Biological Potencial of Colletotrichum typhae H.C Greene mycoherbicide for Typha domingensis Pers

Abstract

24 The anthropic interference in aquatic ecosystems, favors the disordered colonization of T. domingensis, 25 damaging the production of hydroelectric power and river traffic. Thus, the objective of this study was 26 to evaluate the potential of C. typhae as a mycoherbicide in the control of T. domingensis, in vitro and 27 in greenhouse. 107 samples of symptomatic T. domingensis leaves were collected in flooded areas of 28 rivers in Brazil, with identification and isolation of the collected fungal species. The concentration of 29 inoculum was determined to evaluate the incidence and severity of the disease, the influence of 30 temperature on mycelial growth and conidia germination, the effect of temperature and leaf wetness 31 period on T. domingensis infection by C. typhae and the host range test. The growth of the colonies of 32 C. typhae was higher at 25 to 30 ºC, there was no interference of the photoperiod on germination of the 33 spores, but the highest percentage of germination occurred at 17.39 ºC. The influence of environmental 2 34 conditions on infection of inoculated leaves of T. dominguensis indicated that at 15 ºC and the period of 35 leaf wetness of 48 hours promoted the highest incidence of the disease, as well as the severity for the 36 same period of leaf wetness. The specificity test showed that C. typhae is specific and pathogenic to T. 37 domingensis. Being this the first report of the occurrence of this pathogen in aquatic macrophytes of 38 this species and in T. domingensis in Brazil. 39 Keywords: Biological control; Aquatic macrophytes, Leaf wetness 40 41 Introduction 42 Typha domingensis Pers. is an invasive macrophyte found in the Americas, Europe, Africa, Asia and 43 Oceania, being considered as a native species of South America, occurring throughout Brazil [1]. It is 44 propagated either by seeds or vegetatively, by rhizomes, with vigorous growth by the decomposition 45 and assimilation of organic matter as a source of nutrients, reaching about seven tons of rhizomes per 46 hectare [2]. Thus, T. domingensis is used as a biological filter for urban sewage, industrial effluents rich 47 in heavy metals and erosion control in drainage channels and reservoir banks [3]. 48However, anthropic interference in aquatic ecosystems favors the colonization of T. domingensis, 49 which may hinder the production of hydroelectric power, river traffic and agricultural irrigation [4]. In 50 the United States, this macrophyte accounts for the degradation of almost 12.000 ha -1 of Florida 51 marshes, due its aggressive growth in response to eutrophication by nitrates and phosphates from 52 agricultural and urban waste and frequent fires [5]. In Brazil, it is estimated that the intense growth of 53 T. domingensis in reservoirs of the country's hydroelectric dams extends to about 300 ha -1 in the water 54 mirror. These changes contribute to the reduction of water quality and biodiversity patterns in 55 environments colonized by this species [6]. 56Up to a certain limit, the development of aquatic vegetation c...