Identification of Botryosphaeriaceae species that cause stylar-end rot of guavas and characterisation of the disease monocycle

Guava (Psidium guajava L.) stylar-end rot is a serious postharvest disease of guavas in Brazil. The objective of this study was to identify the primary species of Botryosphaeriaceae that cause guava stylar-end rot and to evaluate the temperature and wetness conditions that are favourable for development of the disease monocycle of these pathogens in detached fruit. Morphological and phylogenetic analyses were performed for 56 monosporic isolates from Brazil. The species Botryosphaeria dothidea, Neofusicoccum parvum and Neofusicoccum ribis were identified as causal agents of the disease. Conidial germination of the three species was evaluated at various temperatures and wetness periods. Guava fruit were inoculated with a conidial suspension of each species. The inoculated fruit were maintained under various temperatures and wetness periods. The optimal temperatures for conidial germination were between 25 and 35 A degrees C for each of these three species. At 30 A degrees C, high germination rates were observed for the three species (70 %) under wetness periods longer than 6 h. The range of optimum temperatures for guava colonisation by the three species was 28 to 31 A degrees C. However, the maximum diameter of the lesion was always smaller during the wetness period of 6 h compared to 48 h. The shortest incubation period of the disease was three days at 30 A degrees C and was associated with the 48-h wetness period for the three species. The best conditions for disease development were high temperatures and prolonged periods of wetness. This report is the first to describe the association of N. parvum and N. ribis with guava fruits in Brazil.