CHARACTERIZATION OF Fusarium oxysporum ISOLATES AND RESISTANCE OF PASSION FRUIT GENOTYPES TO FUSARIOSIS

Abstract

Passion fruit wilt, caused by Fusarium spp., is one of the most severe diseases for this crop. Although yellow passion fruit is propagated mostly by seeds, the use of rootstocks tolerant to early death could be a management strategy for cultivation in areas with disease history. Thus, this study characterized Fusarium isolates obtained in Triângulo Mineiro and determined the most suitable genotype to use for grafting to reduce losses caused by this pathogen. Mycelial growth and sporulation of Fusarium isolates, in three different growth media, was quantified by measuring colony diameter and by counting the conidia in Neubauer chamber 10 days after growth in malt extract-agar 2%, PDA or CMA at 22 ± 3ºC and 12 hours lighting. Five days later the color of the colonies was evaluated. The experimental design was a 4x3 factorial completely randomized design, with five replications. Characterization of morphological structures of isolates was done with minimum cultivation in Malt extract-agar 2% amended with sterilized soil + sand (1:1). Three Passiflora species and two seedling types were used as rootstock to evaluate field resistance to fusariosis, in a randomized block design, as a 3x2 factorial, with three Passiflora species (P. alata, P. setacea and P. edulis) and two seedling types (ungrafted or grafted with P. edulis). The medium PDA was the least favorable for mycelial growth of the isolates. The best medium for conidium production was Malt extract and the most sporulating isolates were Fus-01 and Fus-02. Isolate color varied from white to pink to violet. Only Fus-02 and Fus-04 formed macro and microconidia. Shape, dimensions and septa number of macroconidia and microconidia, as well as the presence of characteristic monophyalides allowed the classification of all isolates as Fusarium oxysporum f.sp. passiflorae. Passiflora alata and P. setacea, used as rootstocks for P. edulis in the field, were resistant to fusariosis. Despite its low survival, P. edulis grafted on itsef, promoted similar growth of secondary branches as P. setacea in the field.

Scanning electron microscopy of bio‐fabricated Fe2O3 nanoparticles and their application to control brown rot of citrus

“…Microscopic studies revealed macro conidial septation (Figure 1d). Previous studies have also described similar morphology and macro conidial septation of different F. oxysporum isolates (Hafizi, Salleh, & Latiffah, 2013;Teixeira, Coelho, & Tebaldi, 2017). Isolates produced abundant chlamydospores and could be easily seen after 2 weeks of incubation.…”

<i>Fusarium oxysporum</i> as a Pathogen of Pot Plants: a Case Study of the Easter Lily Cactus (<i>Echinopsis oxygona</i>) in Poland

“…Chlamydospores, another characteristic structures of F. oxysporum, measure 7-11 μm [19,20]. Fusarium oxysporum belongs to the Elegans section and is an ubiquitous species -it inhabits various ecological niches with distinct environmental conditions and nutrient availability [18].…”

“…The observed features included colony growth, as well as the color and occurrence of specific morphological structures like spores. The observations were analyzed according to monographs [18][19][20]. The fungus specimens placed on microscope slides were dyed with LPCB (lactophenol cotton blue, Sigma-Aldrich).…”