The Use of qPCR Reveals a High Frequency of Phytophthora quercina in Two Spanish Holm Oak Areas

Abstract

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.

Assessment of functional and structural changes of soil fungal and oomycete communities in holm oak declined dehesas through metabarcoding analysis

“…Most of the Phytophthora taxa found in our samples were also recorded in a soil analysis in the search for oomycete in natural Q. ilex forests of eastern Spain 29 , where P. psychrophila and P. quercina were the most-relevant taxa, and also a qPCR survey showed P. quercina abundance in dehesas of Extremadura 30 ; P. psychrophila and P. quercina appeared, respectively, as the third- and fourth-most-abundant oomycete species in our study. Both taxa have been confirmed as Q. ilex root pathogens, causing root rot and tree death 74 .…”

Diversity of Phytophthora Species Associated with Quercus ilex L. in Three Spanish Regions Evaluated by NGS

“…The weather conditions of the Extremadura region were more favorable for Phytophthora development in 2013 than in 2012, since in 2012 Extremadura received less precipitation than in 2013, as reported in 2018 by Mora-Sala et al [48]. Redondo et al [57] state that there is a decrease in the diversity of terrestrial Phytophthora communities when temperature and precipitation decreases, precipitation being the main driving factor, except for clades 2 and 8, in which temperature was more conditioning.…”

“…Soil and roots samples were conserved at 5 • C until DNA extraction was performed. Baiting with leaflets of Rhododendron sp., Viburnum tinus L, Quercus ilex L, Quercus suber L, Ceratonia siliqua L. and/or Dianthus caryophyllus L. petals was performed as described in a previous study [48], and the vegetal material from the baitings was conserved at -80 • C until DNA extraction.…”

“…In this context, it is interesting to note that samples from the current study were previously subjected to traditional isolation, baiting and real-time polymerase chain reaction (PCR) methods to detect Phytophthora spp. [48]. The objective of the present study was to unravel the Phytophthora community present in these previously studied areas using NGS technology.…”

Monitoring, Assessment and Management of Forest Insect Pests and Diseases

“…They concluded that visual surveying was more efficient than bark shifting. Meanwhile, Mora-Sala et al [22] demonstrated the efficiency of qPCR approaches to determine the presence and distribution of Phytophthora sp. in holm oak areas.…”