Isolates Of Fusarium Moniliforme Research Articles

Morphological and molecular characterization of Fusarium sp. causing Bakanae disease of rice (Oryza sativa) in western Uttar Pradesh, India

Rice (Oryza sativa L.) is considered as one of the main staple food grains. The Asian countries lead in production and consumption of rice i.e. more than 90% rice is produced and consumed in Asia. India is considered as one of the leading exporters of rice. Rice is affected by number of diseases and pests and among the several diseases which infects the rice crop, a fungal disease commonly known as Bakanae disease or Foot rot of rice is caused by Fusarium moniliforme (Gibberella fujikuroi) fungus. It is one of the important diseases of rice and leads to severe losses in rice yield particularly in basmati rice. According to some previous reports, some other Fusarium species were also found to be causing the disease. Therefore, the following study was conducted in the year 2018–19 at Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut, Uttar Pradesh, India, to find out and identify the Fusarium sp.mainly associated with the Bakanae disease in western Uttar Pradesh. Twelve isolates of Fusarium moniliforme were collected and isolated from different locations of western Uttar Pradesh and their characterization of morphological and molecular characters was carried out. Morphological characters, like fungal growth type, pigmentation, radial growth, colony characters were studied and compared with the standard culture of Fusarium moniliforme obtained from ITCC, New Delhi. The molecular characterization was done with specific primers. The results indicated that Bakanae disease of rice in western Uttar Pradesh is primarily caused by Fusarium moniliforme. The study also confirms that identification based on morphological and culture characteristics must be coupled with molecular characteristics for proper identification of specific fungal sp. causing Bakanae disease

Molecular Characterization of Fumonisin Mycotoxin Genes of Fusarium sp Isolated from Corn and Rice Grains

Fungi mycotoxins can be a serious risk to health and lead to substantial economic loss. The environmental conditions of Saudi Arabia, with its mostly warm temperatures, are conducive to the growth of toxigenic fungi resulting in mycotoxin production in different food items. The current study elucidates the natural occurrence of toxigenic fungi and mycotoxin production in grains in Saudi Arabia. Samples of white rice and corn (yellow, red) grains were collected from different local markets and houses. Three fungal isolates were obtained from the corn and rice grains and examined using Potato Dextrose Agar (PDA) and Carnation Leaf Agar (CLA) media. Fusarium spp. were the most prominent fungi in yellow corn, red corn and white rice grains. Three isolated F. moniliforme strains were identified using molecular characterization of the trichothecene 3-O acetyltransferase (TRI101) toxin gene. The DNA genome of the three Fusarium moniliforme isolates (namely, F. moniliforme_1, F. moniliforme_2 and F. moniliforme_3, which correspond to isolates from yellow corn, red corn and white rice, respectively) were used as a template for PCR to amplify trichothecene 3-O acetyltransferase (TRI101). Partially sequenced fragments amplified using a specific primer set were used to confirm the identification of, and to evaluate the phylogenetic relationships among the three isolates as well as to identify the corresponding antigenic determinants. The epitope prediction analysis demonstrated that there were four epitopes with scores equal to 1 in F. moniliforme_1, F. moniliforme_2 and F. moniliforme_3, respectively. Interestingly, there were great dissimilarities in the epitope sequences among the three isolates except in NSTPRACASEQEVS, STSSRADSSSLSTD and CTLCPRSLMASSVR. This indicates that the unique antigenic determinants predicted in the trichothecene 3-O acetyltransferase (TRI101) toxin gene could be used for designing a broad spectrum antibody for rapid detection of Fusarium spp. in foods.

Random Amplified Polymorphic DNA (RAPD) Analysis to Determine the Genetic Variability among Virulent and Less Virulent Isolates of Fusarium moniliforme, Fusarium oxysporum and Fusarium solani Isolated from Infected Cotton Seedlings

Root-rot of cotton (Gossypium spp.) is one of the most important diseases in Upper Egypt. Isolation has been done from diseased cotton roots and seeds which were collected from 11 counties in Assiut province, Egypt. Identification procedures of the isolated fungi confirmed that the isolated fungi were for Fusarium solani, F. moniliforme and F. oxysporum and Rhizoctonia solani. Thirty six isolates of Fusarium spp. and 10 isolates of Rhizoctonia solani were tested for their pathogenicity on both Giza 80 and Giza 83 cotton seedlings to verify their virulence on seedlings. The pathogenicity test results have grouped the Fusarium spp. isolates into three groups; highly virulent that caused 91-100% mortalities; moderately virulent that caused 81-90% mortalities and low virulent that caused lower than 81.0% mortalities. Data also shows that, in general Giza 80 cotton cultivar was more susceptible for infection with Fusarium spp. when compared with Giza 83 cotton cultivar. In case of Rhizoctonia solani, data revealed that the infection percentage was significantly affected by isolates while cotton cultivars had no significant influence on infection. Four 10-mer primers (1:6-d, 2:6-d, 4:6-d and 5:6-d) were used in RAPD-PCR to determine the genetic variability between six isolates, one virulent and one less virulent, of F. moniliforme, F. oxysporum and F. solani. Our results showed that the primer 2:6-d clearly separated F. moniliforme, F. oxysporum and F. solani and proved to be quite powerful in distinguishing the three different species and isolates of Fusarium spp.

CHARACTERIZATION OF Fusarium moniliforme INVOLVED IN COTTON SEEDLING DAMPING-OFF BY PATHOGENICITY AND ELECTROPHORETIC PROTEIN PROFILES

Pathogenicity of fourteen isolates of Fusarium moniliforme, from different cotton-growing areas of Egypt was evaluated on cotton cultivar Giza 86 under greenhouse conditions. All the tested isolates were pathogenic. They affected all disease variables. Isolates nos. 3, 13, 1, and 10 were the most pathogenic isolates in pre-emergence stage, while isolates nos. 2, 10, and 3 were the most pathogenic isolates in post-emergence stage. All isolates were more pathogenic in pre-emergence stage than post-emergence stage except isolate no. 2, which was more pathogenic in post-emergence stage. All tested isolates significantly reduced both of plant height and dry weight of seedlings. There were no relationship between pathogenicity of the isolates and their geographic origins. There was a negative significant correlation between pre-emergence damping-off and the dry weight of seedlings. Also, there was a negative significant correlation between post-emergence damping-off and survival. Cluster analysis of isolates based on pathogenicity patternes showed that there was no relationship between virulence patternes of isolates and their geographic origin. Electrophoretic protein profiles of isolates showed that the population of Upper Egypt was genetically differed from that of Nile Delta. There was a correlation between protein profiles and geographic origin of isolates, while there was no correlation between protein profiles and pathogenicity of isolates.

Phytotoxicity of Fusarium, other fungal isolates, and of the phytotoxins fumonisin, fusaric acid, and moniliformin to jimsonweed

Ten fungal isolates from jimsonweed (Datura stramonium L.) and 7 from crop species were examined for phytotoxin production and pathogenicity on jimsonweed seedlings in the greenhouse. Four isolates of Fusarium moniliforme, three F. semitectum isolates, a F. oxysporum isolate, a Cephalosporium spp. isolate, and an Alternaria crassa isolate from diseased jimsonweed seedlings, plus seven additional F. moniliforme isolates from seeds and seedlings of crop species were grown on autoclaved rice (Oryza sativa). The fungus-rice mixtures were ground and tested for phytotoxicity on 1- and 2-wk-old jimsonweed seedlings via foliar application. All fungus-infested rice extracts (5 g fungus-rice mixture 50 mL-1 water) caused injury or mortality to the seedlings except the extracts from isolates of F. semitectum, Cephalosporium spp., and A. crassa. Fungus-rice mixtures were quantitatively analyzed for the presence of Fusarium phytotoxins [fumonisin B1 (FB1 fusaric acid, and moniliformin]. No isolate produced more thanoneof these phytotoxins in the fungus-rice extract. FB1 was produced by ail F. moniliforme isoletes in a concentration range of ≤ 5 to 850 μg mL-1 of fungus-rice extract. The F. oxysporum isolate produced moniliformin at 3.5 g mL-1, and no phytotoxins were detected in extracts of F. semitectum, Cephalosporium spp., or A. crassa. Pure fumonisin, fusaric acid, and moniliformin applied to jimsonweed foliage at 6-50, 25-800, and 50-800 (μg mL-1, respectively, caused symptoms similar to that of the fungal isolates that produced these compounds. Pathogenicity tests of spores of all isolates on jimsonweed indicated that the isolates were avirulent, except for A crassa which infected only after a dew period ≥ 12 h.

Genetic Variation in Fusarium moniliforme Isolated from Seeds of Different Host Species from Burkina Faso Based on Random Amplified Polymorphic DNA Analysis

AbstractRandom amplified polymorphic DNA (RAPD) analysis was used to assess genetic variation among 28 isolates of Fusarium moniliforme isolated from seed samples of six host species (rice, sorghum, maize, cotton, hibiscus and parkia) collected in Burkina Faso. Score‐able markers (128) were obtained with 20 random decamer primers. Cluster analysis with UPGMA using genetic distances showed that the isolates were of five main groups. In general, isolates from the same host species were found to group together in the same cluster. The isolates from cotton and hibiscus were more closely related to each other than to the isolates from sorghum, rice and maize. Results indicate that host preference is possibly a factor in the differentiation of isolates.

The effect of fungal competition on colonization of maize grain by Fusarium moniliforme, F. proliferatum and F. graminearum and on fumonisin B 1 and zearalenone formation

The effect of water activity (0.98, 0.95, 0.93) and temperature (15, 25°C) on fungal growth and toxin production from interactions between isolates of Fusarium moniliforme and F. proliferatum producing fumonisin, and an isolate of F. graminearum producing zearalenone, incubated at the same time on irradiated maize grains were determined in vitro. Populations (CFUs) of F. moniliforme and F. proliferatum were reduced to a greater or lesser extent by the presence of F. graminearum under all conditions tested, while that the presence of F. moniliforme or F. proliferatum had a minor inhibitory effect on fungal populations of F. graminearum. Fumonisin B 1 production by F. proliferatum was inhibited under all conditions tested, while fumonisin B 1 production by F. moniliforme was inhibited at 15°C and enhanced at 25°C in the presence of F. graminearum. The level of zearalenone was not significantly modified in the presence of F. moniliforme and F. proliferatum under the conditions tested.

Fumonisin B1, zearalenone and deoxynivalenol production byFusarium moniliforme,F proliferatum andF graminearum in mixed cultures on irradiated maize kernels

The impact on fungal growth and mycotoxin formation of interactions between fumonisin-producing isolates of Fusarium moniliforme and F proliferatum and a zearalenone (ZEA)- and deoxynivalenol (DON)-producing isolate of F graminearum inoculated together on irradiated maize at 15 and 25 °C and at 0.98, 0.95 and 0.93 aw was studied. The presence of F graminearum decreased the fungal populations (CFU g−1 grain) of F moniliforme and F proliferatum under almost all conditions tested. In the presence of F moniliforme, CFUs of F graminearum increased significantly at 25 °C, especially at 0.93 and 0.95 aw, while the presence of F proliferatum caused them to increase at 15 °C. The presence of F graminearum always inhibited FB1 production, except at 25 °C and 0.98 aw where it increased. However, the observed differences were not statistically significant. There was no effect of fungal interaction on ZEA production by F graminearum; however, when paired with F moniliforme and F proliferatum, DON production by F graminearum was significantly stimulated, especially at 0.98 aw. © 2000 Society of Chemical Industry

Vegetative compatibility, biosynthesis of GA3 and virulence of Fusarium moniliforme isolates from bakanae disease of rice

Twenty‐eight isolates of Fusarium moniliforme were established from bakanae‐infected rice plants of a range of cultivars collected from various localities in Haryana, India. They were characterized by vegetative compatibility, virulence pattern on five paddy cultivars, and biosynthesis of gibberellins and were assigned to 10 vegetative compatibility groups (VCGs). Isolates from different VCGs and also within the same VCG varied considerably in virulence and GA3 production. The 28 isolates were categorized into five gibberellic acid production groups (GPG‐I–GPG‐V) and five virulence groups (VG‐I–VG‐V). Vegetative compatibility was independent of pathogenicity and of ability to produce GA3. However, GA3 production was positively correlated (r = 0.731) with pathogenic behaviour.

Colonization of Maize Grain by Fusarium moniliforme and Fusarium proliferatum in the Presence of Competing Fungi and Their Impact on Fumonisin Production

This study was carried out to determine the effect of water activity (aw) and temperature on the pattems of colonization of maize grain by isolates of Fusarium moniliforme and F. proliferatum in the presence of interacting spoilage fungi, such as Aspergillus flavus, A. niger, A. ochraceus, and Penicillium implicatum, over 4-week incubation periods. The impact that such interactions have on Fusarium infection of maize grain and populations and on the production of fumonisins were all evaluated. At 0.93 and 0.95 aw, interactions of the two Fusarium spp. with other species to a large extent resulted in mutual inhibition on contact or overgrowth by the Aspergillus and Penicillium spp., regardless of temperature and growth rates of the species. Seed infection by the Fusarium spp. at 25°C was influenced mainly by A. flavus and A. niger, with a reduction of infection by up to 45 and 30%, respectively, after 2 weeks. At 15°C and lowered aw levels, infection was reduced, and sometimes completely inhibited, by A. niger, A. ochraceus, and P. implicatum. By contrast, populations of the Fusarium spp. (CFU per gram grain) were reduced mainly by A. flavus and P. implicatum. A. niger reduced populations of the Fusarium spp. at 0.93 and 0.95 aw, particularly after 4 weeks of incubation. Interaction with A. niger, A. ochraceus, and A. flavus at 15 and 25°C and 0.98 aw resulted in a significant stimulation in fumonisin production by both Fusarium spp. Interaction with P. implicatum resulted in a decrease in fumonisin production by F. moniliforme. However, interaction with F. proliferatum resulted in an enhanced production at both temperatures and 0.95 and 0.98 aw. This study has shown that fungal interactions may act as an additional control factor in Fusarium spp. development on grain. However, although interactions lead to a decreased colonization by Fusarium, mainly at lower aw, a decrease in fumonisin production accumulation does not occur at the same time. Knowledge of these interactions is essential for improving effective control procedures for preventing growth and mycotoxin production by such fungi.

Environmental factors, in vitro interactions, and niche overlap between Fusarium moniliforme, F. proliferatum, and F. graminearum, Aspergillus and Penicillium species from maize grain

The effects of temperature and water availability on growth and interactions between fumonisin-producing isolates of Fusarium moniliforme and F. proliferatum and seven other fungi from maize grain were determined in vitro . The type of interaction and index dominance ( I d ) between species were markedly influenced by temperature and a w . Generally, F. moniliforme and F. proliferatum were very competitive and dominant against the Penicillium spp. and A. flavus . They were in turn dominated by A. niger , but mutually antagonistic when paired with F. graminearum and A. ochraceus . Under slightly drier conditions (<0.98 a w ) A. ochraceus became more competitive and dominant over the fumonisin-producing species. A. flavus was dominant only at 30°C and <0.96 a w . F. moniliforme and F. proliferatum demonstrated dominance against all species over a range of temperatures and 0.994 to 0.96 a w . At lower a w levels they were less competitive. The growth rate of the two fumonisin-producing species was significantly reduced by F. graminearum , regardless of a w . F. moniliforme and F. proliferatum reduced growth of Penicillium and Aspergillus spp., especially at > 0.96 a w . At < 0.96 a w , growth of these species was unaffected. Using Biolog plates the effect of a w and temperature on utilization patterns of carbon sources in maize were evaluated for the first time. The niche overlap indices relative to F. moniliforme and F. proliferatum were determined and compared with that of each interacting species. NOIs for F. moniliforme and F. proliferatum were > 0.90 at > 0.96 a w and 25 and 30°, indicative of co-existence with other species. Most of species had NOIs > 0.90, except in some cases when paired with F. moniliforme , where NOIs < 0.80 suggested the occupation of different niches. Although there was no significant correlation between the I d and NOI methods both suggested that the niche overlap between species was in a state of flux and significantly influenced by both temperature and water availability. This suggests that interpretation of I d NOIs carried out under one set of environmental conditions may be misleading when considering interactions between species and also where screening for biocontrol potential is being considered.

Correlation of moniliformin, but not fumonisin B1 levels, in culture materials of Fusarium isolates to acute death in ducklings

Five isolates of Fusarium moniliforme and two isolates Fusarium proliferatum of the Section Liseola were each fermented on rice for 21 d at 25 C. Each Fusarium-fermented rice, when dried and mixed into a poultry diet (10% by weight), caused a varied degree of acute mortality in baby Pekin ducklings. The acute (death in less than 48 h) mortality correlated significantly only to the amount of moniliformin in fermented rice, thus in the diet, but not to the amount of fumonisin B1 in fermented rice. This correlation of moniliformin concentration and noncorrelation of fumonisin B1 concentrations to acute toxicity were confirmed by duckling assay using diets containing these purified mycotoxins.

Characterization of chlorate-resistant sectors from isolates of Fusarium moniliforme and F. proliferatum

Fusarium moniliforme and Fusarium proliferatum produce spontaneous chlorate-resistant sectors on chlorate-containing media. Most of these sectors are nitrate non-utilizing mutants ( nit mutants). We recovered nit mutants as spontaneous chlorate-resistant sectors from 18 isolates of F. moniliforme, and 16 isolates of F. proliferatum of Italian origin. Three media, each containing two different chlorate concentrations, were used. The nit mutants were characterized by their colony morphology on different nitrogen sources. In some cases nitrate reductase activity was evaluated by testing for nitrite excretion. We found three classes of mutants ( nit1, nit3, NitM) corresponding to those assigned in previous studies to mutants of Fusarium species, and, with a low frequency, two additional unexpected classes. One of these, designated Nit8, presumably reflected a mutation at a nitrite reductase structural locus as mutants were positive in the nitrite excretion test. Mutants that grew prototrophically only when reduced sulphur sources were added to the medium were assigned to the other class, and considered as sulphate non-utilizing mutants ( sul). The majority of sul mutants responded to thiosulphate supplementation but two required cysteine or methionine. Complementation was also observed when some of these mutants where co-cultured on MM. The pattern of positive reaction obtained suggested that our sul mutants could result from mutations of at least three loci associated with sulphate metabolism. The sul mutants were recovered from F. moniliforme isolates only. Sectoring on chlorate-containing media provides a method for the isolation of Nit8 mutants from F. moniliforme and F. proliferatum, and of sul mutants from F. moniliforme.

Genetic diversity of Fusarium moniliforme detected by vegetative compatibility groups and random amplified polymorphic DNA markers

Genetic diversity among Fusarium moniliforme isolates was analysed using vegetative compatibility group (VCG) and random amplified polymorphic DNA (RAPD) techniques. In the first experiment, RAPD was used to analyse a set of 43 isolates collected from different corn growing areas in Israel and the US. The isolates were assigned to 27 different VCGs. Thirty‐two RAPD haplotypes were also detected by analysing 48 polymorphic bands. RAPD could differentiate all the VCGs, except in two cases where two VCGs were assigned a single RAPD haplotype. In six cases, however, molecular variation was detected among isolates belonging to the same VCG. Cluster analysis of the RAPD data showed a very good agreement with the VCG grouping, e.g. isolates of the same VCG were always closely clustered by the molecular data. In a second experiment, 63 isolates of Fusarium moniliforme were collected from six corn lines growing in a single corn field. Extensive genetic variation was observed among the isolates: 42 different VCGs and 37 RAPD haplotypes were identified. Once again, RAPD patterns could differentiate nearly all the VCGs. However, in four cases, two different VCGs were grouped into a single RAPD haplotype, while in another three cases, isolates of the same VCG could be differentiated by distinct molecular haplotypes. The variation data was used to gain insight on the population structure and the patterns of genetic variation among geographical locations and within a single field. Hierarchical gene diversity analysis of the RAPD data indicated that most of the genetic variability (81%) was distributed within corn lines in the same field, suggesting that RAPD haplotype, or VCG frequencies, were not significantly affected by the plant genotypes grown in this experiment. Most of the RAPD band combinations did not display significant gametic phase disequilibrium, suggesting that active recombination might be occurring in the field. Our results indicate that by using a small number of primers, similar resolution was obtained by RAPD and VCG analysis, respectively. RAPD analysis is however, simpler to perform and its sensitivity in genotyping individuals within Fusarium moniliforme can be increased by analysing more primers, enabling a more detailed population genetic analysis of this important pathogen.

Occurrence and toxigenicity of Fusarium moniliforme from freshly harvested maize ears with special references to fumonisin production in Egypt.

Using the seed-plate technique, 18 different isolates of Fusarium moniliforme were isolated on pentachloronitrobenzene (PCNB) agar medium from 18 samples of a local variety of corn collected from locations in Minia Governorate. The isolates of F. moniliforme were screened for their ability to produce fumonisins on polished rice grains using the solid state fermentation technique. Based on thin layer chromatographic (TLC) analyses using silica gel plates, 14 of the 18 isolates tested produced FB1 and FB2 with Rf (0.17) and (0.24), respectively. Concentration of FB1 was estimated using high performance liquid chromatography (HPLC). Production of FB1 by the 14 isolates of F. moniliforme tested ranged from 69 to 4495 ppm indicating that mouldy corn may represent a health hazard to consumers.

Susceptibility of clinical isolates of Fusarium to antifungal drugs

The inhibitory activities of amphotericin B, fluconazole, itraconazole, miconazole, ketoconazole and terbinafine against nine isolates from clinically apparent infections of Fusarium solani, four isolates of Fusarium moniliforme and 10 isolates of Fusarium oxysporum were determined with an agar diffusion method (Neosensitabs) and an agar dilution method. The inhibition zones obtained with antifungal Neosensitabs need very careful interpretation. We did not find a good correlation between the agar diffusion method using Neo-sensitabs preloaded with azoles and amphotericin B and the agar dilution method. Amphotericin B (12/23) and terbinafine (18/23) showed good activity. Miconazole (7/23) and ketoconazole (3/23) had poor inhibitory activity. Fluconazole and itraconazole (0/23) had no in vitro activity against any of the isolates tested.

Water activity, temperature, and pH effects on growth of Fusarium moniliforme and Fusarium proliferatum isolates from maize.

The effects of water activity (aw, 0.994-0.90 identical to 0.4-14.0 (-)MPa water potential), temperature (4-45 degrees C), and pH (3.6, 5.5, 7.0), and their interactions on growth of isolates of Fusarium moniliforme and Fusarium proliferatum were determined in vitro on a maize extract agar medium. Growth of two isolates of F. moniliforme and four isolates of F. proliferatum were significantly influenced by water activity regardless of solute type used (NaCl, glycerol, or glucose). However, at steady-state aw levels, growth was optimum at 0.994-0.98 aw and reduced significantly at 0.92 aw. Further detailed studies with one isolate of F. moniliforme (25N) and two isolates of F. proliferatum (73N, 131N) showed that growth occurred over the range of 0.994-0.90 aw in the temperature range 20-35 degrees C with slight differences between species. Growth did occur at 4 degrees C and 0.994-0.96 aw, but no growth was recorded at 40 and 45 degrees C regardless of aw. Profiles of aw x temperature relations for growth of these two species were constructed from these data for the first time. Optimum pH and temperature for growth was 5.5 and 25 degrees C for both isolates of F. proliferatum, and pH 7.0 and 30 degrees C for the isolate of F. moniliforme. However, for the latter isolate at < 0.98 aw, optimum pH and temperature for growth changed. The effects of pH, temperature, and aw for single, two-way and three-way interactions were all found to be statistically significant for these three isolates. The ecological significance of this information for understanding these important fumonisin-producing fungi is discussed.

Fumonisins B 1 and B 2 and toxigenic Fusarium strains in feeds from the Spanish market

Natural occurrence of fumonisins B 1 and B 2, incidence of Fusarium species, and capacity to produce fumonisins by Fusarium isolates, were investigated in 50 corn-based samples from Spain destined for animal consumption. Forty-four samples (88%) were found to be contaminated with fumonisins. The levels of contamination were very low, with a mean of 400 ng g in the samples. We investigated the capacity of 11 isolates of Fusarium moniliforme and 19 isolates of F. proliferatum to produce fumonisins. All F. proliferatum isolates and 8 out of the 11 F. moniliforme isolates assayed produced fumonisins on a corn medium. The FB 1 FB 2 ratio in the isolates ranged from 1.1 to 3.5.

Effects of Temperature on Isolates ofFusarium moniliformeCausing Fig Endosepsis andAspergillus nigerCausing Smut

Isolates of Fusarium moniliforme causing endosepsis, two obtained from cultivated fig and three from wild fig pollinator trees, and an isolate of Aspergillus niger causing smut on figs were evaluated for fruit colonization and lesion expansion at five constant temperatures. Surface-disinfested fruit halves from fig pollinator trees were inoculated individually with isolates of F. moniliforme and A. niger on the uncut surfaces and incubated at 15, 20, 25, 30, and 35°C under high humidity (>97%). Lesion sizes of smut and endosepsis were recorded after 3 and 5 days of incubation, respectively. To determine rates of lesion expansion, lesion sizes of endosepsis and smut were recorded at 48- and 24-h intervals after inoculation, respectively. Optimal temperature for F. moniliforme colonization was 30°C. Isolates from cultivated caprifigs failed to colonize at 35°C. Higher temperatures resulted in shorter latent periods for both E moniliforme (40 to 60 h at 30°C) and A. niger (44 h at 35°C). Fusarium moniliforme isolates from the wild caprifigs had a significantly shorter latent period at 30°C (40 h) than isolates from cultivated caprifigs (60 h). Lesion sizes caused by isolates at different temperatures differed significantly (P = 0.0001). At each temperature, isolates from wild caprifigs caused significantly larger lesions and sporulated more than isolates from cultivated caprifigs. Optimal temperature for A. niger colonization was 35°C. At temperatures of <25°C, lesions areas caused by E moniliforme isolates were significantly larger ; at 30 and 35°C, lesion areas caused by A. niger were significantly larger. At 30 and 35°C, the rates of lesion expansion for A. niger were twice as great as rates for any isolate of E moniliforme. Because temperatures of <30°C are not conducive to A. niger development, smut is rare on caprifigs and is common on Calimyrna figs.

Effect of some phytopathogenic fungi and their metabolites on growth ofHeliothis virescens(F.) and its host plants

Eleven fungal isolates and their secondary metabolites incorporated into artificial diet were tested for oral toxicity to the tobacco budworm (TBW) by examining larval weight, efficiency of conversion of ingested food to body tissue (ECI), pupal weight, days to pupation, and mortality. Two isolates of Altemaria alternata, two isolates of Fusarium moniliforme, three isolates of F. oxysporum and an isolated of F. solani reduced larval weight 90–99% after 7 days and inhibited pupation. ECI was reduced 34–96% in control groups. One isolate of A. alternata reduced pupal weight by 67% and increased the time to pupation three‐fold. One isolate of Cladosporium cladosporioides reduced larval weights by 56% and pupal weights by 7%. In a preference test of these isolates incorporated at a 1:4 ratio into artificial diet, 48% of the larvae were found on diet cubes containing autoclaved rice, 19% on standard diet, 10% on C. cladosporioides, 6–9% on F. solani, 8% on A. alternata and 3% on F. moniliforme. The fusarial to...