A new hybrid of Phytophthora from Southeast Europe.

During an investigation of rivers in Bulgaria, an isolate of Phytophthora (RLKam2016/61c) was recovered and initially identified as Phytophthora sansomeana based on internal transcribed spacer region (ITS) sequence data. However, the sequencing of the mitochondrial cytochrome c oxidase subunit I (cox1) gene revealed high similarity to Phytophthora sp. kelmania, and sequencing of other nuclear regions (ß-tubulin [Btub] and translation elongation factor 1-alpha [tef1]) revealed a significant number of polymorphisms, indicating a possible hybridization event. Additional cloning and sequencing of the nuclear ITS and Btub regions showed the presence of two distinct groups of alleles, one of which was highly similar to P. sansomeana, whereas the other was similar to a species complex that includes Phytophthora sp. kelmania. Therefore, the new hybrid was named Phytophthora × sansomeana. It is characterized by fast growth on V8 juice agar (V8A) and carrot agar (CA), moderate aerial mycelium with radiate pattern of the colonies and relatively slower growth rate on malt extract agar (MEA) and potato dextrose agar (PDA), and petaloid to rosaceous pattern of the colonies with fluffy aerial mycelium. The optimum growth temperature for P. × sansomeana was at 25 C, with an average growth rate of 9 mm per day. Abundant sporangium formation of the isolate in spring water was observed, but the hybrid was sterile in culture. Pathogenicity analyses of the hybrid were conducted in comparison with the most closely related subclade 8a species from our collection, P. pseudocryptogea. The inhibition effect on the root growth of young seedlings of two legumes, common pea and vetch, as well as on cuttings of the ornamental plant coleus induced by both phytopathogens was significant. No effect of either the new hybrid or P. pseudocryptogea on the growth of maize seedlings was observed.

Invasive forest pathogens in Europe: Cross-country variation in public awareness but consistency in policy acceptability.

Political action can reduce introductions of diseases caused by invasive forest pathogens (IPs) and public support is important for effective prevention. The public's awareness of IP problems and the acceptability of policies aiming to combat these pathogens were surveyed in nine European countries (N = 3469). Although awareness of specific diseases (e.g., ash dieback) varied, problem awareness and policy acceptability were similar across countries. The public was positive towards policies for informational measures and stricter standards for plant production, but less positive towards restricting public access to protected areas. Multilevel models, including individual and country level variables, revealed that media exposure was positively associated with awareness of IP problems, and strengthened the link between problem awareness and policy acceptability. Results suggest that learning about IPs through the media and recognizing the associated problems increase policy acceptability. Overall, the study elaborates on the anthropogenic dimension of diseases caused by IPs.

IAA production during germination of Orobanche spp. seeds.

Broomrapes (Orobanche spp.) are parasitic plants, whose growth and development fully depend on the nutritional connection established between the parasite and the roots of the respective host plant. Phytohormones are known to play a role in establishing the specific Orobanche-host plant interaction. The first step in the interaction is seed germination triggered by a germination stimulant secreted by the host-plant roots. We quantified indole-3-acetic acid (IAA) and abscisic acid (ABA) during the seed germination of tobacco broomrape (Orobanche ramosa) and sunflower broomrape (O. cumana). IAA was mainly released from Orobanche seeds in host-parasite interactions as compared to non-host-parasite interactions. Moreover, germinating seeds of O. ramosa released IAA as early as 24 h after the seeds were exposed to the germination stimulant, even before development of the germ tube. ABA levels remained unchanged during the germination of the parasites' seeds. The results presented here show that IAA production is probably part of a mechanism triggering germination upon the induction by the host factor, thus resulting in seed germination.