A number of soil-borne fungi are able to form typical ericoid mycorrhizae with plants belonging to Ericales. Together with Hymenoscyphus ericae, the first isolate from roots of ericaceous plants, other fungal species belonging to the genus Oidiodendron and many sterile mycelia have been recognized as mycorrhizal by several authors. A high genetic diversity was even found when a population of ericoid mycorrhizal fungi isolated from a single plant of Calluna vulgaris was analysed with morphological and molecular techniques. Ericoid fungi have a relevant saprotrophic potential, as they can degrade several organic polymers present in the soil matrices. Diffcrcnt cell wall degrading enzymes, which are part of this arsenal and are produced in vitro by several ericoid fungi, have been investigated biochemically. Immunocytochemical studies on the production of pectin degrading enzymes during the infection process of host and non-host plants suggest that regulation mechanisms for the production of cell wall degrading enzymes in vivo may be a crucial step for the establishment of successful mycorrhiza with host plants.RQum6 : Plusieurs champignons du sol peuvent former des mycorhizcs Cricoides typiques avec des plantes appartenant aux Ericales. Avec I'Hymenoscyphus ericae, le premier champignons isolC de racines de plantes CricacCes, d'autres champignons appartenant au genre Oidiodendron et plusieurs myctlium stCriles ont Ct C reconnus comme mycorhiziens, par plusieurs auteurs. On a m&me trouvt un forte diversite gCn6tique lorsqu'une population de champignons mycorhiziens Cricoi'des provenant d'une m&me plante hbte de Calluna vulgaris a Ct C analyste 2 I'aide de mCthodes morphologiques et molCculaires. Les champignons irico'idcs possedent un fort potentiel saprophytique puisqu'ils peuvent degrader plusieurs polymbres organiques dans les litibres des sols. Les auteurs ont examine biochimiquement, differents enzymcs capables de dCgrader les parois cellulaires et qui se retrouvent dans les milieux de culture in vitro de plusieurs champignons 6ricoi'des. Des Ctudes immuno-histochimiques conduites sur la production d'enzymes dtgradant la pectine, au cours de la colonisation de plantes hbtes ou non-hbtes, suggbrent que les mCcanismes de rtgularisation de la production d'enzymes capables de degrader les parois cellulaires in vivo pourraient constituer une Ctape determinante dans la formation de mycorhizes fonctionelles avec la plante hbte.

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A Gram-negative, anaerobic sulfate-reducing bacterium was isolated from hindgut contents of the lower termite Mastotermes darwiniensis Froggatt (strain KMS2). Strain KMS2 is motile by a single polar flagellum. The isolate possesses desulfoviridin and catalase activity. The G+C content of its DNA is in the range of 54.5-55.5 mol% (strain KMS2). It respires hydrogen and different low molecular weight organic compounds in the presence of sulfate, thiosulfate, and sulfite, and also oxygen. The isolated strain ferments pyruvate. Fastest growth with a doubling time of 12.5 h was obtained at 37 degrees C and not at 28 degrees C, the temperature at which the termites were grown. The isolate showed a 16S rDNA sequence homology of 95.9% to Desulfovibrio desulfuricans ATCC 27774 and a DNA-DNA homology of 44.6% to D. desulfuricans Essex 6 (type strain). Based on its biochemical properties and 16S rDNA sequence, the isolate was assigned to a new species named Desulfovibrio intestinalis.

Apple mosaic virus (ApMV), an Ilarvirus is one of the most common pathogens of apple worldwide. During field surveys in commercial plantations of Himachal Pradesh and Jammu & Kashmir, observations of bright chlorotic mosaic like symptoms on apple trees indicated probable infection by the virus, which was later detected by double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA). An incidence of 24 and 28% (based on ELISA) was obtained as 6/25 and 15/53 samples from HP and J&K were positive, respectively. An amplification of approximately 700 and 850 bp was obtained for coat and movement protein genes (CP and MP), respectively. The CP was 223 amino acids in length and showed 87-99% identity when compared to 21 ApMV isolates. Whereas, MP (286 amino acids) showed 91-95% identity with other isolates. However, the gene sequences were quite conserved among Indian isolates and grouped together phylogenetically. CP of the Indian isolates showed maximum identity of 95% with Korean isolate (AY 125977) in apple and in other host these showed a maximum identity of 98% to Czech Republic pear isolate. MP showed maximum identity with Chinese isolate i.e., 95%. The diversity study will also help in analyzing variability among the isolates and also to formulate diagnostic and resistance strategies.

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