Showing papers on "Sclerotinia sclerotiorum published in 1996"
TL;DR: A hybrid endochitinase gene under a constitutive promoter was introduced by Agrobacterium-mediated transformation into a winter-type oilseed rape inbred line and exhibited an increased tolerance to disease as compared with the nontransgenic parental plants.
Abstract: Constitutive overexpression of a protein involved in plant defense mechanisms to disease is one of the strategies proposed to increase plant tolerance to fungal pathogens. A hybrid endochitinase gene under a constitutive promoter was introduced by Agrobacterium-mediated transformation into a winter-type oilseed rape (Brassica napus var. oleifera) inbred line. Progeny from transformed plants was challenged using three different fungal pathogens (Cylindrosporium concentricum, Phoma lingam, Sclerotinia sclerotiorum) in field trials at two different geographical locations. These plants exhibited an increased tolerance to disease as compared with the nontransgenic parental plants.
242 citations
TL;DR: Hphal mycoparasitism, rather than sclerotinia parasitism, is suggested to be the mechanism by which T. harzianum controls S. sclerotiorum under these conditions.
Abstract: Hyphal interactions between the mycoparasite Trichoderma harzianum (BAFC Cult. No. 72) and the soilborne plant pathogenic fungus Sclerotinia sclerotiorum were investigated in dual culture and in sterilized soil, by light and scanning electron microscopy. In dual culture, T. harzianum hyphae grew towards and coiled around the S. sclerotiorum hyphae. Dense coils of hyphae of T. harzianum and partial degradation of the Sclerotinia cell wall were observed in later stages of the parasitism. In sterile soil, conidia of T. harzianum germinated and the developing mycelium made contact with that of S. sclerotiorum, forming short branches and appressorium-like bodies which aided in holding and penetrating the host cell wall. An in vitro system was developed to test the ability of T. harzianum to control Sclerotinia wilt in cucumber and lettuce: coating seeds with T. harzianum conidia reduced the pre- and post-emergence effect of S. sclerotiorum in cucumber by 69 and 80%, respectively, and in lettuce by 46 and 72%, respectively. In the greenhouse, the disease caused by S. sclerotiorum in lettuce was reduced by treating seedlings with a peat-bran preparation of T. harzianum. Despite the non-significance of the reduction in disease, Trichoderma-treated lettuce seedlings were much more developed than controls. In sunflower, significant reductions (in the range of 68 to 84%) in disease incidence were obtained by incorporating the peat-bran T. harzianum preparation into the seedling rooting mixture. Hyphal mycoparasitism, rather than sclerotial parasitism, is suggested to be the mechanism by which T. harzianum controls S. sclerotiorum under these conditions.
142 citations
TL;DR: In seven field experiments conducted in Alberta from 1984 to 1987, the application of Coniothyrium minitans to soil at seeding time reduced apothecial production of sclerotia of Sclerotinia sclerOTiorum under the canopies of bean, canola, wheat, and barley and increased parasitism on sclerotsia produced on diseased bean plants.
Abstract: In seven field experiments conducted in Alberta from 1984 to 1987, the application of Coniothyrium minitans to soil at seeding time reduced apothecial production of sclerotia of Sclerotinia sclerotiorum under the canopies of bean, canola, wheat, and barley. Application of Talaromyces flavus was ineffective, and combinations of T. flavus and C. minitans were as effective or less effective than C. minitans alone, indicating that no synergism occurred between these hyperparasites. Application of C. minitans to soil in the spring reduced apothecial production from sclerotia of S. sclerotiorum buried in the soil, and increased parasitism on sclerotia produced on diseased bean plants.
50 citations
TL;DR: It is suggested that transmissible hypovirulence has potential for use as a management strategy for diseases caused by Sclerotinia sclerotiorum.
Abstract: Thirty isolates of Sclerotinia minor were collected from a 4 ha commercial lettuce crop at Holland Marsh, Ontario, and examined for the presence of transmissible hypovirulence. Three slow-growing isolates with atypical colony morphology were less virulent (P = 0.05) on detached lettuce leaves than other isolates and were considered hypovirulent. These thirty isolates comprised three mycelial compatibility groups with the five least virulent isolates producing variable interactions. Hypovirulence was transmissible among some isolates in culture and on lettuce tissue. When a mycelial suspension of a hypovirulent isolate was sprayed on lesions on lettuce leaves caused by a compatible virulent isolate, there was a reduction in lesion size and number of sclerotia produced in comparison to control treatments. Virulent isolates converted to hypovirulence retained the hypovirulent phenotype after repeated subculturing. All isolates were tested for the presence of double-stranded ribonucleic acid (dsRNA), which is associated with transmissible hypovirulence in Sclerotinia sclerotiorum. Eleven isolates, including some virulent and all hypovirulent isolates, tested positive for dsRNA. However, conclusions could not be drawn concerning associations between certain dsRNA segments and hypovirulence in S. minor because of the variability in the recovery of dsRNA. Results of this study suggest that transmissible hypovirulence has potential for use as a management strategy for diseases caused by S. minor.
48 citations
TL;DR: Production of polygalacturonases and pectinases from Sclerotinia sclerotiorum was induced in vitro by galacturonic acid, leading to a basal enzyme production and constitutive enzymes provide the pathogen with the inherent ability to release galactolonic acid from plant cell walls and to trigger inducible enzyme synthesis.
Abstract: Production of polygalacturonases and pectinases from Sclerotinia sclerotiorum was induced in vitro by galacturonic acid. The inductive effect of galacturonic acid was abolished by the presence of glucose, leading to a basal enzyme production. Zymograms of extracellular enzymes showed that galacturonic acid induced the synthesis of six polygalacturonase and one pectin-methylesterase isoforms. Immunoblotting revealed that an exo-polygalacturonase and an exo-polymethylgalacturonase were secreted in all conditions. They are not glucose repressed and not regulated by galacturonic acid. These constitutive enzymes provide the pathogen with the inherent ability to release galacturonic acid from plant cell walls and to trigger inducible enzyme synthesis.
45 citations
TL;DR: Interactions of environment, BCAs, and white mold were highly complex and suppression of disease by many of the BCAs was most effective under environmental conditions that were least conducive for disease.
Abstract: The interactions of Sclerotinia sclerotiorum and seven biological control agents (BCAs) were examined in controlled environments to determine the influence of selected relative humidities (RH) (90, 95, and 100%) and air temperatures (20, 24, and 28°C) on biological control of white mold of bean. All main effects and interactions were significant (P ≤ 0.0001) among the 72 treatments. In the control treatment, lesions of white mold developed in all environmental treatments but were largest at 20°C x 100% RH, 24°C x 95 and 100% RH, and 28°C x 95% RH. Interactions of environment, BCAs, and white mold were highly complex. Alternaria alternata, Drechslera sp., Myrothecium verrucaria, Trichoderma viride, Gliocladium roseum, and an unidentified pink yeast were all highly dependent on environment for efficacy. Changes of 4°C or 5% RH were associated with variability in disease suppression that ranged from ≤25 to 100%. Epicoccum nigrum was comparatively independent of environment and suppressed disease by 100% in all environments. Suppression of disease by many of the BCAs was most effective under environmental conditions that were least conducive for disease. Assessments of biological control efficacy in various environments can be used to more accurately assess the potential of individual BCAs.
44 citations
TL;DR: Northern-blot analysis of RNA isolated from Sclerotinia sclerotiorum showed that pg1, encoding a neutral polygalacturonase, was not expressed during growth in both media, suggesting that a CREA homolog may be involved in the regulation of pg1.
Abstract: Northern-blot analysis of RNA isolated from Sclerotinia sclerotiorum grown on either glucose or polygalacturonate as the sole carbon source showed that pg1, encoding a neutral polygalacturonase, was not expressed during growth in both media. In contrast, transcripts of this gene were detected during infection of sunflower germlings. Analysis of the promoter sequence revealed a number of cis-acting sequences known to regulate the expression of many fungal promoters. Protein-DNA-binding experiments showed that proteins extracted from mycelia grown on polygalacturonate or glucose interacted with different regions of the promoter. The GST-CREA fusion protein, containing the two zinc fingers of the Aspergillus nidulans repressor CREA involved in carbon catabolite repression, forms several complexes with DNA fragments carrying the consensus 5′-SYGGRG-3′. These results suggest that a CREA homolog may be involved in the regulation of pg1.
37 citations
TL;DR: Coniothyrium minitans was recovered from over 80% ofS.
Abstract: Twenty five isolates ofConiothyrium minitans were screened for antagonism toSclerotinia sclerotiorum in a Petri dish bioassay using tomato stem segments placed on sterile sand. The antagonistic activity of 23 isolates was quite uniform and only two less antagonistic isolates were identified. Antagonism, expressed as a reduction in the rate of tissue colonization byS. sclerotiorum, occurred, whetherC. minitans was co-inoculated at the same time, one day before or one day afterS. sclerotiorum, but was slightly restricted whenS. sclerotiorum was given a lead of one day. On average, 50–80% of sclerotia of S.sclerotiorum formed on the stem pieces were infected byC. minitans two weeks after inoculation. Excluding the less antagonistic isolates,Coniothyrium minitans was recovered from over 80% ofS. sclerotiorum-infected stem segments when co-inoculated but from a maximum of only 7% of stem pieces when exposed toC. minitans alone. When the experiments were carried out on non-sterile soil instead of sterile sand, infection of stem pieces byS. sclerotiorum was reduced and recovery ofS. sclerotiorum andC. minitans from stem segments was decreased. SevenC. minitans isolates were also screened againstSclerotium cepivorum andBotrytis cinerea and, whereas the effect ofC. minitans onS. cepivorum-infected tissue and sclerotia was essentially similar to that observed withS. sclerotiorum, B. cinerea infected tissue and sclerotia were not invaded by the antagonist.
37 citations
TL;DR: Fourteen forms of endopolygalacturonases were purified from the culture medium of Sclerotinia sclerotiorum with ion exchange chromatographies and could be divided into two related groups on the basis of the cross-reactions to antibodies raised against a purified acidic endopolyGalacturonase.
Abstract: Fourteen forms of endopolygalacturonases were purified from the culture medium of Sclerotinia sclerotiorum with ion exchange chromatographies. Individual forms differ in their isoelectric point but exhibit similar molecular masses. On the basis of the cross-reactions to antibodies raised against a purified acidic endopolygalacturonase, these forms could be divided into two related groups. Polygalacturonase activities constitute a complex enzyme system in which the extensive multiplicity is due to the expression of a large gene family.
34 citations
TL;DR: Evidence that establishment of bluebunch wheatgrass on spotted knapweed infested rangeland may be improved by combining S. sclerotiorum with high grass seeding rates is provided.
Abstract: Effectiveness of the common soil fungus Sclerotinia sclerotiorum as a biological control for spotted knapweed and its effect on competitive interactions between spotted knapweed and bluebunch wheatgrass were evaluated in a growth chamber study using addition series methods. Total seeding densities ranged from 2000 to 60 000 seeds/m 2 . Mean bluebunch wheatgrass plant weight was 3.5 times greater than spotted knapweed weight per plant, respectively. Coefficient ratios estimating species interaction showed bluebunch wheatgrass density had a greater influence than spotted knapweed density on both bluebunch wheatgrass and spotted knapweed weights (2.11 and 0.51, respectively) when not under the influence of S. sclerotiorum. Niche differentiation ratios indicated a lack of resource partitioning between species (1.11). S. sclerotiorum reduced spotted knapweed density by 68 to 80% without reducing bluebunch wheatgrass density. Spotted knapweed weight per plant also was reduced by the addition of S. sclerotiorum (1.4 to 1.2 mg) but there was not a corresponding increase in bluebunch wheatgrass weight. S. sclerotiorum decreased competition between spotted knapweed and bluebunch wheatgrass. This study provides evidence that establishment of bluebunch wheatgrass on spotted knapweed infested rangeland may be improved by combining S. sclerotiorum with high grass seeding rates.
29 citations
TL;DR: An immunofluorescence technique was used to study the distribution of ascospores of Sclerotinia sclerotiorum on field-collected canola petals, and the multiple infection transformation successfully linearized the relationships between percentage petals carrying ascospore and the mean numbers of ascosphere per petal.
Abstract: An immunofluorescence technique was used to study the distribution of ascospores of Sclerotinia sclerotiorum on field-collected canola petals. Ascospores could be readily distinguished from the spores of other fungi and were sometimes observed in groups of more than 50. The quantitative relationships among mean numbers of ascospores per petal, the percentage of petals carrying ascospores as judged by immunofluorescent staining, and the percentage of petals carrying viable ascospores as judged by a plating technique were studied by regression analysis. The multiple infection transformation successfully linearized the relationships between percentage petals carrying ascospores and the mean numbers of ascospores per petal. About 30% of ascospores on the petals were viable.
TL;DR: Analysis of mitochondrial DNA (mtDNA) haplotypes of Sclerotinia sclerotiorum points to a common origin of some genotypes from agricultural populations, especially when compared with two wild populations that are sharply distinguished from the agricultural sample and from each other.
Abstract: Analysis of mitochondrial DNA (mtDNA) haplotypes of Sclerotinia sclerotiorum points to a common origin of some genotypes from agricultural populations, especially when compared with two wild populations that are sharply distinguished from the agricultural sample and from each other. Five agricultural population samples from canola (Alberta, Canada and Norway), cabbage (North Carolina, USA), sunflower (Manitoba, Canada and Queensland, Australia) and two Norwegian populations from a wild plant, Ranunculus ficaria were compared. Haplotypes were determined by Southern hybridization of purified organelle DNA from S. sclerotiorum and Neurospora crassa to total genomic DNA of S. sclerotiorum. Each isolate had one haplotype. Haplotypes of S. sclerotiorum from R. ficaria were different between the two wild populations and also from all haplotypes observed in the agricultural populations. Among the wild isolates, DNA fingerprint, mtDNA haplotype and location in the sampling transect were all associated. Among the agricultural isolates, four haplotypes were observed in at least two agricultural populations and one haplotype was observed in all agricultural populations. In the Canadian canola sample some clones had one mtDNA haplotype, indicating association with DNA fingerprint, some clones had more than one haplotype, and some groups of clones shared haplotypes. Some of the haplotype diversity may be due to the presence of extra-chromosomal elements associated with the mitochondria of S. sclerotiorum.
01 Jan 1996
TL;DR: It is known that plant resistance may often be the result of multiple chemical constituents acting at specific sites as mentioned in this paper, which is known as plant resistance can be caused by multiple chemical components acting at different sites.
Abstract: It is known that plant resistance may often be the result of multiple chemical constituents acting at specific sites.
TL;DR: A heat-released elicitor obtained from Sclerotinia sclerotiorum mycelium induced a transient increase in the activity of phenylalanine-ammonia lyase in a carrot cell culture and revealed a complex cell response involving the induction and repression of several mRNAs.
Abstract: A heat-released elicitor (HRE) obtained from Sclerotinia sclerotiorum mycelium induced a transient increase in the activity of phenylalanine-ammonia lyase (PAL) in a carrot cell culture. Differential display reactions carried out on total RNA extracted from cells exposed for 7 h to the HRE revealed a complex cell response involving the induction and repression of several mRNAs. One of these elicitor-induced mRNAs encodes a 42.6-kDa protein. Northern (RNA) blot analysis and reverse-transcription polymerase chain reaction studies showed that noninduced cells have a basal expression of the 42.6-kDa protein mRNA that was stimulated five- to 10-fold by treatment with the elicitor.
01 Jan 1996
01 Apr 1996
01 Aug 1996
TL;DR: The control of Russell lupin (Lupinus polyphyllus) in wildlife habitats in braided riverbeds in the central South Island is discussed and plant pathogens as prospective biological control agents for the plant were carried out.
Abstract: The control of Russell lupin (Lupinus polyphyllus) in wildlife habitats in braided riverbeds in the central South Island is discussed A survey of plant pathogens as prospective biological control agents for the plant was carried out Four pathogens, all of them new records for this host in New Zealand, were identified; Pleiochaeta setosa, Colletotrichum gloeosporioides, Verticillium albo-atrum andFusarium heterosporum Symptoms of a disease very similar to bacterial wilt of lucerne were also found but the suspected causal organism, Clavibacter michiganensis subsp insidiosus, has yet to be verified In the light of experimental infection results, these pathogens were assessed as potential bioherbicides together with Ascochyta pisi, Sclerotinia sclerotiorum and S minor, already recorded on lupin species in New Zealand
TL;DR: A strong karyotypic stability among the strains of S. sclerotiorum is revealed which may be preserved by the sexual mode of reproduction of this species, in contrast to numerous other phytopathogenic fungi.
Abstract: Molecular techniques have been used to characterize different field isolates ofSclerotinia sclerotiorum, an ubiquitous phytopathogen. Chromosomal DNA resolved by pulsed-field gel electrophoresis (PFGE) revealed thatS. sclerotiorum contains at least 16 chromosomes ranging from 1.5 Mb to 4.0 Mb. The size of the haploid genome was estimated to be 43.5 Mb. Six field isolates with different levels of virulence on sunflower germlings or green beans were differentiated by random amplification of polymorphic DNA (RAPD), and analysed by clamped homogeneous electric field electrophoresis. This analysis revealed few chromosome-length polymorphisms among these strains. Chromosomal DNA hybridization indicated that the endopolygalacturonase-encodingpgl gene is localized on the smallest chromosome of all the strains, whereas the ribosomal DNA mapped to different-sized chromosomes. The less-aggressive strain was characterized by the presence of a supernumary small band, presumably consisting of dsRNA. In contrast to numerous other phytopathogenic fungi, this study reveals a strong karyotypic stability among the strains ofS. sclerotiorum which may be preserved by the sexual mode of reproduction of this species
01 Aug 1996
TL;DR: The use of the fungus, Sclerotinia sclerotiorum, as a biological control agent for weeds in New Zealand pastures may be dependent upon specific strain identification to distinguish applied from background strains of the pathogen.
Abstract: The use of the fungus, Sclerotinia sclerotiorum, as a biological control agent for weeds in New Zealand pastures may be dependent upon specific strain identification to distinguish applied from background strains of the pathogen. Using RAPD and rDNA analysis, four New Zealand strains and four derivatives of a USA isolate of S. sclerotiorum were compared with single isolates of S. minor and S. trifoliorum. Few differences were detected between any strains of S. sclerotiorum, although a single band out of 94 scored on RAPDs, consistently divided the isolates into USA and New Zealand strains. Isolates of S. minor and S. trifoliorum were clearly separate from S. sclerotiorum using RAPDs, but no differences were detected in rDNA.
TL;DR: Standard mycological media supported faster radial growth than media with single carbohydrate sources and individual amino acids, but glutamic acid combined with maltose or dextrose was similar with respect to stimulation of sporulation when compared with media such as V8 juice and yeast extract agars.
Abstract: Epicoccum nigrum is a potential biological control agent for certain plant diseases, such as white mold of bean caused by Sclerotinia sclerotiorum. To provide information that could be used to impr...
Journal Article•
TL;DR: Results showed that seed health tests are extremely important in order to assure the maintenance of high quality germplasm, avoiding the conservation and dissemination of pathogens.
Abstract: During the period 1982-1992, 9,952 accessions of 24 species, from field collections and research Centers of EMBRAPA, were evaluated in relation to sanitary conditions before storage Aspergillus and Penicillium were the fungi more frequently found associated with those seeds The main pathogenic fungi detected were Pyricularia oryzae, Drechslera oryzae and Gerlachia oryzae in rice; Drechslera sorokiniana in wheat, D teres in barley, Diplodia maydis and Fusarium moniliforme in corn; Colletotrichum lindemuthianum, Rhizoctonia solani, Macrophomina phaseolina and Sclerotinia sclerotiorum in bean and Colletotrichum dematium, and Phomopsis sojae in soybean These results showed that seed health tests are extremely important in order to assure the maintenance of high quality germplasm, avoiding the conservation and dissemination of pathogens
01 Aug 1996
TL;DR: In autumn 1994, 3 month old Californian thistle plants grown from seed were transplanted at regular spacings into a ryegrass/white clover sward and treated with the herbicides clopyralid and MCPB and mycoherbicide Sclerotinia sclerotiorum.
Abstract: In autumn 1994, 3 month old Californian thistle plants grown from seed were transplanted at regular spacings into a ryegrass/white clover sward. Seven treatments including three topping treatments, the herbicides clopyralid and MCPB, and a mycoherbicide Sclerotinia sclerotiorum, were applied to thistle foliage the following summer. Treatment effects on root mass and bud production were measured in December 1995. Clopyralid and S. sclerotiorum reduced dry root weight relative to control 95% and 60% respectively and also reduced the number of root buds and shoots. MCPB had little effect on root weight but reduced root bud numbers by 60%. Thistles topped twice also showed reductions in root weight and shoot numbers.
Journal Article•
TL;DR: The genetical studies of percentage natural attack observed on eight inbred lines representing a range of reactions, and the hybrids from a factorial cross of these lines, indicated that inheritance is mainly additive, with few interactions.
Abstract: Resistance of sunflowers to terminal bud attack bySclerotinia sclerotiorum was studied by microscopical observations of infection processes and by genetical analyses of trials showing natural infections. Electron microscope studies showed that there were no differences in leaf morphology between susceptible and resistant genotypes, and that both were contaminated by ascospores. Only on the susceptible genotype was considerable ascospore germination observed, followed by mycelial development and leaf penetration. On the resistant genotype, there was little ascosopore germination and no further development. The genetical studies of percentage natural attack observed on eight inbred lines representing a range of reactions, and the hybrids from a factorial cross of these lines, indicated that inheritance is mainly additive, with few interactions.
TL;DR: Among eight fungicides tested, only iprodione provided good control of fruit infection and Koch's postulates were tested, and S. sclerotiorum was confirmed as the cause of the disease.
Abstract: Record rainfall occurred in the Hood River Valley during spring of 1993. In late spring, lesions up to 2 cm in diameter were observed on d'Anjou pear fruitlets on the calyx end or where senescent flower parts adhered to the fruits. Sclerotinia sclerotiorum was consistently isolated from infected tissue. Koch's postulates were tested, and S. sclerotiorum was confirmed as the cause of the disease. Mycelial growth of the pathogen on acidified potato dextrose agar was optimum at 20°C, and the average growth rate was about 10 mm per day. Five pear cultivars were ranked in order of increasing resistance to Sclerotinia rot as follows: d'Anjou, Bosc, Columbia Red d'Anjou, Bartlett, and Comice. Among eight fungicides tested, only iprodione provided good control of fruit infection.
01 Aug 1996
TL;DR: An experiment was conducted in a sheep-grazed pasture in Canterbury to test the hypothesis that control of Californian thistle by Sclerotinia sclerotiorum, applied as a mycoherbicide, is limited because the thistle roots escape from the fungus by rapid growth.
Abstract: An experiment was conducted in a sheep-grazed pasture in Canterbury to test the hypothesis that control of Californian thistle by Sclerotinia sclerotiorum, applied as a mycoherbicide, is limited because the thistle roots escape from the fungus by rapid growth. Replicated field plots were either not treated or treated with the mycoherbicide in spring 1993 and again in spring 1994. The thistles were then either mown on three occasions in each of the summers to limit root growth, or left to develop normally. Both the S. sclerotiorum mycoherbicide and mowing reduced the thistle’s root-bud population, as measured by the shoot population emerging in the summers following treatment, but these effects were not synergistic, providing no support for the
TL;DR: Electrophoretic karyotypes (EKs) of 83 isolates were variable within agricultural and natural populations of Sclerotinia sclerotiorum, as well as among S. sclerota minor, and S. trifoliorum; but Variation in EKs was not observed within six mitotic or three meiotic lineages of isolates.
Abstract: Electrophoretic karyotypes (EKs) of 83 isolates were variable within agricultural and natural populations of Sclerotinia sclerotiorum, as well as among S. sclerotiorum, Sclerotinia minor, and Sclerotinia trifoliorum. Variation in EKs was not observed within six mitotic or three meiotic lineages of isolates. EKs of 8 to 10 chromosome-sized DNAs were observed. Homologous and heterologous probes hybridized to four linkage groups.
Patent•
05 Nov 1996
TL;DR: In this article, a novel isolate of Coniothyrium minitans Campbell designated CON/M/91-08 having D.S.M. DSM-9660 was described. Compositions containing this isolate are suitable for use in methods for controlling pathogenic plant fungi and, in particular, for controlling Sclerotinia sclerotiorum.
Abstract: The invention relates to a novel isolate of Coniothyrium minitans Campbell designated CON/M/91-08 having D.S.M. Accession No. DSM-9660. Compositions containing this isolate are suitable for use in methods for controlling pathogenic plant fungi and, in particular, for controlling Sclerotinia sclerotiorum.
01 Jan 1996
TL;DR: Marinelli et al. as mentioned in this paper investigated the role of changes in the productive system on the development of the Sclerotinia blight of peanuts in the southern part of the most important peanut growing region of Argentina, which used to appear sporadically and with very low incidence in 1960.
Abstract: MARINELLI, A, Y MARCH, G J, 1996: Sclerotinia blight of peanuts (Arachis hypogaea L) caused by Sclerotinia sclerotiorum and Sclerotinia minor in Argentina Bol San Veg Plagas, 22 (3): 501-510 Peanut blight, which used to appear sporadically and with very low incidence in 1960, has increased graduality from about the middle of the last decade in the southern part of the most important peanut growing region of Argentina Important changes to the productive system have ocurred in the early 80's and their influence on the development of disease has not been assessed yet Blight etiology and biology were studied during the 1990/91 to 1993/94 agricultural years; by considering the likely effect of the changes that have taken place in the productive system on blight increase Sclerotinia sclerotiorum (Lib) de Bary and S minor Jagger were identified as the species causing blight, the former being the most important While S minor caused infection for myceliogenic germination of sclerotia, 5 sclerotiorum's was myceliogenic and carpogenic The wide diffusion of Runner type cultivars stands out among the factors determining the substancial expansion of this disease The plant canopy structure density associated with the creeping growth habit determine a favorable microclimate conditions within the plant canopy for the disease Moreover, the extended growth period of these cultivars causes the last stage of the cycle to progress when temperatures are more advantageous for blight outbreaks The monoculture, the use of only 5% of registered seeds and the widespead growth of soybean in the peanut growing region might also have contributed to the evolution of epidemics Not only the epidemiological characteristics of the Sclerotinia species found in the crop but also the presente features of the productive system should be considered when designing integrated management strategies for this disease