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 大规模低成本生产丛枝菌根真菌（arbuscular mycorrhizal fungi，AMF）菌剂，是构建可辅助培育兼具高营养品质与植物检疫安全性菠萝幼苗技术体系的必要前提。但由于该类真菌具有活体营养特性，该目标的实现存在较大挑战。针对球囊孢子的生产需求，AMF菌剂田间扩繁技术是一项颇具应用前景的替代方案。本研究旨在通过田间扩繁方法，对两类分离菌种（根内根孢囊霉Rhizophagus clarus、地表近明球囊霉Claroideoglomus etunicatum）及菠萝、咖啡种植园土著丛枝菌根真菌的菌剂进行扩繁，并评估其对菠萝幼苗根系定殖的影响。试验初始阶段，以双色高粱（Sorghum bicolor）为宿主植物，通过田间扩繁技术对根内根孢囊霉、地表近明球囊霉及菠萝、咖啡来源的土著AMF菌剂进行扩繁。扩繁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测定。结果表明，不同菌剂来源（根内根孢囊霉、地表近明球囊霉、菠萝源土著AMF、咖啡源土著AMF）与土层深度对土壤每100 cm³中的孢子数量无显著影响，土壤平均孢子数为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，地表近明球囊霉来源菌剂的活孢子率（77.93%）显著高于咖啡源土著AMF菌剂（68.06%）。随后，将扩繁得到的孢子接种至菠萝幼苗，以测定其根系定殖率。接种AMF的菠萝幼苗在栽培50天与180天后的平均根系定殖率分别为18%与67.73%，各处理组间未检测到显著差异。综上，田间扩繁技术可有效扩繁根内根孢囊霉与地表近明球囊霉两类分离菌种，以及来源于经济作物（菠萝与咖啡）的土著AMF，所得菌剂孢子活性较高。丛枝菌根真菌可成功定殖菠萝幼苗根系，且对植株生长具有显著促进作用。