Effect of Inoculation of Pineapple Plantlets with Arbuscular Mycorrhizal Fungi Obtained from Different Inoculum Sources Multiplied by the On-Farm Method

ABSTRACT The production of inoculum from arbuscular mycorrhizal fungi (AMF) at a large scale and low cost is essential for establishing methods to assist in producing pineapple plantlets with high nutritional and phytosanitary quality. However, this objective is difficult to accomplish because of the biotrophic nature of these fungi. The on-farm multiplication method for AMF inoculum presents a good alternative to supply the demand for the production of glomerospores. This study aimed to multiply and evaluate AMF inoculum originating from isolated species (including Rhizophagus clarus, Claroideoglomus etunicatum) versus native AMF from pineapple and coffee plantations multiplied by the on-farm method on the colonization in pineapple plantlets. Initially, inocula of R. clarus, C. etunicatum, and native AMF (pineapple and coffee) were multiplied by the on-farm method in Sorghum bicolor. After four months, the number of AMF spores and the percentage of viable spores at the layers of 0.00-0.05 and 0.05-0.10 m were evaluated. There were no differences in spore numbers in relation to the source of the inoculum (R. clarus, C. etunicatum, pineapple, and coffee) and evaluated layers, with an average number of 605 spores per 100 cm3 of soil. The percentage of viable spores was greater at the layer of 0.00-0.05 m (76.32 %) compared to the layer of 0.05-0.10 m (72.05 %), regardless of the inoculum source. The viability of the inoculum obtained from C. etunicatum was higher than that from the coffee crop (77.93 and 68.06 %, respectively). Subsequently, the spores were inoculated in pineapple plantlets to assess the rate of colonization. Pineapple plantlets inoculated with AMF had an average of colonization of 18 and 67.73 % after 50 and 180 days cultivation, respectively, with no significant difference being detected between treatments. Therefore, on-farm inoculum production was effective at multiplying the AMF of both isolates of R. clarus and C. etunicatum, as well as for commercial crops (pineapple and coffee), with spores having high viability. Arbuscular mycorrhizal fungi colonized pineapple plantlets independently of the inoculum utilized and favored its growth.

摘要 大规模低成本制备丛枝菌根真菌（arbuscular mycorrhizal fungi, AMF）接种物，是建立辅助培育兼具高营养品质与植物检疫安全性优质菠萝种苗方法的核心必要前提。然而，由于这类真菌的活体营养特性，该目标的实现难度极大。针对球囊霉孢子的生产需求，AMF接种物的农场原位扩繁法是一种优质的替代方案。本研究旨在通过农场扩繁法，对两类AMF接种物进行扩繁并评估其对菠萝种苗的菌根定殖效果：一类为分离菌株来源的接种物（涵盖Rhizophagus clarus与Claroideoglomus etunicatum），另一类为菠萝与咖啡种植园原生AMF接种物。初始阶段，我们以双色高粱（Sorghum bicolor）为宿主，通过农场原位扩繁法对R. clarus、C. etunicatum以及菠萝、咖啡来源的原生AMF接种物进行扩繁。培养4个月后，分别测定0.00~0.05 m与0.05~0.10 m土层中的AMF孢子数量与活孢子占比。结果显示，不同接种物来源（R. clarus、C. etunicatum、菠萝原生AMF、咖啡原生AMF）与土层深度对土壤孢子数量均无显著影响，每100 cm³土壤的平均孢子数为605个。无论接种物来源如何，0.00~0.05 m土层的活孢子占比（76.32%）均显著高于0.05~0.10 m土层（72.05%）。其中，源自C. etunicatum的接种物活孢子率高于咖啡种植园来源的接种物，二者分别为77.93%与68.06%。后续试验中，我们将上述孢子接种至菠萝种苗，以评估其菌根定殖率。接种AMF的菠萝种苗在栽培50天与180天后，平均定殖率分别为18%与67.73%，各处理组间未检测到显著差异。综上，农场原位扩繁法可有效扩繁R. clarus与C. etunicatum两种分离菌株的AMF，以及商业种植园（菠萝、咖啡）来源的原生AMF，所得孢子均具备较高活性。丛枝菌根真菌均可成功定殖菠萝种苗，且可显著促进其生长。