Mycorrhizal colonization in relation to age of cassava plant in different soil types of semiarid tropics of Tamilnadu

Arbuscular mycorrhizal spore population and AM root colonization were positively correlated with different micronutrients viz., Zn Mn and Cu analyzed from cassava soil semiarid tropics of Tamil Nadu. Loamy soil recorded the highest number of AM spores (123.30 100 g of soil) while the root colonization is 49.24 per cent was the highest in clay loam soils of semiarid tropics of Tamil nadu. Red soil recorded the least of 100 spore 100 g of soil and 40.70 per cent root colonization. The surface layer (0-15 cm) contained the highest spore population. The increase in soil depth up to 90cm showed gradual reduction in spore numbers. A negative correlation existed between the soil depth and number of AM spore present. The genus Glomus was the most predominant followed by either Acaulospora or Gigaspora. The occurrence of Glomus accounted for 45 to 60 per cent of total AM fungi in different soil type’s studies except sand and red soil, which accounted for 35.02 and 38.00 percent of total AM fungi. It was found that more than 50 per cent of total AM spore belonged to Glomus and the remaining 50 per cent of the population of AM spore were found to be shared by Gigaspora, Acaulospora and others. The AM fungus, G. Fasciculatum was found to be most effective for the cassava varieties tested viz., CO-1, M-4, MVT-1 and H-165 followed by G. mosseae, Acaulospora laevis and Gigaspora margarita. However, no specificity existed between varieties and AM fungal species tested.