Lopes Silvio A, Luiz Fernanda Q B F, Oliveira Hermes T, Cifuentes-Arenas Juan C, Raiol-Junior Laudecir L
Fundecitrus, Araraquara, SP, Brazil.
Universidade Estadual Paulista, Jaboticabal, SP, Brazil.
Plant Dis. 2017 Apr;101(4):583-590. doi: 10.1094/PDIS-06-16-0859-RE. Epub 2017 Jan 18.
The major citrus area of Brazil occupies near 450,000 ha between the Triângulo Mineiro (TM) region of Minas Gerais State and the south of São Paulo State (SPS). Significant climatic variation occurs between regions which could affect huanglongbing (HLB) progress, which is lower in TM. To investigate this possibility, young sweet orange shoots were sampled periodically over 2 years to determine 'Candidatus Liberibacter asiaticus' titers in naturally infected trees in orchards in Analândia, central SPS, and Frutal and Comendador Gomes, within TM. Data-loggers recorded local temperature and relative humidity hourly. In the laboratory, five 'Ca. L. asiaticus'-free Diaphorina citri adults were placed on each sampled shoot for 48 h to feed and acquire the pathogen. Shoots and insects were individually analyzed by quantitative polymerase chain reaction to determine 'Ca. L. asiaticus' titers. The incidence of 'Ca. L. asiaticus'-positive shoots, 'Ca. L. asiaticus' titers, and acquisition rates were lower for shoots from Comendador Gomes than those from Frutal or Analândia. Stronger association was observed between 'Ca. L. asiaticus' titers and the number of hours below 15°C (h < 15°C) or above 30°C (h > 30°C), and cumulative rainfall registered during the 15 days prior to sampling of shoots on each occasion. 'Ca. L. asiaticus' titers associated positively with h < 15°C and rainfall and negatively with h > 30°C. The slower spread and lower incidence of HLB in TM may be related to lower incidences of 'Ca. L. asiaticus'-positive young shoots and lower titers of 'Ca. L. asiaticus' in the same shoots as a consequence of the warmer and drier conditions.
巴西的主要柑橘产区位于米纳斯吉拉斯州的三角地区（TM）和圣保罗州南部（SPS）之间，占地近45万公顷。不同地区之间存在显著的气候变化，这可能会影响黄龙病（HLB）的发展进程，在三角地区黄龙病的发展进程较慢。为了研究这种可能性，在两年时间里定期采集幼龄甜橙嫩梢样本，以确定位于圣保罗州中部的阿纳朗迪亚、以及三角地区内的弗鲁塔尔和科门达多·戈麦斯果园中自然感染树木的“亚洲韧皮杆菌”滴度。数据记录器每小时记录当地温度和相对湿度。在实验室中，将五只未感染“亚洲韧皮杆菌”的柑橘木虱成虫放置在每个采集的嫩梢上48小时，使其取食并获取病原体。对嫩梢和昆虫分别进行定量聚合酶链反应分析，以确定“亚洲韧皮杆菌”滴度。与来自弗鲁塔尔或阿纳朗迪亚的嫩梢相比，科门达多·戈麦斯的嫩梢中“亚洲韧皮杆菌”阳性嫩梢的发生率、“亚洲韧皮杆菌”滴度和获取率较低。观察到“亚洲韧皮杆菌”滴度与低于15°C（h < 15°C）或高于30°C（h > 30°C）的小时数，以及每次采集嫩梢前15天内记录的累计降雨量之间存在更强的关联。“亚洲韧皮杆菌”滴度与h < 15°C和降雨量呈正相关，与h > 30°C呈负相关。三角地区黄龙病传播较慢且发病率较低，可能与“亚洲韧皮杆菌”阳性幼嫩梢发生率较低以及由于温暖干燥条件导致同一嫩梢中“亚洲韧皮杆菌”滴度较低有关。
