Effects of temperature and wetness period on Cerotelium fici germination and mulberry rust progress

• Grant number: 23/13515-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2023
• End date: November 30, 2024
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Lilian Amorim
• Grantee: Pedro Catão Guimarães
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Mulberry rust, caused by Cerotelium fici, was recently detected on Morus nigra in Brazil. The host is an important crop for silk industry, as mulberry leaves are the only natural food for silkworm (Bombyx mori). Rust poses an important threat to Brazilian sericulture because the disease can reduce the production and quality of mulberry leaves. However, the epidemiological aspects of the disease in Brazil are poorly understood. The objective of this research will be to quantify the pathogen germination in vitro and ex vivo, and to determine the monocyclic components of mulberry rust in vivo under different environmental conditions. The in vitro experiments will be performed in Petri dishes, containing water-agar media, in which C. fici urediniospores suspensions will be deposited and incubated for 2, 4, 6, 12, and 24 h under the temperatures of 5, 10, 15, 20, 25, 30, and 35°C. For the ex vivo experiments, detached mulberry leaves will be inoculated with C. fici suspensions and incubated in a humid chamber at 20, 25, and 30°C for 6 and 12 h. The pathogen germination in growth media and in detached leaves will be evaluated, respectively, with a light microscope and a scanning electron microscope. The in vivo experiments will be carried out with mulberry potted plants inoculated with suspensions of C. fici and incubated under the same conditions as the ex vivo experiments. The rust monocyclic components density of lesions (number of sporulating lesions per cm2), incubation period (time interval from inoculation until the appearance of 50% of total symptoms), latent period (time interval from inoculation until the appearance of 50% of total sporulating lesions), disease severity (proportion of diseased area) and lesion size (mm2) will be evaluated. The results of this research will help to understand the temporal disease progress and to predict the climate risk for its occurrence in different mulberry producing regions in Brazil.