Host Specialization and Phylogenetic Diversity of Corynespora cassiicola

Abstract

The fungus Corynespora cassiicola is primarily found in the tropics and subtropics, and is widely diverse in substrate utilization and host association. Isolate characterization within C. cassiicola was undertaken to investigate how genetic diversity correlates with host specificity, growth rate, and geographic distribution. C. cassiicola isolates were collected from 68 different plant species in American Samoa, Brazil, Malaysia, and Micronesia, and Florida, Mississippi, and Tennessee within the United States. Phylogenetic analyses using four loci were performed with 143 Corynespora spp. isolates, including outgroup taxa obtained from culture collections: C. citricola, C. melongenae, C. olivacea, C. proliferata, C. sesamum, and C. smithii. Phylogenetic trees were congruent from the ribosomal DNA internal transcribed spacer region, two random hypervariable loci (caa5 and ga4), and the actin-encoding locus act1, indicating a lack of recombination within the species and asexual propagation. Fifty isolates were tested for pathogenicity on eight known C. cassiicola crop hosts: basil, bean, cowpea, cucumber, papaya, soybean, sweet potato, and tomato. Pathogenicity profiles ranged from one to four hosts, with cucumber appearing in 14 of the 16 profiles. Bootstrap analyses and Bayesian posterior probability values identified six statistically significant phylogenetic lineages. The six phylogenetic lineages correlated with host of origin, pathogenicity, and growth rate but not with geographic location. Common fungal genotypes were widely distributed geographically, indicating long-distance and global dispersal of clonal lineages. This research reveals an abundance of previously unrecognized genetic diversity within the species and provides evidence for host specialization on papaya.

Molecular Tools for Detection of Plant Pathogenic Fungi and Fungicide Resistance

“…Many authors have followed this multi-locus diagnostic strategy, e.g. Collado-Romero et al (2008) studied the evolutionary relationships among Verticillium dahliae vegetative compatibility groups by AFLP fingerprints and sequence analysis of actin, -tubulin, calmodulin, and histone 3 genes, the ITS region, and a V. dahliaespecific sequence; Dixon et al (2009) demonstrated the host specialisation and phylogenetic diversity of Corynespora cassiicola using the ITS region, actine gene and two random hypervariable loci; Glienke et al (2011) performed sequence analysis of the ITS region and partial TEF 1, actin and glyceraldehyde-3-phosphate dehydrogenase (GPDH) genes to study the genetic diversity of Phyllosticta spp. allowing differentiation of pathogenic and non pathogenic species and describing two new Phyllosticta species; Inderbitzin et al (2010) verified a high species diversity in Botryosphaeriaceae species performing phylogenetic analyses based on six loci, including the ITS region and TEF 1, GPDH, a heat shock protein, histone-3 and tubulin genes; Shimomoto et al (2011) used RAPDs and sequences from -tubulin, TEF 1 calmodulin and actin genes to detect pathogenic and genetic variation among isolates of Corynespora cassiicola.…”

First report of Corynespora cassiicola on Pueraria phaseoloides (tropical kudzu)

“…Corynespora cassiicola is a pantropical plant pathogen with a wide host range of more than a hundred hosts, including numerous legume species (Farr and Rossman 2015) and has many host-specific strains (Onesirosan et al 1974;Pereira et al 2003;Dixon et al 2009;Macedo et al 2013). This taxon is in need of a monographic work and may represent a complex of species instead of only one entity.…”

Caracterização de isolados de Corynespora cassiicola e avaliação da sensibilidade in vitro a fungicidas

“…Wei, o qual apresenta distribuição mundial, atacando uma ampla gama de hospedeiras, como hortaliças, espécies frutíferas, ornamentais e algumas plantas invasoras (Reis & Boiteux, 2007). Este fungo já foi encontrado parasitando folhas, flores, caules e raízes de vegetais (Dixon et al, 2009), cistos de nematoides (Carris & GLAWE, 1986), até mesmo causando doenças em humanos (Huang et al, 2010;Lv et al, 2011;Yamada et al, 2013). Quando isolado de materiais provenientes de plantas sintomáticas, este fungo é classificado como patogênico, porém, se for proveniente de material decomposto ou de tecido vivo assintomático, este é classificado como saprofítico e endofítico, respectivamente (Déon et al, 2014).…”

“…Em teste de patogenicidade realizado com isolado de C. cassiicola coletado de material em decomposição de mamão (Carica papaya), este foi patogênico ao tomate e ao pepino, porém não patogênico ao mamão, indicando que um único isolado pode ser patogênico e saprofítico (Dixon et al, 2009).…”

“…Com o aumento nos últimos anos do número de casos de mancha-alvo em diferentes culturas de interesse econômico no Brasil e a grande variabilidade de hospedeiras apresentado por esse patógeno, o agrupamento de isolados com base na hospedeira e na diferenciação morfológica dos isolados se torna problemático para predizer patogenicidade e parentesco genético (Dixon et al, 2009). Alguns isolados de C. cassiicola são patogênicos a uma grande diversidade de plantas hospedeiras, enquanto outros mostram-se específicos ao hospedeiro de origem.…”