砂糖橘红鼻子果与韧皮部杆菌侵染相关性研究

Relationship between the"Red Nose"Fruit of Shatangju Tangerine with Candidatus Liberibacter asiaticus

利用TaqMan实时荧光定量PCR技术对广东清远、四会、云浮地区砂糖橘90个红鼻子果样品进行检测。结果表明,韧皮部杆菌(Candidatus Liberibacter asiaticus)阳性检出率高达100%。分别对病树上无症状果实、斑驳叶片以及黄化叶片样品进行实时荧光定量PCR检测,阳性检出率分别为27.3%、91.8%、52.0%,因此,可将砂糖橘红鼻子果作为田间诊断黄龙病的典型症状。红鼻子果的果柄和果轴均可检测到病原,且果柄部位病原浓度明显高于果轴。对红鼻子果果柄韧皮部扫描电镜观察,发现果柄筛管中有大量淀粉粒沉积,且韧皮部筛管明显缢缩,阻碍了植株体内糖分和有机质向果实运输。

Citrus Huanglongbing （HLB） is difficult to identify in the field as the similar symptoms may also occur due to some physiological disorders and water stress, so in HLB management diagnosing HLB is of great importance. TaqMan quantative real-time PCR, targeting 16S rDNA sequence of＇Candidatus Liberibacter asiaticus＇, was used to examine Shatangju tangerine （Citrus reticulate） ＂red nose＂ fruits, non-symptomatic fruits in the HLB infected trees, blotchy mottling leaves and yellowing leaves collected from Qingyuan, Sihui and Yunfu （Guangdong Province）. The results showed that 100% of the ＂ red nose＂ fruit samples were positive for ＇Candidatus Liberibacter asiaticus＇, while 27.3% non-symptom fruits, 91.8% typical blotchy mottling leaves and 52.0% yellowing leaves were positive for ＇Candidatus Liberibacter asiaticus＇. Therefore, ＂red nose＂ fruit could be regarded as a typical symptom of HLB in Shatangju tangerine. The pathogen was detected in fruit axis and pedicle, but the latter one got a higher titer which maight be used as a material for the pathogen observation. A Scanning Electron Microscopy （SEM） showed no pathogen but a mass of starch grains was observed in the phloem sieve tubes of HLB Shatangju tangerine infected with HLB. The phloem was constricted and maight block the sugar movement to fruits.