Strains Of Phytophthora Infestans Research Articles

Antagonistic potential of bacterial strains of the genera <i>Bacillus</i> and <i>Pseudomonas</i> and fungi of the genus <i>Trichoderma</i> isolated in Uzbekistan against <i>Phytophthora infestans</i>

Studies have been carried out on strains of bacteria and fungi isolated in Uzbekistan, which can be used in the biological control of potato late blight. Testing was carried out on two strains of Phytophthora infestans — TVKT-1 and 4MSLK 26 — isolated from affected potato in the Tashkent region of Uzbekistan and in the Moscow region of Russia, respectively. In relation to these strains, the antagonistic activity of strains of fungi belonging to the genus Trichoderma and bacteria of the genera Bacillus and Pseudomonas isolated in Uzbekistan was studied. The maximum antagonistic activity was shown by the Bacillus safensis 3/11 strain, which inhibited the growth of the mycelium of the TVKT-1 strain by 61.9% and 4MSLK 26 by 50%. The strains B. licheniformis 6/25 and Pseudomonas alcaliphila 2/18 were also quite effective. All studied strains of fungi of the genus Trichoderma showed high antagonistic activity; the most active strain was T. asperellum Uz-A4, which inhibited the growth of mycelium of strains TVKT-1 and 4MSLK 26 by 77.1 and 73.1%, respectively.

A COMPREHENSIVE STRATEGY FOR LATE BLIGHT MANAGEMENT IN POTATO AND TOMATO

Late blight is a highly destructive disease primarily affecting potato (Solanum tuberosum) and tomato (Solanum lycopersicum) and some other closely related crops such as aubergine, pepper, solanaceous weeds such as nightshade species, wild tomato etc. This disease is caused by fungus-like organism oomycetes also known as water mold called Phytophthora infestans. Whereas early blight of potato and tomato are caused by fungus Alternaria solani and Alternaria tomatophila respectively. Heinrich Anton De Bary, the father of modern plant pathology studied the epidemics of Late Blight in 1863 and renamed the causal organism Phytophthora infestans (infectious plant destroyer). The disease is severe in areas with high humidity and rainfall and spreads through wind, rain, or contaminated plant material capable of causing entire crop failure if left uncontrolled. Late blight affects foliage, fruit, and tuber and its symptoms include dark, water-soaked lesions on the stem, leaves, and fruit which can rapidly develop into brown, necrotic areas ultimately leading to plant death. Control measures for late blight includes crop rotation, the use of resistant varieties and the application of fungicides. However, the emergence of more virulent strains of Phytophthora infestans and the development of resistance to fungicide application pose ongoing challenges to effective disease management. This paper reviews the current knowledge on management strategies for late blight focusing on integrated disease management approaches. Furthermore, the challenges and prospects of integrated management strategies are discussed.

Evaluación de la sensibilidad de Phytophthora infestans (Mont) Bary al fungicida Oxatiapiprolin

The management of aggressive strains of Phytophthora infestans is a challenge for Mexico, so the objective of study proposed to validate and monitor the efficacy of (Oxatiapiprolin), against the sensitivity of P. infestans micropopulations, isolated from the field. A modified protocol with leaf discs and five concentrations of the fungicide at a pressure of 1.2 bar was tested against a severe late blight isolate from the Toluca Valley, State of Mexico. The fungicide showed an inhibitory effect on a mixed isolate of P. infestans under in vitro conditions, compared to the first five concentrations used in the test (1-0.0016 ppm). It was observed that at a higher concentration, there was an increase in the sensitivity of the pathogen and less damage to the tissue. After 5th concentration, less than 25% of tissue was affected (0–2.6 mm) compared with the damage in control (13 mm) (>95%), when the fungicide was not applied. The mean inhibition (EC50) is high calculated at approximately 0.00034 mgL-1 of the fungicide, which inhibits 50% of the growth of the pathogen.

Morphological and transcriptomic analysis of attenuated and virulent strains of Phytophthora infestans

Phytophthora infestans is a hemibiotroph Oomycete that primarily infects tomato. In this study, the growth status and pathogenicity of attenuated and virulent strains of Phytophthora infestans were determined. Furthermore, RNA-seq technology was used to explore the differences in gene transcription levels between attenuated and virulent strains. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed on the differentially expressed genes (DEGs) obtained by sequencing, and the significant DEGs related to the growth and pathogenicity of the strains were screened from the significantly enriched pathways. The results revealed that compared with the virulent strain, the growth of the attenuated strain was inhibited, the structure of hyphae was destroyed, and the disease index was decreased. The differences in the growth status and disease index of the attenuated strain were related to changes in several metabolic pathways, and the DEGs in the metabolic pathways indicated alterations in the attenuated strain growth and pathogenicity. There were 2,651 DEGs in the attenuated strain, of which 1,086 were upregulated and 1,565 were downregulated. The inhibited growth of the attenuated strain was associated with accumulation of excessive glucose, decomposition of serine/glycine, and reduction of tryptophan synthesis. The reduced pathogenicity of the strain was associated with degradation of the cell wall and reduced formation of melanin and α-keto butyric acid. These results could offer insights into the mechanisms of attenuation of Phytophthora infestans.

Development of a RAPD protocol for typing strains of Phytophthora infestans in Mauritius

In Mauritius, substantial decrease in potato yields due to late blight are reported annually and it has become necessary to track the genetic identity of local Phytophthora infestans strains. The Random Amplified Polymorphic DNA (RAPD) technique is a low-cost and simple genetic characterisation tool that has been widely used for molecular fingerprinting but which requires extensive optimisation. The aim of this study was to carry out a series of experiments to optimise a RAPD protocol for routine P. infestans typing. Amplifications performed with DNA template concentration of 30-50 ng/μl, primer concentration of 2.0 − 3.0 μM and MgCl2 concentration of 3.0 mM gave the best RAPD profiles. These optimised conditions were used to carry out RAPD fingerprinting of 7 P. infestans isolates and codified data were used to construct a consensus dendogram, which grouped the 7 isolates into 3 distinct clusters, consistent with results obtained from other molecular characterisation techniques.

Genotyping of Phytophthora infestans in Eastern Africa Reveals a Dominating Invasive European Lineage.

Strains of Phytophthora infestans, the pathogen causing late blight of potato and tomato, are thought to be moved around the world through infected planting material. Since its first appearance in 1941, late blight has caused important losses to potato production in the eastern-Africa region (EAR). In the current study, the genetic structure of the population in Kenya, Uganda, Tanzania, Burundi, and Rwanda was characterized using 12-plex microsatellite markers with the aim of testing the hypothesis that a strain originating from Europe, 2_A1, has recently dominated the population in EAR. Analyses of 1,093 potato and 165 tomato samples collected between 2013 and 2016 revealed the dominance on potato in all countries of the 2_A1 clonal lineage. On tomato, a host-specialized form of the US-1 lineage appears to persist in Rwanda, Uganda, and Tanzania whereas, in Kenya, most samples from tomato (72.5%) were 2_A1. The US-1 lineage in Tanzania had two private alleles at the Pi02 marker, suggesting a possible independent introduction into the region. US-1 had higher genetic variability than 2_A1, consistent with the earlier establishment of the former. Continuous tracking of P. infestans population changes should help identify new virulent and aggressive strains, which would inform strategic disease management options.

Antifungal power of citrus essential oils against potato late blight causative agent

Three citrus species (Citrus sinensis Cadenera, Citrus limon Eureka and Citrus bergamia Castagnaro) are involved in the biological control as an alternative to the use of chemical fungicides (metalaxyl) against aggressive Algerian strains of Phytophthora infestans, which are responsible for potato late blight. The fungal extracts from two potato-producing areas (El Abbadia, Ain Defla and Bourkika, Tipaza), which were respectively purified and identified as A1 and A2, were studied by in vitro and in vivo tests. The citrus essential oils varied in their in vitro inhibitory effects on sporulation, mycelial growth and survivability of P. infestans isolates. Meanwhile, the in vivo infection rate of detached potato leaves in soaking treatment was found to be significant and confirmed the fungicidal effect of citrus essential oils, which were in good consistency with in vitro results. Bergamot essential oil performed the best in both in vitro and in vivo tests, followed by the orange and lemon essential oils.

An RNA symbiont enhances heat tolerance and secondary homothallism in the oomycete Phytophthora infestans

Some strains of Phytophthora infestans, the potato late blight pathogen, harbour a small extrachromosomal RNA called PiERE1. A previous study reported that this RNA symbiont does not noticeably affect its host. Here it is revealed that PiERE1 exerts subtle effects on P. infestans, which result in greater thermotolerance during growth and an increase in secondary homothallism, i.e. oospore formation in the absence of the opposite mating type. The interaction can be considered mutualistic since these traits may increase the fitness of P. infestans in nature. Assays of biomarkers for cellular stress revealed that an Hsp70 chaperone was upregulated by PiERE1. A genome-wide search for more members of the Hsp70 family identified ten belonging to the DnaK subfamily, one in the Hsp110/SSE subfamily, and pseudogenes. Four DnaK subfamily genes encoding predicted cytoplasmic or endoplasmic reticulum proteins were upregulated in strains harbouring PiERE1. This may explain the greater thermotolerance conferred by the RNA element, and suggests that Hsp70 may be a useful biomarker for testing organisms for the cellular effects of symbiotic elements.

Resistance of Russian strains of Phytophthora infestans to fungicides metalaxyl and dimethomorph

In total, 2000 P. infestans isolates collected during 1988–2004 in different regions of Russia were tested for resistance to metalaxyl. In the majority of field populations, the frequency of resistant strains decreased after 1993–1994. This might be related to changes in the potato industry in Russia. Potato production was concentrated in small private gardens. The part of resistant strains in populations from small private patches was less than that in large commercial fields. Small private gardens became a great source of sensitive genotypes. In recent years, the part of resistant strains in the majority of field populations was less than 30%. A small number of resistant strains in a population occurs even if there has been no treatment with metalaxyl-containing preparations for a long time. In some populations, the frequency of resistant strains has increased, depending on treatments. Variation in the level of resistance to metalaxyl in one clonal lineage is shown. Resistant strains occurred in potato leaves and tubers, and in tomato leaves. They were rare in tomato fruits. Probably, the sensitive strains affecting fruits have a selective advantage. More than 370 strains from different regions were tested for resistance to dimethomorph-containing preparations. Resistant strains were not detected.

Fungicidial Activity of Benthiavalicarb-isopropyl against <i>Phytophthora infestans</i> and Its Controlling Activity against Late Blight Diseases

Benthiavalicarb-isopropyl, a novel member of the amino acid amide carbamate group of fungicides, is effective against all Oomycete fungal plant pathogens except Pythium spp. Our results demonstrate that this fungicide effectively controls potato and tomato late blight caused by metalaxyl-sensitive and -resistant strains of Phytophthora infestans. Experiments in vitro demonstrated that benthiavalicarb-isopropyl was ineffective in stopping the discharge of zoospores from zoosporangia and suppressing their motility; but strongly inhibited mycelial growth, sporulation, and the germination of sporangia and cystospores. Experiments in a greenhouse showed that benthiavalicarb-isopropyl has not only a strong preventive, but also a curative effect; its translaminar properties are effective along with its rainfastness and residual activity. In field trials, it was effective in controlling tomato and potato late blight at 25–75 g a.i./ha. © Pesticide Science Society of Japan

Gene mpl1 , activated during mating in Phytophthora infestans : similar to genes encoding pectate lyases

Clones of genes activated in mating cultures of A1 and A2 mating-type strains of Phytophthora infestans were isolated using the cDNA-representational difference analysis subtraction method. Clone cET58 was selected based on its accumulation in mating cultures and then was used as a probe to isolate cDNA clone cET58L2 from a cDNA library that was constructed from mycelia grown under mating conditions. Sequence analysis revealed that cET58L2 was 1043 bp long and contained a complete open reading frame of 789 bp. The amino acid sequence of the putative protein was similar to a pectate lyase, PLD, of Fusarium solani f. sp. pisi. The central region of the predicted protein was highly similar to the sequence of other pectate lyases. The gene from which the cDNA clones were derived was designated mpl1. A probe corresponding to the protein-coding region of mpl1 was prepared (probe p58L) for Northern and Southern analyses. The maximum rate of oogonia increase and mpl1 transcript accumulation reached a maximum after 5 days in mating culture. More than 13 genes with sequences similar to that of mpl1 were found in the genome, revealing mpl1 to be a multicopy gene. The mpl1 may be a pectate lyase gene that is activated in P. infestans during mating.

A leaf lipoxygenase of potato induced specifically by pathogen infection.

Lipoxygenase (LOX) activity has been identified consistently during pathogen-induced defense responses. Here we report the involvement of a specific leaf LOX gene of potato (Solanum tuberosum), designated POTLX-3 (GenBank/EMBL accession no. U60202), in defense responses against pathogens. The sequence of POTLX-3 does not match any other LOX genes of potato and has the greatest match to a tobacco LOX gene that contributes to a resistance mechanism against Phytophthora parasitica var nicotianae. POTLX-3 transcript accumulation was not detected in untreated, healthy potato organs or in wounded mature leaves. POTLX-3 mRNA accumulation was induced in potato leaves treated with ethylene or methyl jasmonate or infected with either virulent or avirulent strains of Phytophthora infestans, the causal agent of late blight. During the resistance response, POTLX-3 was induced within 6 hours, increased steadily through 24 hours, and its mRNA continued to accumulate for a week after inoculation. In contrast, when a plant was susceptible to P. infestans, induction of mRNA accumulation in response to inoculation was inconsistent and delayed. LOX activity assayed during an incompatible interaction in leaves peaked 3 days earlier than during a compatible interaction. POTLX-3 mRNA accumulation also was induced during hypersensitive response development caused by the incompatible pathogen Pseudomonas syringae pv phaseolicola. Our results show that POTLX-3 may be involved specifically in defense responses against pathogen infection.

Assessment of mating types and resistance to metalaxyl of Canadian populations ofPhytophthora infestans in 1997

The distribution of A1 and A2 mating types, and of metalaxyl-sensitive (MS), metalaxyl-intermediate (MI), and metalaxyl-resistant (MR) strains ofPhytophthora infestans, the causal pathogen of late blight, were determined in Canada in 1997. Potato plants or tubers and tomato plants or fruits, suspected to have late blight infection, were received from seven Canadian provinces in 1997, and were assessed for the presence ofP. infestans. Among 220 samples suspected to have late blight,P. infestans was recovered from 132 samples (60%) received from British Columbia (BC), Manitoba, New Brunswick, Prince Edward Island, and Quebec. From the 132 samples, 364 isolates were obtained and tested for their mating type and response to metalaxyl. Populations ofP. infestans within Canadian provinces were homogeneous for mating types, except within BC, where populations comprised both A1 and A2 mating types both within fields and sometimes within samples. The A2 mating type was found in all provinces where late blight was present. The A1 mating type was found only in Manitoba (1 isolate) and in BC (38 isolates). Unlike the old A1 isolates, those found in BC in 1997 were highly resistant to metalaxyl. These A1 isolates are even more resistant than A2 isolates. Based on assays with 10 ug.ml−1 of metalaxyl, 14% of all tested isolates were MS, 69.8% were MI and 16.2% were MR. In addition, all provinces contained MS, MI, and MR isolates. No specific mating type or metalaxyl sensitivity level were specific to tomato or potato.

Response of solanaceous cultivated plants and weed species to inoculation with A1 or A2 mating type strains of Phytophthora infestans

Hypersensitive response symptoms of late blight were induced when sporangia of Phytophthora infestans were inoculated on discs of excised leaf tissues of black nightshade, eggplant, green pepper, and tobacco. No symptoms due to disease or hypersensitive response were observed in stem piece tissues of these plant species, suggesting that these four are nonhosts for late blight. The Al (US-1), the A2 (US-8), and the more recent Al mating type (US-ll) strains infected both leaf and stem tissues of climbing and hairy nightshade, potato, and tomato but only leaf tissues of petunia. This is the first report of the new strains of P. infestans causing late blight symptoms on climbing nightshade and petunia in Canada. Based on infection levels, infection rates, and spore production, the US-8 and US-ll genotypes were similar and both were more aggressive than the US-1 genotype. Disease severity and sporulation were greater on potato inoculated with US-1 than for the other host plants and were the least on petunia. All susceptible plants were infected at about the same level with US-8, except for petunia, which had a much lower level of infection. Spore production for US-8 was less on tomato and petunia than on the other plants. Infection levels and spore production by US-ll on tomato were as great as or greater than on potato. These results demonstrate that the new strains of P. infestans, US-8 and US-ll, are generally more aggressive than the previous predominating strain, US-1, and that climbing and hairy nightshade and petunia may harbour late blight, while black nightshade, eggplant, green pepper, and tobacco plants do not.

Effects of hot and cold temperatures on the survival of oospores produced by United States strains ofPhytophthora infestans

Oospores produced from matings between US strains ofPhytophthora infestans were subjected to hot or cold temperatures and then evaluated for viability, based on percent germinationin vitro. Of 35 crosses, 3 produced oospores with sufficient germination for replicated assessments of temperature effects. Germination rates were as high as 26%, but the maximum germination percentage varied among crosses. Two additional crosses, one involving isolates from Mexico also had sufficient germination for assessment of temperature effects. Oospores did not germinate after 2 hr treatments at or above 46C, or after 12 hr treatments at 40C. Temperature treatment at -80C suppressed germination. Temperature had a similar effect on oospore germination from all crosses.

Potato Late Blight in the Columbia Basin: An Economic Analysis of the 1995 Epidemic.

The cost of managing late blight in potatoes during a severe epidemic caused by new, aggressive strains of Phytophthora infestans in the Columbia Basin of Washington and Oregon in 1995 was documented. The mean number of fungicide applications per field varied from 5.1 to 6.3 for early- and midseason potatoes, and from 8.2 to 12.3 for late-season potatoes in the northern and southern Columbia Basin, respectively. In 1994, a year when late blight was not severe, the mean number of fungicide applications per field made to early- and midseason potatoes was 2.0; whereas late-season potatoes received a mean of 2.5 applications. The mean per acre cost of individual fungicides applied varied from $4.90 for copper hydroxide to $36.00 for propamocarb + chlorothalonil. Total per acre expenses (application costs plus fungicide material) for protecting the crop from late blight during 1995 ranged from $106.77 to $110.08 for early and midseason potatoes in different regions of the Columbia Basin and from $149.30 to $226.75 for lateseason potatoes in the northern and southern Columbia Basin, respectively. Approximately 28% of the crop was chemically desiccated before harvest as a disease management practice for the first time in 1995, resulting in an additional mean cost of $34.48/acre or $1.3 million for the region. Harvested yields were 4 to 6% less than in 1994. The total cost of managing late blight in the Columbia Basin in 1995 is estimated to have approached $30 million.

Testing for resistance to metalaxyl inPhytophthora infestans isolates from northwestern Washington

Outbreaks of late blight occurred in commercial potato fields in northwestern Washington in 1989 and reached epidemic proportions in 1990. Since most blighted fields reportedly had received 2–4 late-season applications of metalaxyl, the possibility existed that pathogenic strains ofPhytophthora infestans had developed resistance to this systemic fungicide. In testing this hypothesis,P. infestans was isolated consistently from diseased leaves, stems, and tubers of potato when small tissue pieces were surface-disinfected in 0.5% NaOCl for 3 min. Virulence of isolates was assessed on detached leaflets of eight differential (R-gene) potato genotypes. Although simple races (single and double) were recovered, there was also a high frequency of complex race combinations. When tested in metalaxyl-amended media, 81% of the 73 isolates recovered from diseased tissues were highly resistant to 10 μg metalaxyl/ml and 19% yielded intermediate resistance. Sensitive isolates were not recovered. Fifty-five percent of 40 isolates sporulated on potato tuber disks in the presence of ≥10 ug metalaxyl/ml. On leaf tissues, 85% of 20 isolates sporulated in the presence of 10 μg metalaxyl/ml, and 50% sporulated in the presence of 100 μg/ml. This is the first report ofP. infestans resistance to metalaxyl in the U.S.

Changes in the distribution of phenylamide-resistant strains ofPhytophthora infestans (Mont.) de Bary in Ireland 1985–89

Phenylamide-based fungicides were reintroduced to the Irish market in 1985. Mixtures of phenylamides and mancozeb were recommended for no more than 3 sprays in potato late blight control programmes with the last systemic spray to be applied not later than 31 July. Samples of potato foliage infected withP. infestans were collected from the main potato growing areas in Ireland over a five-year period starting in 1985. Using the floating disc method, 11% of the crops sampled in 1985 were found to have phenylamide-resistant strains ofP. infestans present. The number of crops with resistant strains increased rapidly up to 1988 when 83% of the crops sampled had resistance. Factors affecting the distribution of resistance and the efficacy of a phenylamide-based spray programme are discussed.

Resistance to acylalanines in Phytophthora infestans in The Netherlands1

In The Netherlands in 1980 a severe late‐blight epidemic involving metalaxyl‐resistant strains of Phytophthora infestans did considerable damage to the potato crop. As a consequence metalaxyl or metalaxyl‐containing products were withdrawn from the Dutch fungicide market for the control of potato late blight. In 1981 the majority of the P. infestans isolates obtained from various parts of the country were sensitive to metalaxyl. In three areas where metalaxyl mixtures were used on a relatively large scale metalaxyl‐resistant strains dominated the population. Incidental use of metalaxyl mixtures in 1982 and 1983 showed adequate late‐blight control and, when in 1984 an early and in some areas severe epidemic developed, a metalaxyl/mancozeb mixture was reintroduced for curative application in combination with conventional fungicides. Although disease control was adequate, resistant strains were present in a small number of fields. Whether resistant strains will increase in frequency and threaten the usefulness of mixtures of acylalanines will heavily depend on how well potato farmers adopt strategies involving a limited use of mixtures of acylalanines in a spray schedule with conventional late‐blight fungicides.

Strains of Phytophthora infestans from Switzerland with A2 mating type behaviour

Strains of Phytophthora infestans from Switzerland with A2 mating type behaviour