J.H.M. Schneider

Bio: J.H.M. Schneider is an academic researcher. The author has contributed to research in topics: Ribosomal DNA. The author has an hindex of 1, co-authored 2 publications receiving 49 citations.

Identification of Rhizoctonia solani associated with field-grown tulips using ITS rDNA polymorphism and pectic zymograms

Abstract: Methods based on internal transcribed spacers (ITS) ribosomal DNA (rDNA) polymorphism and pectic zymograms (ZG) were compared for their use in routine identification of Rhizoctonia solani isolates occurring in flower bulb fields. Thirty three AG 2-t isolates, pathogenic to tulips, could be distinguished from AG 1-IC, AG 2-2IIIB and AG 2-2IV, AG 3 and AG 5 by means of ITS rDNA fragment length and after digestion with EcoR I from AG 4 and AG 5. AG 2-t isolates and two Japanese isolates, pathogenic to crucifers and tulips, had an estimated fragment size of 710 bp, whereas Dutch AG 2-1 isolates, non-pathogenic to tulips, showed an estimated fragment size of 705 bp on agarose gel. Digestion of AG 2-t and AG 2-1 isolates with EcoR I, Sau3A I, Hae III and Hinc II revealed four and five distinct ITS rDNA digestion patterns, respectively. In AG 2 isolates 2tR114, 21R14 and 21R61 a double digestion pattern, indicating different ITS sequences within an isolate, was found. The observed ITS fragment length polymorphism between isolates pathogenic and non-pathogenic to tulips were considered too small to be used in routine screening of field isolates. Sequencing of AG 2 isolates 21R01, 21R06, 2tR002 and 2tR144 showed a total ITS rDNA fragment length of 715, 713, 714, and 728 bp. As an alternative to ITS rDNA fragment length polymorphism, pectic enzyme patterns were studied using a commercially available vertical gel-electrophoresis system and non-denaturing polyacrylamide gels amended with pectin. Anastomosis tester isolates AG 1 to AG 11 revealed different ZG. Fifty AG 2-t isolates and five AG 2-1 isolates belonged to a homogeneous pectic zymogram group. We propose to assign AG 2 isolates pathogenic to crucifers and tulip to ZG5-1. AG 2-1 isolates, non-pathogenic to tulip, formed a heterogeneous group with 4 distinct ZG. Pectic zymography provides an easy, quick and unambiguous method for routine identification of large numbers of field isolates. Such a technique is needed for research on the dynamics of Rhizoctonia populations to develop environmentally friendly control measures of rhizoctonia disease in field-grown flower bulbs.

Anastomosis Groups, Pathogenicity and Sensitivity to Fungicides of Rhizoctonia solani Isolates Collected on Potato Crops in France

Abstract: A collection of 241 isolates of Rhizoctonia solani obtained from potato plants grown in different areas in France was characterized for anastomosis grouping, symptomatology on tubers of different cultivars and sensitivity to three fungicides. Most isolates collected belonged to (anastomosis groups (AGs)) AG 3, but 2% and 4% of the isolates were AG 5 and AG 2-1. AG 3 and AG 2-1 isolates were mostly obtained from sclerotia on tubers, but all AG 5, some AG 3 and some AG 2-1 isolates were recovered from superficial tuber alterations, like deformations, corky or scabby lesions. Sclerotia were formed on tubers produced by healthy stem cuttings grown in soil artificially infested with AG 3, but not on tubers grown in soil infested with either AG 5 or AG 2-1. No variation in susceptibility to sclerotial formation was observed among five potato cultivars. In all cases, a large proportion of tubers showed superficial corky lesions, often associated with deformations. The proportion of tubers with lesions and deformations was highest in soil infested with AG 2-1 and significantly lower on cv. Samba in all treatments. All isolates were highly sensitive to flutolanil, iprodione and pencycuron, except the AG 5 isolates, moderately sensitive to pencycuron. These results show that, although AG 3 is the most common R. solani group on potato in France, AG 5 and AG 2-1 may be present. Isolates differed for pathogenicity. In vitro sensitivity to fungicides varied among AGs.

Characterization by conventional techniques and PCR of Rhizoctonia solani isolates causing banded leaf sheath blight in maize

Abstract: Rhizoctonia-diseased specimens were collected from various host species growing in or near maize fields in different geographic regions of the Philippines. A greater range of host species, with varying types of disease symptoms, was found in Mindanao than in Luzon. Fifty-two isolates belonged to anastomosis group AG1-IA and caused banded leaf and sheath blight in maize (Zea mays), but they showed considerable variation in virulence. The most and least virulent isolates recovered from maize were both collected from Mindanao. Isolates from necrotic spots/foliar blight of durian and coffee, which were collected from the same region, showed the lowest lesion heights. UPGMA-SAHN clustering analysis from RAPD fingerprint data of 30 haplotypes of R. solani AG1-IA isolates from the Philippines and Japan resolved seven groups of AG1-IA at the 75% similarity level. Variation among isolates from upland crops seemed to be partially correlated with geographical origin and virulence. In the case of paddy rice isolates from Japan and the Philippines, some were closely related, with over 75% similarity, suggesting a common origin. In PCR-RFLP analysis of the rDNA internal transcribed spacer region, no polymorphism was observed among the AG1-IA isolates but they were differentiated from subgroups AG1-IB and AG1-IC using the endonucleases EcoRI, MboI and HinfI.

Comparison of rDNA-ITS Sequences between Potato and Tobacco Strains in Rhizoctonia solani AG-3

Abstract: Genetic diversity among 51 isolates of Rhizoctonia solani AG-3, representing potato and tobacco populations, was inferred from the sequences of the internal transcribed spacer (ITS) and 5.8S ribosomal RNA (rRNA) gene. The 5.8S rDNA sequence was completely conserved not only in AG-3, but across all the AG isolates examined, whereas the rDNA-ITS sequence was found to be variable among the isolates. The nucleotide sequence similarity in the ITS 1 region was high (96-100%) for isolates within each of the two populations, but was 91-92% for isolates from different populations. The AG-3 isolates had 56 to 91% sequence similarities in the ITS 1 region with R. solani isolates of the other AGs. Phylogenetic analysis based on the ITS-5.8S rDNA sequence data indicated that the different populations in AG-3 are distantly related to each other. Genetic divergence between the two populations was also supported by the results of DNA-DNA hybridization studies. This study suggests that AG-3 consists of two genetically isolated groups corresponding to separate subgroups: AG-3 PT (potato type) and AG-3 TB (tobacco type). Specific primer sets for the detection of the two AG-3 subgroups were developed from the aligned rDNA-ITS sequences.