Lamichhane Jay Ram, Bartoli Claudia, Varvaro Leonardo
Department of Science and Technology for Agriculture, Forestry, Nature and Energy (DAFNE), Tuscia University, Viterbo, Italy.
Hazelnut Research Center, Viterbo, Italy.
PLoS One. 2016 Feb 3;11(2):e0147584. doi: 10.1371/journal.pone.0147584. eCollection 2016.
Pseudomonas avellanae (Pav) has been reported as the causal agent of bacterial decline and bacterial canker of hazelnut in Italy and Greece, respectively. Both hazelnut diseases were reported to be similar in terms of symptoms, severity and persistence. In this study, we found that both symptomatic and asymptomatic trees in the field were colonized by Pav. Multilocus Sequence Typing (MLST) analysis showed that Pav strains isolated during this study in Italy belong to the P. syringae phylogroup 1 and they are closely related to Pav strains previously isolated in Greece from hazelnut bacterial canker. On the other hand, strains isolated in earlier studies from hazelnut decline in Italy belong to both phylogroup 1 and 2 of P. syringae. Both phylogroup 1 strains of P. syringae from Greece and Italy are different than strains isolated in this study in terms of their capacity to excrete fluorescent pigments on different media. Despite the same plant genotype and cropping practices adopted, the incidence of hazelnut decline ranged from nearly 0 to 91% across our study sites. No disease developed on plants inoculated with Pav through wounding while leaf scar inoculations produced only mild disease symptoms. Based on our results and the previously reported correlation between pedo-climatic conditions and hazelnut decline, we conclude that hazelnut decline in central Italy could be incited by a combination of predisposing (adverse pedo-climatic conditions) and contributing factors (Pav). Because this is a true decline different from "bacterial canker" described in Greece, we refer to it as hazelnut decline (HD).
在意大利和希腊，分别报道了榛果假单胞菌（Pav）是榛树细菌性衰退和细菌性溃疡病的病原体。据报道，这两种榛树病害在症状、严重程度和持续性方面相似。在本研究中，我们发现田间有症状和无症状的树木均被Pav定殖。多位点序列分型（MLST）分析表明，在本研究期间于意大利分离出的Pav菌株属于丁香假单胞菌菌群1，并且它们与先前在希腊从榛树细菌性溃疡病中分离出的Pav菌株密切相关。另一方面，在早期研究中从意大利榛树衰退病中分离出的菌株属于丁香假单胞菌的菌群1和2。来自希腊和意大利的丁香假单胞菌菌群1菌株在不同培养基上分泌荧光色素的能力方面与本研究中分离出的菌株不同。尽管采用了相同的植物基因型和种植方式，但在我们所有的研究地点，榛树衰退病的发病率从近0%到91%不等。通过创伤接种Pav的植株未发病，而叶痕接种仅产生了轻微的病害症状。基于我们的研究结果以及先前报道的土壤气候条件与榛树衰退病之间的相关性，我们得出结论，意大利中部的榛树衰退病可能是由诱发因素（不利的土壤气候条件）和促成因素（Pav）共同作用引起的。由于这是一种与希腊描述的“细菌性溃疡病”不同的真正衰退病，我们将其称为榛树衰退病（HD）。
