Diversity of Botryosphaeriaceae species associated with canker and dieback of avocado (Persea americana) in Italy
From Firenze University Press Journal: Phytopathologia Mediterranea
Alberto FIORENZA, Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania
Giorgio GUSELLA, Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania
Laura VECCHIO, Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania
Dalia AIELLO, Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania
Giancarlo POLIZZI, Dipartimento di Agricoltura, Alimentazione e Ambiente, University of Catania
Avocado (Persea americana L.) is a tree native to Mexico and has spread to many tropical and subtropical regions (Bost et al., 2013). Consumption of avocado fruit and new plantings of avocados has considerably increased (Bost et al., 2013). The greatest production is in Mexico, followed by Colombia and the Dominican Republic (FAOSTAT, 2022). In Europe, Spain was the first country to develop commercial production of avocados (Pérez-Jiménez, 2008). In Italy, avocado production is spread in the Southern regions, mainly in Sicily, where the cultivated area has increased in the last 10 years (Migliore et al., 2017). In Sicily, avocado provides good agricultural diversification as an alternative crop to citrus (Guarnaccia et al., 2016).Several diseases can affect avocados, and several fungi taxa have been associated with different symp-toms. Traditionally, root diseases have been considered the most important limiting factors for avocado production. Among these, those caused by Phytophthora cinnamomi and Rosellinia necatrix are considered the most important and widespread diseases of avocado, leading to serious losses, especially in the Mediterranean regions where avocado production is well established (Zentmyer, 1980; López-HerreraandMelero-Vara, 1992; Fiorenza et al., 2021). In recent years, species of Nectriaceae have also been shown to be important, especially in Australia where different taxa have been associated with crown root rot disease (Parkinson et al., 2017). In Italy, recent studies have shown the presence of Nectriaceae spp. causing a complex of root symptoms (Vitale et al., 2012; Aiello et al., 2020b).In recent decades, increased research has been carried out on canker diseases of fruit and nut crops (Moral et al., 2019; Guarnaccia et al., 2022a).
These diseases have been re-discovered as important and limiting for perennial crops, especially because they cause polyetic epidemics, a complex of pathogen taxa are involved, and most of the causal agents are polyphagous and live as latent pathogens. Among the taxa associated and respon-sible for shoot, branch and trunk cankers and dieback, Botryosphaeriaceae is a widely investigated group of fungi (Batista et al., 2021). Botryosphaeriaceae includes fungi that can be pathogens, saprobes and endophytes (Slippers and Wingfield, 2007; Phillips et al., 2013), and can be severe threats to fruit, nut, ornamental and forest trees (Slippers and Wingfield, 2007; Moral et al., 2019). DNA-based tools, especially multi-locus phylogeny, have shown that many genera and species within the Botryosphaeriales have been described, synonymized, and reaccommodated (Zhang et al., 2021). On avocado, despite sporadic reports of Diaporthespecies associated with cankered tissues (Guarnac-cia et al., 2016; Torres et al., 2016; Mathioudakis et al., 2020), different Botryosphaeriaceae have been extensive-ly reported worldwide causing canker and dieback on woody tissues and fruit rots, including: Botryosphaeria dothidea, Diplodia aromatica, D. dominicana, D. mutila, D. pseudoseriata, D. seriata, Dothiorella iberica, Lasi-odiplodia laeliocattleyae, L. pseudotheobromae,L. theo-bromae, Neofusicoccum australe, N. luteum, N. mangifer-ae, N. mediterraneum,N. nonquaesitum, N. parvum, and N. stellenboschiana (Peterson, 1978; Hartill, 1991; Har-till and Everett, 2002; Zea-Bonilla et al., 2007; McDon-ald et al., 2009; Ni et al., 2009; McDonald and Eskalen, 2011; Ni et al., 2011; Dann et al., 2013; Auger et al., 2013; Tw i z e y i m a n a et al., 2013; Carrillo et al., 2016; Valencia et al., 2019; Arjona-Girona et al., 2019; Tapia et al., 2020; Guarnaccia et al., 2020; Wanjiku et al., 2020; Qiu et al., 2020; Rodríguez-Gálvez et al., 2021; Avenot et al., 2022).
On avocado, canker and dieback symptoms can appear on shoots, branches, and trunks. Usually, reddish sap that became white/beige with the age has been associ-ated with cankers. The tree bark can be friable or sunken and necrotic, showing cracking, with external dark dis-colouration. Internally, infected wood becomes brown with characteristic wedge-shaped discolourations affect-ing the xylem. Under high disease pressure, severe xylem colonization may be observed, with associated wilting of shoots and leaves, that remain attached.In Italy, the first investigations of avocado branch and trunk canker were reported in 2016, showing the presence of Botryosphaeriaceae (N. parvum), Diaporthaceae (D. foeniculacea and D. sterilis)and Glomerellaceae (Colletotrichum gloeosporioides and C. fructicola) (Guarnaccia et al., 2016). Studies on avocado can-ker diseases in Italy have continued, and in 2018, a new species Neocosmospora persea was described, causing branch and trunk canker, which was also later reported in Greece (Guarnaccia et al., 2018, 2022b). More recently, the new species Neopestalotiopsis siciliana and Ne. rosaewere reported as causing stem lesions and dieback on avocado (Fiorenza et al., 2021). An increased incidence of shoot and branch canker has been observed in Sicilian avocado orchards since 2016. The present study has investigated the diversity of Botryosphaeriaceae associated with symptomatic trees. The aims of the study were: (i) to characterize the Botryosphaeriaceae recovered from symptomatic avocado samples, and (ii) to test their pathogenicity to this host.
DOI: https://doi.org/10.36253/phyto-14057
Read Full Text: https://oajournals.fupress.net/index.php/pm/article/view/14057
