Characterization of Neofabraea actinidiae and N. brasiliensis as causal agents of apple bull’s-eye rot in southern Brazil

Abstract

The causal agents of apple bull's-eye rot in southern Brazil have recently been described as Neofabraea actinidiae and N. brasiliensis. Isolates of both species were evaluated for response of mycelial growth index (MGI) to different temperatures, enzyme production, mycelial growth inhibition and effective concentrations (EC 50 and EC 100) of the fungicides triflumizole, pyrimethanil and thiophanate methyl, as well as aggressiveness on fruits of 'Fuji' hybrid and 'Pink Lady'. There was significantly lower mycelium growth in N. brasiliensis compared with N. actinidiae at all temperatures tested. Neither species grew at 3 and 32°C. There were minor differences in production of enzymes in the two species, with all N. brasiliensis isolates showing digitalcommons.unl.edu B o g o e t a l. i n C a n. J. P l a n t P a t h o l. , 2 0 1 8 2 no production of pectolyase at pH 7. The lowest EC 50 and EC 100 values were observed with thiophanate methyl. In general, 'Fuji' fruits were more susceptible to Neofabraea infection and had larger lesions, while N. brasiliensis isolates showed greater aggressiveness on 'Fuji' hybrid and 'Pink lady' fruits compared with N. actinidiae.

Review of the Impact of Apple Fruit Ripening, Texture and Chemical Contents on Genetically Determined Susceptibility to Storage Rots

“…The inoculated fruit is often kept at room temperature while infections develop. Lesions usually appear within a few days, and the damage can be scored within a week after inoculation, although slow-growing fungi like Neofabraea may require incubation for 15 days [ 39 ] or a whole month before symptoms have developed sufficiently [ 28 ]. In one approach, some fruits were wound-inoculated with Colletotrichum either at harvest or after three months of cold storage [ 30 ].…”

“…Similarly, small pieces of mycelia from N. alba have been inserted as plugs into fruit flesh, or placed in pockets under the skin of the fruit [40,45]. In a slightly modified version, fruit pulp plugs (5 × 3 mm) were extracted from detached fruit and replaced with equal-sized mycelial plugs of 21-day old Neofabraea cultures, covered by moist cotton and sealed with Parafilm [39]. Significant differences in lesion size were found among the inserted fungal isolates, but not between the two apple cultivars.…”

Morphological, Molecular, and Pathogenic Characterization of Neofabraea alba, a Postharvest Pathogen of Apple in Serbia

“…The effects of five culture media (MEA, PDA, TA, PCA (potato-carrot agar; 250 g potato, 200 g carrot, 17 g agar, 1 L of H 2 O)) and OA (oatmeal agar: 30 g oatmeal, 17 g agar, 1 L H 2 O)), eight temperatures (0, 5, 10, 15, 20, 25, 30, 35 • C) and nine pH levels (2,3,4,5,6,7,8,9,10) of MEA medium on the mycelial growth rate of representative isolates of each group were studied. The pH level of the MEA medium was adjusted with 0.1 M KOH and 0.1 M HCl (adjusted after sterilization of culture media).…”

“…), Neofabraea sp. nov. (anamorph: C. kienholzii Seifert, Spotts and Levesque), and two species recently described as apple pathogens Neofabraea actinidiae and Neofabraea brasiliensis [4]. N. alba has been identified in European countries such as Poland, the Czech Republic, Italy, the Netherlands, and Spain as a causal agent of Bull's eye rot [3,[5][6][7][8].…”

<i>Neofabraea actinidiae </i>in New Zealand kiwifruit orchards: current status and knowledge gaps

“…In vitro studies have shown the pathogen is highly susceptible (EC 50 <1 mg/L) to thiophanate methyl, pyrimethanil and triflumizole (Bogo et al 2018) but restrictions on the application of fungicides to fruit after flowering eliminates this as a management option in New Zealand kiwifruit.…”