Pathotype diversity among Algerian isolates of Pyrenophora teres f. teres

Barley Net Blotch caused by Pyrenophora teres f. teres (Ptt) is one of the most important foliar diseases in north western Algeria. The disease could cause appreciable yield losses under favorable environmental conditions. Studies on pathogen variability and distribution of virulence in Ptt are essential to identify effective sources of resistance to net blotch of barley. In this study, pathogenic variability in 48 isolates of Ptt, collected from different barley-growing areas of north-western Algeria were evaluated using 22 barley genotypes as differential hosts. Trials carried out under controlled conditions confirmed the large variation in the virulence of this fungus. The genotypes exhibited variability in response ranging from complete resistance to high susceptibility. This is the first report of pathogenic variability in Ptt in north western Algeria. The 48 isolates tested were further differentiated into 12 pathotypes according to their reaction on the host. Eight differential cultivars were resistant to all isolates tested, but others were susceptible to one or more of the isolates. The variability in the pathogen and the resistance identified in some genotypes used in this study are being investigated further to develop superior, adapted germplasm for use in barley breeding programs in north western Algeria

Relationship between pathogenicity, race and vegetative compatibility grouping among Algerian populations of Fusarium oxysporum f. sp. pisi causing pea wilt

Fusarium oxysporum f. sp. pisi (FOP) is a significant and destructive pathogen of field pea in Algeria. In the present study, 50 isolates of F. oxysporum f. sp. pisi, the causal agent of pea (Pisum sativum) wilt, collected from different parts of western Algeria and representing four races of the pathogen, were analyzed for virulence. The wilt incidence ranged from 6.66 to 88.33% on a highly susceptible cultivar (Little Marvel). Twenty-one isolates belonging to four races of FOP and one nonpathogenic F. oxysporum (FO) isolate were analyzed for vegetative compatibility in order to reveal the genetic structure of the population and to check the reliability of the method for the identification of physiological races of FOP. Obtained results showed that the FOP isolates could be classified into four main vegetative compatibility groups (VCGs) that corresponded to races l, 2A, 2B and 5. The race 6 isolate fell into the race 1 VCG. To our knowledge, this is the first such study in Algeria of its kind

Biocontrol of Chickpea Fusarium Wilt by Bacillus Spp. Rhizobacteria

Abstract: Among 131 rhizobacteria isolates, 29 potentially antagonistic strains were screened in in vitro assays. The five antagonistic Bacillus spp. Rb29, Rb6, Rb12, Rb4, and Rb15 showed the most inhibitory effect against FOC1 (from 25.63 to 71.11%), mycelial growth, and FOC2 (from 28.43 to 60.65%) in vitro. Results also revealed that production of volatile metabolite, components and inhibition of the test pathogen by volatile metabolites varied among different antagonistic rhizobacteria. Isolates Rb29, Rb6, Rb12, Rb4, and Rb15 produced more volatile metabolites which inhibited mycelial FOC growth by 40%. Chickpea Fusarium wilt severity caused by FOC1 was reduced from 60 to 99 % in the susceptible cultivar ILC 482 treated with antagonistic Bacillus spp. (Rb29, Rb6, Rb12, Rb4, and Rb15) in pot assays and by 98, 81, 68, 64, 57.20%, respectively, in the field trials. As for their beneficial effects on disease control, the results revealed that Bacillus spp. may improve plant growth and disease control

Full Length Research Paper - Pathogenic and genetic characterization of Algerian isolates of Fusarium oxysporum f. sp. lentis by RAPD and AFLP analysis

Thirty-two isolates of Fusarium oxysporum f. sp. lentis were isolated from wilted lentil plants collected from different lentil growing areas in north-west Algeria. A pathogenicity test was performed for all isolates. Results indicated that the Fol isolates represent a single race but differ in their aggressiveness on the susceptible lines. The amount of genetic variation was evaluated by polymerase chain reaction (PCR) amplification with a set of 6 RAPD primers and 3 AFLP selective nucleotide primer pairs. All amplifications revealed scorable polymorphisms among the isolates, and a total of 8 polymorphic fragments were scored for the RAPD primers and 93 for the AFLP primers. Genetic similarity between each of the isolates was calculated by using the Jaccard similarity coefficient and cluster analysis was used to generate a dendrogram showing relationship between them. The isolates could be grouped into two subpopulations based on RAPD and AFLP analysis. Results obtained indicate that there is little genetic variability among a subpopulation of Fol as identified by RAPD and AFLP markers and that there is no apparent correlation with geographical origin or aggressiveness of isolates. Also, the data suggest that Fol isolates are derived from two genetically distinct clonal lineages