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  • Author: Lassaâd Belbahri x
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Molecular detection of oomycetes species in water courses

Abstract

In Poland, about 20% of forest nurseries use irrigation water coming from natural superficial reservoirs, presumed to be the first source of infection caused by harmful pathogens belonging to the Oomycota class, especially Phytophthora genus and Pythium genus. The forest nursery is the only place where forest managers can react before pathogens leave it with asymptomatic plants or soil attached to their roots. The aim of this research was detection and identification phytopathogens in water samples. In order to recognise genus Phytophthora or Pythium in water collected from 33 places in five different forest districts in Poland, two DNA-based approaches of identification were applied: (i) the TaqMan probes, and (ii) sequencing of the ITS6/4 region.

The genomic DNA was obtained from 17 of 33 investigated water samples. TaqMan probes helped to identify 8 oomycetes present in 17 water samples. Based on ITS rDNA sequencing data, pathogens were identified in 17 cases, and this to the genus level (6 cases) and to the species level (11 cases). In total five Oomycetes species were identified, i.e. 3 Pythium species (Py. citrinum, Py. angustatum, Py. helicoides) and two Phytophthora species (P. lacustris sp. nov. - former taxon Salixsoil, P. gallica sp. nov.).

Open access
Molecular analysis of Phytophthora species found in Poland

Abstract

Pathogens of Phytophthora genus are common not only in forest nurseries and stands, but also in water courses. Species of Phytophthora spread with plants for plantings (and soil attached to them) and with water courses as well, attacking the plants growing in riparian ecosystems. Several specialized organisms damaging only one tree species were identified like P. alni on alders or P. quercina on oaks. Some Phytophthora species can develop on several hosts like P. plurivora and P. cactorum on oaks, beeches, alders, ashes and horse chestnuts. Other oomycetes like P. gallica species was found for the first time in Poland in water used for plant watering in forest nursery. Species P. lacustris and P. gonapodyides were found in superficial water. Phytophthora species P. polonica was identified in the declining alder stands for the first time in the world, and P. taxon hungarica and P. megasperma were found in the rhizosphere of seriously damaged ash stands for the first time in Poland. The most often isolated species were P. plurivora (clade 2) with frequency 37% and P. lacustris with frequency 33% (clade 6). The best represented clade 6 revealed the occurrence of 6 species: P. gonapodyides, P. lacustris, P. megasperma, P. sp. raspberry, P. taxon hungarica and P. taxon oak soil.

Open access
Four different Phytophthora species that are able to infect Scots pine seedlings in laboratory conditions

Abstract

To investigate susceptibility of young Scots pine seedlings to four Phytophthora species: Phytophthora cactorum, Phytophthora cambivora, Phytophthora plurivora and Phytophthora pini; seven-day-old seedlings of Scots pine (15 seedlings per experiment) were infected using agar plugs of the respective species. Control group also consisted of 15 seedlings and was inoculated with sterile agar plugs. Results unambiguously show that after 4.5 days, all seedlings show clear signs of infection and display severe symptoms of tissue damage and necrosis. Moreover, three and two seedlings in the P. cactorum and P. cambivora infected seedlings groups, respectively, collapsed. The length of largest necrosis measured 13.4±3.90 mm and was caused by P. cactorum. To rule out any putative contamination or infection by secondary pathogens, re-isolations of pathogens from infection sites were performed and were positive in 100% of plated pieces of infected seedlings. All re-isolations were, however, negative in the case of the control group. Detailed microscopic analyses of infected tissues of young seedlings confirmed the presence of numerous Phytophthora species inside and on the surface of infected seedlings. Therefore, our results suggest Phytophthora spp. and mainly P. cactorum and P. cambivora as aggressive pathogens of Scots pine seedlings and highlight a putative involvement of these species in the damping off of young Scots pine seedlings frequently observed in forest nurseries.

Open access