Location: Tropical Crops and Germplasm Research
Project Number: 6090-21000-061-001-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2023
End Date: Oct 1, 2025
Objective:
Coffee fruit rot (CFR) is the one of the most important diseases affecting coffee worldwide. It is attributed to the genus Colletotrichum and is characterized by external necrosis and sunken dark brown spots on green or mature coffee fruits that eventually become mummified. However, recent work by ARS and UPR scientists in Puerto Rico shows that species of the fungus Fusarium in association with the coffee berry borer (insect) are also causing CFR in Puerto Rico. In 2021 coffee fruit rot reached epiphytotic levels in Puerto Rico, and in 2022 it was serious in some areas. According to extension agents, this disease caused coffee crop losses never seen before. The problem was dramatic enough to become front-page news in Puerto Rico. The CFR problem is aggravated because Limaní, one of the most commonly used coffee varieties in Puerto Rico because it is tolerant to coffee leaf rust, is susceptible to CFR. This project has two objectives: 1) Evaluate CFR progress in the field and its relationship with environmental variables in different coffee varieties planted in Puerto Rico and; 2) Test susceptibility of commercial coffee varieties in Puerto Rico and fifteen coffee varieties (IMLVT) from World Coffee Research under consideration for planting in Hawaii, using inoculations with coffee fruit pathogens in the laboratory.
Approach:
Objective 1: Evaluate CFR progress in the field and its relationship with environmental variables in different coffee varieties planted in Puerto Rico.
Coffee varieties Limaní and Frontón will be tested for incidence and severity of CFR throughout the coffee-growing area in farms in Puerto Rico. Disease incidence will be evaluated through time at site level, plant level and branch level. For site level, presence or absence of CFR on 30 randomly-selected trees will be evaluated. For plant level, 10 trees per variety and three branches per tree (from top, middle and bottom) will be evaluated. Fruits with and without rot from each branch will be counted to determine disease incidence at branch level. For fruit disease severity, 30 randomly selected fruits per variety will be evaluated for external and internal rot using a visual scale from 0-100%. Data will be taken every three weeks from July to November, when fruits are developing. As well as coffee variety, elevation and precipitation will be tested for association with CFR.
Objective 2: Inoculate coffee fruit pathogens in the laboratory on fifteen coffee varieties (IMLVT) from World Coffee Research.
Representative isolates of Colletotrichum spp. and Fusarium spp. will be inoculated on green coffee fruits of 15 IMLVT coffee varieties from the World Coffee Research organization. Suspensions of conidia of Colletotrichum spp. and Fusarium spp. will be inoculated on three branches with at least 30 green coffee fruits per branch of each variety. Procedures of disinfection and inoculation will follow those of Serrato-Diaz et al. (2020). Colletotrichum and Fusarium isolates recovered from pathogenicity tests will be identified using morphological parameters such as color of colony, size and shape of the conidia, asci and ascospores, if present. Pathogenicity will be tested using Koch's postulates.
