Picciau Luca, Orrù Bianca, Mandrioli Mauro, Gonella Elena, Alma Alberto
Dipartimento di Scienze Agrarie, Forestali e Alimentari (DISAFA), University of Torino, I-10095 Grugliasco (TO), Italy.
Dipartimento di Scienze della Vita (DSV), University of Modena e Reggio Emilia, I-41125 Modena, Italy.
Insects. 2020 Sep 5;11(9):603. doi: 10.3390/insects11090603.
Phytoplasma transmission takes place by insect vectors through an Acquisition Access Period (AAP), Latency Period (LP) and Inoculation Access Period (IAP). Generally, phytoplasmas are believed to be transmitted more efficiently by nymphs because they need a long LP to reach the salivary glands before becoming infective. The transmission can start from adults as well, but in this case a long LP may exceed the insect's lifespan. However, previous evidence has indicated that adults can undergo a shorter LP, even though little knowledge is available regarding the phytoplasma temporal dynamics during this period. Here, we investigate the minimum time required by the phytoplasma to colonize the vector midgut and salivary glands, and finally to be inoculated into a plant. We used the leafhopper to investigate the life cycle of flavescence dorée phytoplasma (FDP). Phytoplasma-free adults were left on broad beans (BBs) infected with FDP for an AAP of 7 days. Subsequently, they were individually transferred onto a healthy BB for seven different IAPs, each one lasting 24 h from day 8 to 14. Molecular analyses and fluorescence in situ hybridization were performed for FDP detection. FDP was found in the leafhopper midgut from IAP 1 with an infection rate reaching 50%, whereas in the salivary glands it was found from IAP 2 with an infection rate reaching 30%. FDP was also detected in BBs from IAP 4, with infection rates reaching 10%. Our results represent an important step to further deepen the knowledge of phytoplasma transmission and its epidemiology.
植原体通过昆虫介体在获毒期（AAP）、潜伏期（LP）和接种期（IAP）进行传播。一般认为，若虫传播植原体的效率更高，因为它们需要较长的潜伏期才能在具有感染性之前到达唾液腺。成虫也可以传播，但在这种情况下，较长的潜伏期可能会超过昆虫的寿命。然而，先前的证据表明，成虫的潜伏期可能较短，尽管在此期间关于植原体的时间动态知之甚少。在这里，我们研究了植原体定殖于介体中肠和唾液腺并最终接种到植物中所需的最短时间。我们使用叶蝉来研究金黄叶枯植原体（FDP）的生命周期。将无植原体的成虫置于感染FDP的蚕豆（BB）上7天进行获毒期处理。随后，将它们分别转移到健康的蚕豆上进行七个不同的接种期处理，每个接种期从第8天到第14天持续24小时。进行分子分析和荧光原位杂交以检测FDP。在接种期1时在叶蝉中肠中发现了FDP，感染率达到50%，而在唾液腺中从接种期2开始发现，感染率达到30%。在接种期4的蚕豆中也检测到了FDP，感染率达到10%。我们的结果是进一步深化对植原体传播及其流行病学认识的重要一步。
