Root‐lesion nematodes of potato: current status of diagnostics, pathogenicity and management

Root‐lesion nematodes of the genus Pratylenchus are migratory endoparasites with worldwide economic impact on several important crops including potato, where certain species like P. penetrans, P. neglectus and P. scribneri reduce the yield and quality of potato tubers. Morphological identification of Pratylenchus spp. is challenging, and recent advancements in molecular techniques provide robust and rapid diagnostics to differentiate species without need of specialist skills. However, the fact that molecular diagnostics are not available for all Pratylenchus species means that there are limitations in worldwide application. In general, root‐lesion nematodes are difficult to manage once introduced into agricultural land and damage can be related to pathogenicity and population densities. In addition, root‐lesion nematodes interact with fungi such as V. dahliae, resulting in disease complexes that enhance the damage inflicted on the potato crop. Management interventions are often focused on limiting nematode reproduction before planting crops and include the application of nematicides, and cultural practices such as crop rotation, cover crops, biofumigation, and biological control. Understanding the limitations of the available crop protection strategies is important and there are many gaps for further study. This review discusses the status of the diagnosis, distribution, pathogenicity and management of the main species of root‐lesion nematodes, reported to infect potatoes worldwide, and highlights areas for potential future research

Influencia de las condiciones edáficas, densidad de esporas y edad de los nematodos sobre la adherencia de Pasteuria penetrans a Meloidogyne incognita

Several soil variables as soil texture, moisture and temperature, Pasteuria penetrans spore densities and nematode age were tested in the laboratory for their effects on spore attachment to Meloidogyne incognita juveniles. Percentage of juveniles with endospores attached and number of spores per juvenile increased with concentration of spores applied to soil. In a clay-loam soil, hundred-percent attachments were reached at densities of 5 × 105 spores per g of soil and above. Attachment was greater in loamy-sand than in sandy-loam and clay-loam soils, but lower when soil moisture was under 10% than when it was over 25%. Numbers of juveniles with spores attached were greater when soil temperatures were 25 deg C and 35 deg C than at 15 deg C and lower in 7-30 days old juveniles than in 0-6 days old juveniles. All factors that favored nematode mobility in soil increased Pasteuria spore attachment to M. incognita juveniles.Se realizaron diversos ensayos en el laboratorio para analizar el efecto de variables edáficas como textura, humedad y temperatura del suelo, densidad de esporas de Pasteuria penetrans y la edad de los juveniles de M. incognita sobre la adherencia de las esporas a los juveniles de M. incognita. El porcentaje de juveniles con endosporas adheridas y el número de esporas por juvenil de M. incognita se incrementó con la concentración de esporas aplicadas al suelo. En un suelo arcillo-limoso se consiguieron porcentajes de adherencia del 100% cuando las densidades de esporas alcanzaron 5 × 105 esporas por g de suelo. La adherencia de esporas a los juveniles fue mayor en suelos más arenosos, y menor cuando la humedad del suelo estaba por debajo del 10%. El número de juveniles con esporas adheridas fue mayor a 25 grados C y 35 grados C que a 15 grados C y menor en juveniles de 7-30 días que en juveniles de 0 a 6 días de edad. Todos los factores que favorecen la movilidad de los juveniles de M. incognita en suelo incrementaron el porcentaje de juveniles con esporas adheridas y el numero de éstas por juvenil

Mononchida from Japan

The present paper deals with the description/record of 18 species, four new and 14 known, representingthe Order Mononchida from Japan. Clarkus enigmatus sp. n. has body 1.54-2.07 mm long, lip region wide and offset, buccal cavity slightly asymmetrical and 32-36 x 17-19 μm, large dorsal tooth with its apex at 84-87% of stoma length from base, subventral ridge slightly dentate at its proximal end, female genital system amphidelphic, echinulate eggs, and tail conical elongate and curved ventrad. Prionchulus japonicus sp. n. has body 1.58-1.84 mm long, lip region offset and wider than the adjoining body, buccal cavity 34-36 x 19-20 μm, dorsal tooth apex at 80-83% from base of buccal cavity, subventral ridges with 10-13 moderately developed denticles, amphids at level of the anterior end of the buccal cavity, pars refringens vaginae with three drop-shaped sclerotized pieces, uterine egg 117 x 74 μm, tail 104-128 μm long and curved ventrad with a dorsal depression near the terminus and sharply pointed tip. Mylonchulus monhystera sp. n. has body 1.08-1.14 mm long, lip region offset and distinctly wider than the adjoining body, buccal cavity 25- 28 x 15-16 μm, dorsal tooth large and claw-like with its apex at 80-84% from base of buccal cavity, subventral teeth well developed, ventrosublateral denticles arranged in 5 or 6 rows, female genital system mono-prodelphic with very small post-uterine sac, V = 70-75, tail 25-35 μm long, curved ventrad, and often with sudden narrowing near terminus giving a digitate appearance, and caudal glands well developed with terminal spinneret. Miconchus nipponi sp. n. has body 1.87-2.21 mm long, lip region offset by depression, amphid aperture at level with the middle of the praeparietale of buccal cavity, dorsal and subventral teeth similar in shape and size and located at 30-33% from base of stoma, female genital system amphidelphic, three well developed, blister-like vulval papillae present anterior and occasionally also posterior to vulva, spicules slightly curved ventrad and about 1.5 times the body diameter long, gubernaculum with its distal end appearing as two dorsally bent finger-like projections, lateral guiding pieces with bifid distal end, 11 well developed, regularly spaced ventromedian supplements, tail curved ventrad and gradually narrowing to a truncate extremity, and caudal glands grouped and with terminal spinneret. Mononchus truncatus, Clarkus papillatus, C. sheri, Prionchulus muscorum, P. punctatus, Coomansus parvus and Iotonchus parabasidontus are recorded for the first time from Japan. Additional morphometric data are also provided for Actus salvadoricus, Mylonchulus brachyurus, M. sigmaturus, M. oceanicus, Iotonchus arcuatus and Miconchus japonicus. And one specimen of an unknown species of Miconchus has also been described