Two hundred and twenty-five Diaporthe isolates were collected from 2005 to 2019 in almond orchards showing twig cankers and shoot blight symptoms in five different regions across Spain. Multilocus DNA sequence analysis with five loci (ITS, tub, tef-1α, cal and his), allowed the identification of four known Diaporthe species, namely: D. amygdali, D. eres, D. foeniculina and D. phaseolorum. Moreover, a novel phylogenetic species, D. mediterranea, was described. Diaporthe amygdali was the most prevalent species, due to the largest number of isolates (85.3%) obtained from all sampled regions. The second most frequent species was D. foeniculina (10.2%), followed by D. mediterranea (3.6%), D. eres and D. phaseolorum, each with only one isolate. Pathogenicity tests were performed using one-year-old almond twigs cv. Vayro and representative isolates of the different species. Except for D. foeniculina and D. phaseolorum, all Diaporthe species were able to cause lesions significantly different from those developed on the uninoculated controls. Diaporthe mediterranea caused the most severe symptoms. These results confirm D. amygdali as a key pathogen of almonds in Spain. Moreover, the new species, D. mediterranea, should also be considered as a potential important causal agent of twig cankers and shoot blight on this crop.

From 2018 to 2020, surveys of oomycetes associated with root and crown rot of almond (Prunus dulcis) were conducted on diseased young almond trees in commercial orchards and nurseries in six provinces of Spain. A total of 104 oomycete isolates were obtained from plant and soil samples, which h were identified by sequencing the internal transcribed spacer (ITS) region of the ribosomal DNA. Diverse species belonging to the genera Globisporangium, Phytophthora, Phytopythium and Pythium were found, Phytopythium vexans and Phytophthora niederhauserii being the most frequent. The pathogenicity of these two species to one-year-old almond seedlings of ‘Garnem’ (P. dulcis × P. persica) rootstock was studied. All seedlings inoculated with Pp. vexans and Ph. niederhauserii isolates showed severe symptoms at the late stage of the pathogenicity test (defoliation, wilting and dieback) and several plants died. Some isolates of Ph. niederhauserii significantly reduced the dry weight of the roots compared with the control, but this effect was not observed in seedlings inoculated with Pp. vexans. These results provide new information about the oomycete species present in almond crops in Spain and highlight the importance of carrying out frequent phytosanitary surveys for a better knowledge of potential risks posed by these soil-borne pathogens.

The plant nursery industry has become an ideal reservoir for Phytophthora species and other soilborne pathogens. In this context, isolation from tissues and soil of ornamental and forest plants from nurseries in four regions of Spain was carried out. A high diversity of Phytophthora species was confirmed. Fourteen Phytophthora phylotypes (P. cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. crassamura, P. gonapodyides, P. hedraiandra, P. nicotianae, P. niederhauserii, P. palmivora, P. plurivora, P. pseudocryptogea, P. sansomeana, and Phytophthora sp. tropicalis-like 2) were isolated from over 500 plant samples of 22 species in 19 plant genera. Nine species were detected in water sources, two of them (P. bilorbang and P. lacustris) exclusively from water samples. P. crassamura was detected for the first time in Spain. This is the first time P. pseudocryptogea is isolated from Chamaecyparis lawsoniana and Yucca rostrata in Spain.

The diversity of Phytophthora species in declining Fagaceae forests in Europe is increasing in the last years. The genus Quercus is one of the most extended Fagaceae genera in Europe, and Q. ilex is the dominant tree in Spain. The introduction of soil-borne pathogens, such as Phytophthora in Fagaceae forests modifies the microbial community present in the rhizosphere, and has relevant environmental and economic consequences. A better understanding of the diversity of Phytophthora spp. associated with Q. ilex is proposed in this study by using Next Generation Sequencing (NGS) in six Q. ilex stands located in three regions in Spain. Thirty-seven Phytophthora phylotypes belonging to clades 1 to 12, except for clades 4, 5 and 11, are detected in this study, which represents a high diversity of Phytophthora species in holm oak Spanish forests. Phytophthora chlamydospora, P. citrophthora, P. gonapodyides, P. lacustris, P. meadii, P. plurivora, P. pseudocryptogea, P. psychrophila and P. quercina were present in the three regions. Seven phylotypes could not be associated with known Phytophthora species, so they were putatively named as Phytophthora sp. Most of the detected phylotypes corresponded to terrestrial Phytophthora species but aquatic species from clades 6 and 9 were also present in all regions.

Nectarine (Prunus persica (L.) Batsch var. nucipersica (Suckow) C. K. Schneid.) is a fruit crop widely cultivated throughout the Mediterranean basin. In Spain, it is mainly grown in eastern regions...

The struggling Spanish holm oak woodland situation associated with Phytophthora root rot has been studied for a long time. Phytophthora cinnamomi is considered the main, but not the only species responsible for the decline scenario. This study verifies the presence and/or detection of Phytophthora species in two holm oak areas of Spain (southwestern “dehesas” and northeastern woodland) using different isolation and detection approaches. Direct isolation and baiting methods in declining and non-declining holm oak trees revealed Phytophthora cambivora, Phytophthora cinnamomi, Phytophthora gonapodyides, Phytophthora megasperma, and Phytophthora pseudocryptogea in the dehesas, while in the northeastern woodland, no Phytophthora spp. were recovered. Statistical analyses indicated that there was not a significant relationship between the Phytophthora spp. isolation frequency and the disease expression of the holm oak stands in the dehesas. Phytophthora quercina and P. cinnamomi TaqMan real-time PCR probes showed that both P. cinnamomi and P. quercina are involved in the holm oak decline in Spain, but P. quercina was detected in a higher frequency than P. cinnamomi in both studied areas. Thus, this study demonstrates that molecular approaches complement direct isolation techniques in natural and seminatural ecosystem surveys to determine the presence and distribution of Phytophthora spp. This is the first report of P. pseudocryptogea in Europe and its role in the holm oak decline should be further studied.