Charcoal Disease Research Articles

Diversity of Macrophomina phaseolina (Tassi) Goid Based on Chlorate Phenotypes and Pathogenicity

Macrophomina phaseolina (Tassi) Goid causes charcoal disease of oilseed plants. In this study 24 isolates, which were obtained from sunflower, soybean and sesame, were compared based on chlorate phenotypes and pathogenicity tests. For chlorate phenotypes, the isolates were grown on potassium chlorate and stored at 30oC in darkness. For pathogenicity test, seeds of sunflower, soybean and maize plants were placed on 6 – day – old colonies of each Macrophomina isolates grown on PDA and kept at 30oC in the dark. Results indicate that the sesame isolates had more colony radius rate on chlorate minimal medium in comparison to the soybean and sunflower isolates. The sesame isolates were chlorate resistant and grew normally with numerous dark microsclerotia production on the potassium chlorate. The soybean and sunflower isolates were chlorate sensitive and divided into two classes. Class 1, include the isolates that grew sparsely with a feathery like pattern, and the other one had a completely restricted radial growth meaning that M. phaseolina isolates differed in their ability to use certain nitrogenous compounds. Analysis of variance showed a significant difference between the colony radius rates of the isolates at 1% probability level. Based on Duncan’s test, the isolates have been divided in 14 classes. Results of pathogenicity test showed that there was significant difference (P< 0.01) between the isolates. The results confirmed that the feathery like pattern of the isolates was more virulent on soybean and sunflower.

The Occurrence of Charcoal Disease Caused by Biscogniauxia mediterranea on Chestnut-Leaved Oak (Quercus castaneifolia) in the Golestan Forests of Iran.

The chestnut-leaved oak (Quercus castaneifolia) is native to the Alborz Mountains, including the Golestan Forests, in northern Iran. Trees grow up to 35 (-50) m tall with a trunk up to 2.5 (-3.5) m in diameter. During 2010, we received reports of a decline of oak trees in the Ghorogh Region of the Golestan Forests. The decline began with discolorations and browning of the leaves, resulting in drying of the foliage. Viscous liquid exudates were observed on the trunks, resulting in a brown-black discoloration of phloem and bark. In January 2011, all infected trees were dead and exhibited symptoms of charcoal disease with carbonaceous, perithecial stromata erupting from the bark on stems. Perithecia were obovoid, containing short-stipitate, amyloid asci with dark brown, ellipsoid ascospores, 14 to 19 × 7 to 9 μm, with straight germ slits along the spore length. On the basis of these morphological characteristics, the fungus was identified as Biscogniauxia mediterranea. Blast searches of the NCBI GenBank nucleotide database were done using ITS sequences derived from three cultures (CBS 129072 to 129074). GenBank Accession Nos. JF295127 to JF295129 of the isolated fungus differed by one nucleotide from B. mediterranea (GenBank Accession No. AF280624) (1,3). Pathogenicity tests were conducted using an isolate of B. mediterranea under greenhouse conditions. Six-month-old Q. castaneifolia seedlings were inoculated by means of stem wounds with a mycelial plug of colonized potato dextrose agar. After 6 months, typical decline disease symptoms associated with charcoal disease were observed and the same fungus was reisolated. Perithecia were observed on the surface of black carbonaceous stromata, which usually developed on stems of inoculated plants. The decline is known as charcoal disease because fungal growth induces a typical charcoal-black surface on diseased branches and trunks. The pathogen can easily spread through large cavity vessels, colonize bark and woody tissues, and is able to kill the host in a single, growing season. B. mediterranea causes necrosis on stems and branches of Quercus spp., including Q. suber, Q. cerris, Q. frainetto, Q. pubescens (4), Q. alba, Q. ilex, Q. imbricaria, Q. lusitanica, Q. palustris, and Q. pyrenaica (2) in Europe, North America, Africa, New Zealand, and Asia (China and India). On the basis of our current knowledge, Q. castaneifolia represents a new host of B. mediterranea, and this is the first report of this fungal pathogen from Iran causing charcoal disease on Q. castaneifolia trees in the Golestan Forest. Given its new introduction into Iran, it is highly likely that it will spread to species of Fagus, Zelkova, and other woody hosts in the area.

Response of endophytic Biscogniauxia mediterranea to variation in leaf water potential of Quercus cerris

SummaryEndophytic behaviour of Biscogniauxia mediterranea, the causal agent of charcoal disease of oak, was studied over two growing seasons on Quercus cerris in a forest in central Italy. Isolation of the fungus from asymptomatic tissues varied with tissue type, period of sampling and year. Presence of the fungus in asymptomatic plants was significantly higher in fall, compared with that in spring and summer. However, a significant effect of tissue water content on the presence of B. mediterranea was recognized. The results suggest that proliferation of B. mediterranea is favoured during the endophytic phase by a decrease in host water potential.

The incidence and spreading of Macrophomina phaseolina(Tassi) Goidanovich on sunflower in the Czech Republic

VEVERKA K., PALICOVÁ J., KŘÍŽKOVÁ I. (2008): . Plant Protect. Sci., 44: 127–137. The warm climate pathogen &lt;i&gt;Macrophomina phaseolina&lt;/i&gt; (Tassi) Goid., which causes charcoal disease, has been reported in the Czech Republic since 1999. The aim of our work was to study the incidence of disease between 2000–2007 in the main sunflower growing regions and analyse the relationship between weather conditions and the occurrence of the pathogen. The first and highest incidence of disease was in the Žatec region. However, in the region south of Brno there was no disease in 2000, 2001 and 2003, and only individual low incidence in other years until 2007, when the disease was found in nine localities. The incidence of the disease is increasing year by year indicating a spread of the pathogen. The warm and dry periods throughout the end of July and August have promoted the disease. However in some years where weather conditions were favourable for the pathogen, in several cases no disease was found. It is assumed, that the pathogen was not yet present in these localities. Soil conditions are critical. Diseased plants are usually distributed in several dispersed groups in the stand, especially on higher and drier parts of the field. Disease is also often found on plants suffering from compressed roots. Diseased plants had poorly developed heads and seeds.

First reported outbreak of charcoal disease caused by Biscogniauxia mediterranea on Turkey oak in Slovenia

In August 2003, in an area of coppice-grown Turkey oak ( Quercus cerris ) covering c. 180 ha, about 50% of leaves turned brown. In spring 2004, whole trees were dead and the bark of the others died off in strips; there were shoots only from parts of the tree crowns. The same phenomenon also occurred patchily over c . 16 000 ha of mixed forests in the Karst region of Slovenia. The bark began to crack and fall off in June 2004, and in August the first perithecial stromata of Biscogniauxia mediterranea were observed in bark cracks on tree trunks and branches. At the beginning of March 2005 there were a large number of stromata on the bark of dead trees: more than 100 stromata could be found on a single tree with a diameter of 27 cm at chest height. Stromata measured (3–) 19·6 ( − 36) × (1·5–) 3·4 ( − 7·5) cm; perithecia were tubular (0·43–) 0·62 ( − 0·81) × (0·08–) 0·14 ( − 0·22) mm; ascospores measured (13–) 16 ( − 19·5) × (6–) 7·5 ( − 9) μ m; asci (114–) 145 ( − 175) × (8·5–) 10·5 ( − 14) μ m; the outer dehiscing layer was (0·07–) 0·16 ( − 0·24) mm thick. Measurements indicate that the fungus could be classified as B. mediterranea var. microspora (Ju et al ., 1998). The perithecial stromata and pure cultures were deposited in the Herbarium of the Slovenian Forestry Institute with accession numbers 1505–1507. Disease symptoms appeared after severe drought and unusually hot weather. Total rainfall before the onset of symptoms in June, July and August 2003 was 27, 12 and 66%, respectively, of the 30-year average, while average monthly temperatures for the same months were 5·8, 3·6 and 5·6 ° C higher than the 30-year average. The development of charcoal disease on oaks after drought is well documented (Vannini & Valentini, 1994). The endophytic presence of this fungus in living bark enables it quickly to overgrow the stressed tissues of the host and destroy them (Vannini, 1998). Charcoal disease is a serious problem in cork oak ( Quercus suber ) and Turkey oak in the Mediterranean area, but had never been detected further north than southern Tuscany (Vettraino et al ., 2002). The appearance of this new disease in Slovenia, c . 350 km north-east of Tuscany, indicates that climate change could lead to outbreaks of this disease further north.

Real-time PCR detection of Biscogniauxia mediterranea in symptomless oak tissue

Real-time PCR, based on TaqMan chemistry, was used to detect Biscogniauxia mediterranea, a fungal pathogen that after a long endophytic phase may cause charcoal disease in oak trees. Specific primers and probe were designed and tested on axenic cultures of B. mediterranea and other fungi commonly colonizing oaks. Twig samples were collected in Tuscany from apparently healthy oaks (Quercus cerris, Quercus ilex and Quercus pubescens) growing near trees infected with the fungus. Twigs were divided into two groups: one for isolation in agar plates, and one for real-time PCR after DNA extraction. The detection limit of the assay was 0.01 pg/DNA, whereas the amounts of fungal DNA detected in asymptomatic tissue were >0.5 pg microg(-1) total DNA extracted. In the apparently healthy twigs the frequency of isolation found on agar was 25.0%, much lower than that with real-time PCR (96.4%). Real-time PCR is a sensitive and fast technique able to specifically detect and quantify the DNA of B. mediterranea in oak tissue. This diagnostic method is a precise tool to localize fungi in symptomless plant tissues and promises to advance our understanding of fungal infection during their latent phase.

Hypoxylon mediterraneum . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Hypoxylon mediterraneum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On trunks and branches of deciduous trees, particularly Quercus suber , usually following injury, but also occurring on Castanea, Eucalyptus, Fagus sylvatica, Malus, Platanus hybrida, Platanus orientalis, Populus tremuloides, Quercus alba, Quercus ilex, Quercus imbricaria, Quercus lusitanica, Quercus palustris, Quercus pyrenaica and Shorea robusta . DISEASES: Cause of 'charcoal disease' of Quercus suber , attacking trees of all ages, affecting the base of the trunk, large and small branches, but not the roots. Reaches epidemic proportions in Morocco (31: 409), Algeria and Tunisia (32: 458). Dark exudations with a strong tannin odour appear soon after infection, the bark then ruptures to disclose the carbonaceous stroma which destroys and lies in the place of the phloem (Barbosa, 1958). Trees are most susceptible when in poor condition, e.g. on poor soil, or when damaged by drought or fire. Cause of a disease of sal ( Shorea robusta ) in India (Bakshi, 1963). The disease is less severe on other hosts. GEOGRAPHICAL DISTRIBUTION: Algeria, China, Fiji, France, Germany (Rhine), India, Italy, Morocco, New Zealand, North America, Philippines, Portugal, Samoa, Tasmania, Venezuela. TRANSMISSION: Penetrates the living tissues by wind-borne conidia and possibly ascospores entering through wounds.