US Department of Agriculture, Agricultural Research Service, Fort Pierce, FL, USA.
Phytopathology. 2011 Oct;101(10):1242-50. doi: 10.1094/PHYTO-11-10-0323.
Huanglongbing is an economically damaging disease of citrus associated with infection by 'Candidatus Liberibacter asiaticus'. Transmission of the organism via infection of seeds has not been demonstrated but is a concern since some citrus varieties, particularly those used as rootstocks in commercial plantings are propagated from seed. We compared the incidence of detection of 'Ca. Liberibacter asiaticus' DNA in individual fruit peduncles, seed coats, seeds, and in germinated seedlings from 'Sanguenelli' sweet orange and 'Conners' grapefruit fruits sampled from infected trees. Using real-time quantitative PCR (qPCR) we detected pathogen DNA in nucleic acid extracts of 36 and 100% of peduncles from 'Sanguenelli' and from 'Conners' fruits, respectively. We also detected pathogen DNA in extracts of 37 and 98% of seed coats and in 1.6 and 4% of extracts from the corresponding seeds of 'Sanguenelli' and 'Conners', respectively. Small amounts of pathogen DNA were detected in 10% of 'Sanguenelli' seedlings grown in the greenhouse, but in none of 204 extracts from 'Conners' seedlings. Pathogen DNA was detected in 4.9% and in 89% of seed coats peeled from seeds of 'Sanguenelli' and 'Conners' which were germinated on agar, and in 5% of 'Sanguenelli' but in none of 164 'Conners' seedlings which grew from these seeds on agar. No pathogen DNA was detected in 'Ridge Pineapple' tissue at 3 months post-grafting onto 'Sanguenelli' seedlings, even when pathogen DNA had been detected initially in the 'Sanguenelli' seedling. Though the apparent colonization of 'Conners' seeds was more extensive and nearly uniform compared with 'Sanguenelli' seeds, no pathogen DNA was detected in 'Conners' seedlings grown from these seeds. For either variety, no association was established between the presence of pathogen DNA in fruit peduncles and seed coats and in seedlings.
黄龙病是一种对柑橘具有经济破坏性的疾病，与感染‘亚洲韧皮杆菌’有关。该生物通过感染种子进行传播尚未得到证实，但令人担忧的是，一些柑橘品种，特别是那些用于商业种植的砧木，是通过种子繁殖的。我们比较了从感染树上采集的‘Sanguenelli’甜橙和‘Conners’葡萄柚果实的单个果柄、种皮、种子和发芽幼苗中检测到‘Ca. Liberibacter asiaticus’DNA 的发生率。使用实时定量 PCR（qPCR），我们分别检测到 36%和 100%的‘Sanguenelli’和‘Conners’果实果柄、37%和 98%的种皮以及相应种子的 1.6%和 4%的种子中存在病原体 DNA。在温室中生长的 10%的‘Sanguenelli’幼苗中检测到少量病原体 DNA，但在 204 个‘Conners’幼苗的提取物中均未检测到。从‘Sanguenelli’和‘Conners’种子上发芽的琼脂上，分别有 4.9%和 89%的种皮和 89%的种皮中检测到病原体 DNA，而从这些种子上发芽的琼脂上分别有 5%和 164 个‘Conners’幼苗中均未检测到病原体 DNA。在嫁接到‘Sanguenelli’幼苗上 3 个月后，‘Ridge Pineapple’组织中未检测到病原体 DNA，即使最初在‘Sanguenelli’幼苗中检测到了病原体 DNA。尽管与‘Sanguenelli’种子相比，‘Conners’种子的明显定植范围更广且更均匀，但从这些种子中发芽的‘Conners’幼苗中未检测到病原体 DNA。对于任何一种品种，均未发现果柄和种皮以及幼苗中病原体 DNA 的存在与果实之间存在关联。
