Arbuscular Mycorrhizal Fungi Colonization in Upland Rice as Influenced by Agrochemical Application

Mycorrhizal status of rice under upland conditions was studied using potted seedlings. Percentage of arbuscular mycorrhizal fungi (AMF) root colonization varied between 17.35% and 37.18% over an age series of 7 to 70 days old rice plants. AMF root colonization was increased up to 35-42 days, beyond which the root colonization steadily declined. The vesicles appeared after two weeks and reached their maximum intensity on the 35th day. The arbuscules were formed late on the 42nd day (2.93%) and slightly varied up to the 70th day (3.03%). Higher dosage of urea application suppressed plant growth whereas the superphosphate treatment had no marked impact on plant growth. Generally, application of these agrochemicals registered less influence on the hyphal colonization of AMF in rice plants, whereas arbuscular colonization was adversely affected by higher dosages of fertilizers. There were pronounced decreases in both the plant growth and their AMF colonization due to the application of systemic fungicides, carbendazim and thiophanate methyl. The application of single sprays of fungicides was less deleterious over multiple sprays.