Assessing the pathogenicity of Piptoporellus baudonii, the plant pathogen in cashew and Eucalyptus from the Southern regions of Tanzania

The southern regions of Tanzania are defenseless to food insecurity, the collapse of the forest industry and poverty due to the failure of the main cash crop caused by a pathogenic mushroom, Piptoporellus baudonii. This macrofungus leads to the wilting of cashew trees and cassava, which are the main cash crop and staple food respectively, in the region. To confirm the pathogenicity of P. baudonii, we employed Koch’s postulates. First, the fungal culture was isolated from P. baudonii basidiocarp and then inoculated into susceptible plant species including cashew trees (Anacardium occidentale) and eucalyptus (Eucalyptus tereticornis), under controlled environments. Direct inoculation of the fungal culture was done on both damaged and undamaged plants. Initially, the inoculated plants grew normally for the first 2 months, but later symptoms of abnormal growth started manifesting. These symptoms included leaf chlorosis, gum with different colors; and wilting. To confirm the presence of P. baudonii in the wilting plants and ascertain its identity, DNA obtained from the fungal fruiting body was sequenced and compared with the DNA sequence of the fungi isolated from infected plants. The compared sequences showed a sequence identity of 99.67% for Internal Transcribed Spacer (ITS) and 99.79% for Large Subunit (LSU), confirming that they are of the same species. This study revealed that P. baudonii is pathogenic to different plant hosts, specifically cashew and eucalyptus trees. Immediate mitigation measures are required to avoid further losses to farmers and safeguard forests.