Trichoderma Harzianum WKY1: an indole acetic acid producer for growth improvement and anthracnose disease control in sorghum

The efficiency of two isolates of Trichoderma harzianum (WKY1 and WKY5) as bio-control agents against anthracnose disease in sorghum was investigated. In vitro, T. harzianum WKY1 isolate showed superiority in terms of inhibition of both mycelial growth and spore germination of Colletotrichum sublineolum, the causative agent of sorghum anthracnose, as well as induction of the sorghum seed germination over T. harzianum WKY5 isolate. The culture filtrate of the selected isolate (T. harzianum WKY1) was analysed using GC-MS system to determine their chemical constituents. Twenty-nine components with varied existence percentages were identified. Although T. harzianum WKY1 produced the phytohormone indole-3-acetic acid (IAA) on tryptophan free medium, a marked dependency on tryptophan for the production of IAA was noticed. Nutritional components were optimized for maximizing IAA production using the central composite design. The optimum levels were 1.06, 29.86 and 2.93?g?L^?1 from tryptophan, sucrose and NaNO₃, respectively, with a maximum IAA biosynthesis (138.9?µg?mL^?1) after five days of incubation. Production of IAA in the culture filtrate of T. harzianum WKY1 was qualitatively and quantitatively analysed by LC-MS system using a reference standard of IAA. Under greenhouse conditions, application of T. harzianum WKY1 and/or its filtrate reduced greatly the disease severity as well as improved the plant growth of sorghum. From the present data, we can recommend the application of T. harzianum WKY1 as a dual purpose bio-agent for biological control of anthracnose disease and plant growth promotion.     

Isolation of Trichoderma and Evaluation of their Antagonistic Potential against Alternaria porri

Nine isolates of Trichoderma were collected from Assiut Governorate, Egypt, as leaf surface and endophytic fungi associated with onion flora stalks. Four isolates were identified as Trichoderma harzianum, while five isolates were belonging to Trichoderma longibrachiatum. The antagonistic activity of these isolates against onion purple blotch pathogen Alternaria porri was studied in vitro using dual culture assay. All tested Trichoderma isolates showed mycoparasitic activity and competitive capability against the mycelial growth of A. porri. Mycoparastic activity of Trichoderma was manifested morphologically by the overgrowth upon the mycelial growth of the pathogen and microscopically by production of coiling hyphae around pathogen hyphae. Isolates of T. harzianum exhibited high ability to compete on potato dextrose agar (PDA) medium causing the maximum rate of pathogen inhibition (73.12%), while isolates of T. longibrachiatum showed inhibition rate equalling 70.3%. Chitinase activity of Trichoderma was assayed, and T. harzianum Th‐3013 showed the maximum value contributing 2.69 U/min. Application of T. harzianum Th‐3013 to control purple blotch disease in vivo under greenhouse conditions caused disease reduction up to 52.3 and 79.9% before and after 48 h of pathogen inoculation, respectively, while the fungicide Ridomil Gold Plus caused disease reduction comprising 56.5 and 71.7%, respectively. This study proved that T. harzianum Th‐3013 as a biocontrol agent showed significant reduction in onion purple blotch disease compared with the tested fungicide.     

Biological control of Botrytis cinerea on tomato using naturally occurring fungal antagonists

Abstract

In order to evaluate the potential of naturally occurring filamentous fungi having potential as biocontrol agents effective against grey mould and post-harvest fruit rot caused by Botrytis cinerea on tomato, fungal saprophytes were isolated. They were obtained from leaves, fruits and flowers belonging to different species of cultivated and spontaneous Solanaceous plants collected at the horticultural area of La Plata, Argentina. Of 300 isolates screened for inhibition of B. cinerea using the dual culture technique on agar plate, 12 strains inhibited strongly mycelial growth of the pathogen. Among the antagonists one isolate of Epicoccun nigrum (126), four of Trichoderma harzianum (110, 118, 248 and 252) and four isolates of Fusarium spp. decreased the spore germination of B. cinerea between 30 and 70%. These isolates were probed on tomato fruits to evaluate their biocontrol activity against post-harvest grey mould. In growth chamber tests, E. nigrum (27), F. equiseti (22, 105) and T. harzianum (118, 252) reduced the diameter of fruit lesions by 50 – 90% and were selected for further biocontrol assays of tomato plants in the greenhouse. Although there were not significant differences between the treatments and the control, F. equiseti (105), E. nigrum (27) and T. harzianum (118) reduced by 20, 22 and 22 respectively the disease on whole plants. The targeted application of isolates of E. nigrum, T. harzianum and F. equiseti provides a promising alternative to the use of fungicide spray to control B. cinerea on tomatoes.     

Studies on the transmission of some Fusarium spp. to potato progeny tubers from mother plants and its biological control

Fusarium spp. attack potato roots causing root-rot, damping-off and wilt disease in Assuit Governorate. Forty-five Fusarium isolates were isolated from F. nygamai, F. acutatum, F. solani, F. proliferatum, F. subglutinans, and F. oxysporum. Isolates were tested for their pathogenic capability on Burn potato variety during growing season 2007/2008. Isolates infect potato plants causing either damping-off or wilt symptoms. Isolates varied in their virulence. Role of potato tuber seed in the transmission of the causal pathogen to daughter using Electrophoresis. Protein profiles of the tested isolates divided into four sub-clusters at similarity levels 93.79, 91.55 and 92.62% while isolate of Fusarium profile No. 11 formed separate sub-clusters at similarity level 69.79%. F. nygamai and F. solani were notable exception because profile No. 4 of F. nygamai from roots and profile No. 4 from sprouts were almost identical (similarity level 96.81%); similarity level between profile No. 8 from roots and profile no/8 from sprouts was 95.44%. Results prove that F. nygamai and F. solani are potato tuber seed-borne fungus. T. harzianum, T. viride, T. longibrachiatum, G. virens and E. nigrum or its filtrate inhibited the growth of F. nygamai, F. acutatum, F. solani, F. proliferatum, F. subglutinans and F. oxysporum. The formulation of T. harzianum, T. longibrachiatum and G. virens against tested pathogenic fungi reduce disease incidence under greenhouse conditions.     

Ecological management of tropical sugar beet (TSB) root rot (Sclerotium rolfsii (Sacc.) by rhizosphere Trichoderma species

Trichoderma species are collected from different location of sugarbeet growing areas of Tamil Nadu and it is effective against Sclerotium rolfsii pathogen caused by sugarbeet ecosystems. Out of thirty-one isolates of Trichoderma viride and four isolates of Trichoderma harzianum collected and tested for their antagonistic activity against S. rolfsii by dual culture technique, one isolate was found to be effective T. viride (TVB1) that recorded the maximum (73.03%) inhibition on the mycelial growth recording only 2.40 cm growth as against 8.90 cm in the control. The isolates of T. harzianum THB-1 recorded 71.19% mycelial growth reduction over control. The colonisation behaviour of T. viride (TVB1) revealed that it completely over grew on pathogen within 48 h after interaction with the pathogen, and speed of growth on pathogen was also high and it possesses a higher level of competitive saprophytic ability. The best four isolates of TVB1, TVB-2, TVB-3 and TVB31 and two isolates of T. harzianum THB-1 and THB-2 were compared with other species of Trichoderma longibrachiatum, Trichoderma reesei, Trichoderma koningii and Chaetomium globosum and tested under in vitro condition. BA of neem cake at 150 kg ha^?1 + T. viride isolate (TVB1) at 2.5 kg/ha recorded least root rot disease incidence of 17.05% which accounted for 75.37% disease reduction over control and highest recorded maximum root yield 65.73 t ha^?1 and increasing sugar content.     

Prof. Dr. Lothar Behr

A damping-off disease of wheat was shown in a wheat field in Kidwan village, El-Minia city, Egypt, during December, 2000. Pythium diclinum was the causal agent of such disease and this is the first reported work of its isolation as a disease to wheat. Wheat seedlings collected from that field showed browning lesions at the basal part and wilting followed by damping-off. Examination of root pieces and other infected parts yielded only Pythium diclinum. The pathogen was characterized by its typically filamentous zoosporangia, diclinous antheridia and aplerotic thick-walled oospores. Pathogenicity of this fungus was determined on wheat under greenhouse conditions and P. diclinum was proved to be pathogenic on wheat. Two isolates of each of Gliocladium roseum and Trichoderma harzianum were tested for their bio-control activity against damping-off disease of wheat caused by P. diclinum. Incorporation of G. roseum or T. harzianum isolates into carboxymethylcellulose seed coating successfully eliminated pre-emergence damping-off of the wheat caused disease, whereas post-emergence damping-off was prevented by adding inocula of each of the two fungi separately to the infested soil with P. diclinum.     

Evaluation of Trichoderma harzianum strain T22 as biological control agent of Calonectria pauciramosa

The objective of this research was to evaluate Trichoderma harzianum strain T22 as a biocontrol agent of collar and root rot caused by different Calonectria pauciramosa isolates. Thus, the microsclerotia-forming ability and virulence of twenty C. pauciramosa isolates were assessed. Microsclerotia production varied partially among the isolates and dual culture with T22 on carnation leaf agar revealed isolates with both high and low microsclerotia-forming ability. Inoculation tests on red clover (Triflolium pratense) demonstrated its susceptibility to the pathogen. On red clover, the degree of virulence and T22 effects in controlling infections were highly variable among the isolates tested. A nursery trial performed on Feijoa sellowiana seedlings confirmed previous results, clearly indicating virulence variability among C. pauciramosa isolates. For three isolates tested in nursery trial, T22 effectiveness in controlling infection was inversely related to their degree of virulence. Overall, T. harzianum strain T22 showed good antagonist activity in reducing microsclerotia production on carnation leaf and the incidence and severity of collar and root rot on both selected hosts. This data could be crucial in developing integrated pest management strategies in ornamental plant nurseries.     

Variability among strains of Trichoderma harzianum in their ability to reduce take-all and to produce pyrones

Antagonism tests on agar-plates and glasshouse screening indicated that three isolates of Trichoderma harzianum varied in their ability to antagonize the take-all fungus (Gaeumannomyces graminis var. tritici). Isolate 71 which was the most effective in suppressing take-all of wheat, produced two pyrones and other undetermined analogues. Isolates of T. koningii and T. hamatum shown to suppress take-all, produced a simple pyrone compound. Although T. harzianum isolates 70 and 73 did not produce any pyrones, they reduced the disease albeit to a much lesser extent than isolate 71; with isolate 73 showing distinct host growth promotion effects. It is proposed that the success of isolate 71 of T. harzianum was related to the pyrones it produces and that the ability of isolates 70 and 73 to reduce take-all may be related to mechanisms other than those involving antibiotics.     

Biocontrol efficacy of Trichoderma spp. against sesame wilt caused by Fusarium oxysporum f. sp. sesami

Sesame (Sesamum indicum L.) is one of the most important oilseed crops in Egypt and worldwide. It is being infected with many pathogens, among these pathogens Fusarium oxysporum f.sp. sesami (Zap.) Cast is causing severe economic losses on sesame. In this study, antagonistic capability of 24 isolates of Trichoderma spp. was assessed in vitro against F. oxysporum f.sp. sesami. Two strains; T. harzianum (T9) and T. viride (T21) were revealed to have high antagonistic effect against F. oxysporum f.sp. sesami in vitro with inhibition percentage about 70 and 67%, respectively. These two isolates proved to have high ability to control Fusarium wilt disease under greenhouse conditions. The highest reduction in disease severity was achieved with T. viride followed by T. harzianum with reduction in disease severity about 77 and 74%, respectively. This study revealed that the time of application of bioagents is a decisive factor in determining the efficacy of Trichoderma isolates to control Fusarium wilt of sesame. It was revealed that the highest reduction in the disease severity was achieved when either Trichoderma viride or T. harzianum were applied 7 days before challenging with the F. oxysporum f.sp. sesami.     

Application of Soil‐borne Actinomycetes for Biological Control against Fusarium Wilt of Chickpea (Cicer arietinum) caused by Fusarium solani fsp pisi

Black root rot, caused by Fusarium solani f.sp. pisi, is a devastating soil‐borne disease in chickpea in Iran with no effective control measures. With the aim of finding applicable biocontrol agents to alleviate the malady, isolates of Actinomycetes isolated from soil and their antagonistic effect against F. solani f.sp. pisi were evaluated both in vitro and in vivo. More than 100 Actinomycetes isolates were screened for their antifungal activities against the pathogen. The most active isolates were evaluated in greenhouse for their biocontrol performance. Based on the results of dual cultures in screening evaluations, the size of inhibition zone of fungal growth, and the most effective antagonist isolates (S3, S12 and S40) were selected for further studies. Identity of active isolates was determined, in this regard, 16S rDNA of isolates were amplified using universal bacterial primers FD1 and RP2. The PCR products were purified and sequenced. Sequence analysis of 16S rDNA was then performed using NCBI BLAST method. Comparison of the near full length 16S rRNA sequence of isolates to GenBank sequences demonstrated that isolates S3 and S12 were most similar to Streptomyces antibioticus, while isolate S40 was most similar to Streptomyces peruviensis. Biocontrol studies of these isolates in control of the disease in greenhouse significantly decreased the disease severity. Actinomycetes isolate S12 demonstrated the greatest effect in reducing disease than the other two. Results of this research are at preliminary stage for developing biocontrol agents. These data can be utilized as a platform for future studies with the aim of commercializing these biocontrol products and hoping to step towards sustainable agriculture.     

Potential for Biocontrol of Lasiodiplodia theobromae (Pat.) Griff. & Maubl. in Banana Fruits by Trichoderma Species

Fifteen Trichoderma isolates were tested for their antagonistic ability against Lasiodiplodia theobromae. Trichoderma harzianum exhibited the greatest inhibition in dual culture. Microscopic investigation demonstrated direct parasitism and coiling of T. harzianum and T. viride around hyphae of L. theobromae, causing swollen, deformed, shortened, or rounded cells of the pathogen. Granulation of cytoplasm and disintegration of the hyphal walls of L. theobromae also were noted in dual culture. Trichoderma viride reduced rotting by 29.07 to 65.06% in artificially inoculated banana fruits. Treatment of banana fruits with T. viride 4 h prior to inoculation with L. theobromae provided better protection than simultaneous application or treatment 4 h after inoculation.     

Antagonistic Effects of Trichoderma harzianum Isolates against Ceratocystis radicicola: pioneering a Biocontrol Strategy against Black Scorch Disease in Date Palm Trees

Date palm is an important subsistence crop in arid regions due to its ability to grow under adverse environmental conditions such as high temperature, salinity and drought. Nevertheless, ideal conditions for its growth and production are also favourable to fungal diseases such as black scorch disease caused by Ceratocystis radicicola. The aim of this study was to develop a method of biological control through the isolation, identification and examination of the effectiveness of bioagents in controlling black scorch disease. Twenty‐five isolates of Trichoderma spp. were isolated from the rhizosphere of healthy date palm trees and morphological, microscopic and molecular approaches confirmed the identity of 11 isolates as Trichoderma harzianum species complex (THSC). In vivo study, application of both spore suspension and culture filtrates of T. harzianum decreased the size of necroses caused by C. radicicola. Additionally, scanning electron microscopy (SEM) showed lysis of the hyphal pathogen and phialoconidia along with scattered aleurioconidia. Results from the volatile metabolic assay and SEM suggested potential roles of cell wall degradation enzymes and volatile substances produced by T. harzianum as two collective mechanisms leading to degrade the cell wall of the pathogen and inhibit fungal growth. Altogether, results from our study demonstrated the efficacy and utility of using bioagents to control black scorch disease which could improve date palm yield.     

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.     

Biological efficacy of <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> isolate to control some fungal pathogens of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) in Turkey

Gaeumannomyces graminis var. tritici, Fusarium culmorum and F. moniliforme are highly important and widespread pathogens of wheat in Turkey. Trichoderma isolates have been used as biocontrol agents to protect plants against soilborne diseases in several crops. The present work was carried out to evaluate the potential of Trichoderma harzianum isolate T1 as biocontrol agents for G. graminis, F. culmorum and F. moniliforme under field conditions in 2001 and 2002. Quantitative differences were found in microbial number in soil. T. harzianum T1 had considerable effect on population densities of the tested pathogens. The total number of G. graminis, F. culmorum and F. moniliforme were lower in the T. harzianum T1 application made to seed. T. harzianum T1 application to seed had increasing affect on the yield components of wheat through better control over pathogens. The greatest counts of T. harzianum T1 were detected on root segments. Seed application by T. harzianum T1 had increasing effect on yield components of wheat.     

Neokomagataea gen. nov., with Descriptions of Neokomagataea thailandica sp. nov. and Neokomagataea tanensis sp. nov., Osmotolerant Acetic Acid Bacteria of the α-Proteobacteria

Isolates AH11^T and AH13^T were isolated from flowers of lantana and candle bush respectively collected in Thailand. In phylogenetic trees based on 16S rRNA gene sequences, the two isolates formed an independent cluster, which was then connected to the type strain of Saccharibacter floricola. The calculated pair-wise 16S rRNA gene sequence similarities of isolate AH11^T were 95.7–92.3% to the type strains of the type species of the 12 genera of acetic acid bacteria. The DNA base composition was from 51.2 to 56.8 mol % G+C, with a range of 5.6 mol %. When isolate AH11^T was labeled, DNA-DNA similarities were 100, 12, 4, 5, and 4% respectively to isolates AH11^T and AH13^T and the type strains of Saccharibacter floricola, Gluconobacter oxydans, and Acetobacter aceti. The two isolates were non-motile and did not oxidize either acetate or lactate. No growth was found in the presence of 0.35% acetic acid w/v. The two isolates were not osmophilic but osmotolerant, produced 2,5-diketo-D-gluconate from D-glucose, and did not oxidize lactate, thus differing from strains of Saccharibacter floricola, which showed weak lactate oxidation. The two isolates contained unsaturated C_18:1ω7c fatty acid as the major fatty acid, and were unique in the presence of a considerable amount of straight-chain C_18:12OH fatty acid. Q-10 was present as the major isoprenoid quinone. Neokomagataea gen. nov. was proposed with the two species, Neokomagataea thailandica sp. nov. for isolate AH11^T (=BCC 25710 ^T =NBRC 106555^T), which has 56.8 mol % G+C, and Neokomagataea tanensis sp. nov. for isolate AH13^T (=BCC 25711^T=NBRC 106556^T), which has 51.2 mol % G+C.     

Trichoderma species on Agaricus bisporus farms in Serbia and their biocontrol

Twenty Trichoderma isolates were collected on 13 Serbian Agaricus bisporus farms and one in Bosnia and Herzegovina during 2006–2010. Twelve isolates were classified into five species by standard mycological studies and ITS1/ITS4 sequence analyses, namely Trichoderma atroviride, Trichoderma koningii, Trichoderma virens, Trichoderma aggressivum f. europaeum and Trichoderma harzianum. Eight isolates were not identified to the species level but were shown to be related to T. harzianum. The isolates of T. harzianum exhibited the highest virulence to the harvested A. bisporus pilei and T. virens and T. aggressivum f. europaeum the lowest. Antifungal activity of two biofungicides based on Bacillus subtilis and tea tree oil and the fungicide prochloraz manganese were tested in vitro to all Trichoderma isolates. Prochloraz manganese and B. subtilis were highly toxic to all tested Trichoderma isolates, their ED₅₀ values were below 0.3 and 1.3 mg L^?1, respectively. Tea tree oil did not exhibit a significant antifungal activity (ED₅₀ = 11.9–370.8 mg L^?1). The effectiveness of biofungicides was evaluated against T. harzianum in a mushroom growing room, and they were applied alone or in combination with the fungicide at a respective proportion of 20:80%. Prochloraz manganese showed higher effectiveness than both tested biofungicides or their respective mixtures. The biofungicide based on B. subtilis demonstrated greater effectiveness in preventing disease symptoms than tea tree oil. B. subtilis combined with the fungicide revealed less antagonism in effectiveness against pathogen than tea tree oil.     

Suppression of sugar beet damping-off caused by Rhizoctonia solani using bacterial and fungal antagonists

Rhizoctonia damping-off caused by Rhizoctonia solani Kühn, is one of the most damaging sugar beet diseases. It causes serious economic damage wherever sugar beets are grown. Biological control is an efficient and environmentally friendly way to prevent damping-off disease. Suppression of damping-off disease caused by R. solani was carried out by four isolates of Bacillus subtilis (Ehrenberg) Cohn as well as three isolates of each of Trichoderma harzianum Rifai and Trichoderma hamatum (Bonord.) Bainier. The effect of Bacillus and Trichoderma isolates against R. solani was investigated in vitro and tested on sugar beet plants under greenhouse conditions. Isolates of Bacillus and Trichoderma were able to inhibit the growth of R. solani in dual culture. Furthermore, Trichoderma isolates gave high antagonistic effect than isolates of B. subtilis. Under greenhouse conditions, coating seeds by T. harzianum and B. subtilis separately, reduced seedling damping-off significantly. However, applications of T. harzianum increased the percentage of surviving plants more than B. subtilis in comparison to control. The obtained results indicate that T. harzianum and B. subtilis are very effective biocontrol agents that offer potential benefit in sugar beet damping-off and should be harnessed for further biocontrol applications.     

Determination of the growth and solubilization capabilities of <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> T1

The growth capability of Trichoderma harzianum Rifaii Tl was tested on Malt Extract and Czapeks Dox agar containing different concentrations of Cu²⁺, Zn²⁺, Mn²⁺, Fe²⁺ and Ca²⁺. The T. harzianum Tl isolate was observed to produce mycelia and spores in various mineral-containing media. It showed the lowest tolerance to Ca²⁺ and the highest tolerance to Fe²⁺. Solubilization capability of T. harzianum Tl for some insoluble minerals via acidification of medium has been tested on MnO₂, CuO, Fe₂O₃ and metallic Zn. T. harzianum Tl was able to solubilize MnO₂ and metallic Zn in a liquid medium.     

Trichoderma harzianum and its Metabolite 6-Pentyl-alpha-pyrone Suppress Fusaric Acid Produced by Fusarium moniliforme

The interaction of the pathogen Fusarium moniliforme and two antagonistic Trichoderma harzianum isolates was studied especially with respect to their secondary metabolites fusaric acid (FA) and 6‐pentyl‐alpha‐pyrone (6PAP). Among 10 isolates of F. moniliforme screened for FA production on maize kernels, the isolate 8 accumulated the highest amount of FA (678 μg/g). Mycelial growth and production of FA by isolate 8, determined in different liquid media revealed that the highest biomass and FA were produced in Czapek Dox Broth (CDB) followed by Richard’s solution. The amount of FA per gram mycelial dry weight reached its maximum in CDB and Richard’s solution after 14 days of incubation. Mycelial growth and conidia production of both Trichoderma isolates (T16 and T23) were retarded by increasing concentrations of FA in agar medium. At FA concentration of 300 mg/ml the radial mycelial growth of the isolates T16 and T23 were retarded by 32.5% and 45%, respectively. Conidia production was diminished in a similar extent as mycelial growth. Both T. harzianum isolates were capable to degrade FA in potato dextrose broth medium, particularly when lower doses of FA were present. In the presence of 50 mg/ml FA in the culture medium, the isolates T23 and T16 reduced FA by 51.4% and 88.4%, respectively, 9 days post‐inoculation. The antifungal metabolite 6PAP, isolated from T. harzianum T23 cultures, was introduced at different concentrations into 2‐day‐old cultures of F. moniliforme. After further 5 days of incubation of F. moniliforme in the presence of 6PAP, the FA contents per gram mycelial dry weight were significantly decreased compared to control cultures where 6PAP was absent. Dosages of 300 and 400 mg/l of 6PAP in the cultures retarded FA accumulations by 62.5% and 77.2%, respectively. The current results, however, provided the first evidence for activity of 6PAP, as a Trichoderma secondary metabolite, on degrading/synthesis suppression of the Fusarium toxin FA.     

Evidences of biological control capacities of Streptomyces spp. against Sclerotium rolfsii responsible for damping-off disease in sugar beet (Beta vulgaris L.)

Ten antibiotic-producing Streptomyces spp. isolated from Moroccan soils were evaluated for their ability to inhibit in vitro Sclerotium rolfsii development. Four isolates having the greatest pathogen inhibitory capabilities were subsequently tested for their ability to inhibit sclerotial germination in sterile soil. This test was carried out by using biomass inoculum, culture filtrate, and spore suspension of the isolates as treatment. Treatment with biomass inoculum and culture filtrate gave the highest inhibition of sclerotia. Biological control tests against Sclerotium rolfsii damping-off of sugar beet seeds showed that the selected Streptomyces isolates reduced significantly the disease severity, the J-2 isolate being the more potent. In addition, treatment with the isolate J-2 resulted in a significant increase (P ≤ 0.05) in seedling development compared to the control. All antagonistic Streptomyces selected here were able to grow in the rhizosphere soil from infected sugar beet culture.