The Multi-Resistant Reaction of Drought-Tolerant Coffee 'Conilon Clone 14' to Meloidogyne spp. and Late Hypersensitive-Like Response in Coffea canephora.

Root-knot nematodes (RKN), Meloidogyne spp., have major economic impact on coffee production in Central and South America. Genetic control of RKN constitutes an essential part for integrated pest management strategy. The objective of this study was to evaluate the resistance of Coffea canephora genotypes (clones) to Meloidogyne spp. Sensitive and drought-tolerant coffee genotypes were used to infer their resistance using nematode reproduction factor and histopathology. Eight clonal genotypes were highly resistant to M. paranaensis. 'Clone 14' (drought-tolerant) and 'ESN2010-04' were the only genotypes highly resistant and moderately resistant, respectively, to both M. incognita races 3 and 1. Several clones were highly resistant to both avirulent and virulent M. exigua. Clone 14 and ESN2010-04 showed multiple resistance to major RKNs tested. Roots of 'clone 14' (resistant) and 'clone 22' (susceptible) were histologically studied against infection by M. incognita race 3 and M. paranaensis. Reduction of juvenile (J2) penetration in clone 14 was first seen at 2 to 6 days after inoculation (DAI). Apparent early hypersensitive reaction (HR) was seen in root cortex between 4 and 6 DAI, which led to cell death and prevention of some nematode development. At 12 to 20 DAI, giant cells formed in the vascular cylinder, besides normal development into J3/J4. From 32 to 45 DAI, giant cells were completely degenerated. Late, intense HR and cell death were frequently observed around young females and giant cells reported for the first time in coffee pathosystem. These results provide rational bases for future studies, including prospection, characterization, and expression profiling of genomic loci involved in both drought tolerance and resistance to multiple RKN species.

Filling a gap in the taxonomy of phyllachoroid fungi: Proposition of Neopolystigma, gen. nov., and the new family Neopolystigmataceae.

A Polystigma-like found on an herbaceous to shrubby species of Fabaceae (Andira humilis) in the Brazilian Cerrado was morphologically close to Polystigma pusillum, a leaf parasite on Andira inermis collected in Central America and Brazil. Phylogenetic analyses using a combination of the rDNA 28S, 18S, and internal transcribed spacer (ITS) regions placed both fungi in the Phyllachorales, and not in Polystigamataceae/Xylariales, where Polystigma species belong, and characteristically found on members of the Rosaceae, causing red leaf blotch containing bright-colored fungal stromata spread on the lesions. This disease prevails in orchards in the Northern Hemisphere, infecting Amygdalus, Cerasus, Padus, and Prunus species, but never in the Tropics. Polystigma species infecting other botanical families have been reallocated in different families, orders, and even classes in Ascomycota. In our phylogenetic analyses, the two species on Andira were allocated in Phyllachorales but separated in a well-supported cluster from Phyllachoraceae and Phaeochoraceae. In relation to Telimenaceae, the statistical support is not strong; however, considering that its type genus, Telimena, was never sequenced, we choose to accept Neopolystigma (type N. saraivae) as the type genus of a new family, Neopolystigmataceae. The sister species of N. saraivae, Polystigma pusillum found on A. inermis, was recombined into N. pusillum.

Native-plant hosts of Meloidogyne spp. from Western Paraná, Brazil

The present study was focused on the parasitism of Meloidogyne species on the roots of native nursery plants from the Atlantic forest. Native plants were selected from a commercial nursery in Western Paraná, searching for the natural infection of Meloidogyne. Also, the seeds of native plants were cultivated in sterile soil and inoculated with M. incognita. In both the experiments, the number of galls and number of eggs and J2 per root, allied to the reproduction factor of M. incognita on each inoculated plant were assessed. Natural infection by M. javanica was found on Cordia ecalyculata, Citharexyllum myrianthum and Aspidosperma subincanum and by M. incognita on Croton urucurana, Lonchocarpus muehlbergianus, Tabebuia impetiginosa and T. serratifolia. Meloidogyne incognita induced galls formation on Genipa americana, Schinus terebinthifolius and Rollinia mucosa after inoculation, which suggested that those plants could host this nematode in natural biomes. Nursery soil should be disinfested before seeding the native forest plants for reforestation purposes.

Characterization of a chorismate mutase from the potato cyst nematode Globodera pallida.

SUMMARY Some plant endoparasitic nematodes are biotrophic and induce remarkable changes in their hosts in order to ensure a continuous supply of food. Proteins secreted from oesophageal gland cells have been implicated in this pathogenic process. A potentially secreted chorismate mutase has been isolated from the potato cyst nematode Globodera pallida. The gene encoding this protein is expressed in the subventral oesophageal gland cells of the nematode, and the mRNA derived from this gene is only present in the early parasitic stages. Sequence analysis of this gene shows that, like other genes involved in the host-parasite interaction of plant parasitic nematodes, it is likely to have been acquired by horizontal gene transfer from bacteria. The presence of a signal peptide in the deduced amino acid sequence of the G. pallida chorismate mutase and its expression in the subventral oesophageal gland cells suggest that it is secreted from the nematode, pointing to a role for the protein in the host-parasite interaction. The shikimate pathway, of which chorismate mutase is normally a part, is not found in animals but is present in plants and bacteria. In plants it gives rise to a variety of compounds which are important in amino acid synthesis and defence signalling pathways, as well as auxins, which have been implicated in the early development of nematode feeding sites. The potential roles of a nematode chorismate mutase are discussed.