophytically and competitively colonizing the dead cotyledons of subterranean clover used as bait material. Exposure of the inoculum to increasing numbers of microbes by adding greater proportions of nonsterile fields, oil to the growth medium of the plant had no significant effect on survival rate and fresh shoot weight of subterranean clover. However, microbes present in the field soil reduced the severity of root rot of subterranean clover. P. clandestina was, able to spread between 15–30 mm through pasteurized soil within a period of 20 days.     

Expression of genes associated with carbohydrate metabolism in cotton stems and roots

Background  

Cotton (Gossypium hirsutum L) is an important crop worldwide that provides fiber for the textile industry. Cotton is a perennial plant that stores starch in stems and roots to provide carbohydrates for growth in subsequent seasons. Domesticated cotton makes these reserves available to developing seeds which impacts seed yield. The goals of these analyses were to identify genes and physiological pathways that establish cotton stems and roots as physiological sinks and investigate the role these pathways play in cotton development during seed set.     

Food selection in three leaf-shredding stream invertebrates

Leaf disks (Betula papyrifera) were conditioned for two weeks by six species of aquatic hyphomycetes. Mass losses of the leaves were determined, and their concentrations of protein (extracted at pH 7, 10 and 12.8), phenolics (Folin-Ciocalteu and BSA-precipitation), lipids, and ergosterol (as indicator of fungal biomass) were measured. Enzymatic activities of the culture filtrates against cellulose, xylan and pectin were estimated. Gammarus tigrinis, Pycnopsyche guttifer and Tipula caloptera were given a choice of the six leaf/fungus combinations. G. tigrinus and P. guttifer consistently preferred some combinations over others; T. caloptera appeared to feed randomly. There were no significant correlations between consumption and any of the measured characteristics of leaf disks. With G. tigrinus and P. guttifer, the sequence of preference could be reproduced by extracting mycelia with non-polar solvents and applying the extracts to unconditioned leaf disks. Consumption of extract-coated disks was lower than consumption of conditioned disks. Numbers of endosymbiotic gut bacteria increased from G. tigrinus to P. guttifer to T. caloptera; diet diversity showed the opposite trend.     

Relationship of inoculum ofVerticillium dahliae to disease in tomato plants

Summary Tomato (Lycopersicon esculentum Mill.) seedlings were inoculated by dipping roots in suspensions of conidia ofVerticillium dahliae Kleb. There was a linear relationship between inoculum concentration and infection at 21 days after inoculation in steam-disinfested soil. Thereafter the number of infections per plant increased. At higher concentrations data indicated a synergistic interaction between conidia. Synergism was more pronounced and was detected earlier in soil not disinfested before inoculation. When conidia from 3-, 7-, and 14-day-old cultures were used, the greatest response was from 3-day-old cultures. A lower total response and lower rate of response to older inoculum indicated a decrease in aggressiveness of conidia with age. Older plants were less affected by the pathogen when plants inoculated at the fourth and sixth leaf stages with minimum root disturbances were compared. There was also an increase in infection with an increase in the volume of root zone infested. In field experiments infection reduced stand when roots were disturbed at inoculation. With minimum root disturbance yields were reduced without a reduction in stand. Part of thesis to be submitted by the senior author to the University of Stellenbosch in partial fulfilment of the Ph.D. (Agric.) degree.     

Evaluation of commercial arbuscular mycorrhizal inocula in a sand/peat medium

Eight commercial inocula of arbuscular mycorrhizal fungi (AMF) were tested for their ability to colonize plant roots in the sand/peat medium specified by the U.S. Golf Association for use in putting greens. Using the standard assay for potency of inocula (Zea mays grown for 6 weeks in containers), inocula were added at the rate recommended by the manufacturer as well as at five and ten times the recommended rate. To ensure that growth conditions were conducive to AM formation, a soil-based inoculum of native AMF also was assessed for inoculum potential. Only three of the commercial inocula formed mycorrhizas when used at the recommended rate, and the extent of colonization ranged from 0.4 to 8%. Increasing the amount of inoculum resulted in colonization levels of 8.6 to 72.5% at the highest rate (10×). Mean colonization using the native AMF was 60%. One inoculum that did not form mycorrhizas at the recommended rate or at 5× produced 8.6% colonization at 10×. An inoculum that did not produce mycorrhizas at any application rate did contain a fungus tentatively identified as a root pathogen (Olpidium brassicae) that colonized the corn roots. The failure of five of the eight commercial inocula to colonize roots when applied at the recommended rate suggests that preliminary trials should be made before commercial AMF inocula are used in important plantings.     

THE ROLE OF ENDOMYCORRHIZAE IN REVEGETATION PRACTICES IN THE SEMI-ARID WEST. II. A BIOASSAY TO DETERMINE THE EFFECT OF LAND DISTURBANCE ON ENDOMYCORRHIZAL POPULATIONS

Populations of the endomycorrhizal fungus Glomus fasciculatus were significantly reduced following land disturbance in western Colorado soil. A bioassay was developed to measure changes in the endomycorrhizal population. In the bioassay, inoculum levels were measured by comparing the percentage infection in corn (Zea mays) root systems thirty days after planting in undisturbed or disturbed soils. The percentage infection was 2% in the disturbed soil compared to 77% in the adjacent undisturbed soil. Glomus fasciculatus was identified as the endophyte in both soils. Considering the importance and function of endomycorrhizal fungi to their plant hosts the reduction of active inoculum in the disturbed soil may be an important ecological factor in subsequent succession.     

Geographic range, impact, and parasitism of lepidopteran species associated with the invasive weed Lantana camara in South Africa

Six isolates of Trichoderma were screened for antagonism to Armillaria in tea stem sections buried in the soil. The inability of Armillaria to invade Trichoderma-colonized stem sections and the reduction of its viability in the plant materials following invasion of these by Trichoderma were used as indicators of antagonism. Four isolates of the species Trichoderma harzianum significantly (P<0.001) reduced the incidence of the pathogen in the plant materials. Isolate T4 completely eliminated the pathogen from plant materials in sterile soil and also antagonized two different isolates of the pathogen in nonsterile soil. Application of this T. harzianum isolate to the soil as a wheat bran culture significantly (P<0.001) reduced viability of Armillaria in woody blocks of inoculum. Soil amendment with coffee pulp also reduced the inoculum viability but did not affect the incidence of Trichoderma in the blocks of inoculum. We conclude that the direct application of wheat bran-formulated T. harzianum into soil surrounding woody Armillaria inoculum sources can suppress the pathogen. Further, no organic amendment is needed to enhance development of the antagonist in the soil as a pre-requisite to suppressing the pathogen.     

Conditions for Cultivation of the Fungus Penicillium melinii UzLM-4 and Its Biosynthesis of Lipases

Cultivation of the fungus Penicillium melinii UzLM-4 on a Raistrick's medium of our own modification made it possible to increase the biosynthesis of lipases by three to four times. The following conditions ensured a high rate of synthesis of the extracellular lipase: age of the inoculum, 15 days; concentration of the inoculum, 15 × 10⁶ conidia per 100 ml medium; initial pH of the nutrient medium, 8.0; and cultivation in a shaker at 150 rpm and 25°C.     

Transmission of Alternaria macrospora in Cotton Seeds

Alternaria macrospora was isolated from seeds only after the natural opening of the bolls and exposure of seeds to an environment in which the fungus was present. The fungus lacks the ability to penetrate the boll wall and reach the seed site. Attempts to isolate the pathogen from seeds of immature bolls at different developmental stages failed. Internal infection by slow injection resulted in seed infection and partial shedding of the injected plant parts which was high in buds and decreased with the ripening to mature bolls. Severity of seed infection was not dependent on either inoculum level, boll physiological age or even if the boll itself was not diseased. Infection of flowers under field conditions caused flower shedding. Naturally infected seeds or inoculated seeds with inoculum levels of 100 spores/ml and above resulted in diseased cotyledons, the incidence of which was, for inoculated seeds, positively correlated with inoculum level. A small difference was observed between cultivars in susceptibility to artificial inoculation at the cotyledon stage. A. macrospora survived on commercial cotton seeds and on post-season plants left growing at the field edges. Survival in plant debris under field conditions was minimal and may only have a minor effect on field reinfestation.     

Fermentation of Cellulose to Methane and Carbon Dioxide by a Rumen Anaerobic Fungus in a Triculture with Methanobrevibacter sp. Strain RA1 and Methanosarcina barkeri

The fermentation of cellulose by a rumen anaerobic fungus in the presence of Methanobrevibacter sp. strain RA1 and Methanosarcina barkeri strain 227 resulted in the formation of 2 mol each of methane and carbon dioxide per mol of hexose fermented. Coculture of the fungus with either Methanobrevibacter sp. or M. barkeri produced 0.6 and 1.3 mol of methane per mol of hexose, respectively. Acetate, formate, ethanol, hydrogen, and lactate, which are major end products of cellulose fermentation by the fungus alone, were either absent or present in very low quantities at the end of the triculture fermentation (≤0.08 mol per mol of hexose fermented). During the time course of cellulose fermentation by the triculture, hydrogen was not detected (<1 × 10⁻⁵ atm; <0.001 kPa) and only acetate exhibited transitory accumulation; the maximum was equivalent to 1.4 mol per mol of hexose at 6 days which was higher than the total acetate yield of 0.73 in the fungus monoculture. The effect of methanogens is interpreted as a shift in the flow of electrons away from the formation of electron sink products lactate and ethanol to methane via hydrogen, favoring an increase in acetate, which is in turn converted to methane and carbon dioxide by M. barkeri. The maximum rate of cellulose degradation in the triculture (3 mg/ml per day) was faster than previously reported for bacterial cocultures and within 16 days degradation was complete. The triculture was used successfully also in the production of methane from cellulose in the plant fibrous materials, sisal (fiber from leaves of Agave sisalona L.) and barley straw leaf.