The phoma-like dilemma.

Species of Didymellaceae have a cosmopolitan distribution and are geographically widespread, occurring in diverse ecosystems. The family includes several important plant pathogenic fungi associated with fruit, leaf, stem and root diseases on a wide variety of hosts, as well as endophytic, saprobic and clinically relevant species. The Didymellaceae was recently revised based on morphological and phylogenetic analyses of ex-type strains subjected to DNA sequencing of partial gene data of the LSU, ITS, rpb2 and tub2 loci. Several poly- and paraphyletic genera, including Ascochyta, Didymella and Phoma were redefined, along with the introduction of new genera. In the present study, a global collection of 1 124 Didymellaceae strains from 92 countries, 121 plant families and 55 other substrates, including air, coral, human tissues, house dust, fungi, insects, soil, and water were examined via multi-locus phylogenetic analyses and detailed morphological comparisons, representing the broadest sampling of Didymellaceae to date. Among these, 97 isolates representing seven new genera, 40 new species and 21 new combinations were newly introduced in Didymellaceae. In addition, six epitypes and six neotypes were designated to stabilise the taxonomy and use of older names. A robust, multi-locus reference phylogenetic tree of Didymellaceae was generated. In addition, rpb2 was revealed as the most effective locus for the identification of Didymellaceae at species level, and is proposed as a secondary DNA marker for the family.

First Report of Sexual Reproduction of Fusarium solani f. sp. piperis in Bahia, Brazil.

Black pepper (Piper nigrum L.) is a popular spice native of India, and Brazil is one of its most important producing countries. The main disease of black pepper in Brazil is fusariosis, caused by Fusarium solani f. sp. piperis. Symptoms include leaf chlorosis and defoliation, blight of stems or stem cuttings, and root and foot decay. During surveys conducted in the south of the state of Bahia, municipalities of Taperoá (13°34'S, 39°10'W) and Valencia (13°20'S, 39°14'W), stems of diseased plants covered with red or salmon-colored perithecia were observed, while twigs showed leaf chlorosis, leading to early death of the plants. Ascomata were solitary or in groups, mostly superficial or surrounded by mycelia, globose, subglobose, ovoid, and 122 to 400 µm diameter. Microscopic examination revealed unitunicate, cylindric asci, 60 to 90 × 8.5 to 16 µm, thin-walled, containing eight ascospores arranged obliquely in two rows. Ascospores are hyaline, elliptical to oblong, one-septate, constricted at the central septum, 10 to 16 × 4 to 6.5 µm (means ± S.D.: 13.1 ± 1.4 × 5.1 ± 0.6 µm), length/width (L/W) 1.9 to 3.7. Single-spored cultures were transferred to SNA medium (incubated at 20°C for 7 days with 12-h photoperiod) and on potato dextrose agar (25°C in dark) for characterization. The anamorph is characterized by the presence of chlamydospores, canoe-shaped sporodochial macroconidia with three to four septae, and microconidia formed on long monophialidic conidiophores. Based on morphological markers, isolates were identified as F. solani. The partial fragment of the TEF-1α gene of single-spored isolates (CML 2186, 2187, 2188, 2189, 2190, and 2191) were sequenced. BLAST analysis of the sequence resulted in 94 to 99% identity with a reference strain of F. solani f. sp. piperis (NRRL 22570, CML 1888). For pathogenicity tests, cv. Bragantina was used and two isolates were inoculated as 5-mm diameter mycelial plugs on the stem of four plants each. Four control plants were treated only with sterile culture medium. Plants were maintained in the greenhouse at 25°C and 75 to 85% relative humidity under 70% shade. All inoculated plants showed initial symptoms of stem necrosis in inoculated branches 7 days after inoculation. Symptoms were not observed on stems of control plants. Isolates were successfully reisolated and identified as F. solani f. sp. piperis, fulfilling Koch's postulates. Representative isolates were deposited at the Coleção Micológica de Lavras (CML) at Universidade Federal de Lavras, Brazil. Production of perithecia of the pathogen has been previously reported only in Pará and Espírito Santo States (1,3). It is not yet confirmed if this taxon is homothallic or heterothallic. To our knowledge, this is the first report of the associated teleomorph of F. solani f. sp. piperis infecting and causing black pepper fusariosis in Bahia, Brazil. The results suggest that the spread of ascospores from perithecia is likely to be one of the main inoculum sources of the disease on adjacent vines. There is evidence that this special form of F. solani actually represents a distinct species pathogenic to black pepper (2). References: (1) F. C. Albuquerque and S. Ferraz. Experientiae 22:133, 1976. (2) K. O'Donnell. Mycologia 92:919, 2000. (3) J. A. Ventura et al. Fitopatol. Bras. 11:361, 1986.

Volatile Substances Produced by Fusarium oxysporum from Coffee Rhizosphere and Other Microbes affect Meloidogyne incognita and Arthrobotrys conoides.

Microorganisms produce volatile organic compounds (VOCs) which mediate interactions with other organisms and may be the basis for the development of new methods to control plant-parasitic nematodes that damage coffee plants. In the present work, 35 fungal isolates were isolated from coffee plant rhizosphere, Meloidogyne exigua eggs and egg masses. Most of the fungal isolates belonged to the genus Fusarium and presented in vitro antagonism classified as mutual exclusion and parasitism against the nematode-predator fungus Arthrobotrys conoides (isolated from coffee roots). These results and the stronger activity of VOCs against this fungus by 12 endophytic bacteria may account for the failure of A. conoides to reduce plant-parasitic nematodes in coffee fields. VOCs from 13 fungal isolates caused more than 40% immobility to Meloidogyne incognita second stage juveniles (J2), and those of three isolates (two Fusarium oxysporum isolates and an F. solani isolate) also led to 88-96% J2 mortality. M. incognita J2 infectivity decreased as a function of increased exposure time to F. oxysporum isolate 21 VOCs. Gas chromatography-mass spectrometry (GC-MS) analysis lead to the detection of 38 VOCs produced by F. oxysporum is. 21 culture. Only five were present in amounts above 1% of the total: dioctyl disulfide (it may also be 2-propyldecan-1-ol or 1-(2-hydroxyethoxy) tridecane); caryophyllene; 4-methyl-2,6-di-tert-butylphenol; and acoradiene. One of them was not identified. Volatiles toxic to nematodes make a difference among interacting microorganisms in coffee rhizosphere defining an additional attribute of a biocontrol agent against plant-parasitic nematodes.

New hosts of Myrothecium spp. in Brazil and a preliminary in vitro assay of fungicides

Myrothecium roridum and M. verrucaria are two plant pathogenic species causing foliar spots in a large number of cultivated plants. This paper aims to study the causal agents of foliar spots in vegetable crops (sweet pepper, tomato and cucumber), ornamental plants (Spathiphyllum wallisii, Solidago canadensis, Anthurium andreanum, Dieffenbachia amoena) and a solanaceous weed plant (Nicandra physaloides). Most of the isolates were identified as M. roridum; only the isolate 'Myr-02' from S. canadensis was identified as M. verrucaria. All the isolates were pathogenic to their original plant hosts and also to some other plants. Some fungicides were tested in vitro against an isolate of M. roridum and the mycelial growth recorded after seven days. Fungicides with quartenary ammonium, tebuconazole and copper were highly effective in inhibiting the mycelial growth of M. roridum. This paper confirms the first record of M. roridum causing leaf spots in sweet pepper, tomato, Spathiphyllum, Anthurium, Dieffenbachia and N. physaloides in Brazil. We also report M. roridum as causal agent of cucumber fruit rot and M. verrucaria as a pathogen of tango plants.

New hosts of Myrothecium SPP. In brazil and a preliminary In Vitro assay of fungicides.

Myrothecium roridum and M. verrucaria are two plant pathogenic species causing foliar spots in a large number of cultivated plants. This paper aims to study the causal agents of foliar spots in vegetable crops (sweet pepper, tomato, cucumber), ornamental plants (Spathiphyllum, Solidago canadensis, Anthurium, Dieffenbachia) and a solanaceous weed plant (Nicandra physalodes). Most of the isolates were identified as M. roridum; only the isolate 'Myr-02' from S. canadensis was identified as M. verrucaria. All the isolates were pathogenic to their original plant hosts and also to some other plants. Some fungicides were tested in vitro against an isolate of M. roridum and the mycelial growth recorded after seven days. Fungicides with quartenary ammonium, Tebuconzole and copper were highly effective in inhibiting the mycelial growth of M. roridum. This paper confirms the first record of M. roridum causing leaf spots in sweet pepper, tomato, Spathiphyllum, Anthurium, Dieffenbachia and N. physalodes. We also report M. roridum as causal agent of cucumber fruit rot and also M. verrucaria in tango plants.

Variability of non-mutualistic filamentous fungi associated with Atta sexdens rubropilosa nests.

A survey of the filamentous fungi other than the symbiotic one found in association with Atta sexdens rubropilosa colonies was carried out. Different fungal species (27 taxa) were isolated a few days after treating the workers with toxic baits (sulfluramid; Mirex-S), from 40 laboratory and 20 field nests. Syncephalastrum racemosum (54%) and Escovopsis weberi (21%), Trichoderma harzianum (38%) and Fusarium oxysporum (23%) were the prevalent species in laboratory and field nests, respectively. Acremonium kiliense, Acremonium strictum, E. weberi, F. oxysporum, Fusarium solani, Moniliella suaveolens and T. harzianum were found in both nests' groups. We revealed that many filamentous fungi can co-exist in a dormant state inside the nests of these insects and some of them appear to be tightly associated with this environment.