Micorrizas vesiculares-arbusculares em cana-de-açúcar

Abstract

This dissertation presents a qualitative and quantitative survey of naturally occurring vesicular-arbuscular fungi in the rhizosphere of sugarcane. Spore number variations were studied in relation to temperature and rainfall of the growing season and the effect of vinasse application and min eral fertilizers upon spore numbers and root infection was investigated.Of all the factors under investigation only temperature and moisture influenced the development of VA --mycorrhiza. There was no interaction between P, K, Mg and pH levels of the soil, including vinasse, and spore numbers or root-infection percentages in sugarcane.High spore counts (433-1,620 spores/l00 ml soil )were obtained, but root infection was generally low (3-45%) .ix.In spite of the great number of spores there was only a limit ed amount of fungal species present, as follows: Ac.aulo.6poha.6 e.no bic.ulat a, Giga..6 poha. gilmohei, Glomu.6 na..6 c.i c.ula.t u.6 and GlE_ mu.6 le pt otic.hu.6, plus a new unidentified species of Gi9a1.>po ha..Two experiments with sugarcane were conducted in the green-house. In the first experiment sugarcane wa, s planted in natural and autoclaved soil, while the second con sisted of natural soil, soil sterilized by four differe nt meth.cxE and sterile soil reinoculated with a soil filtrate, in addition to one treatment inoculated with Giga.1.>poha. gilmohei. In the first experiment there was a much lower growth of plants in natural soil, probably due to a great incidence of root path ogens like Pha.tylenc.hu.6 zea.e, Fu.6ahium spp. and Pythium spp., which affected more than 50% of the root systems. In the second experiment plant h1ghts were measured 60 days after instal lation. The only significant growth effect which could be observed was again the smaller size of the plants in natural soil, when compared to all others. .• APÊNDICEApêndice 1 -Resultados da análise de esp:>ros em 100 ml de solo, referente às seis é poca s de arrostragem.