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Robusta coffee (Coffea canephora) is of great economic importance to Uganda. However, its production is recently impeded by the ambrosia twig borer Xylosandrus compactus. A survey was conducted in 10 randomly selected districts in the main Robusta coffee-growing regions of mid-eastern, central and mid-western Uganda to determine (1) diversity, incidence and abundance of twig borers attacking C. canephora in Uganda and (2) ambrosia fungi associated with these twig borers. In each district, 10 randomly selected farms were inspected for twig borer species attacks. Up to 20 twigs infested by twig borers per farm were sampled and dissected to morphologically identify borer species inside the twigs and enumerate different stages of the borers per twig. Ambrosia fungi from galleries of each distinct twig borer were isolated and identified using molecular techniques. Five twig borer species, X. compactus, Xylosandrus sp., Hypothenemus sp. and two unidentified twig borers (K1 and K2), were found attacking C. canephora. Whereas the rest of these species were detected in only single coffee twigs from single farms, X. compactus occurred in nine of the 10 study districts. The proportion of X. compactus-infested farmsin each of these districts ranged from 0.1 to 1 and the number of X. compactus individuals per twig per district ranged from 2.5 ± 1.9 to 29 ± 28.1. Fusarium solani was isolated from galleries of both X. compactus and K1, whereas Glomerella cingulata was isolated from a gallery of K2. [ABSTRACT FROM AUTHOR]

Studies were conducted on fungi isolated from coffee trees affected by Fusarium xylarioides (Heim & Saccas) Steyaert to establish their pathogenicity and identify possible alternate hosts. Coffee and banana plant samples were collected from individual coffee farmers from the coffee growing districts of Mukono, Mpigi, Mubende, Kabarole and Kibaale. The studies were aimed at isolating the type of Fusarium species affecting coffee trees, identifying and characterizing them. Various Fusarium species were found associated with robusta coffee berries, stems and roots. These included Fusarium xylarioides, F. stilboides Wollen-webber & Reiking, F. solani (Mart.) Saccas, F. lateritium Nees, F.semitectum Berk & Rav, F. oxysporum Schlecht, F. moniliforme Sheldon and F. acuminatum Ell. & Ev. Also recovered from banana roots and pseudo-stem were F. xylarioides, F. oxysporum, F. solani, F. acuminatum and F. moniliforme. Fusarium xylarioides, F. oxysporum and F. solani were isolated most frequently from roots followed by stems and rarely on berries. Both F. stilboides and F. lateritium were next in abundance and were isolated mostly from berries. In culture, F. xylarioides isolates showed two types of colonies: one was soft, slimy and smooth, while the other was wrinkled. The two F. xylarioides isolates were not compatible. The five commonly isolated Fusarium species from robusta coffee produced symptoms on inoculated robusta coffee clones but F. xylarioides isolates induced the more severe symptoms, killing the greatest number of shoots. [ABSTRACT FROM AUTHOR]

Tracheomycosis or coffee wilt has emerged as a major disease of robusta coffee in Uganda in the past 10 years. Coffee wilt historically has been associated with Fusarium xylarioides Steyaert (teleomorph Gibberella xylarioides Heim and Sacc.), a species that has been classified as a member of Fusarium section Lateritium. We investigated the molecular phylogenetics of fusarial coffee wilt isolates by generating partial DNA sequences from two protein coding regions, translation elongation factor 1-alpha and beta-tubulin, in 36 isolates previously identified as F. xylarioides and related fusaria from coffee and other woody hosts, as well as from 12 isolates associated with a current coffee wilt outbreak in Uganda. These isolates fell into two morphologically and phylogenetically distinct groups. The first group was found to represent previously unidentified members of the Gibberella fujikuroi species complex (GFC), a clade that replaces the artificial Fusarium section Liseola. This group of isolates fit the original description of F. xylarioides, thus connecting it to the GFC. The second group, which was diverse in its morphology and DNA sequences, comprised four distinct lineages related to Fusarium lateritium. Our finding of unrelated species associated with coffee wilt disease has important implications regarding its epidemiology, etiology and control.