Sporulation of Fusarium oxysporum f. sp. lycopersici on Stem Surfaces of Tomato Plants and Aerial Dissemination of Inoculum

Abstract

Plants exhibiting symptoms of wilt and xylem discoloration typical of Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici were observed in greenhouses of cherry tomatoes at various sites in Israel. However, the lower stems of some of these plants were covered with a pink layer of macroconidia of F. oxysporum. This sign resembles the sporulating layer on stems of tomato plants infected with F. oxysporum f. sp. radicis-lycopersici, which causes the crown and root rot disease. Monoconidial isolates of F. oxysporum from diseased plants were assigned to vegetative compatibility group 0030 of F. oxysporum f. sp. lycopersici and identified as belonging to race 1 of F. oxysporum f. sp. lycopersici. The possibility of coinfection with F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici was excluded by testing several macroconidia from each plant. Airborne propagules of F. oxysporum f. sp. lycopersici were trapped on selective medium in greenhouses in which plants with a sporulating layer had been growing. Sporulation on stems was reproduced by inoculating tomato plants with races 1 and 2 of F. oxysporum f. sp. lycopersici. This phenomenon has not been reported previously with F. oxysporum f. sp. lycopersici and might be connected to specific environmental conditions, e.g., high humidity. The sporulation of F. oxysporum f. sp. lycopersici on plant stems and the resultant aerial dissemination of macroconidia may have serious epidemiological consequences. Sanitation of the greenhouse structure, as part of a holistic disease management approach, is necessary to ensure effective disease control.

Clinical and Epidemiological Aspects of Infections Caused byFusariumSpecies: a Collaborative Study from Israel

“…are usually considered pathogens of various field and vegetable crops during the summer (17). However, there are two agriculturally significant F. oxysporum forms that are considered winter pathogens (9,17). Moreover, in Israel, fusarial infections are unrelated to rain and wind, in contrast to previous reports from other countries (3,10,30), since Israeli summers are rainless and hot (around 30°C).…”

“…Interestingly, in Israeli agricultural practice, Fusarium spp. are usually considered pathogens of various field and vegetable crops during the summer (17). However, there are two agriculturally significant F. oxysporum forms that are considered winter pathogens (9,17).…”

PCR detection of Fusarium oxysporum f.sp. radicis-lycopersici and races of F. oxysporum f.sp. lycopersici of tomato in protected tomato growing areas of Eastern Mediterranean Region of Turkey

“…However, the formae speciales and races of F. oxysporum are very difficult to discriminate this way (Nelson et al 1983;Burgess et al 1994). As a result, the complexity of identification of these 2 formae speciales causes difficulties in controlling the diseases caused by them (Katan et al 1997;Rosewich et al 1999;Gale et al 2003). Although tester plants have been widely used for the discrimination of the special forms and races of F. oxysporum, molecular techniques for rapid and reliable identification have come to the fore in recent years (Garibaldi 1975;Woo et al 1996).…”

FoSTUA, Encoding a Basic Helix-Loop-Helix Protein, Differentially Regulates Development of Three Kinds of Asexual Spores, Macroconidia, Microconidia, and Chlamydospores, in the Fungal Plant PathogenFusarium oxysporum

“…1D). These asexual spores play important roles in the disease cycle: macroconidia and microconidia are produced on the stem surfaces of infected plants and serve as secondary inocula to spread the fungus to neighboring host plants, and chlamydospores are endurance organs in soil and act as primary inocula when suitable host plants are planted in soil (17,26,39,44,45).…”