Arbuscular mycorrhizal fungal diversity in wheat agroecosystems in Southern Chile and effects of seed treatment with natural products

Arbuscular mycorrhizal (AM) fungi are important for P uptake in Andisols cultivated with wheat. We assessed AM fungal diversity in field experiments established with wheat cultivated after AM host plants and non-host plants at three locations of the Araucania Region. Wheat seed was treated with two natural products: Fosfobio (FOS), mixture of P-solubilizing bacteria and N-2-fixing bacteria; and Myconate (MYC), product containing formononetin. For investigations of AM fungal diversity, soil samples were taken before planting and after harvest of wheat. The morphological spore analyses resulted in 26 species, belonging to 10 families and 16 genera; 5 species belonged to Acaulospora (31.2% of total), and 3 to Claroideoglomus (18.8%). Claroideoglomus claroideum was the prevalent while Ambispora leptoticha, Dominikia aurea, and Glomus badium presented the lowest frequency. The AM fungal species distribution was strongly dependent on the location, and richness at planting of wheat was higher when a non-host for AM fungi had been grown before. There appeared to be a tendency that through wheat cultivation, the richness of AM fungal species decreased from time of planting to harvest when the pre-crop was a non-host; when the pre-crop was AM host there was no apparent decrease in AM species richness through wheat cultivation. Natural products did not significantly influence grain yields. However, there was a tendency that MYC increased average grain yields by 7%. It is discussed that increased AM root colonization, as by MYC and improved P-uptake by AM fungi is more important than inoculation of seed with P-solubilizing microbes