Cifuentes-Arenas Juan Camilo, de Oliveira Hermes Teixeira, Raiol-Júnior Laudecir Lemos, de Carvalho Everton Vieira, Kharfan Daniela, Creste André Luís, Gastaminza Gerardo, Salas Hernán, Bassanezi Renato Beozzo, Ayres Antônio Juliano, Lopes Silvio Aparecido
Departamento de Pesquisa e Desenvolvimento, Fundo de Defesa da Citricultura, Araraquara, Brazil.
Departamento de Fitossanidade, Universidade Estadual Paulista 'Júlio de Mesquita Filho', Jaboticabal, Brazil.
Front Plant Sci. 2022 Dec 5;13:1005557. doi: 10.3389/fpls.2022.1005557. eCollection 2022.
The severe Asian form of huanglongbing (HLB), a vascular disease associated with the phloem-limited bacterium ' Liberibacter asiaticus', is transmitted by the Asian citrus psyllid (ACP) . Disease impacts are known for sweet oranges and acid limes but not lemons.
In a five-year study (2017-2021) we compared yield and fruit quality between naturally-infected and healthy 5-yr-old trees of Sicilian lemon 'Femminello', and shoot phenology on both lemon and 'Valencia' orange, both grafted onto 'Swingle' citrumelo, grown in southeastern São Paulo State, Brazil. HLB severity (percentage of tree canopy area with HLB symptoms) was assessed every 3-4 months, fruit yield and quality in May (2017 to 2019) or June/July (2020-2021), and vegetative and reproductive shoots fortnightly on 50-cm-long branches. The development of ACP on one-year-old seedlings of five lemon varieties, 'Tahiti' acid lime, 'Valencia' orange, and orange jasmine was evaluated.
Symptoms increased from 11% in 2017 to 64% in 2021, and a monomolecular model estimated 10 years for symptoms to occupy >90% of the tree canopy. On average, production of trees with symptom on 20%, 50% or 80% of the canopy respectively dropped by 18%, 38%, and 53% compared to healthy trees. Fruits of symptomatic branches of lemons were 4.22% lighter and the number of dropped fruits did not correlate with symptom severity. Flushing on symptomatic branches started earlier by 15 to 55 days as compared to the healthy branches of lemon and orange. On diseased trees, vegetative and reproductive shoots respectively increased by 24.5% and 17.5% on lemon and by 67.2% and 70.6% on sweet orange, but fruit set was reduced by 12.9% and 19.7% on lemon and orange trees, respectively. ACP reproduced similarly on all tested plants.
The fast symptom progress, significant yield reduction, and earlier flushing on diseased trees, providing conditions highly favorable for the pathogen to spread, reinforce the need of prompt diseased tree removal and frequent ACP preventive control to manage HLB in lemons as in any other citrus crop.
亚洲柑橘黄龙病（HLB）的严重亚洲型是一种与韧皮部受限细菌“亚洲韧皮杆菌”相关的维管束病害，由亚洲柑橘木虱（ACP）传播。病害对甜橙和酸橙的影响已有报道，但对柠檬的影响尚不清楚。
在一项为期五年（2017 - 2021年）的研究中，我们比较了巴西圣保罗州东南部种植的、嫁接到“斯温格尔”枳柚上的5岁西西里柠檬“费米内洛”自然感染树和健康树的产量及果实品质，以及柠檬和“巴伦西亚”橙的新梢物候。每3 - 4个月评估一次HLB严重程度（有HLB症状的树冠面积百分比），在2017年至2019年5月或2020 - 2021年6月/7月评估果实产量和品质，每两周对50厘米长枝条上的营养枝和结果枝进行评估。评估了ACP在五个柠檬品种、“塔希提”酸橙、“巴伦西亚”橙和九里香一年生幼苗上的繁殖情况。
症状从2017年的11%增加到2021年的64%，单分子模型估计症状占据树冠>90%需要10年。平均而言，树冠有20%、50%或80%症状的树的产量分别比健康树下降了18%、38%和53%。柠檬有症状枝条上的果实重量轻4.22%，落果数量与症状严重程度无关。与柠檬和橙子的健康枝条相比，有症状枝条的抽梢开始时间提前了15至55天。在患病树上，柠檬的营养枝和结果枝分别增加了24.5%和17.5%，甜橙分别增加了67.2%和70.6%，但柠檬和橙子树的坐果率分别降低了12.9%和19.7%。ACP在所有测试植物上的繁殖情况相似。
症状快速发展、产量显著降低以及患病树抽梢提前，为病原体传播提供了非常有利的条件，这强化了像管理其他柑橘作物一样，通过及时清除患病树和频繁进行ACP预防性防治来管理柠檬HLB的必要性。
