Analysis of Spanish populations of Ophiostoma ulmi and O. novo-ulmi using phenotypic characteristics and RAPD markers

One hundred and six isolates of the Dutch elm disease (DED) fungi Ophiostoma ulmi and Ophiostoma novo-ulmi were collected from elm trees with symptoms in 15 regions of Spain. Isolates were compared with eight reference strains belonging to O. ulmi and the two subspecies of O. novo-ulmi. The purpose of this study was to assign Spanish isolates to species and subspecies of the DED fungi and to analyse the genetic variability within the Spanish populations of these pathogens. Isolates were examined for their growth rates, colony morphologies and fertility responses and by using random amplified polymorphic DNA (RAPD) markers. Six isolates were identified as O. ulmi , 16 as O. novo-ulmi ssp. novo-ulmi and 78 as O. novo-ulmi ssp. americana . Nei's and Shannon's diversity indices and the upgma dendrogram from RAPD profiles indicated a high level of variation among isolates, probably reflecting post-epidemic status of DED in Spain. Although most isolates were separated into three major clusters representing the three taxa of DED fungi in the RAPD analysis, two isolates from central Spain clustered between O. novo-ulmi ssp. americana and O. novo-ulmi ssp. novo-ulmi , and four isolates from Mallorca clustered between O. ulmi and the group representing O. novo-ulmi ssp. novo-ulmi . Mating tests conducted with these isolates revealed a variety of fertility responses. The novel combinations between molecular profile and fertility reaction suggest that three isolates from Mallorca may be interspecific hybrids of the DED fungi.     

Evaluating Verticillium dahliae for biological control of Ophiostoma novo-ulmi in Ulmus minor

The ability of isolate Vd-48 of Verticillium dahliae to induce resistance against subsequent challenge with Ophiostoma novo-ulmi was examined in Ulmus minor . In the first experiment, conditioning inoculation of 5-year-old elm trees (2–3 m in height) with Vd-48 15 days prior to challenge inoculation with O. novo-ulmi significantly reduced wilting ( P  ≤ 0·05) compared with trees not conditioned with Vd-48. However, in another experiment on 6-year-old trees (2–3·5 m in height), no protection was achieved when the length of time between conditioning and challenge inoculations was 45 or 60 days. In a further experiment, inoculations with Vd-48 alone resulted in severe wilting in 22 out of 118 trees (6–10 years old and 4–7 m in height). Across the 2 years of this last trial, nine trees showed massive feeding wounds made by Scolytus sp., while O. novo-ulmi strains were isolated from six trees. Vd-48 provided a variable prophylactic effect against O. novo-ulmi in U. minor . Major difficulties with this approach to control Dutch elm disease are discussed.     

Genetic evidence for natural hybridization between the Dutch elm disease pathogens Ophiostoma novo-ulmi ssp. novo-ulmi and O. novo-ulmi ssp. americana

The Dutch elm disease pathogen Ophiostoma novo-ulmi is separated into subspecies novo-ulmi , formerly known as the Eurasian (EAN) race, and subspecies americana , formerly known as the North American (NAN) race. Both subspecies occur in Europe, and hybrids between them are suspected to have emerged in parts of Europe where their ranges overlap. Authenticated isolates of both subspecies were examined in order to determine whether fixed mutations occur in the cerato-ulmin ( cu ) and in the colony type gene ( col1 ). One and six mutations were detected between subspp. novo-ulmi and americana in cu and col1 , respectively. The mutation in cu and one mutation in col1 proved to be located within restriction sites, and were used for PCR-RFLP. This method provides a quick and reliable diagnostic method to differentiate the two subspecies. Seven isolates of O. novo-ulmi from Austria were suspected to be hybrids between subspp. novo-ulmi and americana , and were tested by PCR-RFLP of their cu and col1 genes. Two of the suspected hybrids from Austria (isolates AT73 and AT146) had the cu PCR-RFLP profile of ssp. americana and the col1 PCR-RFLP profile of ssp. novo-ulmi . Furthermore, a ssp. novo-ulmi tester isolate from Poland (P150) showed a similar hybrid pattern. This is the first evidence revealing recombination between two genes and thus hybridization between the two subspecies of O. novo-ulmi in nature.     

人工接种对新月弯孢菌侵染玉米籽粒的影响

研究了人工接种不同接种时期和方法对新月弯孢菌侵染玉米籽粒的影响,结果表明:玉米弯孢叶斑病菌可以侵染玉米果穗籽粒,使玉米籽粒产生褐色病斑。伤口接种法能使玉米果穗100%发病;花丝通道接种也可导致果穗发病,但其发病频率很低;而花丝喷雾接种和苞叶喷雾接种病菌不能成功侵染玉米果穗籽粒;吐丝后10 d和乳熟期接种只能引起接种点籽粒发病,病菌扩展不好;但籽粒形成期接种的玉米果穗籽粒不仅接种点发病,而且其周围的籽粒也感染了病菌,病菌扩展情况较好。试验明确,玉米籽粒形成期采用伤口接种是使玉米籽粒发生弯孢叶斑病的一种较为理想的人工接种方法。     

Rapid emergence of hybrids between the two subspecies of Ophiostoma novo-ulmi with a high level of pathogenic fitness

During the 1970s Europe was invaded by two subspecies of the Dutch elm disease pathogen Ophiostoma novo-ulmi : subsp . americana from the west and subsp. novo-ulmi from the east. As a result their geographic ranges began to overlap in several areas. Only a weak prezygotic barrier to hybridization exists between the subspecies and in 1980 two hybrids were detected in the Netherlands. A subset of 107 O. novo-ulmi isolates collected in a subspecies overlap zone in Limburg, Netherlands in 1983 was characterized for three phenotypic markers and seven RAPD PCR markers. By phenotype, 33% were shown to be hybrid whereas by RAPD markers 69% were shown to be hybrid. Some isolates shown to be hybrid by phenotype were not revealed to be hybrid by PCR and vice versa. Combining the phenotype and RAPD data the estimated hybrid frequency was ∼78%. The mean growth rate of Limburg hybrid isolates was significantly faster than that of the Limburg subsp. novo-ulmi isolates but not significantly different from Limburg subsp. americana isolates. The Limburg hybrid isolates were just as pathogenic as the parent subspecies on both clonal Ulmus procera and on U.  × Commelin. A subset of 100 isolates collected in another subspecies overlap zone at Orvieto, Italy in 1986 was also assessed with RAPD markers and ∼ 72% were shown to be hybrids. When 20 isolates of a 'pure' subsp. novo-ulmi population in the Baltic Ports area of Poland collected in 1980 were assessed by RAPD markers three isolates exhibited early introgression of subsp. americana DNA. This study therefore demonstrates very rapid emergence of O. novo-ulmi subspecies hybrids and introgressants in Europe in the early 1980s. In terms of two major fitness characters, growth rate and pathogenicity, these early hybrids were as fit as their parent subspecies. It is likely that complex hybrid swarms are now expanding across the continent.     

Disease Resistance of Tissue-cultured Seedlings of Rhododendron after Treatment with Streptomyces sp. R-5

An endophytic actinomycete, Streptomyces sp. R-5, which had been isolated from a field-grown rhododendron plant, was used to protect rhododendron seedlings in tissue culture from Pestalotia disease caused by Pestalotiopsis sydowiana. R-5 had intense antagonistic activity against P. sydowiana without adversely affecting the seedlings in glass flasks. A suspension of R-5 was spread on the surface of the multiplication medium in glass flasks in which seedlings were growing. Ten days later, the 4th upper leaf of seedlings was inoculated with P. sydowiana and incubated for 14 days. In controls untreated with R-5, substrate mycelia of P. sydowiana grew on all leaves and stems above and below the 4th leaf within 2–3 days of inoculation. Such growth resulted in the wilting death of 54% of seedlings by 14 days. In contrast, only the inoculated leaves turned brown in ca. 90% of seedlings growing on medium treated with R-5. None of these seedlings died. Thus, treatment of the medium surface with R-5 efficiently protects the seedlings from infection by P. sydowiana. Scanning electron microscopy revealed that substrate mycelia of R-5 grew on and beneath the cuticle of leaves of the treated seedlings. Fluorescent microscopy showed that R-5 was also inside the leaves. Received 8 June 2001/ Accepted in revised form 4 July 2001     

烯丙异噻唑刺激稻株体内超氧自由基产生与水稻抗稻瘟病的关系

 病原菌与寄生植物相互作用是个十分复杂的过程,涉及到两者很多因子的相互作用。     

Ethylene-insensitive tobacco shows differentially altered susceptibility to different pathogens

ABSTRACT Transgenic tobacco plants (Tetr) expressing the mutant etr1-1 gene from Arabidopsis thaliana are insensitive to ethylene and develop symptoms of wilting and stem rot when grown in nonautoclaved soil. Several isolates of Fusarium, Thielaviopsis, and Pythium were recovered from stems of diseased Tetr plants. Inoculation with each of these isolates of 6-week-old plants growing in autoclaved soil caused disease in Tetr plants but not in nontransformed plants. Also, when 2-week-old seedlings were used, nontransformed tobacco appeared nonsusceptible to the Fusarium isolates, whereas Tetr seedlings did develop disease. Tetr seedlings were not susceptible to several nonhost Fusarium isolates. In contrast to results with Fusarium isolates, inoculation of 2-week-old seedlings with a Thielaviopsis isolate resulted in equal symptom development of nontransformed and Tetr tobacco. In order to explore the potential range of pathogens to which Tetr tobacco plants display enhanced susceptibility, the pathogenicity of several root and leaf pathogens was tested. Tetr plants were more susceptible to the necrotrophic fungi Botrytis cinerea and Cercospora nicotianae and the bacterium Erwinia carotovora, but only marginally more to the bacterium Ralstonia solanacearum. In contrast, the biotrophic fungus Oidium neolycopersici, the oomycete Peronospora tabacina, and Tobacco mosaic virus caused similar or less severe symptoms on Tetr plants than on nontransformed plants. Total peroxidase activity of Tetr plants was lower than that of nontransformed plants, suggesting a role for peroxidases in resistance against necrotrophic microorganisms. A comparable range of pathogens was examined on Arabidopsis and its ethylene-insensitive mutants etr1-1 and ein2-1. With the exception of one Fusarium isolate, ethylene insensitivity increased susceptibility of Arabidopsis plants to a similar spectrum of necrotizing pathogens as in tobacco. Thus, both ethylene-insensitive tobacco and Arabidopsis plants appear to be impaired in their resistance to necrotrophic pathogens.     

Antifungal effect and reduction of <Emphasis Type="Italic">Ulmus minor</Emphasis> symptoms to <Emphasis Type="Italic">Ophiostoma novo-ulmi</Emphasis> by carvacrol and salicylic acid

There are still no effective means to control Dutch elm disease (DED), caused by the vascular fungi Ophiostoma ulmi and O. novo-ulmi. Plant phenolics may provide a new strategy for DED control, given their known antifungal activity against pathogens and their involvement in plant defence mechanisms. The in vitro antifungal activity of salicylic acid, carvacrol, thymol, phenol, o-cresol, m-cresol, p-cresol, and 2,5-xylenol against the DED pathogens was tested. Also, the protective effect of watering Ulmus minor seedlings with these compounds was tested against O. novo-ulmi. Salicylic acid, carvacrol, and thymol showed the strongest antifungal in vitro activity, while carvacrol and salicylic acid provided the strongest in vivo protection against O. novo-ulmi (63 and 46% reduction of leaf wilting symptoms with respect to controls, respectively). The effect of the treatments on tree phenology was low, and a significant negative relation was observed between the number of days to bud burst and the leaf wilting symptoms after inoculation, probably determined by genetic differences among the elm tree progenies used. The treatments with salicylic acid, carvacrol and thymol induced the highest shift in phenolic metabolite profile with respect to control trees. The protective effect of carvacrol and salicylic acid is discussed in terms of their combined activity as antifungal compounds and as inductors of tree defence responses.     

Suppression of Septoria tritici and Puccinia recondita of wheat by an antibiotic-producing fluorescent pseudomonad

A fluorescent Pseudomonas sp. (strain LEC 1) isolated from soil suppressed Septoria tritici by 88% and Puccinia recondita by 98% when applied to wheat seedlings 3 h prior to inoculation with the pathogens. Fractionation and analysis of two inhibitory compounds from cultures of strain LEC 1 on thin-layer chromatography plates yielded the phenazine antibiotics 1-hydroxyphenazine (phOH) and chlorora-phin. 1-hydroxyphenazine reduced the growth of Pythium aphanidermatum, Fusarium oxysporum f.sp. vasinfectum, Sclerotinia sclerotiorum and S. rolfsii on a denned medium, with greatest activity against P. aphanidermatum and least against S. rolfsii. Application of 160 mg/l phOH to wheat seedlings reduced S. tritici by 61% and P. recondita by 75%. Lower concentrations of the antibiotic were less effective. Growth of 5. tritici in liquid medium was reduced by phOH at 5–20 mg/l and prevented at 40 mg/l. When phOH was added to the medium 48 h after inoculation (logarithmic growth phase), growth was interrupted but later recovered with phOH concentrations up to 40 mg/l; there was no recovery at 60 mg/l. Chlororaphin inhibited the growth of S. tritici on malt agar medium.     

Protection of Citrus Rootstocks Against Phytophthora spp. with a Hypovirulent Isolate of Phytophthora nicotianae

ABSTRACT Phytophthora root rot of citrus in Florida is caused by Phytophthora nicotianae and P. palmivora. A naturally occurring isolate of P. nicotianae (Pn117) was characterized as hypovirulent on citrus roots. Pn117 infected and colonized fibrous roots, but caused significantly less disease than the virulent isolates P. nicotianae Pn198 and P. palmivora Pp99. Coincident inoculation of rootstock seedlings of Cleopatra mandarin (Citrus reticulata) or Swingle citrumelo (C. paradisi x Poncirus trifoliata) with the hypovirulent Pn117 and the virulent isolates Pn198 and Pp99 did not reduce the severity of disease caused by the virulent Phytophthora spp. When either rootstock was inoculated with the hypovirulent Pn117 for 3 days prior to inoculation with virulent isolates, preinoculated seedlings had significantly less disease and greater root weight compared with seedlings inoculated with the virulent isolates alone. Recovery of the different colony types of Phytophthora spp. from roots of sweet orange (C. sinensis) or Swingle citrumelo was evaluated on semiselective medium after sequential inoculations with the hypovirulent Pn117 and virulent Pp99. Pn117 was isolated from roots at the same level as the Pp99 at 3 days post inoculation. Preinoculation of Pn117 for 3 days followed by inoculation with Pp99 resulted in greater recovery of the hypovirulent isolate and lower recovery of the virulent compared with coincident inoculation.     

Monoclonal antibodies to specific components of the Dutch elm disease pathogen Ophiostoma ulmi

The potential of polyclonal antisera and monoclonal antibodies to differentiate the EAN and NAN aggressive subgroups of Ophiostoma ulmi was explored. Polyclonal antisera, when tested by ELISA, cross-reacted widely with unrelated species and failed to distinguish between the two aggressive subgroups but small quantitative differences were found, particularly between antigens secreted overnight, by EAN and NAN germlings. Monoclonal antibodies were raised in mice against mycelial homogenates. From two fusions, 33 cell lines were raised that secreted antibodies positive for O. ulmi. Approximately one third were non-specific; 11 were specific either to species or subspecies. Two cell lines differentiated mycelial antigens of the aggressive isolates of O. ulmi from those of the non-aggressive subgroup, but not antigens from surface washings. Only quantitative differences were detected between the EAN and NAN aggressive subgroups. Almost all the monoclonal antibodies and antiserum recognized antigens present in surface washings of cultures on solid medium, in cell-free extracts of mycelial homogenates, in cell-free culture fluids, and in substances secreted overnight by germinating spores. Specific detection of such molecules promises to provide a highly sensitive mechanism for studying early pathogen/host plant interactions. Most of the monoclonal antibodies appeared to have potential diagnostic value; they gave readings twofold to tenfold higher with extracts from diseased than from healthy tissue. However, one cell line that secreted antibodies specific to O. ulmi cross-reacted strongly with extracts of healthy tissue.     

Modes of Action of Pantoea agglomerans CPA-2, an Antagonist of Postharvest Pathogens on Fruits

Pantoea agglomerans CPA-2 is an effective antagonist against the postharvest pathogens Penicillium digitatum and Penicillium italicum on citrus fruits but its mode of action is unknown. Possible mechanisms studied in this work were antibiosis, induced resistance, competition and production of chitinolytic enzymes. P. agglomerans CPA-2 was unable to produce antibiotics or chitinolytic enzymes under the conditions tested. Induction of resistance by P. agglomerans CPA-2 was studied in oranges by measuring phenylalanine ammonia lyase and peroxidase enzyme activity in the orange peel at different time points after inoculation with the antagonist and/or the pathogen. No significant augmentation of enzyme activity after inoculation of oranges with P. agglomerans CPA-2 in the presence or absence of the pathogen was observed. P. agglomerans was effective only when it is in close contact with the pathogens. Competition for nutrients was studied using tissue culture plates with cylinder inserts, which allowed competition for nutrients to be studied without competition for space since physical contact between pathogen and antagonist was avoided. The presence of P. agglomerans in the tissue culture wells clearly decreased the germination of Penicillium conidia present in the cylinder when diluted orange peel extract or diluted potato dextrose broth was the nutrient source. Germination of Penicillium conidia, however, was almost completely inhibited when pathogen and antagonist were in physical contact. These results indicate that competition for nutrients is one of the modes of action of P. agglomerans CPA-2, but that physical contact between pathogen and antagonist is important for effective control.     

5种杀螨剂对苹果树红蜘蛛田间药效评价

测定了5种不同作用机理杀螨剂对苹果树红蜘蛛的防效,并对其田间的应用效果进行评价。结果表明：三唑锡20%悬浮剂800倍液和唑螨酯5%悬浮剂2 000倍液速效性和持效性均较好,药后2d防效即达到90%以上,持效期25d以上;矿物油99%乳油和阿维菌素1.8%乳油速效性一般,但持效期较长,也能达到25d以上,哒螨灵40%可湿性粉剂防效一般。三唑锡20%悬浮剂和唑螨酯5%悬浮剂可快速有效地防治苹果树红蜘蛛,对天敌等影响较小,对作物安全,可作为防治的首选药剂使用。     

Impact of Foliar Diseases on Photosynthesis, Protein Content and Seed Yield of Alfalfa and Efficacy of Fungicide Application

Foliar pathogens attack alfalfa wherever the crop is grown, but their impact, especially on seed production, is poorly understood. In greenhouse trials, leaf spot injury caused by inoculation with various pathogens reduced the crude protein content of infected alfalfa leaves by 22% compared with a healthy control. There was a negative relationship between disease injury and the photosynthetic efficiency of alfalfa plants, as determined by measuring chlorophyll fluorescence in leaves from inoculated vs. non-inoculated seedlings. In field trials at two sites in Alberta from 2001 to 2003, inoculation with Phoma medicaginis increased disease incidence in four of six trials, Phoma sclerotioides increased incidence in four of five trials, and Leptosphaerulina trifolii and Stemphylium botryosum increased incidence in two of six trials. There was a trend for inoculation treatments to reduce seed yield, despite high levels of background infection by indigenous pathogens. The fungicides benomyl and propiconazole inhibited radial growth of Phoma spp. in vitro and reduced disease incidence in inoculated greenhouse experiments. In field trials, applications of benomyl and propiconazole reduced disease incidence, but did not always increase seed yield.     

Induction of resistance in cocoa against Crinipellis perniciosa and Verticillium dahliae by acibenzolar- S-methyl (ASM)

The benzothiadiazole compound acibenzolar- S -methyl (ASM) was assessed as an inducer of resistance against Crinipellis perniciosa , agent of witches' broom, and Verticillium dahliae , agent of vascular wilt, both on cocoa. ASM induced a reduction in incidence of witches' broom of up to 84·5% when sprayed 30 days before inoculation on cocoa seedlings of cv. Catongo. ASM also induced a reduction in severity of Verticillium wilt to 55·4% on cv. Theobahia. For both pathosystems, effects of dose on disease were not clearly observed. The efficacy of the inducer increased with the interval between sprayings and the respective inoculations with the pathogens. In another experiment, the effect of ASM on the control of witches' broom on cocoa seedlings was compared with that of cuprous oxide and tebuconazole, all sprayed 15 days before inoculation. ASM reduced disease incidence by 60·1% compared with the inoculated control. ASM was superior to tebuconazole, and there was also a tendency for ASM to be better than cuprous oxide. To understand the mechanism of action of ASM as an inducer of resistance, alterations in the levels of total phenolics, polyphenol oxidases and peroxidases were evaluated 3, 15 and 30 days after spraying of seedlings of cv. Catongo. Enzyme activities from seedlings of cv. Theobahia were evaluated 30 days after spraying. On cv. Catongo, no significant differences in total phenolic content and polyphenol oxidase activity were detected after spraying. However, an increase in peroxidase activity was detected at all times of evaluation. On cv. Theobahia, significant increases in activities of peroxidase and polyphenol oxidase were detected, indicating that defence responses due to ASM were dependent on host genotype.     

蛋白质激发子Hrip1对小麦黄矮病的诱抗作用

小麦黄矮病是由大麦黄矮病毒（barley yellow dwarf virus,BYDV）引起的一种小麦病毒病,其传播介体是小麦蚜虫,在小麦生产中造成巨大的经济损失。近年来,植物诱导抗性作为一种新兴的植物病虫害防治措施引起了广泛的关注。蛋白质激发子Hrip1可以激活多种植物的免疫防御反应诱导植物产生广谱抗性。本研究评价了Hrip1对小麦黄矮病的诱抗效果。用30 μg/mL的Hrip1溶液进行小麦浸种和幼苗喷雾,随后接种BYDV,接种后第14 d,Hrip1对小麦黄矮病控制效果在50%以上,接种后第21 d控制效果仍在30%以上。实时荧光定量PCR检测结果显示,在Hrip1处理的小麦幼苗体内,BYDV外壳蛋白mRNA的数量显著低于对照组;EPG结果显示,在Hrip1处理的小麦幼苗上,麦二叉蚜寻找叶片刺吸位点和韧皮部取食位点的时间增加。以上结果表明：Hrip1能够有效地抑制BYDV在小麦体内的增殖;影响传毒媒介麦二叉蚜的取食行为,抑制其传毒能力。此外,Hrip1处理小麦能有效缓解BYDV引起的叶片黄化和植株矮化的症状。因此,Hrip1可以作为生物诱导剂综合控制小麦黄矮病。     

Antibacterial activity of two chitosan solutions and their effect on rice bacterial leaf blight and leaf streak

BACKGROUND: Bacterial leaf blight and leaf streak are the two most damaging bacterial diseases of rice. However, few bactericidal chemicals are available for controlling both diseases. The antibacterial properties of two kinds of chitosan with different molecular weights and degrees of N‐deacetylation and their effect on rice bacterial leaf blight and leaf streak were evaluated. RESULTS: Results showed that the two kinds of chitosan solution possess a strong antibacterial activity against both rice bacterial pathogens and significantly reduced disease incidence and severity by comparison with the control under greenhouse conditions. However, the interaction between chitosan and rice pathogens was affected by the type and concentration of chitosan, the bacterial species and the contact time between chitosan and bacteria. The direct antibacterial activity of chitosan may be attributed to both membrane lysis and the destruction of biofilm. In addition, both chitosan solutions significantly increased the activities of phenylalanine ammonia lyase, peroxidase and polyphenol oxidase in rice seedlings following inoculation of two rice pathogens by comparison with the control. CONCLUSION: The role of chitosan in protection of rice against bacterial pathogens has been shown to involve direct antibacterial activity and indirect induced resistance. Copyright © 2012 Society of Chemical Industry     

Positive correlations between in vitro growth rate and pathogenesis in Ophiostoma ulmi

In vitro radial growth rate was found to be positively correlated with pathogenicity in two experiments involving NAN aggressive isolates of O. ulmi. One of the correlations was detected in a sample of B mating-type, but not in equivalent A mating-type isolates. Another was detected in a sample of pathogenic phase, but not in comparable saprophytic phase isolates. The significance of these results for the vascular wilt syndrome and population biology of O. ulmi is discussed.     

Nonpathogenic Binucleate Rhizoctonia spp. and Benzothiadiazole Protect Cotton Seedlings Against Rhizoctonia Damping-Off and Alternaria Leaf Spot in Cotton

ABSTRACT Recent reports have shown induction of resistance to Rhizoctonia root rot using nonpathogenic strains of binucleate Rhizoctonia spp. (np-BNR). This study evaluates the biocontrol ability of several np-BNR isolates against root and foliar diseases of cotton in greenhouse trials, provides evidence for induced systemic resistance (ISR) as a mechanism in this biocontrol, and compares the disease control provided by np-BNR with that provided by the chemical inducer benzothiadiazole (BTH). Pretreatment of cotton seedlings with np-BNR isolates provided good protection against pre- and post-emergence damping-off caused by a virulent strain of Rhizoctonia solani (AG-4). Seedling stand of protected cotton was significantly higher (P < 0.05) than that of nonprotected seedlings. Several np-BNR isolates significantly reduced disease severity. The combination of BTH and np-BNR provided significant protection against seedling rot and leaf spot in cotton; however, the degree of disease reduction was comparable to that obtained with np-BNR treatment alone. Significant reduction in leaf spot symptoms caused by Alternaria macrospora occurred on cotyledons pretreated with np-BNR or sprayed with BTH, and the np- BNR-treated seedlings had significantly less leaf spot than BTH-treated seedlings. The results demonstrate that np-BNR isolates can protect cotton from infections caused by both root and leaf pathogens and that disease control was superior to that observed with a chemical inducer.