Distribution and Fungicide Sensitivity of Colletotrichum Species Complexes from Rubber Tree in Hainan, China

Abstract

Colletotrichum gloeosporioides and C. acutatum species complexes are causal agents of Colletotrichum leaf disease (CLD) of rubber trees worldwide. To determine the geographic distribution of Colletotrichum species complexes associated with CLD of rubber trees in Hainan, China, and their sensitivity to fungicides used in the region, a total of 275 Colletotrichum isolates were collected from 52 rubber tree plantations in 11 counties. These isolates were identified based jointly on morphological characteristics and PCR-based methodology. Of these isolates, 78 and 22% belonged to the C. gloeosporioides species complex (CGSC) and the C. acutatum complex (CASC), respectively. The incidence of CGSC isolates was greater than the CASC in all counties sampled. The incidence of CASC isolates appeared to be lower in the western and central south of Hainan than in other regions. There was no association in their presence at a given plantation between the two species complexes. The in vitro sensitivity of these two species complexes to carbendazim, chlorothalonil, and four demethylation inhibitor (DMI) fungicides (difenoconazole, propiconazole, myclobutanil, and prochloraz) was determined. Carbendazim was effective against CGSC but not against CASC with mean ED50 values of 0.176 and 2.182 µg/ml, respectively. CASC isolates were more sensitive to difenoconazole, propiconazole, and myclobutanil (mean ED50 values of 0.177, 0.129, and 1.424 µg/ml, respectively) than CGSC isolates (mean ED50 values of 0.710, 0.348, and 3.496 µg/ml, respectively). Mean ED50 values of CGSC against chlorothalonil and prochloraz were 173.341 and 0.035 µg/ml, respectively; corresponding values for CASC were 151.441 and 0.040 µg/ml. These results suggest that prochloraz, propiconazole, and difenoconazole are effective against both species complexes.

Characteristics and distribution of Colletotrichum species in coffee plantations in Hainan, China

“…A recent study also indicated that the C . gloeosporioides species complex is the dominant species complex in rubber tree in Hainan (Cao et al ., ). The compositions of Colletotrichum species differ in different regions and coffee varieties, and a large‐scale survey is needed to confirm this differential distribution.…”

“…Responses to common commercial fungicides vary among Colletotrichum species (Cao et al ., ). The present results confirmed this variable sensitivity to fungicides among Colletotrichum isolates.…”

“…These results are consistent with the fungicide sensitivity of isolates in the C . gloeosporioides complex from rubber tree in Hainan (Cao et al ., ).…”

“…Fungal sensitivity was represented by ED 50 values, namely concentrations at which mycelial growth is inhibited by 50%. ED 50 was estimated for each isolate and fungicide combination in regression analysis where the percentage of mycelial growth inhibition was regressed against the log 10 of fungicide concentrations (Cao et al ., ). The experiment was repeated once.…”

Selection Pressure Pathways and Mechanisms of Resistance to the Demethylation Inhibitor-Difenoconazole in Penicillium expansum

“…High control efficacy of DIF has been reported in several ascomycetes such as Phacidiopycnis spp., Venturia inaequalis, Colletotrichum spp., Marssonina coronaria, Alternaria spp., and Fusarium spp. ( Munkvold and O’Mara, 2002 ; Villani et al, 2015 ; Fonseka and Gudmestad, 2016 ; Cao et al, 2017 ; Dang et al, 2017 ; Ali et al, 2018 ) and the basidiomycete Rhizoctonia solani ( Bartholomäus et al, 2017 ). Given the widespread occurrence of resistance to two of the three current postharvest fungicides and the stringent limitations to new postharvest fungicides registration, DIF could be a valuable additional tool to manage blue mold of pome fruit in the years to come if used appropriately and if its efficacy against other major postharvest diseases is proven.…”