Biological Control of Rhizoctonia solani AG1-1A, the Causal Agent of Rice Sheath Blight with Trichoderma Strains

Sheath blight caused by Rhizoctonia solani is one of the most serious rice diseases worldwide. The disease is currently managed only by the excessive application of chemical fungicides which are toxic and not environmentally friendly. Therefore, greater emphasis should be given to biological control as being both safe and effective. Trichoderma species are ubiquitous fungi in the soil and have an antagonistic activity against several soil-borne plant pathogens including R. solani. The present study was undertaken to evaluate the potential of indigenous Trichoderma strains from Mazandaran province, Northern Iran (a Mediterranean region on the southern coast of the Caspian Sea) against R. solani AG1-IA  in vitro, and against sheath blight disease in the glasshouse, in order to find biocontrol isolates for application in the field. More than 200 Trichoderma strains were isolated from the soil, plant debris and the phyllosphere in rice felds. Strains were first screened for their antagonism to R. solani by in vitro antagonism tests including dual culture, antibiosis, the effect of Trichoderma strains on the production and viability of R. solani sclerotia, and hyperparasitism on microscopic slides. According to the in vitro experiments, several strains belonging to T. harzianum, T. virens and T. atroviride showed excellent biocontrol. These potential antagonist strains were further evaluated for their effectiveness in controlling sheath blight under glasshouse conditions. Among the 55 selected strains, seven significantly controlled the disease. T. harzianum AS12-2 was the most effective strain in controlling rice sheath blight, better even than propiconazole, the most commonly used fungicide in Iran

Population genetic structure of Sclerotinia sclerotiorum on canola in Iran

The genetic structure of 276 Sclerotinia sclerotiorum isolates representing 37 field populations from four provinces in northern Iran were analysed with six polymorphic microsatellite loci. In total, 80 haplotypes were detected with 19 haplotypes (23.7%

First Report of Pyricularia oryzae Causing Blast on Sorghum halepense (Johnson Grass) in Iran

International audienc

Low genetic diversity of Rhynchosporium commune in Iran, a secondary centre of barley origin

Rhynchosporium commune is a destructive pathogen of barley, causing leaf scald. Previous microsatellite studies used Syria as a representative of cultivated barley's centre of origin, the Fertile Crescent. These suggested that R. commune and Hordeum vulgare (cultivated barley) did not co‐evolve in the host's centre of origin. The present study compares R. commune populations from Syria with those from Iran, which represents a secondary centre of origin for barley at the eastern edge of the Iranian Plateau. Results from this study also suggest that R. commune and barley did not co‐evolve in the centre of origin of cultivated barley. This was evidenced by the low pathogen genetic diversity in Iran, which was even lower than in Syria, indicating that the pathogen may have been introduced recently into Iran, perhaps through infected barley seed. Hierarchical analyses of molecular variance revealed that most genetic diversity in Iran and Syria is distributed within populations, with only 14% among populations. Analyses of multilocus association, genotype diversity and mating type frequency suggest that Iranian populations reproduce predominantly asexually. The presence of both mating types on barley and uncultivated grasses suggest a potential for sexual reproduction. Rhynchosporium commune was also found on Hordeum murinum subsp. glaucum, H. vulgare subsp. spontaneum, Lolium multiflorum and, for the first time, on Avena sativa. The variety of wild grasses that can be infected with R. commune in Iran raises concerns of these grasses acting as evolutionary breeding grounds and sources of inoculum

Scald on gramineous hosts in Iran and their potential threat to cultivated barley

There are five described Rhynchosporium species, Rhynchosporium commune, R. secalis, R. agropyri, R. orthosporum and R. lolii, that cause scald diseases on Poaceae. This study used morphological (conidial shape and size) and phylogenetic analyses of two loci (the internal transcribed spacer region (ITS) and β-tubulin (TUBB)) to identify Rhynchosporium species and their host ranges in Iran. Despite the large variation observed for Rhynchosporium conidial dimensions, the phylogenetic analyses of the ITS region and concatenated ITS and TUBB loci revealed that all isolates from wild grasses in Iran belong to R. commune. R. commune was isolated from Hordeum murinum ssp. glaucum, Hordeum vulgare ssp. spontaneum, Lolium multiflorum and Avena sativa in Iran. A. sativa has only been reported from Iran as a host for R. commune. After cross inoculation, A. sativa was considered as the most resistant host showing the lowest susceptibility to R. commune isolates. Of the grass hosts tested, H. vulgare ssp. spontaneum was the most susceptible. The most aggressive isolate across all tested hosts was isolated from Hordeum murinum ssp. glaucum. Cross-infection of the R. commune isolates from all hosts onto uncultivated grasses and cultivated barley suggests the potential of the uncultivated grasses as inoculum sources for cultivated barley epidemics and pathogen evolution. Thus, management of uncultivated grasses in the vicinity of barley fields should assist in managing the disease on cultivated barley.This study was funded by Isfahan University of Technology (grant number NA

Biological control of Rhizoctonia solani AG1-1A, the causal agent of rice sheath blight with Trichoderma strains

<p class="MsoNormal" style="margin: 0cm 0cm 10pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small;"><span style="font-family: Calibri;">Sheath blight caused by <em style="mso-bidi-font-style: normal;">Rhizoctonia solani</em> is one of the most serious rice diseases worldwide. The disease is currently managed only by the excessive application of chemical fungicides which are toxic and not environmentally friendly. Therefore, greater emphasis should be given to biological control as being both safe and effective. <em style="mso-bidi-font-style: normal;">Trichoderma</em> species are ubiquitous fungi in the soil and have an antagonistic activity against several soil-borne plant pathogens including <em style="mso-bidi-font-style: normal;">R. solani</em>. The present study was undertaken to evaluate the potential of indigenous <em style="mso-bidi-font-style: normal;">Trichoderma</em> strains from Mazandaran province, Northern Iran (a Mediterranean region on the southern coast of the Caspian Sea) against <em style="mso-bidi-font-style: normal;">R. solani</em> AG1-IA<span style="mso-spacerun: yes;">&nbsp; </span>in vitro, and against sheath blight disease in the glasshouse, in order to find biocontrol isolates for application in the field. More than 200 <em style="mso-bidi-font-style: normal;">Trichoderma</em> strains were isolated from the soil, plant debris and the phyllosphere in rice felds. Strains were first screened for their antagonism to <em style="mso-bidi-font-style: normal;">R. solani</em> by in vitro antagonism tests including dual culture, antibiosis, the effect of <em style="mso-bidi-font-style: normal;">Trichoderma</em> strains on the production and viability of <em style="mso-bidi-font-style: normal;">R. solani</em> sclerotia, and hyperparasitism on microscopic slides. According to the in vitro experiments, several strains belonging to <em style="mso-bidi-font-style: normal;">T. harzianum</em>, <em style="mso-bidi-font-style: normal;">T. virens</em> and <em style="mso-bidi-font-style: normal;">T. atroviride</em> showed excellent biocontrol. These potential antagonist strains were further evaluated for their effectiveness in controlling sheath blight under glasshouse conditions. Among the 55 selected strains, seven significantly controlled the disease. <em style="mso-bidi-font-style: normal;">T. harzianum</em> AS12-2 was the most effective strain in controlling rice sheath blight, better even than propiconazole, the most commonly used fungicide in Iran.</span></span></span></p

Study on genetic diversity of Gibberella moniliformis and G. intermedia from corn and rice, and determination of fertility status and of mating type alleles

Abstract Genetic diversity, fertility status and distribution of the mating type alleles of Gibberella moniliformis and G. intermedia from corn and rice were studied. One hundred and twenty one isolates of these fungi were collected from rice growing areas of Guilan and Mazandaran provinces, and from various corn growing areas of Iran. 46 isolates of G. moniliformis and G. intermedia from rice and corn were studied by RAPD-PCR using four random primers. The isolates of G. moniliformis were separated from the isolates of G. intermedia on the basis of their hosts. Furthermore, fertility status of G. intermedia from corn and rice, and of G. moniliformis from rice were surveyed using standard tester isolates. A multiplex PCR technique was used to distinguish and amplify the fragments of the MAT-1 and MAT-2. The results of the field isolates with opposite mating types that were crossed each other showed that all of the isolates were male fertile. In spite of the existence of the MAT-1 and MAT-2 in populations of both fungi, the sexual reproduction did not occur among field isolates. Considering male fertile of the above mentioned isolates, genetic diversity resulted from the RAPD-PCR cannot necessarily show the occurrence of the sexual reproduction