Fusarium Oxysporum F. Sp. Lycopersici Research Articles

Fusarium oxysporum f. sp. lycopersici races and their genetic discrimination by molecular markers in West Mediterranean region of Turkey

Fusarium oxysporum f. sp. lycopersici (FOL) races and F. oxysporum f. sp. radicis lycopersici (FORL), the causal agents of root rot and crown rot diseases, respectively, cause serious economic losses in tomato greenhouses where production is intensive in the West Mediterranean region of Turkey. The isolates were collected from West Mediterranean region of Turkey and were characterized by specific primers based on three races (r1, r2, r3), besides pathogenicity tests in in vivo conditions Additionally, a scheme was developed using newly tested ISSR and SRAP markers to a genotyping database and to determine the possible origin of these pathogens. The present study provided new information on these pathogens based on their races and their dominant existence in this region that has not been reported before. Genetic diversity detected in the same races of the pathogen may be associated with difficulties in controlling the pathogen and a possible resistance formation effort exerted by the pathogen to chemicals used in plant protection in tomato greenhouses. Molecular analyses indicated genetic diversity in pathogen isolates identified as r3, r2 and FORL, which may be associated with abiotic stress to which the pathogens were exposed.

Resistance in pepper plants induced by Fusarium oxysporum f. sp. lycopersici involves different defence‐related genes

Inoculation with Fusarium oxysporum f. sp. lycopersici (FOL) protects pepper plants from subsequent infection with Phytophthora capsici. In the present paper, the level of local and systemic protection achieved by plants induced with FOL was evaluated by quantifying the pathogen biomass and using real-time PCR. Differences in the amount of pathogen were found in stems and roots between FOL-treated and untreated plants, while pathogen biomass could not be detected in leaves of induced plants. Five defence-related genes coding for a PR-1 protein, a beta-1,3-glucanase, a chitinase, a peroxidase and a sesquiterpene cyclase were up-regulated 48 h after treatment in all the tissues studied, and maximal mRNAs levels were found in leaves.

Biological control of Fusarium wilt of tomato with hypovirulent binucleate Rhizoctonia in greenhouse conditions

Four isolates of hypovirulent binucleate Rhizoctonia (HBNR), G1, L2, W1, and W7 were used for control of Fusarium wilt of tomato (FWT) caused by Fusarium oxysporum f. sp. lycopersici (FOL). HBNR isolates could significantly reduce disease severity (foliar symptoms and discoloration inside the stem) among five experiments under single and double applications. Reduction of disease severity by HBNR isolates, however, differed depending on HBNR isolates and treatments. Of four isolates, isolate HBNR W7 could significantly and consistently reduce (P=0.05) disease severity. Application of HBNR isolates significantly reduced (P=0.01) the number of colonyforming units of FOL in stems and roots of tomato. Among the HBNR isolates, G1, W1, and W7 could significantly increase (P=0.05) fresh weight of the plants (stems and leaves). These results indicate that isolates of HBNR have a greater potential as biocontrol agents against FWT. This is the first report of biocontrol of FWT by HBNR under greenhouse conditions.

Systemic Resistance to Fusarium Wilt in Tomato Induced by Phytopthora cryptogea

AbstractUnder climate chamber conditions, suppression of tomato wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL) was obtained by spraying a suspension of Phytophthora cryptogea (Pc) zoospores on the green parts of two tomato cultivars, Danish Export (susceptible) and Elin F1 (moderately resistant). Direct competitive or antagonistic interaction between Pc and FOL in the soil or on the root surfaces was ruled out, but not interaction within the stems of plants. After Pc application followed by FOL inoculation, the two cultivars showed no wilt disease symptoms during the 50 days following FOL inoculation, whereas the FOL‐control plants were destroyed by wilt within about 40 days. Over a period of 7 weeks, both Pc and FOL were detected inside the stems of plants, for all treatments. Pc and FOL were also found inside the petioles of plants, except for one treatment, Pc application followed by challenge inoculation with FOL. Systemic induced resistance was assumed to be responsible for the observed elimination of disease incidence. It was concluded that, under climate chamber conditions, Pc application to the green parts of tomato plants is a viable alternative for control of disease incidence caused by FOL.

Repeated applications of Penicillium oxalicum prolongs biocontrol of fusarium wilt of tomato plants

The suppression of fusarium wilt of tomato achieved by Penicillium oxalicum (PO) applied one or several times (up to four) was assessed during three glasshouse experiments. The first application of PO (106 conidia g-1 substrate) to the growing substrate (peat and vermiculite, 1 : 1, v : v) was performed prior to its infestation with Fusarium oxysporum f. sp. lycopersici (FOL) (104–106 chlamydospores g-1). Repeated applications of PO prolonged the duration of control of fusarium wilt especially when disease incidence was high. The timing of repeated applications of PO did not affect the efficacy of the control. Disease reduction was not associated with a decrease in density of FOL in the rhizosphere, irrespective of the number of applications of PO. Density of PO in the tomato rhizosphere was higher when repeated applications were made. No relationship was observed between reduction of disease and high densities of PO. Reasons for a longer disease reduction in tomato plants following several applications with PO are discussed.

Biological control of Fusarium oxysporum f. sp. lycopersici

Fungi known to produce lytic enzymes were used in an attempt to control wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL). Some of the fungal species (Penicillium oxalicum, Penicillium purpurogenum and Aspergillus nidulans) damaged hyphae of FOL in vitro and reduced the numbers of microconidia in the soil. Treatments with fungi did not result in a reduction in either chlamydospores of FOL in soil or populations of FOL in the rhizosphere of tomato. P. oxalicum was the most effective agent of biocontrol, and it reduced disease severity in both non‐autoclaved (20% decrease) and sterile soil. In sterile soil, P. oxalicum reduced disease with different levels of severity (27% decrease at high levels and 50% decrease at low levels). Disease control by A. nidulans and P purpurogenum was only achieved when disease severity was low in sterile soil (55% and 45%, respectively).

Production of Intraspecific Hybrids of Fusarium oxysporum f. sp. radicis‐lycopersici and Fusarium oxysporum f. sp. lycopersici by Protoplast Fusions

AbstractThe fusion of protoplasts from the cycloheximide‐resistant mutant FOL(C) of Fusarium oxysporum f. sp. lycopersici (FOL) and the mycostatin‐resistant mutant FORL(M) of F. oxysporum f. sp. radicis‐lycopersici (FORL), produced hybrids which expressed significant differences from the parents in their pathogenicity and growth and in the electrophoretic separation patterns of their proteins, enzymes and isoenzymes. The results suggest a transformed genetic basis for these altered expressions and the feasibility of using protoplast fusion technology for examining the biology of pathogenicity genes and for elucidating the disease and virulence potential for new races from within hybridisable taxa of Fusarium spp. Such information would be useful for the design and development of long‐term control systems for Fusarium diseases, particularly in breeding programs for disease resistance in crops.