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

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 435-435 ◽  
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.

scholarly journals 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 ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 898-908 ◽  
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.

scholarly journals Population Genetic Structure of Phytophthora infestans in Ecuador

1997 ◽  
Vol 87 (4) ◽  
pp. 375-380 ◽  
Author(s):  
Gregory A. Forbes ◽  
Ximena C. Escobar ◽  
Catalina C. Ayala ◽  
Jorge Revelo ◽  
Maria E. Ordoñez ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Phytophthora Infestans ◽  
Mating Type ◽  
Population Genetic Structure ◽  
Population Genetic ◽  
Nuclear Dna ◽  
Dna Fingerprint ◽  
Clonal Lineage ◽  
Metalaxyl Sensitivity ◽  
Neutral Markers

The population genetic structure of Phytophthora infestans in Ecuador was assessed from 101 isolates collected from 1990 to 1992 and 111 isolates collected in 1993. All isolates were analyzed for mating type and allozyme genotype. Both samples were dominated (>95%) by a clonal lineage (EC-1) defined from neutral markers: 90/100 genotype for glucose-6-phosphate isomerase, 96/100 genotype for peptidase, A1 mating type, and a previously unreported nuclear DNA fingerprint. The remaining isolates belonged to the US-1 clonal lineage, which has a worldwide distribution. Isolates in the 1993 sample were analyzed for virulence and metalaxyl sensitivity. All representatives of EC-1 had complex patho-types, with three pathotypes representing >60% of the collection. There was variation for metalaxyl sensitivity. There was no evidence for geographical substructuring on the basis of neutral markers, but there was evidence for limited substructuring based on metalaxyl sensitivity and specific virulence. We hypothesize that EC-1 has been recently introduced to Ecuador.

scholarly journals Did a novel virus contribute to late blight epidemics?

2018 ◽  
Author(s):  
Guohong Cai ◽  
Kevin Myers ◽  
William E. Fry ◽  
Bradley I. Hillman
Keyword(s):  
North America ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Molecular Mechanisms ◽  
Rna Virus ◽  
Causal Agent ◽  
Clonal Lineage ◽  
Significant Similarity ◽  
Tomato Production ◽  
The Us

AbstractPhytophthora infestansis the causal agent of potato and tomato late blight. In this study, we characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2). The PiRV-2 genome is 11,170 nt and lacks a polyA tail. It contains a single large open reading frame (ORF) with short 5’- and 3’-untranslated regions. The ORF is predicted to encode a polyprotein of 3710 aa (calculated molecular weight 410.94 kDa). This virus lacks significant similarity to any other known viruses, even in the conserved RNA-dependent RNA polymerase region. Comparing isogenic strains with or without the virus demonstrated that the virus stimulated sporangia production inP. infestansand appeared to enhance its virulence. Transcriptome analysis revealed that it achieved sporulation stimulation likely through down-regulation of ammonium and amino acid intake inP. infestans. This virus was faithfully transmitted through asexual reproduction. Survey of PiRV-2 presence in aP. infestanscollection found it in most strains in the US-8 lineage, a very successful clonal lineage ofP. infestansin North America. We suggest that PiRV-2 may have contributed to its success, raising the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.Author SummaryPotato late blight, the notorious plant disease behind the Irish Potato Famine, continues to pose a serious threat to potato and tomato production worldwide. While most studies on late blight epidemics focuses on pathogen virulence, host resistance, environmental factors and fungicide resistance, we present evidence in this study that a virus infecting the causal agent,Phytophthora infestans, may have played a role. We characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2) and examined its effects on its host. By comparing identicalP. infestansstrains except with or without the virus, we found that PiRV-2 stimulated sporulation ofP. infestans(a critical factor in late blight epidemics) and increased its virulence. We also profiled gene expression in these strains and identified potential molecular mechanisms through which PiRV-2 asserted its sporulation stimulation effect. In a survey of PiRV-2 presence in aP. infestanscollection, we found PiRV-2 in most isolates of the US-8 clonal lineage, a very successfull ineage that dominated potato fields in North America for several decades. We suggest that PiRV-2 may have contributed to its success. Our findings raise the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.

scholarly journals The early days of late blight

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Paul RJ Birch ◽  
David EL Cooke
Keyword(s):  
Late Blight ◽  
Dna Sequencing ◽  
Phytophthora Infestans ◽  
19Th Century ◽  
Large Scale ◽  
Clonal Lineage ◽  
The 19Th Century

Large-scale DNA sequencing of samples of foliage collected in the 19th century from plants infected with late blight has shown that the potato famines of the 1840s were triggered by a single clonal lineage of Phytophthora infestans, called HERB-1, which persisted for at least 50 years.

Resistance to Phytophthora infestans Clonal Lineage US-23 in Potato Cultivars and Its Relationship with Early Blight Resistance and Tuber Yield

Plant Disease ◽  
2021 ◽  
Author(s):  
Weiya Xue ◽  
Kathleen G. Haynes ◽  
Xinshun Qu
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Early Blight ◽  
Tuber Yield ◽  
Late Blight Resistance ◽  
Field Trials ◽  
Potato Cultivars ◽  
Blight Resistance ◽  
Clonal Lineage ◽  
Progress Curve

Resistance to late blight, caused by Phytophthora infestans clonal lineage US-23, in 217 old and modern potato cultivars was evaluated in field trials in 2016 and 2017 in Pennsylvania. Significant differences in resistance were found among these cultivars (P < 0.0001). Significant interaction between cultivars and environments was found (P < 0.0001). The values of relative area under the disease progress curve ranged from 0 to 0.5841 in 2016 and from 0 to 0.5469 in 2017. Broad-sense heritability of late blight resistance was estimated to be 0.91 with a 95% confidence interval of 0.88 to 0.93. Cluster analysis classified the cultivars into 5 groups: resistant, moderately resistant, intermediate, moderately susceptible, and susceptible. Thirty cultivars showing resistance and 32 cultivars showing moderate resistance were identified. The 217 cultivars were also evaluated for foliar maturity, tuber yield and resistance to early blight, caused by Alternaria solani. A few cultivars with late blight resistance independent of late maturity were found. Late blight resistance and early blight resistance were positively correlated, and 17 cultivars possessed resistance to both diseases. Yield tradeoff associated with late blight resistance was not observed among the cultivars in the absence of disease pressure.

scholarly journals Effect of Temperature on Growth and Sporulation of US-22, US-23, and US-24 Clonal Lineages of Phytophthora infestans and Implications for Late Blight Epidemiology

2015 ◽  
Vol 105 (4) ◽  
pp. 449-459 ◽  
Author(s):  
Anna C. Seidl Johnson ◽  
Kenneth E. Frost ◽  
Douglas I. Rouse ◽  
Amanda J. Gevens
Keyword(s):  
Growth Rate ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Growth Rates ◽  
Weather Data ◽  
Effect Of Temperature ◽  
Clonal Lineage ◽  
Tomato Production ◽  
The Us ◽  
Lesion Growth

Epidemics of late blight, caused by Phytophthora infestans (Mont.) de Bary, have been studied by plant pathologists and regarded with great concern by potato and tomato growers since the Irish potato famine in the 1840s. P. infestans populations have continued to evolve, with unique clonal lineages arising which differ in pathogen fitness and pathogenicity, potentially impacting epidemiology. In 2012 and 2013, the US-23 clonal lineage predominated late blight epidemics in most U.S. potato and tomato production regions, including Wisconsin. This lineage was unknown prior to 2009. For isolates of three recently identified clonal lineages of P. infestans (US-22, US-23, and US-24), sporulation rates were experimentally determined on potato and tomato foliage and the effect of temperature on lesion growth rate on tomato was investigated. The US-22 and US-23 isolates had greater lesion growth rates on tomato than US-24 isolates. Sporulation rates for all isolates were greater on potato than tomato, and the US-23 isolates had greater sporulation rates on both tomato and potato than the US-22 and US-24 isolates. Experimentally determined correlates of fitness were input to the LATEBLIGHT model and epidemics were simulated using archived Wisconsin weather data from four growing seasons (2009 to 2012) to investigate the effect of isolates of these new lineages on late blight epidemiology. The fast lesion growth rates of US-22 and US-23 isolates resulted in severe epidemics in all years tested, particularly in 2011. The greater sporulation rates of P. infestans on potato resulted in simulated epidemics that progressed faster than epidemics simulated for tomato; the high sporulation rates of US-23 isolates resulted in simulated epidemics more severe than simulated epidemics of isolates of the US-22 and US-24 isolates and EC-1 clonal lineages on potato and tomato. Additionally, US-23 isolates consistently caused severe simulated epidemics when lesion growth rate and sporulation were input into the model singly or together. Sporangial size of the US-23 isolates was significantly smaller than that of US-22 and US-24 isolates, which may result in more efficient release of sporangia from the tomato or potato canopy. Our experimentally determined correlates of fitness and the simulated epidemics resulting from their incorporation into the LATEBLIGHT model suggest that US-23 isolates of P. infestans may have the greatest fitness among currently prevalent lineages and may be the most likely lineage to persist in the P. infestans population. The US-23 clonal lineage has been documented as the most prevalent lineage in recent years, indicating its overall fitness. In our work, US-23 had the highest epidemic potential among current genotypes. Given that epidemic potential is a component of fitness, this may, in part, explain the current predominance of the US-23 lineage.

scholarly journals Can Weed Hosts Increase Aggressiveness of Phytophthora infestans on Potato?

2012 ◽  
Vol 102 (4) ◽  
pp. 429-433 ◽  
Author(s):  
L. Grönberg ◽  
B. Andersson ◽  
J. Yuen
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Genotypic Variation ◽  
Latency Period ◽  
Potato Production ◽  
Potato Late Blight ◽  
Hairy Nightshade ◽  
Weed Hosts ◽  
Lesion Growth ◽  
Sporulation Capacity

Potato late blight, caused by Phytophthora infestans, is a major disease in potato production throughout the world. In southern Sweden, hairy nightshade (Solanum physalifolium), an alternative non-crop host to the pathogen, is an increasing weed problem. Single-lesion leaves infected by P. infestans were collected from potato and hairy nightshade to determine phenotypic and genotypic population differentiation of P. infestans between the two hosts. Genotypic variation was estimated using microsatellites as markers. The results showed no genotypic differentiation in the samples between the two hosts. Aggressiveness tests were performed using the sampled isolates to cross-inoculate potato and hairy nightshade. The proportion of infected leaves, latency period, lesion growth rate, and sporulation capacity were measured. For isolates from hairy nightshade, the odds of infection were higher on both hosts combined. When tested on potato leaves, isolates from hairy nightshade showed a significantly shorter latency period and higher sporulation capacity compared with isolates from potato. This indicates that an alternative host can filter populations of P. infestans toward a higher aggressiveness, which could lead to increasing problems in controlling potato late blight.

scholarly journals First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-24 on Potato (Solanum tuberosum) in Wisconsin

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 152-152 ◽  
Author(s):  
A. J. Gevens ◽  
A. C. Seidl
Keyword(s):  
Solanum Tuberosum ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Weather Conditions ◽  
Clonal Lineage ◽  
Banding Patterns ◽  
First Report ◽  
The Us ◽  
Epidemiological Characteristics ◽  
The U.S

Potato (Solanum tuberosum) crops are grown on over 25,090 ha in Wisconsin annually. Late blight, caused by Phytophthora infestans (Mont.) deBary, is a potentially devastating disease that affects tomato and potato crops in Wisconsin every few years when inoculum is introduced and weather conditions favor disease. Incidence and severity of late blight are highly variable in these few years due to differences in pathogen clonal lineages, their timing and means of introduction, and weather conditions. Prevention of this disease through prophylactic fungicide application can cost producers millions of dollars annually in additional chemical, fuel, and labor expenses. Populations of P. infestans in the U.S. have recently undergone significant genetic change, resulting in isolates with unique clonal lineages and epidemiological characteristics (1). In 2010, late blight epidemics were of low severity in discrete portions of a few fields and were seen exclusively on potato in two counties of central Wisconsin. Symptoms included water-soaked to dark brown circular lesions with pale green haloes accompanied by white fuzzy pathogen sporulation typically on leaf undersides in high humidity conditions. Infected plants were collected by professional crop consultants and submitted to the authors at the University of Wisconsin Vegetable Pathology Laboratory in Madison, Wisconsin. Eight isolates of P. infestans were generated from individual leaf samples, representing separate fields, by removing sporangia from sporulating lesions and placing onto Rye A agar amended with rifampicin and ampicillin. Axenic, single zoospore-derived cultures of isolates were generated from parent cultures and maintained on Rye A agar for further characterization. Mycelium was coenocytic with hyphal diameter of 5 to 8 μm (n = 50). Sporangia were limoniform to ovoid, semi- to fully papillate, caducous, had short pedicels, and were 36.22 × 19.11 μm (height × width; n = 50). The average length-width ratio was 1.91. Allozyme banding patterns at the glucose-6-phosphate isomerase (Gpi) locus indicated a 100/100/111 profile, consistent with the US-24 clonal lineage (3,4). Mating type assays confirmed the isolates to be A1 and intermediate insensitivity to mefenoxam was observed in vitro (4). Genomic DNA was extracted with a phenol:chloroform:isoamyl alcohol solution and restriction fragment length polymorphism (RFLP) analysis was performed using the RG-57 probe on a representative isolate and resulted in banding patterns consistent with US-24 (2,3). Clonal lineages of P. infestans documented in Wisconsin in previous epidemics included US-8 in the mid-1990s and US-1 in the 1970s. The US-24 (A1) clonal lineage was very widespread in the U.S. in 2010 and its presence in Wisconsin in the same year as identification of US-22 (A2) posed great concern for potential sexual recombination, oospore production, and soil persistence. Fortunately, the opposite mating types were separated spatiotemporally. To the best of our knowledge, this is the first report of the P. infestans clonal lineage US-24 causing late blight on potato in Wisconsin. References: (1) K. Deahl. (Abstr.) Phytopathology 100:S161, 2010. (2) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (3) Hu et al. Plant Dis. 96:1323, 2012. (4) A. C. Seidl and A. J. Gevens. (Abstr.) Phytopathology 101:S162, 2011.

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

Plant Disease ◽  
2004 ◽  
Vol 88 (7) ◽  
pp. 771-771 ◽  
Author(s):  
K. L. Deahl ◽  
D. S. Shaw ◽  
L. R. Cooke
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Control Strategies ◽  
Natural Infection ◽  
Solanum Nigrum ◽  
Research Centre ◽  
Mitochondrial Haplotype ◽  
Natural Occurrence ◽  
Black Nightshade ◽  
Plant Pathol

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.

scholarly journals First Report of Late Blight Caused by Phytophthora infestans on Cape Gooseberry (Physalis peruviana) in Colombia

Plant Disease ◽  
2007 ◽  
Vol 91 (4) ◽  
pp. 464-464 ◽  
Author(s):  
A. M. Vargas ◽  
A. Correa ◽  
D. C. Lozano ◽  
A. González ◽  
A. J. Bernal ◽  
...  
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Morphological Characteristics ◽  
Control Measures ◽  
Distilled Water ◽  
First Report ◽  
Physalis Peruviana ◽  
Potato Slice ◽  
Solanaceae Family ◽  
Cape Gooseberry

Late blight caused by Phytophthora infestans is the most limiting disease for several species of the Solanaceae family in Colombia. A potential host for P. infestans is Cape gooseberry (Physalis peruviana), a species belonging to the Solanaceae family. Its center of origin is the highlands of Peru and it is grown at approximately 1,500 to 3,000 m above sea level. Cape gooseberry has become an important export fruit in Colombia. Consequently, in the last few years, the area cultivated with Physalis peruviana has increased dramatically. P. infestans was isolated from this crop in the province of Cundinamarca, Colombia. Symptoms caused by this oomycete appeared initially on the leaf margins as small, irregular, necrotic spots that expanded and merged, increasing the necrotic area. These spots had a soft texture resulting from the degradation of plant tissue by the pathogen. On old lesions, white mycelia and sporangia were observed. Affected plants were rarely killed, but under favorable conditions, severe symptoms were observed in leaves and yield was reduced. Ten isolates were obtained from infected tissue by placing a lesion directly on a potato slice in a moist chamber (2). Mycelia grown on the potato slice were then transferred to rye agar. Identification of the pathogen was performed based on morphological characteristics, specifically, sporangiophores of P. infestans are compoundly branched and develop sympodially, with swellings at the points where sporangia were attached (1). Further confirmation was obtained by sequencing the internal transcribed spacer (ITS) regions (GenBank Accession Nos. EF173467-EF173476). Koch's postulates were completed in the laboratory by spray inoculating detached leaves of Cape gooseberry with a zoospore suspension obtained from each of the 10 isolates. Inoculum was prepared by flooding 10-day-old cultures with sterile distilled water to obtain a 104/ml sporangial suspension followed by zoospore induction at 4°C. Leaves were sprayed with this suspension, placed in moist chambers, and incubated at 20°C in the dark. Control leaves were sprayed with sterile distilled water. Two separate leaves were inoculated with each isolate. The pathogen was reisolated from leaf lesions in all cases. The period between infection and the appearance of symptoms ranged from 5 to 7 days. To our knowledge, this is the first report of P. infestans causing damage on Cape gooseberry in Colombia. Chemical control measures are to some extent successfully applied in most regions where solanaceous crops are grown in Colombia. Nevertheless, suitable disease management for Physalis peruviana has not been achieved and further studies on the epidemiology of the disease on this new host are needed. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul, MN, 1996. (2) G. A. Forbes et al. Phytopathology 87:375, 1997.

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