Improved Microassays Used to Test Natural Product-Based and Conventional Fungicides on Plant Pathogenic Fungi

Abstract

Seven important plant pathogenic fungi (Botrytis cinerea, Colletotrichum acutatum, C. fragariae, C. gloeosporioides, Fusarium oxysporum, Phomopsis obscurans, and P. viticola) valuable in screening fungicides were tested. Our procedure included washing conidia to reduce germination times, incorporating Roswell Park Memorial Institute 1640 as a medium of known composition, and using coverslips in the 24-well cell culture clusters to document the effect of fungicides on fungal morphology. The natural product-based fungicide, sampangine, a sampangine analog, 4-bromosampangine, plus seven conventional fungicides (benomyl, captan, cyprodinil, fenbuconazole, fenhexamid, iprodione, and kresoxim-methyl) were tested in vitro for their ability to inhibit germination and growth of the seven fungal species. Sampangine inhibited germination in all fungi except C. acutatum. Comparison of results of germination and morphology microbioassays with results of microtiter assays suggests that some fungicides stop fungal germination, whereas others only slow down fungal growth. We hypothesize that sampangine, except against C. acutatum, has the same physical mode of action, germination inhibition, as the conventional fungicides captan, iprodione, and kresoxim-methyl. 4-Bromosampangine caused morphological anomalies including excessive branching of germ tubes of C. fragariae and splaying and branching of germ tubes of B. cinerea.

Antifungal activity of medicinal plant extracts against phytopathogenic fungus Alternaria spp

“…Spores of the fungus were collected from cultures on agar plates after 7 d as described by Broekaert et al (1990). The sporangial suspension concentration was estimated using a cellcounting chamber and adjusted to 2 × 10 6 spores mL -1 (Abril et al, 2008). The fungal spore suspensions were stored in 20% glycerol at -40 °C.…”

Epidemiological Significance of Crown Rot in the Fruiting Field in Relation to Colletotrichum gloeosporioides Infection of Strawberry Nursery Plants

“…Active ingredients used in this study (thiophanate-methyl and cyprodinil) were effective in previous studies by Zhang and Timmer (2007) in reducing the incidence of postharvest anthracnose of tangerine caused by C. gloeosporioides when applied 2 days before harvest. Abril et al (2008) found that cyprodinil was strongly inhibitory to the germination and growth of C. gloeosporioides in vitro. Our results are in agreement with these previous studies; however, complete recovery from QI with one dip treatment or even complementary multiple in-field applications is likely not possible, especially if infections occur in the crown during the nursery production cycle.…”

Antimicrobial Activity of Artemisia herba-alba Extract against Pathogenic Fungi of Pigeon Droppings

“…These concentrations were prepared in glass bottles (100 ml) capacity, each bottle contained 50 ml sterilized potato dextrose broth medium used as diluent. Sporangial suspension concentration of each fungal isolate was estimated using a hemocytometer and adjusted to 2 × 10 6 spores/ml (Abril et al, 2008). Ten ml from the fungal suspension was inoculated into each bottle separately.…”