Leszek Lenc

Dynamics of the root/soil pathogens and antagonists in organic and integrated production of potato

Microbial communities in the root, rhizoplane, and rhizosphere and non-rhizosphere soil in potato, in organic and integrated production systems, were compared at the emergence and flowering phases of plant development. Microorganisms were identified on the basis of their morphology. The dominant groups included Clonostachys + Gliocladium + Trichoderma, Fusarium + Gibberella + Haematonectria + Neonectria, Paecilomyces, Penicillium and Phoma. Microbial density at the flowering phase was often significantly greater in roots and non-rhizosphere soil than in the rhizoplane and rhizosphere. Diversity of the communities often remained stable or was greater at the emergence phase. The density of bacteria changed with time. The density of Pseudomonas often decreased while Streptomyces significantly increased with time. Changes in densities of pathogens and antagonists decreased the suppressiveness of the habitat towards soil-borne potato pathogens at the flowering phase. The study contributes information that will help to: (a) understand the epidemiology of some potato diseases, (b) make decisions on the economic and ecological aspects of chemical control in potato, (c) develop strategies for manipulation of the soil microbial environment as a viable crop management technique, and (d) develop prognosis models for potato diseases in central Europe.

Characteristics of Polish Isolates of Fusarium sambucinum: Molecular Identification, Pathogenicity, Diversity and Reaction to Control Agents

Pathogenicity of 28 Polish isolates of F. sambucinum to potato tubers, their sensitivity to control agents, diversity among isolates and molecular methods of species identification were examined. All isolates were pathogenic to potato tubers and differences in pathogenicity were found. Isolates on the PDA were classified into three different color groups of mycelium (B - bright-beige, P - salmon pink, R - rose) that varied in pathogenicity and mycelium growth rate on PDA. P colonies showed the greatest tuber damage, but they grew the slowest on the PDA. Isolates showed varied reaction to different concentrations of 4 control agents (M - mancozeb, C- captan, CO - copper oxychloride and GE - grapefruit extract). The highest mycelium growth inhibition (MGI) was caused by M and the lowest by CO. Strong MGI by GE was observed especially for P isolates. Individual isolates showed different susceptibility to the control agents. Identification of isolates was determined in PCR assay with species specific FSF1/FSR1 primers, by sequencing of DNA fragments derived from ITS regions and the translation elongation factor-1 alpha gene (TEF). Sequence of the ITS regions were identical for all isolates. Analysis of the TEF DNA fragments showed one SNP (transition C↔T) in the sequences of isolates from the three different color groups.ResumenSe examinaron la patogenicidad de 28 aislamientos polacos de F. sambucinum de tubérculos de papa, su sensibilidad a agentes de control, su diversidad entre aislamientos y métodos moleculares de identificación de especies. Todos los aislamientos fueron patogénicos a los tubérculos de papa y se encontraron diferencias en patogenicidad. Se clasificaron aislamientos en PDA en tres diferentes grupos de color del micelio (B - crema brillante, P – rosa salmón, R – rosa) que variaron en patogenicidad y en nivel de crecimiento del micelio en PDA. Las colonias P mostraron el mayor daño de tubérculo, pero fueron las de crecimiento más lento en PDA. Los aislamientos mostraron varias reacciones a diferentes concentraciones de cuatro agentes de control (M – mancozeb, C – captan, CO – oxicloruro de cobre, y GE – extracto de toronja). La mayor inhibición de crecimiento de micelio (MGI) fue causada por M y la más baja por CO. Se observó fuerte MGI por GE, especialmente para los aislamientos P. Aislamientos individuales mostraron diferente susceptibilidad a los agentes de control. Se determinó la identificación de los aislamientos en ensayos de PCR con iniciadores específicos por especie FSF1/FSR1 mediante la secuenciación de fragmentos de ADN derivados de regiones ITS y la traducción del factor-1 de elongación del gen alpha (TEF). La secuencia de las regiones ITS fueron idénticas para todos los aislamientos. El análisis de los fragmentos del ADN TEF mostraron una SNP (transición C↔ T) en las secuencias de los aislamientos de los tres diferentes grupos de colores.

Simultaneous selection for yield-related traits and susceptibility to Fusarium head blight in spring wheat RIL population

Fusarium head blight (FHB), caused by the fungal plant pathogen Fusarium, is a fungal disease that occurs in wheat and can cause significant yield and grain quality losses. The present paper examines variation in the resistance of spring wheat lines derived from a cross between Zebra and Saar cultivars. Experiments covering 198 lines and parental cultivars were conducted in three years, in which inoculation with Fusarium culmorum was applied. Resistance levels were estimated by scoring disease symptoms on kernels. In spite of a similar reaction of parents to F. culmorum infection, significant differentiation between lines was found in all the analyzed traits. Seven molecular markers selected as linked to FHB resistance QTLs gave polymorphic products for Zebra and Saar: Xgwm566, Xgwm46, Xgwm389, Xgwm533, Xgwm156, Xwmc238, and Xgwm341. Markers Xgwm389 and Xgwm533 were associated with the rate of Fusarium-damaged kernels (FDK) as well as with kernel weight per spike and thousand kernel weight in control plants. Zebra allele of marker Xwmc238 increased kernel weight per spike and thousand kernel weight both in control and infected plants, whereas Zebra allele of marker Xgwm566 reduced the percentage of FDK and simultaneously reduced the thousand kernel weight in control and infected plants.

Pathogenicity and potential capacity for producing mycotoxins by Fusarium sambucinum and Fusarium solani isolates derived from potato tubers

Pathogenicity and potential capacity for producing mycotoxins by Fusarium sambucinum and Fusarium solani isolates derived from potato tubers Studies of potential abilities of F. sambucinum to produce trichothecenes was conducted on isolates previously confirmed as belonging to this species by PCR. In all cases, A positive result for the presence of Tri5 gene, coding the ability to synthesize these mycotoxins. There was no potential to synthesize trichothecenes by F. solani. Further analysis concerned the potential ability of F. sambucinum to produce group B trichothecenes (DON and NIV). No isolate gave the expected amplification product (282 bp for deoxynivalenol and 312 bp for nivalenol), which would indicate the potential for producing these mycotoxins. Studies have shown the ability to produce trichothecenes of group A. Analysis of the potential ability for the synthesis of enniatins by F. sambucinum showed that 91% of isolates gave of 332 bp amplification product, which proves them as potencial producers of these mycotoxins. There were significant differences in the pathogenicity of F. sambucinum and F. solani represented by the size of decay caused by these species. The rotten tissue area caused by F. sambucinum was about 10 times bigger than after inoculation by F. solani. Furthermore, isolates within the same species (F. sambucinum) showed diverse pathogenicity. It should be noted, however, that the concentration of mycotoxins does not depend on the size of rotten tissue of potato tubers. Isolate, which caused the most severe disease symptoms, produced low concentrations of mycotoxins.