Effect of nitrogen form and application method on incidence and severity ofPhytophthora crown and root rot of apple trees

Utkhede, R. S.; Smith, E. M.

doi:10.1007/bf01874784

Cited by 19 publications

(15 citation statements)

References 17 publications

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“…infestans [42]. Some other oomycete diseases are also believed to be stimulated by fertilization, as are some fungal diseases [66–68]. Whether all oomycetes respond similarly is unknown, as there is diversity in their nitrate assimilation pathways.…”

Section: Discussionmentioning

confidence: 99%

Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis

et al. 2016

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To help learn how phytopathogens feed from their hosts, genes for nutrient transporters from the hemibiotrophic potato and tomato pest Phytophthora infestans were annotated. This identified 453 genes from 19 families. Comparisons with a necrotrophic oomycete, Pythium ultimum var. ultimum, and a hemibiotrophic fungus, Magnaporthe oryzae, revealed diversity in the size of some families although a similar fraction of genes encoded transporters. RNA-seq of infected potato tubers, tomato leaves, and several artificial media revealed that 56 and 207 transporters from P. infestans were significantly up- or down-regulated, respectively, during early infection timepoints of leaves or tubers versus media. About 17 were up-regulated >4-fold in both leaves and tubers compared to media and expressed primarily in the biotrophic stage. The transcription pattern of many genes was host-organ specific. For example, the mRNA level of a nitrate transporter (NRT) was about 100-fold higher during mid-infection in leaves, which are nitrate-rich, than in tubers and three types of artificial media, which are nitrate-poor. The NRT gene is physically linked with genes encoding nitrate reductase (NR) and nitrite reductase (NiR), which mobilize nitrate into ammonium and amino acids. All three genes were coregulated. For example, the three genes were expressed primarily at mid-stage infection timepoints in both potato and tomato leaves, but showed little expression in potato tubers. Transformants down-regulated for all three genes were generated by DNA-directed RNAi, with silencing spreading from the NR target to the flanking NRT and NiR genes. The silenced strains were nonpathogenic on leaves but colonized tubers. We propose that the nitrate assimilation genes play roles both in obtaining nitrogen for amino acid biosynthesis and protecting P. infestans from natural or fertilization-induced nitrate and nitrite toxicity.

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Section: Discussionmentioning

confidence: 99%

Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis

et al. 2016

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“…In general, the effects of nitrogen on Phytophthora diseases vary with different hostpathogen combinations and with the form of nitrogen applied (HUBER and WATSON 1974;ScHMiTTHENNER and CANADAY 1983). It is known that crown rot of apple trees by P. cactorum (UTKHEDE and SMITH 1995), root rot of citrus trees by P. parasitica (KLOTZ et al 1958) and littleleaf disease of pines in New Zealand (NEWHOOK and PODCER 1972) are increased by nitrogen fertilization, especially if the nitrogen:phosphate ratio becomes imbalanced; however, there are also many examples where nitrogen decreases disease severity (SCHMITTHENNER and C AN AD AY 1983).…”

Section: Discussionmentioning

confidence: 99%

Isolation, identification and pathogenicity of Phytophthora species from declining oak stands

Jung¹,

Blaschke²,

Neumann

1996

European Journal of Forest Pathology

304

404

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Summary Within the scope of a research project on the condition of roots of declining oaks (Quercus robur, Quercus petraea), samples of fine roots and surrounding soil, specimens of stripe cankers on the stem base, and samples of stream water were examined for the presence of Phytophthora species using both baiting methods and selective agar media. At 27 sites in Germany (Bavaria, Rheinland‐Pfalz, Schleswig‐Holstein), Switzerland, Hungary, Italy and Slovenia the following species were isolated (mainly from soil): Phytophthora citricola, Phytophthora cactorum, Phytophthora cambivora, Phytophthora gon‐apodyides, Phytophthora undulata, a species with affinity to Phytophthora drechsleri, and two additional species with close affinity to the Phytophthora cactorum group. Moreover, Pythium group P, Pythium anandrum, Pythium chamaehyphon, and many other Pythium species that have not yet been identified could be recovered. In a soil infestation test most isolates induced dieback of long root tips and necrotic lesions in the root cortex and at the root collar of Quercus robur seedlings. All Phytophthora species tested and Pythium group P caused cortical necrosis after stem inoculation of young Quercus robur trees. It could be shown in vitro that Phytophthora gonapodyides and Pythium group P were able to produce a wilting toxin. Nitrogen input and climatic changes are discussed as predisposing factors for root damage observed in the field.

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“…High concentrations of soluble Al have been shown to be detrimental to Phytophthora species (Erwin & Ribeiro, 1996), and although there are examples of high Ca concentrations suppressing root rot caused by Phytophthora species, the diseases are generally considered to be less severe at low Ca concentrations (Schmitthenner & Canaday, 1983). The influence of N on the disease seems to depend on the host‐pathogen combination and the form of soil N (Klotz et al ., 1958; Newhook & Podger, 1972; Schmitthenner & Canaday, 1983; Utkhede & Smith, 1995; Erwin & Ribeiro, 1996). Jung et al .…”

Section: Introductionmentioning

confidence: 99%

Pathogenicity of Swedish isolates of Phytophthora quercina to Quercus robur in two different soils

et al. 2003

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Summary• Several studies have demonstrated the involvement of soil-borne Phytophthora species, especially Phytophthora quercina , in European oak decline. However, knowledge about the pathogenicity of P. quercina in natural forest soils is limited.• The short-term effects of two south-Swedish isolates of P. quercina on root vitality of Quercus robur seedlings grown in two different soils, one high pH, nutrient-rich peat-sand mixture and one acid, nitrogen-rich but otherwise nutrient-poor forest soil are described. Pathogenicity of P. quercina was tested using a soil infestation method under a restricted mesic water regime without prolonged flooding of the seedlings.• There was a significant difference in dead fine-root length between control seedlings and seedlings grown in soil infested with P. quercina . Trends were similar for both soil types and isolates, but there was a higher percentage of fine-root die-back and more severe damage on coarse roots in the acid forest soil. No effects on aboveground growth or leaf nutrient concentration between control seedlings and infected seedlings were found.• The results confirm the pathogenicity of south-Swedish isolates of P. quercina in acid forest soils under restricted water availability. Stress-induced susceptibility of the seedlings and/or increased aggressiveness of the pathogen in the forest soil are discussed as key factors to explain the difference in root die-back between soil types.

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Effect of nitrogen form and application method on incidence and severity ofPhytophthora crown and root rot of apple trees

Cited by 19 publications

References 17 publications

Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis

Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis

Isolation, identification and pathogenicity of Phytophthora species from declining oak stands

Pathogenicity of Swedish isolates of Phytophthora quercina to Quercus robur in two different soils

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