Phytophthora infestans Produces Oospores in Fruits and Seeds of Tomato

Abstract

Tomato fruits at the mature green stage coinoculated with A1 + A2 sporangia of Phytophthora infestans, the late blight causal fungus, showed abundant oospores in the vascular tissues, pericarp, columella, and placenta. Oospores were also formed on the surface of fruits kept in moisture-saturated atmosphere. Occasionally, oospores were enclosed between the epidermal hairs of the seed coat. In a few seeds, oospores were detected inside the embryo. The data suggest that blighted tomato fruits may carry a large number of oospores, thus making them a threatening source of blight inoculum. Such fruits may also release airborne oosporic inoculum that may introduce recombinant genotypes within a growing season. Although Phytophthora infestans is seedborne in tomato, to our knowledge, this is the first report on the occurrence of oospores in tomato seeds. Whether such tomato seeds produce blighted seedlings remains to be shown.

Inheritance of resistance against Phytophthora infestans in Lycopersicon pimpenellifolium L3707

“…de Bary is a most devastating disease of tomato and potato world-wide. This oomycete pathogen attacks leaves, stems, fruits and seeds of tomato (Rubin et al, 2001;Rubin & Cohen, 2004a). Disease may be initiated by air borne sporangia or by oospores harboring the soil or the seeds (Rubin & Cohen, 2004a).…”

Transmission of Colletotrichum coccodes via tomato seeds

“…The infected seeds produced plants with cassava anthracnose symptoms (Fokunang et al 1997). Oospores of Phytophthora infestans, the causal agent of late blight in tomato, were reported to infect tomato seeds and in a few cases (<0.1%), oospores were detected inside the embryo (Rubin et al 2001).…”

Homothallism in Pseudoperonospora humuli

“…Sexual recombination and the formation of resting structures is important for creating genetic diversity within pathogen populations and survival during periods of unfavourable environmental conditions or host dormancy (McDonald & Linde, ). In oomycetes, oospores are the sexual structures and may be important for persistence and transmission of some pathogens including Plasmopara halstedii in sunflower (Cohen & Sackston, ) and Phytophthora infestans in tomato (Rubin et al ., ). Oospores may be particularly critical sources of primary inoculum of biotrophic organisms such as the downy mildews, given that these pathogens require living tissue of a susceptible host to complete their life cycle (Pratt & Janke, ; Morgan, ; Tran Manh Sung et al ., ; van der Gaag & Frinking, ; Gobbin et al ., ; Montes‐Borrego et al ., ).…”