First report of transmission of Xylella fastidiosa through citrus seeds
Xylella fastidiosa (EPPO A1 list), among other diseases, is responsible for citrus variegated chlorosis which severely affects citrus orchards in Brazil. So far, it has been shown that this disease was transmitted by sharpshooters (Cicadellidae), infected bud wood and natural root grafts. Studies were done in Brazil to characterize the distribution of X. fastidiosa in various parts of sweet orange (Citrus sinensis) fruit and seeds and to determine whether the bacterium could be transmitted through seeds to seedlings. Symptomatic and asymptomatic fruits of C. sinensis cvs Pera, Valencia and Natal were collected and tested (PCR assays) for the presence of X. fastidiosa. The bacterium could be detected in samples of peduncles, peel, endocarp, septum, locular membrane and central axis of symptomatic fruits. It was also observed that fresh weight of affected fruits was reduced by 25% compared to healthy fruits. X. fastidiosa was detected on seeds collected from diseased fruits, both in the embryo and seed coat. No apparent symptoms were observed on diseased seeds. However, the weight of affected embryos was reduced by 25 % compared to healthy ones, and seed germination was lower. Finally, X. fastidiosa was detected in seedlings (PCR assays and in vitro isolation) grown from seeds which had been collected on symptomatic fruits. The authors concluded that this is the first report of seed transmission of X. fastidiosa. They felt that further studies should be done on citrus rootstocks (such as Rangpur lime) as these are multiplied by seedlings, as well as on coffee varieties and rootstocks which are also largely multiplied by seedlings and affected by X. fastidiosa (causing coffee leaf scorch).
Li, W.B.; Pria, W.D.; Lacava, Jr P.M.; Qin, X.; Hartung, J.S. (2003) Presence of Xylella fastidiosa in sweet orange fruit and seeds and its transmission to seedlings.
Phytopathology, 93(8), 953-958.