Emergence of Prochloraz-Resistant Populations ofCalonectria pauciramosaandCalonectria polizziiin Ornamental Nurseries of Southern Italy

Abstract

Guarnaccia, V., Aiello, D., Polizzi, G., Perrone, G., Stea, G., and Vitale, A. 2014. Emergence of prochloraz-resistant populations of Calonectria pauciramosa and Calonectria polizzii in ornamental nurseries of southern Italy. Plant Dis. 98:344-350.Management of Calonectria spp. infections in nurseries requires scheduled fungicide applications, particularly with methyl benzimidazole carbamates (MBCs) and sterol demethylation inhibitors (DMIs). Due to rising concerns about the occurrence of MBC resistance in different Calonectria populations and variability in prochloraz efficacy in controlling these pathogens, a detailed study on prochloraz sensitivity distributions of Calonectria isolates belonging to the Calonectria scoparia complex was carried out. In total, 105 isolates collected in two distinct periods (1993 to 1996 and 2005 to 2009) were analyzed for prochloraz sensitivity. Based on DNA sequencing and phylogenetic analyses of ß-tubulin, histone H3, and translation elongation factor-la gene sequences, 69 and 36 isolates were identified as C. pauciramosa and C. polizzii. respectively. The isolates collected more recently (group B) had a reduced prochloraz sensitivity, as indicated by greater values for the effective dose to reduce growth by 50% than those collected earlier (group A). The reduced sensitivity detected in vitro corresponded to partial loss of fungicide efficacy in controlling infections in red clover and feijoa under controlled and semi-field conditions, respectively. Frequent prochloraz application in nurseries for controlling Calonectria spp. infections is discouraged.

Calonectria species isolated from Eucalyptus plantations and nurseries in South China

“…candelabrum complex include some important nursery pathogens ( Crous 2002 , Lombard et al . 2010b , d , Guarnaccia et al . 2014 , Alfenas et al .…”

New species, hyper-diversity and potential importance of Calonectria spp. from Eucalyptus in South China

“…Calonectria seminaria and C. tetraramosa were found together with C. microconidialis in the nursery sampled in this study. These species represent new members of the C. candelabra complex ( Schoch et al., 1999 , Lombard et al., 2015 ), which includes several well-known nursery pathogens ( Schoch et al., 1999 , Koike et al., 1999 , Polizzi and Crous, 1999 , Polizzi, 2000 , Koike and Crous, 2001 , Polizzi and Catara, 2001 , Polizzi and Vitale, 2001 , Crous, 2002 , Polizzi et al., 2006 , Polizzi et al., 2007 , Polizzi et al., 2009 , Vitale et al., 2009 , Lombard et al., 2010a , Lombard et al., 2010d , Vitale et al., 2013 , Guarnaccia et al., 2014 , Alfenas et al. 2015 ).…”

In vitro sensitivity testing of Cladobotryum mycophilum to carbendazim and prochloraz manganese

“…November/December 2015 in a practical resistance once the frequency of phenotypes prevents commercially acceptable disease control levels to be achieved under standard usage regimes. 23 The fact that resistance has developed in L. fungicola 21,24 and many other pathogens of field crops, [25][26][27] combined with the fact that most Cladobotryum spp. produce abundant conidia and have repeated infection cycles, may suggest that Cladobotryum spp.…”