Identification of QoI fungicide-resistant genotypes of the wheat pathogen Zymoseptoria tritici in Algeria

Septoria tritici blotch caused by Zymoseptoria tritici is currently one of the most damaging diseases on bread and durum wheat crops worldwide. A total of 120 monoconidial isolates of this fungus were sampled in 2012 from five distinct geographical locations of Algeria (Guelma, Annaba, Constantine, Skikda and Oran) and assessed for resistance to Quinone outside Inhibitors (QoI), a widely used class of fungicides for the control of fungal diseases of wheat. Resistance was screened using a mismatch PCR assay that identified the G143A mitochondrial cytochrome b substitution associated with QoI resistance. The isolates were QoI-sensitive, since all possessed the G143 wild-type allele, except for three isolates (two from Guelma and one from Annaba), which had fungicide resistance and possessed the A143 resistant allele. QoI resistance was confirmed phenotypically using a microplate bioassay in which the resistant isolates displayed high levels of half-maximal inhibitory azoxystrobin concentrations (IC50s) when compared to sensitive reference isolates. Genetic fingerprinting of all isolates with microsatellite markers revealed that the three resistant isolates were distinct haplotypes, and were are not genetically distinguishable from the sensitive isolates. This study highlights QoI-resistant genotypes of Z. tritici in Algeria for the first time, and proposes a management strategy for QoI fungicide application to prevent further spread of resistance across the country or to other areas of Northern Africa

Mating type distribution provides evidence for sexual reproduction of Mycosphaerella graminicola in Algeria

International audienceSeptoria tritici blotch caused by Mycosphaerella graminicola is currently the most frequently occurring and economically damaging disease on wheat crops worldwide. A total of 120 single-conidial isolates of this fungus (60 from bread wheat and 60 from durum wheat) were sampled in 2012 from five distinct geographical locations of Algeria and analyzed for mating type distribution to provide insight into the potential of sexual reproduction. The mating type of each isolate was identified using a multiplex PCR that amplifies either a MAT1-1 or a MAT1-2 fragment from mating type loci. Both idiomorphs were scored at equal frequencies according to the χ2 test at different scales. They were found to occur at equal proportions at the whole country level (46 % MAT1-1 vs. 54 % MAT1-2) and at the level of each sampled location. The two mating types were also found at equal frequencies on both host species at the country scale (47 % MAT1-1 vs. 53 % MAT1-2 on bread wheat and 45 % MAT1-1 vs. 55 % MAT1-2 on durum wheat) and irrespective of the sampled locations. This equal mating type distribution at both geographic and host species levels suggests a large potential for sexual reproduction of M. graminicola in Algeria and indicates a lack of specificity between mating types and host species in the case of the wheat-M. graminicola pathosystem

Two Novel Bacillus Strains (subtilis and simplex Species) with Promising Potential for the Biocontrol of Zymoseptoria tritici, the Causal Agent of Septoria Tritici Blotch of Wheat

Two novel Algerian field-collected isolates were selected for their antifungal activity against Zymoseptoria tritici (teleomorph Mycosphaerella graminicola). The novel strains, termed Alg.24B1 and Alg.24B2, were identified as Bacillus subtilis and Bacillus simplex since their respective nucleotide sequences of the 16S rRNA gene were 100% and 99.93% identical to those of B. subtilis and B. simplex, respectively. The antifungal activities of Alg.24B1 and Alg.24B2 were evaluated by the well diffusion method and compared to those of other Bacillus species. The maximum activity was obtained after two days of confrontation of the bacterial strain supernatants with the fungus for Alg.24B1 and three days for Alg.24B2. Furthermore, the metabolites responsible for the antifungal activity of both strains were detected by the investigation of either gene presence (PCR) or molecule production (activity detection of lytic enzymes and HPLC detection of lipopeptides). Overall, this study showed that in addition to their ability to produce lytic enzymes (protease and β-glucanase), both strains coproduce three types of lipopeptides viz. surfactin, iturin, and fengycin. Thus, the biofungicide activity of both strains may be a result of a combination of different mechanisms. Therefore, they had a great potential to be used as biocontrol agents to effectively manage septoria tritici blotch of wheat (STB)