Petkar Aparna, Ji Pingsheng
Department of Plant Pathology, Coastal Plain Experiment Station, University of Georgia, Tifton 31794.
Phytopathology. 2017 Jul;107(7):828-833. doi: 10.1094/PHYTO-12-16-0429-R. Epub 2017 May 15.
Fusarium wilt incited by Fusarium oxysporum f. sp. niveum is a seed-transmitted disease that causes significant yield loss in watermelon production. The pathogen may infect watermelon seeds latently, which can be an important inoculum source and contribute to severe disease outbreak. However, information regarding infection courts of F. oxysporum f. sp. niveum leading to infestation of watermelon seeds is limited. To determine how seeds in watermelon fruit can be infested by F. oxysporum f. sp. niveum during the watermelon growing season, greenhouse and field experiments were conducted in 2014 and 2015 where watermelon flowers and immature fruit were inoculated with F. oxysporum f. sp. niveum. Seeds were extracted from mature watermelon fruit, and infestation of watermelon seeds was determined by isolation of F. oxysporum f. sp. niveum and further confirmed by real-time polymerase chain reaction (PCR) analysis. Inoculation of the pericarp of immature fruit resulted in 17.8 to 54.4% of infested seeds under field conditions and 0.6 to 12.8% of infested seeds under greenhouse conditions when seeds were not surface disinfested prior to isolation. Seed infestation was also detected in 0 to 4.5% of the seeds when seeds were surface disinfested prior to isolation. Inoculation of pistil resulted in 0 to 7.2% and 0 to 18.3% of infested seeds under greenhouse and field conditions when seeds were surface disinfested or not disinfested before isolation, respectively. Inoculation of peduncle resulted in 0.6 to 6.1% and 0 to 10.0% of infested seeds in the greenhouse and field experiments when seeds were surface disinfested or not disinfested before isolation, respectively. Seed infestation was also detected in all the experiments using real-time PCR assay when pericarp or pistil was inoculated, and in three of four experiments when peduncle was inoculated, regardless of whether seeds were surface disinfested or not disinfested. Pericarp and peduncle of immature watermelon fruit and pistil of watermelon flowers could be potential infection courts for F. oxysporum f. sp. niveum leading to infestation of seeds in asymptomatic watermelon fruit.
尖孢镰刀菌西瓜专化型（Fusarium oxysporum f. sp. niveum）引起的枯萎病是一种种子传播病害，会导致西瓜生产中产量大幅损失。该病原菌可能会潜伏感染西瓜种子，这可能是一个重要的接种源，并导致严重的病害爆发。然而，关于尖孢镰刀菌西瓜专化型侵染西瓜种子的侵染位点的信息有限。为了确定在西瓜生长季节，西瓜果实中的种子如何被尖孢镰刀菌西瓜专化型侵染，于2014年和2015年进行了温室和田间试验，对西瓜花和未成熟果实接种尖孢镰刀菌西瓜专化型。从成熟西瓜果实中提取种子，通过分离尖孢镰刀菌西瓜专化型来确定西瓜种子的侵染情况，并通过实时聚合酶链反应（PCR）分析进一步确认。在田间条件下，对接种未成熟果实的果皮，当种子在分离前未进行表面消毒时，侵染种子的比例为17.8%至54.4%；在温室条件下，这一比例为0.6%至12.8%。当种子在分离前进行表面消毒时，在0至4.5%的种子中也检测到种子侵染。对接种雌蕊，在温室和田间条件下，当种子在分离前进行表面消毒或未消毒时，侵染种子的比例分别为0至7.2%和0至18.3%。对接种果梗，在温室和田间试验中，当种子在分离前进行表面消毒或未消毒时，侵染种子的比例分别为0.6%至6.1%和0至10.0%。在所有使用实时PCR检测的试验中，当接种果皮或雌蕊时均检测到种子侵染，当接种果梗时，在四个试验中的三个试验中检测到种子侵染，无论种子是否进行表面消毒。未成熟西瓜果实的果皮和果梗以及西瓜花的雌蕊可能是尖孢镰刀菌西瓜专化型导致无症状西瓜果实种子侵染的潜在侵染位点。
