Structural Colonization of Arbuscular Mycorrhizal Fungi in Three Acacia Species of Different Sizes in Riyadh, Saudi Arabia: Experimental Investigation

In this chapter, we investigated the status of Arbuscular Mycorrhiza Fungi (AMF) living natural symbiotically with different sizes of the acacia. Regardless of tree species or size, AMF caused varying degrees of root colonisation and infection in Acacia tortilis, Acacia ehrenbergiana, and Acacia gerrardii. A. ehrenbergiana medium size was found to have the highest infection overall at the Raudhat Khuraim site (70%) and was followed by A. tortilis short size (60%), A. gerrardii medium size (58.7%), and short size (57.7%) at the Washlah site. A. gerrardii large size had the lowest infection rate in Khuraim (6%). The maximum vesicles were found in A. tortilis large (95%) followed by A. ehrenbergiana medium (91%) at Khuraim, A. tortilis medium (67.3) at Washlah, A. gerrardii and A. tortilis short size (51.7),(50.0) at Khuraim and Huraymila. The minimum was recorded with A. gerrardii medium (4%) in Khuraim. At Washlah, large size A. torilis had the lowest infection rate (4.7%). In each individual tree, the intensity of infection and spore population varied widely and independently. The medium size A. gerrardii at Washlah had the most spores (230), while the short size A. gerrardii in Khuraim had the fewest (21). In conclusion, our findings show that AMF infection is most common in the roots of short acacia trees, followed by medium-sized trees, and least common in large trees.