Panicle and shoot blight of pistachio caused by species of Botryosphaeriaceae fungi remains one of the major diseases of pistachio in California, with the highest potential for crop destruction because buds and fruit clusters (panicles) are killed. Pistachio fruit can also be damaged by various insect pests. For instance, hemipteran insects are considered major pests of pistachio and can attack maturing fruit, causing necrotic areas on the fruit epicarp (epicarp lesion). Surveys in pistachio orchards showed a putative association of punctures of pistachio fruit with infection by Botryosphaeriaceae fungi, resulting in panicle and shoot blight. This study was undertaken to determine any association of Botryosphaeriaceae fungi with fruit bearing epicarp lesions and whether hemipteran insects can actively carry propagules of the pathogens to healthy fruit and cause disease. Three large insects of the order Hemiptera (Thyanta pallidovirens, Acrosternum hilare, and Leptoglossus clypealis) were used in pathogen-spread and infection experiments. The most frequently isolated species of the family Botryosphaeriaceae in pistachio, Neofusicoccum mediterraneum, was used in these transmission experiments. Significantly higher incidence of fruit infected by N. mediterraneum was recorded when pistachio clusters were sprayed with a spore suspension of N. mediterraneum and caged with the above insects than the level of infected fruit sprayed similarly with the pathogen but caged without any insects. Furthermore, increasing the number of insects caged with pistachio clusters resulted in an increase of insect feeding punctures and, subsequently, disease incidence. Similarly, increasing the number of wounds per fruit made with a needle, simulating injuries caused by the insect's stylet, resulted in significantly higher incidence of infected fruit than for wounded fruit with fewer injured sites. In addition, bird-injured fruit were also associated with higher incidence of panicle blight than fruit not injured by birds, especially in orchards with high disease incidence. In laboratory experiments, wounding or applying fruit sap to nonwounded fruit resulted in significantly higher incidence of infected fruit than in nonwounded fruit without sap. In field experiments, wounding of fruit before or after inoculation with N. mediterraneum resulted in higher disease incidence than nonwounded and inoculated fruit. Additionally, fruit sap enhanced initial mycelial growth of N. mediterraneum. Protecting fruit clusters from injuries by hemipteran insects or birds using mesh cages significantly reduced the incidence of panicle and shoot blight. The association of wounding by hemipteran insects and birds with high incidence of infected pistachio fruit may explain partially the broad distribution of Botryosphaeria panicle and shoot blight among pistachio orchards of the central San Joaquin Valley, even in areas where inoculum sources are not nearby.

译文

:由葡萄球菌属真菌引起的开心果的穗状茎和茎叶枯萎病仍是加利福尼亚州开心果的主要疾病之一,由于杀死芽和果实簇(穗),其对农作物的破坏潜力最高。阿月浑子果实也可能被各种害虫破坏。例如,半翅目昆虫被认为是开心果的主要害虫,可侵袭成熟的果实,在果实果皮(表皮病)上造成坏死区域。阿月浑子果园的调查显示,开心果刺穿与Botryosphaeriaceae真菌感染有关,导致穗和枯萎病。这项研究的目的是确定葡萄球菌真菌与带有果皮果皮损伤的果实之间是否存在关联,以及半翅目昆虫是否可以将病原体的繁殖体主动携带到健康的果实上并引起疾病。在病原体传播和感染实验中使用了半翅目的三种大型昆虫(Thyanta pallidovirens,Acrosternum hilare和Leptoglossus clypealis)。在这些传播实验中,使用了开心果中最频繁分离的葡萄球菌科物种,Neofusicoccum mediterraneum。当用开心果簇用中生猪笼草的孢子悬浮液喷洒并用上述昆虫进行笼养时,记录到被中生猪笼草感染的水果的发生率要比类似地喷洒病原体但笼中没有任何昆虫的被感染果实的水平高。此外,被开心果簇包裹的昆虫数量的增加导致昆虫摄食穿刺的增加,进而导致疾病的发生。同样,模拟用昆虫的探针引起的伤害,增加每个针头刺伤每个水果所产生的伤口数量,会导致感染水果的发生率明显高于受伤部位较少的受伤水果。此外,与没有受到鸟类伤害的果实相比,鸟类受伤的果实与穗枯萎病的发病率也更高,尤其是在发病率高的果园中。在实验室实验中,对未受伤的水果进行创伤或应用水果树汁会导致感染水果的发生率显着高于没有树液的未受伤水果。在田间试验中,接种中性猪笼草前后对水果的伤害要比未受伤和接种的水果高。此外,水果树液增强了中性猪笼草的初始菌丝生长。使用网状笼子保护果实免受半球虫或鸟类伤害,显着降低了穗和枯萎病的发生率。半昆虫昆虫和鸟类造成的伤害与开心果受感染的发生率高有关,这可能部分解释了葡萄孢的穗状花序广泛分布和圣华金山谷中部开心果果园的枯萎病,即使在附近没有接种源的地区也是如此。

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