Abstract

Fiber of Urena lobata L. (Caesar weed or Malva) has been produced from plants cultivated in floodplain areas of Brazilian Amazonas state since 1970s. Plants must be harvested before flooding and because of such a short cultivation season plants never reach fructification. Thus, local farmers depend on acquiring seeds collected in areas of spontaneous occurrence in drylands to sow their crop fields each year. This scenario might change, as this species is gaining socioeconomic important and there is interest in the development of cropping systems for seed production on a commercial scale. The objective of this study was to investigate the occurrence of endophytic fungi in U. lobata, evaluating the influence of the plant organ (leaf and seed) and farming site (two experimental fields of seed production: Manaus and Anori municipalities), once endophytic interaction can be beneficial or become harmful to the plants. The frequency and degree of colonization, Shannon-Weaver and Simpson diversity and Pielou uniformity indexes and the dominance component curve were calculated. The occurring genus were: Phomopsis, Colletotrichum, Fusarium, Pestalotiopsis, Curvularia and Cochliobolus. The greatest diversity and richness of fungi was found in Manaus site with high colonization present in the leaves. The genus Curvularia and Fusarium presented preference for seeds while Colletotrichum was more frequent in leaves. The similarity was greater between plant organs than between the farming sites, which indicates that the coevolution of these fungi and its host has resulted in a balanced mutual or antagonistic interaction (Crane & Acuna, 1945; Souza, 2012).

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