Exploring Anastomosis of Hyphae and Mating-Type Compatibility of Pochonia chlamydosporia Isolates of the Meloidogyne, Heterodera and Globodera Biotypes

The endophytic and nematophagous fungus Pochonia chlamydosporia is an efficient biological control agent of plant-parasitic nematodes. Isolates of the fungus can be allocated to a biotype group according to the nematode host, but it is unknown if genetic interchange can occur between different biotypes, which may affect their parasitic performance. An anastomosis assay was conducted in vitro to assess hyphae vegetative compatibility/incompatibility followed by a PCR-based mating-type assay genotyping of five isolates of P. chlamydosporia var. chlamydoporia of the Meloidogyne sp. (Pc10, Pc190, Pc309), Globodera sp. (Pc280) and Heterodera avenae (Pc60) biotypes, including 16 pairwise isolates combinations in four replicates. Pairwise combinations were tested on glass slides and mycelia were stained to confirm nuclei migration between anastomosing hyphae using fluorescence microscopy. Anastomosis only occurred between mycelium hyphae of the same isolate and biotype. Mating-type PCR-based molecular assays showed that all isolates were heterothallic. The MAT1-1 genotype was found in isolates Pc10, Pc190, Pc280, Pc309, and the MAT1-2 genotype in Pc60. The results showed a vegetative incompatibility among isolates, suggesting the occurrence of such interactions for their respective biotypes. Anastomosis and PCR mating-type results suggest that different fungal biotypes can occur in the same niche but that genetic incompatibility mechanisms, such as mating-type, may limit or impede viable heterokaryosi

Redescription of Cardiosporidium cionae (Van Gaver and Stephan, 1907) (Apicomplexa: Piroplasmida), a plasmodial parassite of ascidian haemocytes

Cardiosporidium cionae (Apicomplexa), from the ascidian Ciona intestinalis L., is redescribed with novel ultrastructural, phylogenetic and prevalence data. Ultrastructural analysis of specimens of C. intestinalis collected from the Gulf of Naples showed sporonts and plasmodia of C. cionae within the host pericardial body. Several merogonic stages and free merozoites were found in the pericardial body, together with sexual stages. All stages showed typical apicomplexan cell organelles, i.e. apicoplasts, rhoptries and subpellicular microtubules. Merogonic stages of C. cionae were also produced inside haemocytes. A fragment of the rSSU gene of C. cionae was amplified by PCR using DNA extracted from the pericardial bodies. The amplified product showed closest affinity with other apicomplexan representatives and a 66 bp unique insertion, specific for C. cionae, at position 1644. Neighbour-joining phylogenetic analysis placed C. cionae in a clade with other piroplasm genera, including Cytauxzoon, Babesia and Theileria spp. The parasite was found in different populations of C. intestinalis with highest prevalence in October–November. Ultrastructural and DNA data showed that the organism, described in 1907 from the same host but not illustrated in detail, is a member of a novel marine apicomplexan radiation of tunicate parasites

Sustainable strategies for management of the “false root-knot nematode” Nacobbus spp.

The genus Nacobbus, known as the false root-knot nematode, is native to the American continent and comprises polyphagous species adapted to a wide range of climatic conditions. Alone or in combination with other biotic and abiotic factors, Nacobbus spp. can cause significant economic yield losses on main food crops such as potato, sugar beet, tomato, pepper and bean, in South and North America. Although the genus distribution is restricted to the American continent, it has quarantine importance and is subject to international legislation to prevent its spread to other regions, such as the European Union. The management of Nacobbus spp. remains unsatisfactory due to the lack of information related to different aspects of its life cycle, survival stages in the soil and in plant material, a rapid and reliable diagnostic method for its detection and the insufficient source of resistant plant genotypes. Due to the high toxicity of chemical nematicides, the search for alternatives has been intensified. Therefore, this review reports findings on the application of environmentally benign treatments to manage Nacobbus spp. Biological control strategies, such as the use of different organisms (mainly bacteria, fungi and entomopathogenic nematodes) and other eco-compatible approaches (such as metabolites, essential oils, plant extracts, phytohormones and amendments), either alone or as part of a combined control strategy, are discussed. Knowledge of potential sources of resistance for genetic improvement for crops susceptible to Nacobbus spp. are also reported. The sustainable strategies outlined here offer immediate benefits, not only to counter the pathogen, but also as good alternatives to improve crop health and growth

Complete nucleotide sequence of Pelargonium zonate spot virus and its relationship with the family Bromoviridae

The complete sequence of the Pelargonium zonate spot virus (PZSV) genome was determined. It comprises 8477 nt, distributed in three positive-strand RNA species encoding four proteins. RNA-1 is 3383 nt long, with an ORF that encodes a polypeptide with a molecular mass of 108 419 Da (denoted protein 1a). This protein contains the conserved sequence motifs I-III of type I methyltransferases and the seven consensus motifs of the helicases of superfamily 1. RNA-2 is 2435 nt long and encodes a major polypeptide with a molecular mass of 78 944 Da (denoted protein 2a), which shows identity to the RNA-dependent RNA polymerases of positive-strand RNA viruses. RNA-3 is 2659 nt long and contains two major ORFs. The first ORF is located in the 5' portion of the genome and sequence comparison of the putative translation product revealed similarities with the 30K superfamily of virus movement proteins. The second ORF is located in the 3' half and encodes the viral coat protein, which is expressed via a subgenomic RNA, RNA-4. The transcription initiation site of RNA-4 maps to the intergenic region of RNA-3. The organization of the PZSV genome, including the primary structure of terminal non-coding regions, strongly suggests that this virus belongs to the family Bromoviridae. The overall biological and genomic characteristics of PZSV indicate affinities in diverging directions with one or other of the virus species in this family, thus enabling it to be considered as a possible representative of a new genus within the family Bromoviridae