Soybean and sunflower oils increase the infectivity of Colletotrichum gloeosporioides f. sp. aeschynomene to northern jointvetch

Soybean and sunflower oils increased the level of infection of northern jointvetch, Aeschynomene virginica, plants by Colletotrichum gloeosporioides f. sp. aeschynomene. Inoculation of seedlings with spore suspensions containing 10% (v:v) soybean oil or 10% sunflower oil resulted in more disease than when inoculated with suspensions of spores in water alone. The lengths of the dew periods required to establish equivalent levels of disease by spore suspensions containing 10% soybean or 10% sunflower oil were approximately 4-8 h less compared to aqueous suspensions. Incubation of spores in 10% soybean oil followed by removal and resuspension in water did not affect the infectivity of spores when compared to spores incubated in aqueous suspensions. Spore germination and appressoria formation were unaffected by either of the oils tested in in vitro assays; however, in in vivo assays, 10% soybean oil and 10% sunflower oil increased spore germination in comparison to spores that were suspended in water.