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Poster: Biology & Disease Mgmt: Mycology


Determining infection courts for Fusarium oxysporum f. sp. niveum leading to watermelon seed infestation
A. PETKAR (1), P. Ji (1) (1) University of Georgia, U.S.A.

Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum (FON) is a seedborne and seed transmitted disease. Seeds latently infected by the pathogen serve as a significant inoculum source and may result in serious disease in the field. It is unknown how watermelon seeds can get infected by the pathogen. To determine potential infection courts leading to watermelon seed infestation, experiments were conducted in 2013 to 2015 using different methods to inoculate watermelon plants with FON. Watermelon seeds were harvested when mature and seed infestation by FON was determined by isolation on peptone PCNB agar and real-time polymerase chain reaction (PCR) analysis. Swab-inoculation of immature fruit resulted in infestation of 18 to 54% of the seedlots under field conditions and 0.5 to 13% under greenhouse conditions when seeds were not surface sterilized before isolation. Seed infestation was detected on 0 to 15% of the seedlots when seeds were surface sterilized before isolation. Inoculation of stigma of female flowers resulted in infestation of 0 to 14% of the seedlots. Inoculation of peduncle also resulted in infestation of 0 to 10% of the seedlots in the field experiments when seeds were not surface sterilized before isolation. The results suggest that watermelon tissues including immature fruit, flowers and peduncle could be potential infection courts of FON leading to seed infestation by the pathogen.