Purpose

This study aimed at elucidating the biotic components of crop decline affecting kiwifruit (Actinidia deliciosa) orchards.

Methods

The study was carried out on soil samples originating from an over twenty-year-old orchard showing typical yield decline (Old), one in full production phase (Adult), one fallow after a kiwifruit cultivation (Fallow), an abandoned one (Virgin). Soil health of those soil samples was assessed with an in-pot growth assay using kiwifruit plantlets in which root endophytic fungi and rhizosphere bacteria communities were assessed using qPCR and NGS analysis.

Results

Plant growth in the Old field was significantly lower than the others, in line with the crop decline of that field. The Old treatment differed from the others in the following soil features: i. a great reduction of total bacteria, Pseudomonas, actinomycetes and Bacillus compared to the Adult orchard; ii. a significant increase of Nitrosospira and other nitrifying bacteria which persisted in kiwifruit rhizosphere even under the optimal conditions; iii. a reduction of potentially beneficial genera among which Massilia, Rubrobacter and Kaistobacter. Old, Adult and Fallow were similar in root fungal community composition, with Dactylonectria as dominant genus (about 50%); whilst in the Virgin prevailed saprophytic non-pathogenic fungi.

Conclusions

Bacterial communities in over-30-year-old kiwifruit orchards were greatly reduced and modified, thus suggesting being a cause of the reduced ability of soil to support plant growth. In addition, kiwifruit manifested a legacy effect on soil-borne fungal communities, including root endophytes.

中文翻译：

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土壤细菌的数量减少和微生物的质量变化：与猕猴桃衰退相关的生物成分

目的

本研究旨在阐明影响猕猴桃 ( Actindia deliciosa ) 果园的作物衰退的生物成分。

方法

该研究的土壤样本来自一个超过 20 年的果园，显示典型的产量下降（老），一个处于全面生产阶段（成人），一个猕猴桃种植后休耕（休耕），一个废弃的（处女） ）。这些土壤样品的土壤健康通过使用猕猴桃幼苗的盆内生长测定进行评估，其中使用 qPCR 和 NGS 分析评估根内生真菌和根际细菌群落。

结果

老田的植物生长明显低于其他田，这与该田的作物下降一致。Old 处理与其他处理的不同之处在于以下土壤特征： i．与成年果园相比，总细菌、假单胞菌、放线菌和芽孢杆菌大大减少；ii. 即使在最佳条件下，仍然存在于猕猴桃根际的亚硝化螺旋体和其他硝化细菌显着增加；iii. 减少潜在的有益菌属，其中包括Massilia、Rubrobacter和Kaistobacter。Old、Adult 和 Fallow 根部真菌群落组成相似，Dactylonectria作为优势属（约 50%）；而在处女座盛行腐生非致病真菌。

结论

超过 30 年树龄的猕猴桃园中的细菌群落大大减少和改变，这表明这是土壤支持植物生长的能力降低的一个原因。此外，猕猴桃对土壤传播的真菌群落（包括根内生菌）表现出遗留效应。