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Copyright of Assiut Journal of Agricultural Sciences is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The plant growth-promoting fungus (PGPF), Phoma sp. GS8-3, isolated from a zoysia grass rhizosphere, is capable of protecting cucumber plants against virulent pathogens. This fungus was investigated in terms of the underlying mechanisms and ability to elicit systemic resistance in Arabidopsis thaliana. Root treatment of Arabidopsis plants with a culture filtrate (CF) from Phoma sp. GS8-3 elicited systemic resistance against the bacterial speck pathogen Pseudomonas syringae pv. tomato DC3000 ( Pst), with restricted disease development and inhibited pathogen proliferation. Pathway-specific mutant plants, such as jar1 (jasmonic acid insensitive) and ein2 (ethylene insensitive), and transgenic NahG plants (impaired in salicylate signalling) were protected after application of the CF, demonstrating that these pathways are dispensable (at least individually) in CF-mediated resistance. Similarly, NPR1 interference in npr1 mutants had no effect on CF-induced resistance. Gene expression studies revealed that CF treatment stimulated the systemic expression of both the SA-inducible PR-1 and JA/ET-inducible PDF1.2 genes. However, pathogenic challenge to CF-treated plants was associated with potentiated expression of the PR-1 gene and down-regulated expression of the PDF1.2 gene. The observed down-regulation of the PDF1.2 gene in CF-treated plants indicates that there may be cross-talk between SA- and JA/ET-dependent signalling pathways during the pathogenic infection process. In conclusion, our data suggest that CF of Phoma sp. GS8-3 induces resistance in Arabidopsis in a manner where SA and JA/ET may play a role in defence signalling. [ABSTRACT FROM AUTHOR]

Isolates of Rhizoctonia solani AG 2 from tobacco (Ntisolates) were reported to anastomose with isolates of AG-BI in high frequency (fusion frequency [FF] ≥ 50%) compared to isolates of AG 2-1 (FF < 50%), even though mature culture and thiamine requirement of the isolates were closely similar to AG 2-1. In this study, whole-cell fatty acid compositions of Nt-isolates (four isolates), isolates of AG 2-1 (eight isolates) and AG-BI (two isolates) were compared by gas-liquid chromatography analysis. Four isolates of AG 2 from tulip (AG 2-t) were also included. Palmitic (16:0), oleic (18: 1 cis9) and linoleic (18 : 2 cis9,12) acids were the three major fatty acids identified which constituted 89.6-93.4% of whole-cell fatty acid content. Myristic (14 : 0), pentadecanoic (15 : 0), palmitoleic (16 : 1 cis9), stearic (18 : 0) and linolenic (18 : 3 cis9,12) acids were present at low levels. Heptadecanoic (17 : 0) and 9-heptadecenoic (17 : 1 cis9) acids were also present in Nt-isolates and isolates of AG 2-1 but not in isolates of AG 2-t and AG-BI. With the exception of oleic acid, percentage composition of fatty acids of Nt-isolates were similar with those of isolates of AG 2-1 and AG 2-t but were different from isolates of AG-BI. Although fatty acid compositions of Nt-isolates and isolates of AG 2-1 were qualitatively and quantitatively similar, principal component and cluster analyses based on all detected fatty acids showed separation of the former from the latter groups indicating that Nt-isolates are a homogenous population in AG 2-1. Additionally, isolates of AG 2-t were closely related to isolates of AG 2-1. Isolates of AG-BI were distinctly separated from isolates of AG 2-1, AG 2-t and Nt-isolates. Results of fatty acid analysis support the designation of Nt-isolates as a member of AG 2-1 based on sequence similarity of rDNA-ITS. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies (MAbs) were raised against surface antigens from Pythium sulcatum . The immunogens were prepared from salt extractable cell wall protein to produce monoclonal antibodies. The MAbs showed high specificity to seven P. sulcatum isolates among 26 species of soil-borne fungi. Weak cross-reactivities were observed with Pythium aristosporum , Pythium myriotylum , and Pythium zingiberum in indirect enzyme-linked immunosorbent assay (ELISA), but no reaction was obtained in Western blot analysis. The MAbs recognized glycoproteins in cell wall. Pythium sulcatum was detected in naturally infected carrot tissues and soil using indirect competition ELISA. [ABSTRACT FROM AUTHOR]

Cellular fatty acid analysis was employed to differentiate three varieties of Rhizoctonia circinata; var. circinata, var. oryzae and var. zeae. Eight fatty acids including myristic (14:0), pentadecanoic (15:0), palmitic (16:0), palmitoleic (16:1 cis9), stearic (18:0), oleic (18:1 cis9), linoleic (18: 2 cis9,12) and linolenic (18: 3 cis9,12) acids were present in isolates of all three varieties of R. circinata. Heptadecanoic acid (17:0) was detected in isolates of R. circinata var. zeae but not in isolates of R. circinata var. circinata or R. circinata var. oryzae. Palmitic, oleic and linoleic acids were the major fatty acids found, comprising 94-98% of the whole-cell fatty acid content. The remaining fatty acids were present in small amounts. Based on the composition (%) of fatty acids, isolates of R. circinata var. circinata, R. circinata var. oryzae and R. circinata var. zeae were clearly differentiated into three groups as shown by principal component and cluster analyses. This finding agrees well with the grouping of R. circinata into three varieties based on differences in colony morphology of the vegetative state. In principal component and cluster analysis, isolates of R. circinata var. circinata from Japan and Alaska were indistinguishable. [ABSTRACT FROM AUTHOR]

Whole-cell fatty acid compositions of binucleate Rhizoctonia AG-D (R. cerealis) isolates representing subgroups I [AG-D (I)] and II [AG-D (II)] obtained from various host plants were compared. Ten fatty acids including myristic (14 : 0), pentadecanoic (15 : 0), palmitic (16 : 0), palmitoleic (16 : 1 cis9), heptadecanoic (17 : 0), 9-heptadecenoic (17 : 1 cis9), stearic (18 : 0), oleic (18 : 1 cis9), linoleic (18 : 2 cis9,12) and linolenic (18 : 3 cis9,12) were consistently present in all isolates of Rhizoctonia AG-D. The major fatty acids found were palmitic, oleic and linoleic acids, comprising 88–93% of the whole-cell fatty acid content. The remaining fatty acids were present in smaller amounts ranging from 0.01 to 5.03% of the whole-cell fatty acid content. Palmitic and oleic acids were present in approximately two and three times higher concentrations in isolates of AG-D (I) than in isolates of AG-D (II), respectively. On the other hand, linoleic acid was about two times lower in isolates of AG-D (I) than in isolates of AG-D (II). Principal component and cluster analyses of the percentage composition of fatty acids showed distinct separation between AG-D (I) and AG-D (II). The results indicated that fatty acid analysis is useful for differentiating AG-D (I) and AG-D (II) and supported previous differentiation of the two subgroups on the basis of cultural characteristics, pathogenicity and DNA analyses. In addition, a Rhizoctonia AG-Q isolate from bentgrass and Rhizoctonia AG-D isolates causing foot rot of wheat and stem rot of mat rush were grouped in AG-D (I), based on the percentage composition of fatty acids. [ABSTRACT FROM AUTHOR]

Two-hundred and forty-eight isolates of Rhizoctonia spp. were obtained from 13 locations in Gifu Prefecture in Japan using the plant debris particles isolation, colonization of bait tissue, and soil-clump plating methods. Of the isolates, 143 were binucleate Rhizoctonia spp., 60 were R. solani and 45 were R. zeae. Three isolates of R. solani and 54 of binucleate Rhizoctonia spp, were hypovirulent on radish, whilst all isolates of R. zeae were highly virulent, Hypovirulent strains were isolated most frequently by the plant debris particles isolation method. Hypovirulent isolates of R. solani belonged to anastomosis group 4, whilst the hypovirulent binucleate Rhizoctonia isolates belonged to AG A, AG Ba, AG G, and AGO. Thirty-two isolates of Rhizoctonia spp. selected for hypovirulence on radish were tested on cucumber in vitro. Only five binucleate Rhizoctonia isolates and one R. solani isolate were hypovirulent on both species, and these isolates were also hypovirulent on seven other crop species. Cucumber showed wide variation in disease susceptibility to different isolates but hypovirulent isolates exhibited a consistent reaction on five different host cultivars. Pathogenicity tests using cucumber grown in soil also showed consistent reactions with isolates selected either for hypovirulence or virulence. The results support the use of cucumber in bioassays for identifying hypovirulent isolates of binucleate Rhizoctonia spp. [ABSTRACT FROM AUTHOR]

A buried-slide method of inducing teleomorph development was compared with a soil method for isolates of Rhizoctonia solani in anastomosis group 2. The teleomorph (Thanatephorus cucumeris) developed frequently in the buried-slide method. For non-self-anastomosing isolates, which cannot grow through soil, the teleomorph was observed only in the buried-slide method. One of the five soils tested was particularly favourable. The buried-slide method allows easy examination of the teleomorph with minimum disturbance to the hymenium. It has demonstrated the identity of non-self-anastomosing isolates with T. cucumeris. [ABSTRACT FROM AUTHOR]