PDF(Pubmed)
Abstract：
Early detection and prompt response are key factors in the eradication of \'huanglongbing\' (HLB) in California. Currently, qPCR testing of leaf tissue guides the removal of infected trees. However, because of the uneven distribution of \'Candidatus Liberibacter asiaticus\' (CLas) in an infected tree and asymptomatic infection, selecting the best leaves to sample, from a mature tree with more than 200,000 estimated leaves, is a major hurdle for timely detection. The goal of this study was to address this issue by testing alternative tissues that might improve the CLas detection rate. Using two years of field data, old and young leaves, peduncle bark of fruit, and feeder roots were evaluated for the presence of CLas. Quadrant-peduncle (Q-P) tissue sampling consistently resulted in better CLas detection than any other tissue type. Q-P samples had a 30% higher qPCR positivity rate than quadrant-leaf (Q-L) samples. No significant seasonal patterns were observed. Roots and single peduncles had similar detection rates; both were higher than single leaves or Q-L samples. If symptoms were used to guide sampling, 30% of infected trees would have been missed. Taken together, these results suggest that Q-P tissue sampling is the optimal choice for improved CLas detection under California growing conditions.
摘要：
早期发现和迅速反应是根除加利福尼亚“黄龙病”（HLB）的关键因素。目前,叶组织的qPCR测试指导被感染的树的去除。然而,由于受感染的树和无症状感染中的“亚洲念珠菌”（CLas）分布不均，选择最好的树叶取样，从一棵估计有超过20万叶子的成熟树上，是及时发现的主要障碍。这项研究的目的是通过测试可能提高CLas检出率的替代组织来解决这个问题。使用两年的现场数据，古老和年轻的叶子，水果的花梗树皮，和饲养根评估CLas的存在。象限花梗（Q-P）组织采样始终比任何其他组织类型都能获得更好的CLas检测结果。Q-P样品的qPCR阳性率比象限叶(Q-L)样品高30%。没有观察到明显的季节性模式。根和单花梗的检出率相似；两者均高于单叶或Q-L样品。如果症状被用来指导采样，30%的受感染树木会被遗漏。一起来看,这些结果表明,在加州生长条件下,Q-P组织取样是改善CLas检测的最佳选择.
