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Surveys of three nurseries in northwestern Algeria have shown the presence of several cases of withering on olive seedlings.This study aims to confirm the pathogenesis of isolated species mycoflora associated with the young trees in nurseries with the symptom of dieback and wilting. In order to minimize the danger of the use of chemical substances in olive cultivation and establish a successful control strategy for this disease, the biological control potential of Trihoderma spp. isolates derived from rhizospheric soils of intact olive trees against Fusarium oxysporum (FO), Fusarium solani (FS) and Rhizoctonia solani (RS) under laboratory and greenhouse conditions was estimated. The results indicated that the symptoms observed in nursery were the result of a fungal complex comprising several primary and secondary pathogens contributing to the appearance of various symptoms. The results revealed the presence of dieback ranging from 13 to 26%. As regards the biological control test, all isolates of Trihoderma spp. were capable to inhibit pathogens mycelial growth significantly in vivo, the maximumwas recorded with the T4 isolate (78.89%) antifungal activity against FO. Results of greenhouse (in vivo) tests showed that plants injected only with antagonists or in combination with a fungal pathogen had a lower incidence of wilt disease than plants inoculated with a single pathogen. The decrease in the incidence of wilt disease was 80%, 58% and 50% FO, RS and FS respectively compared to the uninoculated control. Our results also showed that the four mixed Trichoderma isolates were able to stimulate plant growth parameters, which mainly resulted in better axial growth and higher biomass.The results obtained under greenhouse, shows the incorporation of Trichoderma directly into soil or composts for nursery soils as preventive and curative treatments. [ABSTRACT FROM AUTHOR]

Abstract: Twenty seven rhizobial strains associated with Acacia saligna grown in northern and southern Algeria were characterized, including generation time, host-range, the 16S rRNA gene and 16S–23S rRNA intergenic spacer restriction patterns, 16S rRNA gene sequence analysis and tolerance to salinity and drought. Cross inoculation tests indicated that 11 slow-growing isolates from northern nurseries were able to nodulate introduced Australian acacias exclusively, whereas 16 fast-growing isolates, mainly from southern nurseries, were capable of also nodulating native acacias. Restriction patterns and sequence analysis of the 16S rRNA gene showed that strains of the first group belonged to Bradyrhizobium while strains of the second group were related to Sinorhizobium meliloti and Rhizobium gallicum. Interestingly, five strains of the first group formed a distinct cluster phylogenetically close to Bradyrhizobium betae, a non-nodulating species causing tumour-like deformations in sugar beet roots. Bradyrhizobium strains were in general more sensitive to NaCl and PEG than the S. meliloti and R. gallicum representatives. Among the latter, strains S. meliloti BEC1 and R. gallicum DJA2 were able to tolerate up to 1M NaCl and 20% PEG. This, together with their wide host-range among Acacia species, make them good candidates for developing inoculants for A. saligna and other acacia trees growing in arid areas. [Copyright &y& Elsevier]

A field survey conducted on asymptomatic grapevine propagation material from nurseries and symptomatic young grapevines throughout different regions of Algeria yielded a collection of 70 Phaeoacremonium -like isolates and three Cadophora -like isolates. Based on morphology and DNA sequence data of β-tubulin ( tub2 ) and actin, five Phaeoacremonium species were identified including Phaeoacremonium minimum (22 isolates), Phaeoacremonium venezuelense (19 isolates), Phaeoacremonium parasiticum (17 isolates), Phaeoacremonium australiense (8 isolates), and Phaeoacremonium iranianum (4 isolates). The latter two species ( P. australiense and P. iranianum ) were reported for the first time in Algeria. Multilocus phylogenetic analyses (internal transcribed spacer, tub2 , and translation elongation factor 1-α) and morphological features, allowed the description of the three isolates belonging to the genus Cadophora (WAMC34, WAMC117, and WAMC118) as a novel species, named Cadophora sabaouae sp. nov. Pathogenicity tests were conducted on grapevine cuttings cultivar Cardinal. All the identified species were pathogenic on grapevine cuttings.