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Caractérisation phénotypique et génotypique d’isolats de Phytophthora infestans (Mont.) de Bary, agent causal du mildiou de la pomme de terre et de la tomate dans la région du nord-ouest d’Algérie
| Content Provider | Semantic Scholar |
|---|---|
| Author | Rekad, Fatma Zohra |
| Copyright Year | 2018 |
| Abstract | A total of 161 Phytophthora infestans isolates, collected from infected potato and tomato plants during 2008e2014, were characterized based on mating type, metalaxyl sensitivity and polymorphism at 12 simple sequence repeat (SSR) loci, in order to investigate the population of P. infestans in the north-west of Algeria, an emerging potato production region. The majority of isolates were of A2 mating type (112 isolates). A high percentage (89 %) of resistance to metalaxyl among isolates was detected. The metalaxyl resistant phenotype was present in both mating types with a higher percentage in A2 mating type isolates. SSRbased genotypic analysis of P. infestans population showed a low diversity. Genotype 13_A2 was the predominant in the population with a frequency of 67 % followed by 2_A1 (21 %) and 23_A1 (5 %). Genotype 23_A1 was detected only in tomato and potato isolates collected in 2013 and 2014. a 2017 British Mycological Society. Published by Elsevier Ltd. All rights reserved. Introduction disease in theworld. Under favourable conditions it candestroy Late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary, is considered to be the most important potato Z. Rekad), olgacacciola@u . Published by Elsevier L the whole potato haulm and cause considerable yield loss. P. infestans is responsible of $ 6.7 billion annually in potato, and crop losses up to 100 % in tomato (Chowdappa et al. 2015). In nict.it (S.O. Cacciola). td. All rights reserved. 468 F. Z. Rekad et al. the19th century thispathogencaused the famousGreatFamine in Ireland resulted in the death of approximately one million and the emigration of a million more people (Fry & Godwin 1997). Since this period, migration probably within exported seed tubers, allowed the late blight pathogen to spread throughout the world (Fry et al. 1993). As a consequence of the latest of these movements, populations of P. infestans have changed in several North European countries during the 1980s. Several studies on characterization of P. infestans showed that the ‘old’ European populations of the pathogen were rapidly being replaced by ‘new’ populations, genetically different and probably originated fromcentralMexico (Fry et al. 1993). Acrossmany potato growing regions, populations of P. infestans have been dominated by clonal lineages that are defined using a combination of genotypic and phenotypic characters (Cooke & Lees 2004). A successful A2 mating type, metalaxyl resistant lineage with increased aggressiveness and virulence that originated in Europe was named genotype 13_A2 (Cooke et al. 2012; Lees et al. 2012). Itwasfirst reported in theNetherlands andGermany in 2004, Poland in 2006, 2008 and 2009 (Chmielarz et al. 2014) and reached 80 % of the population in Great Britain in 2008 (Cooke et al. 2012). The 13_A2 lineage was responsible for severe late blight outbreaks on potato and tomato in southern India and has replaced the prior population represented by the US-1 and other genotypes (Chowdappa et al. 2015). In Algeria, late blight is a very common disease on potato, but it was also reported on tomato in some areas of the country and it is controlled through extensive use of chemical fungicides, especially metalaxyl, as in many other regions in the world. In north-western Algeria, an emerging potato production region, this disease reached epidemic proportions in 2007e2008, probably due to the favourable weather conditions. Consequently, heavy yield losses were recorded despite the widespread use of late blight fungicides and potato production has decreased by 30 % in this period. InAlgeria, potato and tomato are themost important vegetable crops, grown on 156176 and 22 646 ha, with an annual production of 4.67 and 1 million tones, respectively (FAOSTAT 2014). Potato is planted in three seasons, from Aug. to Jun. The late season, from Jan. to Jun. is the main cropping period in all production regions, but early and very early crops are typical practices in coastal regions. The majority of seed potato tubers are imported from European countries, especially the Netherlands, France, Denmark and Scotland. Conversely, tomato is grown all year round in greenhouses and open fields. In some areas, potato and tomato are grown inadjacent fields increasing the risk of the spread of late blight from one crop to another. In addition, some cultural practices, such as absence of crop rotation, sprinkler irrigation, and the widespread use of susceptible cultivarsmayalso promote early attacks. The practice of leaving infected potato tubers in fields after harvest could also be a potential source of primary inoculum for late blight epidemics. A study of some P. infestans isolates collected from the northwestern Algeria during 2008 revealed the appearance of metalaxyl resistance and the presence of the two mating types, A1 and A2, with a high prevalence of A2 (Corbi ere et al. 2010). Thus, monitoring pathogen insensitivity, especially to systemic fungicides, is an important aspect of disease management (Gisi & Cohen 1996). The development of P. infestans isolates’ resistance to metalaxyl was reported also in many regions of the world (Deahl et al. 1993; Gisi & Cohen 1996; Hammi et al. 2002; Cooke et al.2010;Hamada&Harbaoui2010;Chmielarzetal.2014). Phytophthora infestans is a heterothallic, hemi-biotrophic oomycete with two mating types (A1 and A2). The presence of both mating types enables sexual reproduction, which generates genotypic diversity in the pathogen population leading to increased adaptability. Another effect of sexual reproduction is the production of oospores, which are highly tolerant to adverse environmental conditionsand can survive in soil between growingseasonsandoverseveralyears (Turkensteen et al.2000). Before 2008 there were no data on Algerian P. infestans population characteristics. The first report of the presence of the A1 and A2 mating types in Algeria (Corbi ere et al. 2010) indicates that all A2 P. infestans isolates collected during 2007e2008 have highly complex virulence patterns. Despite the importance of late blight disease on potato and tomato cultivation in Algeria, very little is known about the characteristics of the P. infestans population in this country. The aim of this study was to characterize P. infestans populations in order to understand the repeated epidemics recorded in the north-western Algeria region since 2008 and thus develop new efficient late blight control strategies. Phenotypic and genotypic traits were analyzed to determine: (i) the mating type distribution in the Algerian population; (ii) the population level of metalaxyl sensitivity; (iii) their genotypic diversity using microsatellite markers. Materials and methods Sampling and isolations Samples were collected during 2008e2014 from potato crops grown in the field and tomatoes grown in the field and greenhouses, located in different sites in north-western Algeria (Fig 1). Two most important potato production areas from this region, Mostaganem (coastal region) and Ain Defla (interior region) were chosen to compare the populations of Phytophthora infestans for mating type ratio, level of metalaxyl resistance and genotypes frequency. One to four fields were sampled per site at the onset of the epidemic and at 15e20 d thereafter. Five to ten samples with a single lesion were randomly collected from each field. Sampleswere packed individually in paper bags andmaintained at 4 C until isolation. Phytophthora infestanswas isolated from potato and tomato leaves, stems, fruits and tubers showing typical late blight symptoms by placing small pieces of infected tissue under potato tuber slices of susceptible cultivar Spunta. After four to five days of incubation at 18 C in darkness, small tufts of mycelium growing above the potato slice were transferred to Petri dishes containing pea agar medium (protocol from Corbi ere & Andrivon 2003) amended with rifamycin (30 mg L ) and ampicillin (200mg L ). Pure cultures were obtained by repetitive transfers on pea agar medium. |
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| Alternate Webpage(s) | http://e-biblio.univ-mosta.dz/bitstream/handle/123456789/691/Th%C3%A8se_Rekad_2018%20S.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
