Arbuscular mycorrhizal fungi in rosewood (Aniba rosaeodora Ducke) and mahogany (Swietenia macrophylla King) in the Manaus region

In the State of Amazonas there are two distinct periods of rainfall distribution, which are concentrated between December and April and a dry period, which runs from June to September. This climate characteristic can interfere in the establishment of the mycorrhizal association in forest species, considering that soil moisture can interfere with the germination of mycorrhizal fungi spores. The soil moisture near the field capacity favors the development of symbiosis, and alternations between dry and rainy periods can favor the sporulation of AMF. However, there are discrepancies among the studies regarding the establishment of mycorrhizal fungi as a function of soil moisture. The restriction of water availability in the months of low precipitation induces in the microorganisms associated with the plant, the activation of adaptation mechanisms, such as increased sporulation. The mycorrhization occurs mainly in thin and new roots, which must be present at the time the AMF are observed, a situation that may vary according to the plant species and their location in the forest system. Mahogany (Swietenia macrophylla King) and rosewood (Aniba rosaeodora Ducke) are native species from the Amazon of high economic value. The cultivation of these plants involves the use of appropriate agricultural practices to obtain productive forest stands. The success of the establishment of these species depends on the ability to withstand edaphoclimatic variations and, consequently, to present high percentages of survival in the field and less need for cultural treatments, therefore, the association with mycorrhizal fungi can be of fundamental importance for the establishment of these species, as it can improve mineral nutrition and water absorption for the metabolism of plants in periods of less precipitation. These factors must be considered: seasonality, edaphic factors, host dependency, host plant ages, the sporulation skills and the patterns of distribution of FMA spores in soils.
There are several studies carried out with mycorrhizal associations in the Amazon with annual crops (Miranda, Vilela, & 2005; Silva, Siqueira & Stürmer , 2009), as well as with perennial species (Oliveira, 2001; Oliveira & Oliveira, 2004; Moreira, Oliveira, Maia & Oliveira, 2019b). However, more researches are needed to better understand how mycorrhizal relationships are established in regional plant species.
The present study verified the occurrence of mycorrhizal fungi in rosewood (Aniba rosaeodora Ducke) and mahogany (Swietenia macrophylla King) cultivated in two rural properties in the Community of Brasileirinho, in the municipality of Manaus, in three different periods, and to verify how these associations contribute to the nutrition of these two species.

在亚马逊州的雨量分布呈现出两个明显的时期，即集中在十二月至四月间的降雨期，以及从六月至九月的旱季。这一气候特征可能干扰森林物种中菌根联合体的建立，鉴于土壤湿度可能影响菌根真菌孢子的萌发。接近田间持水量的土壤湿度有利于共生关系的发展，而干湿交替则可能促进丛枝菌根真菌的孢子形成。然而，关于土壤湿度对菌根真菌建立的影响，不同研究之间存在差异。降水量较低的月份内，水分供应的限制会导致与植物相关的微生物激活适应机制，如增加孢子形成。菌根化主要发生在细新根上，这些根必须存在于观察到的丛枝菌根真菌时，这种情况可能因植物种类及其在森林系统中的位置而异。红木（Swietenia macrophylla King）和香榧木（Aniba rosaeodora Ducke）是亚马逊地区具有重要经济价值的本土物种。这些植物的栽培涉及采用适宜的农业实践以获得生产性林分。这些物种建立的成败取决于其抵御土壤气候变率的能力，以及因此能在田间展现出高生存率并减少文化处理的必要性，因此，与菌根真菌的联合对于这些物种的建立可能具有根本性的意义，因为它可以改善植物在降水较少时期内的矿物营养和水吸收，以促进植物代谢。必须考虑以下因素：季节性、土壤因素、宿主依赖性、宿主植物年龄、孢子形成能力和土壤中丛枝菌根真菌孢子分布模式。在亚马逊地区，已有关于菌根联合体在年度作物（Miranda, Vilela, & 2005；Silva, Siqueira & Stürmer, 2009）以及多年生物种（Oliveira, 2001；Oliveira & Oliveira, 2004；Moreira, Oliveira, Maia & Oliveira, 2019b）中的研究，但为了更好地理解菌根关系在区域植物物种中的建立方式，仍需进行更多研究。本研究验证了在布拉西莱里尼奥社区马瑙斯市两个农村地产种植的香榧木（Aniba rosaeodora Ducke）和红木（Swietenia macrophylla King）中菌根真菌的发生，以及在不同三个时期内这些联合体如何为这两种物种提供营养。