Amaranthus spinosus, Leonotis nepetaefolia,andLeonurus sibiricus:New Hosts ofPhomopsisspp. in Brazil

Abstract

Phomopsis spp. was isolated from Amaranthus spinosus, Leonotis nepetaefolia and Leonurus sibiricus, common weeds in soybeans [Glycine max] grown in southern Brazil. The latter 2 hosts were symptomless carriers of Phomopsis spp. Pycnidia produced by cultures of Phomopsis spp. isolated from the 3 weed hosts gave rise to alpha and beta conidia typical of Diaporthe phaseolorum. The Phomopsis spp. isolates from L. nepetaefolia and L. sibiricus, but not from A. spinosus, reduced seed germination, radicle length, and emergence of UFV1 soybeans but not of ''Rico 23'' common bean (Phaseolus vulgaris) grown in infested sand and soil. These weed isolates colonized soybean stems and produced pycnidia. Isolates from A. spinosus did not produce pycnidia on common bean stems.