Phylogeny, distribution and pathogenicity of Botryosphaeriaceae species associated with gummosis of Anacardium in Brazil, with a new species of Lasiodiplodia
Mariote S. B. Netto1, Waléria G. Lima1, Kamila C. Correia2, Christiana F. B. da Silva3, José R. Pacheco-Arjona4, Michael Thon4, Ricardo B. Martins5, Sami J. Michereff1, Marcos P. S. Câmara1*
1 Departamento de Agronomia, Universidade Federal Rural de Pernambuco, 52171-900 Recife, Pernambuco, Brazil
2 Centro de CiênciasAgrárias e da Biodiversidade, Universidade Federal doCariri, 63133-610 Crato, Ceará, Brazil
3 EmbrapaAgroindústria Tropical, 60511-110 Fortaleza, Ceará, Brazil
4 Centro Hispano Luso de InvestigacionesAgrarias (CIALE), Universidad de Salamanca, 37185 Villamayor, Spain
5 Campus Arapiraca, Universidade Federal de Alagoas, 57309-005 Arapiraca, Alagoas, Brazil
* Corresponding author: M. P. S. Câmara – e-mail: marcos.camara@ufrpe.br
Telephone number: +55 8133206209
Fax number: +55 8133206200
Abstract
In this study we identified and characterized Botryosphaeriaceae species associated with gummosis on Anacardiumin Brazil. A total of 138 isolates were sampled and identifications were made using a combination of morphology together with a phylogenetic analysis based on partial translation elongation factor 1-α sequence (EF-1α) and internal transcribed spacers (ITS). Ten taxa were identified, namely, Lasiodiplodiabrasiliense, L. euphorbicola, L. gonubiensis, L. iraniensis, L. jatrophicola,L. multiestriata sp. nov.,L. pseudotheobromae, L. theobromae, Neofusicoccumbatangarum and Pseudofusicoccumstromaticum. Only L. theobromae has previously been reported in cashews, while all the other species are reported for the first time in association with this host in Brazil and worldwide. Lasiodiplodiatheobromae was the most prevalent species. All species of Botryosphaeriaceae were pathogenic on detached green shoots of cashew. There were significant differences in virulence among the species, withNeofusicoccumbatangarum, L. iraniensis, L. jatrophicola and L. multiestriatabeing the most virulent species, while L. euphorbicola, L. pseudotheobromae were the least virulent.
Keywords
Cashew, EF1-α, ITS, Pathogenicity, Phylogeny, Virulence
Introduction
Cashew (Anacardiumoccidentale L.) is a tropical nut crop cultivated worldwide with a center of origin in the Amazonian forest of Brazil. Out of the eight species identified within the genus Anacardium, only cashew (A. occidentale) has economic importance, due to its edible hypocarp (apple) and nutritious kernel from the drupaceous nut (Aliyu 2012). The cashew nuts are highly valued as an export commodity, which is widely consumed in Europe and the USA. In 2013, Brazilian production of cashew nuts was 259,900 t and the cashew production area reached 708,430 ha. In this year, 12,165 t of cashew nuts were exported generating about US$ 79 million. The northeastern region is responsible for 99% of the Brazil’s cashew nut production (Agrianual 2015). The cashew industry accounts for the largest share of the northeastern Brazilian economy and is one of the main sources of income and labor in rural areas (Moreira et al. 2013).
Many diseases may compromise the production of cashew nuts. Gummosis caused by Lasiodiplodiatheobromae (Pat.) Griff. &Maubl. was first reported early in 1990 (Freire 1991) and soon became one of the most important disease of cashew in northeastern Brazil (Freire et al. 2002, Moreira et al. 2013). As a destructive disease, cashew gummosis has drawn the attention of research specialists for its potential adverse impact on the cashew industry (Cysne et al. 2010). Symptoms of gummosis include swollen cankers in the trunk or in woody branches, which may eventually crack and ooze a transparent resin-like gum, and branch dieback and blight of inflorescence (Freire et al. 2002). Damage from gummosis is caused by the reduction of water and nutrient transport, destruction of branches, reduction in photosynthesis, dieback, and plant death (Moreira et al. 2013).
Only L. theobromaehas been found associated with cashew gummosis (Freire et al. 2002, Cardoso et al. 2004, Muniz et al. 2012, Moreira et al. 2013). However, identification of causal agents were based primarily on morphological and cultural data, which is now considered to be unreliable for species discrimination inLasiodiplodia (Phillips et al. 2013).
Lasiodiplodia is a member of the Botryosphaeriaceae, a genus-rich family in the Dothideomycetes, containing numerous species found on a large variety of plant hosts as saprophytes, parasites and endophytes (Slippers and Wingfield 2007, Phillips et al. 2013). Besides cashew, several other crops of economic importance are affected by Botryosphaeriaceae species in Brazil, especially avocado (Perseaamericana Mill.), banana (Musa spp.), barbados cherry (Malpighiaglabra L.), cacao (Theobromae cacao L.), castor bean (Ricinuscommunis L.), citrus (Citrus spp.), coconut palm (Cocosnucifera L.), custard apple (Annonasquamosa L.), grapevine (Vitis spp.), guarana (PaulliniacupanaDucke), guava (Psidiumguajava L.), mango (Mangiferaindica L.), muskmelon (Cucumismelo L.), papaya (Carica papaya L.), passion fruit (Passifloraedulis Sims), physic nut (Jatrophacurcas L.), soursop (Annonamuricata L., ), table grape (Vitis spp.) and watermelon (Citrulluslanatus (Thunb.) Matsum. &Nakai) (Costa et al. 2010, Marques et al. 2013a, Machado et al. 2014, Netto et al. 2014, Correia et al. 2016). In addition to Lasiodplodia, other Botryosphaeriaceae have been reported to cause disease of plants in Brazil, such as Botryosphaeria, Fusicoccum, Macrophomina, Neofusicoccum, NeoscytalidiumandPseudofusicoccum (Marques et al. 2013b, Machado et al. 2014).
The taxonomy of species in the Botryosphaeriaceae is commonly based on the morphology of the anamorph states, which are most frequently encountered in nature. However, overlapping morphological characteristics has emphasized the utility of applying DNA sequence comparisons to resolve species (De Wet et al. 2008). The application of DNA sequence analysis and phylogenetic
inference has had a major impact on the systematics of the Botryosphaeriaceae(Phillips et al. 2013).
Despite the pathogenic importance attributed to Botryosphaeriaceae on several host plants, there are no phylogenetic studies of this family associated with cashew. The increasing economic importance of cashew gummosis and the recent discovery of several new species of Botryosphaeriaceae associated with tropical plants suggests that more than one species of this family may be associated with cashew gummosis in Brazil. The disease etiology is crucial for epidemiological studies and for a better understanding of the distribution and importance of individual species, as well as finding effective management strategies for each pathogen. Therefore, the objectives of this study were (a) to identify species of Botryosphaeriaceae associated with cashew gummosis, (b) to investigate the prevalence and distribution of the species in Brazil and (c) to evaluate their pathogenicity and virulence in excised green shoots of cashew.