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）菌剂，是建立培育兼具优良营养与植物检疫品质菠萝种苗方法的核心前提。但由于这类真菌具有活体营养特性，该目标的实现颇具挑战。针对球囊霉孢子生产的需求，AMF菌剂的田间原位扩繁方法是极具潜力的替代方案。本研究旨在对比评估两类AMF菌剂的扩繁效果：一类为分离得到的纯菌种（包括根内根孢囊霉（Rhizophagus clarus）、地表球囊霉（Claroideoglomus etunicatum）），另一类为采用田间原位扩繁方法获得的菠萝与咖啡种植园原生AMF，并考察其对菠萝种苗的根系侵染效果。首先，采用田间原位扩繁方法，以双色高粱（Sorghum bicolor）为宿主植物，对R. clarus、C. etunicatum以及菠萝、咖啡来源的原生AMF菌剂进行扩繁。培养4个月后，分别对0.00~0.05 m与0.05~0.10 m土层中的AMF孢子数量及活孢子占比进行检测。结果显示，不同菌剂来源（R. clarus、C. etunicatum、菠萝原生AMF、咖啡原生AMF）与不同土层的孢子数量均无显著差异，每100 cm³土壤的平均孢子数为605个。无论菌剂来源如何，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，由C. etunicatum制备的菌剂活孢子占比（77.93%）高于咖啡原生AMF菌剂（68.06%）。随后，将所得孢子接种至菠萝种苗，以评估根系侵染率。接种AMF的菠萝种苗在栽培50天与180天后，平均根系侵染率分别为18%与67.73%，各处理组间无显著差异。综上，田间原位扩繁方法可有效扩繁R. clarus与C. etunicatum两类纯分离菌种，以及来自商业种植园（菠萝与咖啡）的原生AMF，所得孢子活性较高。丛枝菌根真菌可成功侵染菠萝种苗，且不受菌剂来源影响，同时可促进种苗生长。