Identification and pathogenicity assessment of Colletotrichum isolates causing bitter rot of apple fruit in Belgium

Abstract

Worldwide Colletotrichum spp. have been identified as a problem in the apple production. This is the first study executed and confirming the presence of Colletotrichum spp. causing the postharvest disease bitter rot on apple fruits in Belgium. The identification, genetic diversity of Colletotrichum isolates (present in Belgian apple orchards) their morphological traits and pathogenicity on two apple cultivars (cvs. Pinova and Nicoter) with a different level of susceptibility were studied. Based on sequence analysis of six different gene regions beta-tubuline (TUB2), histone H3 (HIS3), glyceraldehyde-3phosphate dehydrogenase (GAPDH), chitin synthase 1 gene (CHS-1), actin (ACT) and the Internal Transcriber Spacer (ITS) gene region, six different Colletotrichum spp., belonging to either the C. acutatum or C. gloeosporioides complexes, were isolated from twenty-one apple cultivars in three Belgian orchards: C. fioriniae, probably C. kahawae, C. salicis, C. rhombiforme, C. acutatum and C. godetiae. Colletotrichum godetiae was found to be the most present and pathogenic species in Belgian orchards. The species C. rhombiforme was found and identified on apple fruit for the first time. Reliable morphological discrimination between species, based on features such as in vitro growth rate, colony colour and spore measurements, is not possible. As such, molecular identification appears to outperform morphological analysis and was in this study the most ideal tool for identifying unknown isolates of Colletotrichum species. Inoculation assays on two apple cultivars revealed a significant difference in pathogenicity among isolates and among Colletotrichum species. The pathogenicity tests also showed that isolates coming from another host species, e.g. strawberry, are also pathogenic on apple fruits. Cultivar Pinova appeared to be more susceptible to bitter rot than cv. Nicoter. Given the difficulties with managing Colletotrichum infections, additional knowledge on the pathogen and the plant-pathogen interaction is essential for effective disease control.

Latent postharvest pathogens of pome fruit and their management: from single measures to a systems intervention approach

“…is a widespread fruit disease occurring in most countries where apples are cultivated (Shi et al 1996). C. acutatum species complex (SC) infections on apples in Europe are frequently reported with increasing numbers of recent reports from Belgium, England, Italy, France, Norway and Slovenia (Børve and Stensvand 2015;Grammen et al 2019;Mari et al 2012;Munda 2014;Munir et al 2016;Nodet et al 2016). Studies from Germany and Sweden describe postharvest losses of apple fruits of 10 and 25%, respectively, by C. acutatum SC (Børve and Stensvand 2017;Weber and Palm 2010).…”

“…(Blazek et al 2007;Hortova et al 2014;Soto-Alvear et al 2013) and for Colletotrichum spp. (Biggs and Miller 2001;Grammen et al 2019). Unravelling resistance mechanisms in fruits can be very helpful to make progress in breeding programs.…”

Pathological, Morphological, Cytogenomic, Biochemical and Molecular Data Support the Distinction between Colletotrichum cigarro comb. et stat. nov. and Colletotrichum kahawae

“…The CBD pathogen was placed along with non-CBD causing isolates into two subspecies within C. kahawae. This taxonomic framework led, in recent years, to the identification of "C. kahawae" (no subspecies given) in other hosts and regions [32][33][34][35], raising concern among plant pathologists dealing with coffee diseases, especially when the spread of C. kahawae out of Africa is so feared [13].…”

Fungal pathogens in pome fruit orchards and causal agents of postharvest decay

“…is a widespread fruit disease occurring in most countries where apples are cultivated (Shi et al, 1996). C. acutatum species complex (SC) infections on apples in Europe are frequently reported with increasing numbers of recent reports from Italy, Belgium, Slovenia, England, Norway and France (Børve and Stensvand, 2015;Grammen et al, 2018;Mari et al, 2012;Munir et al, 2016;Nodet et al, 2016). Studies from Germany and Sweden describe postharvest losses of apple fruits of 10 and 25%, respectively, by C. acutatum SC (Børve and Stensvand, 2017;Weber and Palm, 2010).…”

“…Fruit cultivars may show a large variation in susceptibility to (latent) postharvest diseases (Tian et al, 2016), as was demonstrated among apple cultivars for Colletotrichum spp. (Biggs and Miller, 2001;Grammen et al, 2018) and bull's eye rot caused by Neofabraea spp. (Blazek et al, 2003;Hortova et al, 2014;.…”