A new mechanism for reduced sensitivity to demethylation‐inhibitor fungicides in the fungal banana black Sigatoka pathogen Pseudocercospora fijiensis

Abstract

The Dothideomycete Pseudocercospora fijiensis, previously Mycosphaerella fijiensis, is the causal agent of black Sigatoka, one of the most destructive diseases of bananas and plantains. Disease management depends on fungicide applications, with a major contribution from sterol demethylation-inhibitors (DMIs). The continued use of DMIs places considerable selection pressure on natural P. fijiensis populations, enabling the selection of novel genotypes with reduced sensitivity. The hitherto explanatory mechanism for this reduced sensitivity was the presence of non-synonymous point mutations in the target gene Pfcyp51, encoding the sterol 14α-demethylase enzyme. Here, we demonstrate a second mechanism involved in DMI sensitivity of P. fijiensis. We identified a 19-bp element in the wild-type (wt) Pfcyp51 promoter that concatenates in strains with reduced DMI sensitivity. A polymerase chain reaction (PCR) assay identified up to six Pfcyp51 promoter repeats in four field populations of P. fijiensis in Costa Rica. We used transformation experiments to swap the wt promoter of a sensitive field isolate with a promoter from a strain with reduced DMI sensitivity that comprised multiple insertions. Comparative in vivo phenotyping showed a functional and proportional up-regulation of Pfcyp51, which consequently decreased DMI sensitivity. Our data demonstrate that point mutations in the Pfcyp51 coding domain, as well as promoter inserts, contribute to the reduced DMI sensitivity of P. fijiensis. These results provide new insights into the importance of the appropriate use of DMIs and the need for the discovery of new molecules for black Sigatoka management.

Induced expression of CYP51 associated with difenoconazole resistance in the pathogenic Alternaria sect. on potato in China

“…Constitutive over-expression may be caused by insertions in its promoter region, for example additional promoters in M. fructicola, 33,34 transcriptional enhancers in Venturia inaequalis and Penicillium digitatum [35][36][37] and repeated sequences in Pseudocercospora fijiensis. 38 However, some studies found constitutive over-expression but no insertion in its upstream region. 39,40 In our study, we observed that induced expression of CYP51 was associated with DMI resistance in all resistant isolates with two genotypes.…”

New Geographical Insights of the Latest Expansion of Fusarium oxysporum f.sp. cubense Tropical Race 4 Into the Greater Mekong Subregion

“…This replacement has been highly successful to quench the Fusarium wilt epidemic that was caused by Foc Race 1 strains. Since then, “Cavendish” production expanded into large global monocultures, which are evidently prone to disease threats, including black Sigatoka and Panama disease (Ordoñez et al, 2015b ; Arango Isaza et al, 2016 ; Diaz-Trujillo et al, 2018 ). However, this has not resulted in global research efforts to neutralize these problems.…”

Functional genetics and genomics of the banana black Sigatoka pathogen Pseudocercospora fijiensis

“…Banana is one of these crops, albeit a major staple food for millions of people and despite its status as the top global fruit (FAO, 2015). Disease control is mostly accomplished by extensive fungicide applications due to the vulnerability of the global Cavendish banana monoculture (Diaz-Trujillo et al, 2018). Here, we report the first Agrobacterium-mediated transformation of P. fijiensis, which is an important step to aid mining the genome of this major plant pathogen .…”

“…We disrupted Pfavr4, the first effector described in this pathogen, as a starting point to further unravel the banana -P. fijiensis interaction . Recently, we also engineered P. fijiensis strains with modification of Pfcyp51 promoters, to identify a new mechanism of fungicide sensitivity (Diaz-Trujillo et al, 2018).…”

“…A growth reduction was observed in the Pfku70 strains and its function should be accessed in further studies. This was not due to the transformation process since other generated knock-out strains were not affected in fitness and so these were used as a basis for swapping promoter domains of the Pfcyp51 gene (Diaz-Trujillo et al, 2018). In Penicillium chrysogenum, Hoff (2010) showed that genes related to stress response were upregulated in ku70 disruptant strains.…”