Natural Occurrence of Phytophthora infestans on Black Nightshade (Solanum nigrum) in Wales

There is only one published record of natural infection of black nightshade (Solanum nigrum L.) by Phytophthora infestans (Mont.) de Bary in England (3) and none from Wales. In August 2001, brown, necrotic leaf lesions with pale green margins were found on black nightshade weeds in a potato trial naturally infected with P. infestans at Henfaes Research Centre, University of Wales, Bangor. Although the plants were low growing with large, succulent leaves 4 to 5 cm long instead of having a more erect habit and smaller leaves, their identity was confirmed as S. nigrum; their atypical appearance may relate to the known phenotypic plasticity of this species (4). Infected leaflets incubated in moist chambers produced sporangia typical of P. infestans, and zoospores were released after chilling in water. Five isolates obtained from leaf fragments had growth on rye agar that was indistinguishable from that of P. infestans from potato. Detached leaflets of S. nigrum and S. tuberosum cv. Green Mountain inoculated with the S. nigrum isolates developed sporulating lesions under high humidity in 7 to 10 days; uninoculated controls remained symptomless. Inoculation of attached leaves of 10 potted S. nigrum plants resulted in seven plants developing necrotic lesions with a few sporangia 10 to 14 days later; sporulation developed mainly on lower leaves of plants that were older or had senesced. The remaining plants developed necrotic lesions with no sporulation, and P. infestans was reisolated from sporulating and nonsporulating lesions. All isolates were A1 mating type, metalaxyl-sensitive, and mitochondrial haplotype IIa, which are characteristics found commonly in isolates of P. infestans from potato in Wales (1). Single-sporangial isolates from each isolate were homozygous for glucose-6-phosphate isomerase and peptidase (Gpi 100/100, Pep 100/100). RG57 fingerprint analysis further established that all five black nightshade isolates were identical to each other and to some local P. infestans isolates from potato. P. infestans in Wales belongs to the new population (1), which may infect a wider host-range than the old US-1 clonal lineage. However, infected black nightshade was only found after late blight was widespread in potato fields. In subsequent years at the same site, weeds of S. nigrum have remained noninfected despite high levels of late blight pressure on adjacent potato plots. There is no evidence to suggest that this species acts as an overwintering host in Wales since it is an annual and lacks frost resistance. Field infection of S. nigrum by P. infestans has recently been reported in the Netherlands (2). Our observations confirm the potential of P. infestans to infect another solanaceous plant species. Alternative hosts may interfere with current disease control strategies because infected weeds would escape fungicide application and could serve as reservoirs of inoculum throughout the growing season. References: (1) J. P. Day and R. C. Shattock. Eur. J. Plant Pathol. 103:379, 1997. (2) W. G. Flier et al. Plant Pathol. 52:595, 2003. (3) J. M. Hirst and O. J. Steadman. Ann. Appl. Biol. 48:489, 1960. (4) B. S. Rogers and A. G. Ogg Jr. Page 30 in: Biology of Weeds of the Solanum Nigrum Complex (Solanum Section Solanum) in North America. USDA Publication ARM-W-23, 1981.

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Population Structure of the Late Blight Pathogen Phytophthora infestans in a Potato Germplasm Nursery in Two Consecutive Years

Phytopathology ◽

10.1094/phyto-03-14-0073-r ◽

2015 ◽

Vol 105 (6) ◽

pp. 771-777 ◽

Cited By ~ 11

Author(s):

Yuee Tian ◽

Junliang Yin ◽

Jieping Sun ◽

Hongmei Ma ◽

Yunfang Ma ◽

...

Keyword(s):

Population Structure ◽

Genetic Structure ◽

Late Blight ◽

Phytophthora Infestans ◽

Plant Pathogens ◽

Control Strategies ◽

Northwestern China ◽

Potato Seed ◽

Low Level ◽

Potato Germplasm

As the causal agent of late blight on potato, Phytophthora infestans is one of the most destructive plant pathogens worldwide and widely known as the Irish potato famine pathogen. Understanding the genetic structure of P. infestans populations is important both for breeding and deployment of resistant varieties and for development of disease control strategies. Here, we investigate the population genetic structure of P. infestans in a potato germplasm nursery in northwestern China. In total, 279 isolates were recovered from 63 potato varieties or lines in 2010 and 2011, and were genotyped by mitochondrial DNA haplotypes and a set of nine simple-sequence repeat markers. Selected isolates were further examined for virulence on a set of differential lines containing each resistance (R) gene (R1 to R11). The overall P. infestans population was characterized as having a low level of genetic diversity and resistance to metalaxyl, and containing a high percentage of individuals that virulent to all 11 R genes. Both A1 and A2 mating types as well as self-fertile P. infestans isolates were present but there was no evidence of sexual reproduction. The low level of genetic differentiation in P. infestans populations is probably due to the action of relatively high levels of migration as supported by analysis of molecular variance (P < 0.01). Migration and asexual reproduction were the predominant mechanisms influencing the P. infestans population structure in the germplasm nursery. Therefore, it is important to ensure the production of pathogen-free potato seed tubers to aid sustainable production of potato in northwestern China.

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Late Blight Caused by Phytophthora infestans on Solanum sarrachoides in Northeastern Maine

Plant Disease ◽

10.1094/pd-89-0435a ◽

2005 ◽

Vol 89 (4) ◽

pp. 435-435 ◽

Cited By ~ 3

Author(s):

K. L. Deahl ◽

R. Jones ◽

L. A. Wanner ◽

A. Plant

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Morphological Characteristics ◽

Dna Fingerprint ◽

Penicillin G ◽

Mitochondrial Haplotype ◽

Clonal Lineage ◽

Growth Responses ◽

Hairy Nightshade ◽

Solanum Sarrachoides

The area bordering three 110-ha (270-acre) fields of blighted potatoes (Solanum tuberosum L.) in three northeastern Maine locations was surveyed during the summer of 2004 for the occurrence of late blight on cultivated and noncultivated host plants. Special attention was directed to solanaceous weed species. Hundreds of Solanum sarrachoides Sendt. ex. Mart. (hairy nightshade) plants with numerous leaf lesions and moderate defoliation were seen. The frequency of blighted hairy nightshade approximated the frequency of late blight in the adjoining potato fields. Lesions typically contained extensive, white, superficial mycelia colonizing the abaxial and adaxial leaf surfaces. Samples placed in a moist chamber produced lemon-shaped sporangia. On the basis of morphological characteristics, the pathogen was tentatively identified as Phytophthora infestans (Mont.) de Bary. Isolates were obtained by surface-disinfecting leaf sections collected from two locations for 2 to 3 min in 0.5% NaOCl and placing the sections on rye grain medium amended with antibiotics (100 ppm each of penicillin G, pimaricin, and polymyxin). P. infestans was confirmed after reisolating onto rye-lima bean medium. Pathogenicity was tested on detached potato, tomato, and hairy nightshade leaves; the undersides of all leaflets from replicate plants were inoculated with droplets of swimming zoospores (≥500 zoospores per droplet), the leaves were kept at 17°C and 100% humidity, and the extent of sporulation was evaluated after 4, 6, and 7 days. With eight isolates obtained from S. sarrachoides, Koch's postulates were completed on potato and hairy nightshade. Radial growth responses of these strains on rye grain agar amended with 1, 10, or 100 μg per ml of metalaxyl (Ridomil 2E) yielded 50% effective dose values greater than 100 μg per ml, since percentage growth at the highest fungicide concentration exceeded 50% of the no metalaxyl control. These resistance levels are typical of the metalaxyl-insensitive strains of P. infestans isolated from potatoes in this area in recent years, which were previously found to correlate with metalaxyl resistance in bioassays using potato tissues (1). Eight single-sporangial isolates were homozygous for glucose-6-phosphate isomerase and peptidase (Gpi 100/111/122, Pep 100/100). All eight were A2-mating type and mitochondrial haplotype Ia, characteristics common to the US-8 clonal lineage of P. infestans from potato (2), which may infect a wider host range than the old US-1 clonal lineage. When evaluated on differential hosts, three isolates were tomato race PH-1 and complex potato race R 0,1,2,3,4,9,11. DNA fingerprint analysis with probe RG57 further established that the eight hairy nightshade isolates were identical to each other and to local P. infestans isolates from potato. To our knowledge, this is the first report of infection of S. sarrachoides by P. infestans in Maine. The pathogen was previously isolated from this host during field surveys in southern California in the 1980s in connection with late blight of tomato (4). Hairy nightshade has been shown to be a host for US-1, US-8, and US-11 isolates of P. infestans in a laboratory setting (3). The epidemiological significance of S. sarrachoides as an alternative or overwintering host of P. infestans is currently being assessed. References: (1) K. L. Deahl et al. Am. Potato J. 70:779, 1993. (2) S. B. Goodwin et al. Phytopathology 88:939, 1998. (3) H. W. Platt. Can. J. Plant Pathol. 21:301, 1999. (4) V. G. Vartanian and R. M. Endo Plant Dis. 69:516, 1985.

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Investigating the Host Range of the US-22, US-23, and US-24 Clonal Lineages of Phytophthora infestans on Solanaceous Cultivated Plants and Weeds

Plant Disease ◽

10.1094/pdis-09-13-0924-re ◽

2014 ◽

Vol 98 (6) ◽

pp. 754-760 ◽

Cited By ~ 5

Author(s):

Anna C. Seidl Johnson ◽

Amanda J. Gevens

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Host Range ◽

Management Strategies ◽

The United States ◽

Cultivated Plants ◽

Production Region ◽

Black Nightshade ◽

The Us ◽

Bittersweet Nightshade

Phytophthora infestans causes late blight, one of the most important diseases of potato and tomato worldwide. Recently in the United States, three newly identified clonal lineages, US-22, US-23, and US-24, have become widespread. While potato and tomato are the most commonly infected solanaceous hosts for P. infestans, new lineages may have a broader or different host range. Under controlled conditions, we determined the host range of isolates representing US-22, US-23, and US-24 genotypes of P. infestans on detached tissues of cultivated solanaceous plants and solanaceous weeds common to the upper midwestern production region. None of the isolates representing the clonal lineages produced late blight symptoms or signs on foliage of selected cultivars of eggplant, pepper, tomatillo, or ground cherry in a detached leaf assay. Symptoms and signs were evident on the potato and tomato cultivars tested, although with the US-24 isolate, infection on tomato was limited. None of the isolates sporulated on the common weed black nightshade, but some sporulation and necrosis was observed with all representatives of the lineages on bittersweet nightshade and petunia. Hairy nightshade supported abundant sporulation and symptoms, and sporangial production was not significantly different than that on tomato for each of the isolates representing the three lineages, indicating the potential for this weed to be a source of inoculum and contribute substantially to late blight epidemics. Interestingly, black nightshade had the highest incidence of sporulation on berries, but the lowest on leaves, suggesting the importance of testing multiple plant organs when determining susceptibility of a species. Our results update knowledge of the host range of the ever-changing P. infestans populations and will help to improve late blight management strategies by targeting these additional hosts.

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Resistance to potato late blight (Phytophthora infestans (Mont.) de Bary) in Solanum nigrum, S. villosum and their sexual hybrids with S. tuberosum and S. demissum

Euphytica ◽

10.1007/bf00023508 ◽

1992 ◽

Vol 66 (1-2) ◽

pp. 55-64 ◽

Cited By ~ 38

Author(s):

I. T. Colon ◽

R. Eijlander ◽

D. J. Budding ◽

M. T. Van Ijzendoorn ◽

M. M. J. Pieters ◽

...

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Potato Late Blight ◽

Solanum Nigrum

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Occurrence of Leaf Blight on Petunia Caused by Phytophthora infestans in Maryland

Plant Disease ◽

10.1094/pdis.2003.87.8.1004a ◽

2003 ◽

Vol 87 (8) ◽

pp. 1004-1004 ◽

Cited By ~ 6

Author(s):

K. L. Deahl ◽

D. R. Fravel

Keyword(s):

Phytophthora Infestans ◽

Natural Infection ◽

Leaf Tissue ◽

Significant Loss ◽

Leaf Blight ◽

Mitochondrial Haplotype ◽

Multilocus Genotype ◽

Plastic Bags ◽

Greenhouse Growers ◽

Heterothallic Species

In April 2001, late blight was detected on petunia (Petunia × hybrida Hort.) in a glasshouse in central Maryland. Symptomatic plants had extensive light gray, irregularly shaped, slightly sunken lesions up to 3 cm long on upper leaves and branches. Stems were distorted or dead above points where lesions had coalesced to cause stem girdling. Disease initially occurred as scattered foci but rapidly spread through the crop causing significant loss. The disease reappeared in the same and adjacent greenhouses in 2002. Phytophthora infestans Mont deBary was observed sporulating on leaves and stems of plants in both years. Isolates PE-01, PE-02, and PE-03 were isolated on rye medium from symptomatic stem and leaf tissue (1). To confirm pathogenicity, leaves and stems of 6-wk-old petunia (cv. White Madness) were sprayed with water or with aqueous suspensions of 105 sporangia per ml. Plants were placed in plastic bags in a growth chamber at 20 to 22°C. Bags were removed after 3 days. Five to seven days after spraying, necrotic leaf lesions similar to those on naturally infected plants developed on inoculated plants only. Lesions occurred at leaf margins or near midribs and were 1 to 6 mm, irregular in shape, slightly sunken, grayish, and accompanied by white, fluffy mycelial and sporangial growth. P. infestans was reisolated onto rye agar from lesions from all inoculated plants, completing Koch's postulates. Lesions contained abundant, nonseptate sporangia on obvious sporangiophore structures whose morphology matched that of P. infestans (2). Sporangia from these lesions were 39 to 50 μm (average 45 μm) long × 26 to 28 μm (average 27 μm) wide with a length/breadth ratio of 1.66. Sporangia were caducous and limoniform to ovoid in shape. Oospores were not observed. The fungus grew more slowly on potato dextrose agar (PDA) than on rye medium at 18°C (2.7 versus 9.8 mm per day) and 25°C (1.6 versus 3.0 mm per day). All three isolates mated with an A1 type isolate of P. infestans forming oogonia (36.14 μm in diameter), amphigynous antheridia (22.39 μm × 17.00 μm wide), and aplerotic oospores (16.91 μm in diameter), indicating that the petunia isolates were the A2 mating type. These characteristics were consistent with a heterothallic species such as P. infestans (3). Tomato and potato plants were susceptible to PE-01. The three petunia isolates were US-8 multilocus genotype, resistant to Ridomil and mitochondrial haplotype Ia, characteristics typical of P. infestans from potato in North America. All isolates were monomorphic and homozygous for glucose-6-phosphate isomerase and peptidase (Gpi 100/100; Pep 100/100). Restriction fragment length polymorphism (RG-57) analysis confirmed the close similarity of the petunia and potato isolates. Greenhouse growers who cultivate more than one Solanaceous species should be aware that petunia transplants may have incipient Phytophthora spp. infections serving as reservoirs of inoculum, and that some strains are resistant to metalaxyl-based fungicides. P. infestans has been reported to cause leaf blight on petunia in the northeastern United States (2,4). To our knowledge, this is the first report of natural infection of P. infestans on petunia in Maryland. References: (1) C. E. Caten and J. L. Jinks. Can. J. Bot. 46:329, 1968. (2) M. Daughtrey and M. Becktell. Grower Talk Mag. 66:90, 2002. (3) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society St. Paul, MN, 1996. (4) M. C. Rathbone et al. (Abstr.) Phytopathology 92 (Suppl.):S145, 2003.

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Resistance to Phytophthora Infestans in Three Solanum Nigrum F3 Families

Plant Breeding and Seed Science ◽

10.2478/v10129-011-0058-2 ◽

2014 ◽

Vol 66 (1) ◽

pp. 63-73 ◽

Cited By ~ 2

Author(s):

Jadwiga Śliwka ◽

Iga Tomczyńska ◽

Marcin Chmielarz ◽

Emil Stefańczyk ◽

Renata Lebecka ◽

...

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Single Gene ◽

Late Blight Resistance ◽

Solanum Nigrum ◽

The Other ◽

Blight Resistance ◽

Inheritance Of Resistance ◽

Detached Leaf ◽

Complex Inheritance

AbstractSolanum nigrumis a self-pollinating, hexaploid weed and one of a fewSolanaceaespecies native to Europe. It used to be described as a non-host forPhytophthora infestans. However, now it is known that, like its distant relatives: potato (Solanum tuberosumL.) and tomato (Solanum lycopersicumL.),S. nigrumcan suffer from potato late blight caused by this pathogen. Both susceptible and resistantS. nigrumgenotypes have been previously identified and inheritance of resistance originating from one accession has been described based on population of F2plants and 15 F3lines. The goal of this study was to evaluate resistance of three families of F3lines, originating from crosses between a susceptible and three different resistantS. nigrumaccessions followed by two self-pollinations. Parental accessions were tested for the spectrum of late blight resistance against 48P. infestansisolates. The three families consisted of 106, 96 and 115 F3lines, respectively, and from each line 20 plants were tested for resistance toP. infestans. Laboratory detached leaf assays were performed in two dates and two replications of three leaves each. Segregation of the trait within the line allowed us to distinguish hetero- and homozygous lines. In one F3family, the ratio of resistant homozygotes: heterozygotes: susceptible homozygotes was 1:2:1, indicating that a single gene is most likely underlying the late blight resistance in this case. In the other two, observed segregations of the trait significantly deviated from this model suggesting more complex inheritance patterns.

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Increased Difficulties to Control Late Blight in Tunisia Are Caused by a Genetically Diverse Phytophthora infestans Population Next to the Clonal Lineage NA-01

Plant Disease ◽

10.1094/pdis-06-13-0610-re ◽

2014 ◽

Vol 98 (7) ◽

pp. 898-908 ◽

Cited By ~ 9

Author(s):

Kalthoum Harbaoui ◽

Walid Hamada ◽

Ying Li ◽

Vivianne G. A. A. Vleeshouwers ◽

Theo van der Lee

Keyword(s):

Genetic Diversity ◽

Late Blight ◽

Phytophthora Infestans ◽

Agricultural Practices ◽

Weather Conditions ◽

Genotypic Diversity ◽

Mitochondrial Haplotype ◽

Potato Seed ◽

Clonal Lineage ◽

High Genetic Diversity

In Tunisia, late blight caused by Phytophthora infestans is a serious threat to potato and tomato. The Mediterranean weather conditions can be conducive to infection in all seasons and the host crops, tomato and potato, are grown year round. Potato is planted and harvested in two to four overlapping intervals from August to June and tomato is grown both in open fields and in greenhouses. The consequences of these agricultural practices and the massive import of seed potato on the genetic variation of P. infestans are largely unknown. We conducted a survey in which 165 P. infestans isolates, collected from five subregions in Tunisia between 2006 and 2008, on which we studied genotypic diversity through nuclear (simple-sequence repeat [SSR]) markers and combined this with a previous study on their mitochondrial haplotypes (mtDNA). The phylogenetic analysis revealed the presence of a major clonal lineage (NA-01, A1 mating type, mitochondrial haplotype Ia). Isolates belonging to this clonal lineage were found in all regions and showed a relatively simple virulence pattern on a potato differential set carrying different Solanum demissum resistance genes. Apart from isolates belonging to this NA-01 clonal lineage, a group of isolates was found that showed a high genetic diversity, comprising both mating types and a more complex race structure that was found in the regions where late blight on potato was more difficult to control. The population on potato and tomato seems to be under different selection pressures. Isolates collected from tomato showed a low genetic diversity even though potato isolates collected simultaneously from the same location showed a high genetic diversity. Based on the SSR profile comparison, we could demonstrate that the four major clonal lineages found in the Netherlands and also in other European countries could not be found in Tunisia. Despite the massive import of potato seed from Europe, the P. infestans population in Tunisia was found to be clearly distinct.

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Methods of evaluating tomato susceptibility to late blight (Phytophthora infestans (Mont.) de Bary) under field conditions

Acta Agrobotanica ◽

10.5586/aa.1989.008 ◽

2013 ◽

Vol 42 (1-2) ◽

pp. 95-104

Author(s):

Elżbieta Horodecka

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Natural Infection ◽

Field Conditions ◽

Artificial Infection

The purpose of the investigations carried out in 1983-1985 was to assess the usefulness of natural and artificial infections under field conditions for evaluating tomato resistance to late blight in Poland. It was found, that the degree of natural infection by this fungus was a better indicator of tomato resistance than the degree of artificial infection obtained under field conditions.

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Field Evaluation of Potato Resistance Against Phytophthora Infestans under Natural Infection Pressure

Plant Breeding and Seed Science ◽

10.1515/plass-2017-0017 ◽

2017 ◽

Vol 76 (1) ◽

pp. 25-28

Author(s):

Jarosław Plich ◽

Beata Tatarowska

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Potato Breeding ◽

Natural Infection ◽

Field Evaluation ◽

Field Resistance ◽

Field Conditions ◽

Breeding Programs ◽

Infection Pressure ◽

Potato Resistance

Abstract Although development of potato cultivars resistant to late blight has long been one of the primary goals of potato breeding programs, several different methods of field resistance evaluation have been used by potato breeders. Recently, within the EucaBlight network (www.euroblight.net), common methods of late blight evaluation have been agreed on, and these methods are currently highly recommended for use by all those interested in evaluating the resistance of the potato to late blight. Here, we describe a method of evaluating potato resistance in field conditions routinely used at Młochów Research Center, which is compliant with recommendations of the EucaBlight protocol.

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Phytophthora Infestans: Isolation of Pure Cultures, Storage and Inoculum Preparation

Plant Breeding and Seed Science ◽

10.1515/plass-2017-0015 ◽

2017 ◽

Vol 76 (1) ◽

pp. 9-15 ◽

Cited By ~ 2

Author(s):

Sylwester Sobkowiak ◽

Jadwiga Śliwka

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Plant Species ◽

Control Strategies ◽

Plant Tissues ◽

Pure Cultures ◽

Oomycete Pathogen ◽

Inoculum Preparation ◽

Important Disease

Abstract Phytophthora infestans causes potato and tomato late blight, economically the most important disease of these plant species. The Oomycete pathogen is frequently sampled, isolated to pure cultures, stored, and characterized. The knowledge of its diversity, migrations and evolution is essential for breeding resistant plants and for designing appropriate control strategies. The article presents methods for collection, storage and preparation of P. infestans isolates for inoculation of plant tissues, based on the publication by Zarzycka (2001), later updated and modified.

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