Abstract
Fifty fungal isolates were sampled from diseased tomato plants as result of a survey conducted in seven tomato crop areas in Algeria from 2012 to 2015. Morphological criteria and PCR-based identification, using the primers PF02 and PF03, assigned 29 out of 50 isolates to Fusarium oxysporum (Fo). The banding patterns amplified for genes SIX1, SIX3 and SIX4 served to identify races 2 and 3 of Fo f. sp. lycopersici (FOL), and Fo f. sp. radicis lycopersici (FORL) among the Algerian isolates. All FOL isolates showed pathogenicity on the susceptible tomato cv. “Super Marmande,” while nine of out 10 Algerian FORL isolates were pathogenic on tomato cv. “Rio Grande.” Inter simple sequence repeat (ISSR) fingerprints showed high genetic diversity among Algerian Fo isolates. Seventeen Algerian Trichoderma isolates were also obtained and assigned to the species T. asperellum (12 isolates), T. harzianum (four isolates) and T. ghanense (one isolate) based on ITS and tef1α gene sequences. Different in vitro tests identified the antagonistic potential of native Trichoderma isolates against FORL and FOL. Greenhouse biocontrol assays performed on “SM” tomato plants with T. ghanense T8 and T. asperellum T9 and T17, and three Fo isolates showed that isolate T8 performed well against FORL and FOL. This finding was based on an incidence reduction of crown and root rot and Fusarium wilt diseases by 53.1 and 48.3%, respectively.
Highlights
Fusarium oxysporum Schlecht (Fo) is a free-living ascomycete fungus with no known sexual state
All of the 31 (29 from Algeria and two control) isolates of Fo were utilized in the pathogenicity tests performed on tomato plants with the aim to confirm the identification of each isolate as being either FOL and FORL as shown by the SIX1 PCR amplifications
Plants inoculated with isolates F2 and F6 gave the highest symptom severity indexes, these values being significantly different from those obtained for the seven other Algerian FORL isolates, no differences were detected with that of Forlc
Summary
Fusarium oxysporum Schlecht (Fo) is a free-living ascomycete fungus with no known sexual state. Radicis-lycopersici Jarvis and Shomaker (FORL), Algerian Fusarium Oxysporum and Trichoderma responsible for crown and root rot, and by f. Spp. infect the same host plant, FOL and FORL have strict host specificity. Three physiological races of FOL (1, 2, and 3) have been differentiated depending on their ability to infect tomato cultivars carrying different resistance loci (Mes et al, 1999). Since pathogenic strains of Fo cannot be identified morphologically, pathogenicity tests are commonly used on different tomato cultivars. These methods are very timeconsuming and expensive (Baysal et al, 2009), and the results of these types of biological tests can be affected by variations in temperature (Boix-Ruíz et al, 2015)
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