Inoculum production of arbuscular mycorrhizal fungi native to soils under different forest covers

ABSTRACT The low natural fertility of Brazilian soils requires the use of inoculants that facilitate the absorption of nutrients by plants. Arbuscular mycorrhizal fungi such as obligatory biotrophics of active roots perform this function, but access to this resource is limited by the difficulty in producing inoculants. The objective of this study was to investigate the production of AMF inoculants native of soils under different forest covers in Vitória da Conquista, BA, by means of spore quantification, colonization rate and species identification. For this purpose, soils were collected from sites under Mata Nativa (native forest) and plantations of Madeira Nova (Pterogyne nitens) and Eucalyptus, placed into separate 500 mL disposable cups with seeds of Brachiaria sp. and cultivated for five months. Spores were quantified and the AMF species identified in the control soil (without brachiaria) and in the cups cultivated with brachiaria at each month. From the first month, the colonization rate of brachiaria roots was evaluated. The inoculants produced showed differences in the number of spores and species, in the AMF species identified, and in the root colonization rate as a function of the forest cover. Thus, considering the increase in the number of spores, species and colonization over time, the inoculant produced from the soil under native forest was more promising for utilization.

摘要：巴西土壤自然肥力偏低，需借助菌剂促进植物对养分的吸收。丛枝菌根真菌（Arbuscular Mycorrhizal Fungi, AMF）作为根系专性活体营养生物，可发挥该功能，但菌剂生产难度较大导致该资源可及性受限。本研究旨在通过孢子计数、根系定殖率测定及物种鉴定，探究巴西巴伊亚州（BA）维多利亚达孔基斯塔（Vitória da Conquista）境内不同林分覆盖下土壤来源的土著丛枝菌根真菌菌剂的制备方法。试验采集原生林（Mata Nativa）、新木（Madeira Nova，Pterogyne nitens）人工林及桉树人工林的土壤，分别装入500 mL一次性塑料杯中，播种臂形草（Brachiaria sp.）种子后培养5个月。每月对未播种臂形草的对照土壤及各培养组土壤进行孢子计数与丛枝菌根真菌物种鉴定，并自试验第1个月起测定臂形草根系的菌根定殖率。结果表明，所制备的菌剂在孢子数量、物种组成、鉴定得到的丛枝菌根真菌种类及根系定殖率上，均随林分覆盖类型存在显著差异。综合孢子数量、物种丰富度及定殖率随培养时间的增长趋势，原生林土壤制备的菌剂展现出更优的应用潜力。