Fusarium oxysporum f. sp. radicis-lycopersici (FORL) leading to fusarium crown and root rot is one of the most destructive soilborne diseases of tomatoes occurring in greenhouse and field crops. Physiological races of FORL were not defined but nine vegetative compatibility groups (VGCs) were identified. Infection followed by wounds and natural holes and infection is not systemic. The optimum soil temperature for pathogen development is 18°C. Infection may cause plants to wilt and die completely or infection may lower fruit quality. Fusarium oxysporum f. sp. radicis-lycopersici has the ability to produce a specific enzyme, tomatinase, which breaks down α-tomatine and protects the pathogen. In contrast tomato also has a defence system which consists of the enzymes chitinase and β-1, 3-glucanase. Tomato resistance to Fusarium oxysporum f. sp. radicis-lycopersici is determined by a single dominant gene Frl, localized on the long arm of chromosome 9. It was introduced to cultivars from Licopersicum peruvianum (L.) Mill.

Trichodermaspp. - The Cause of Green Mold on Polish Mushroom FarmsThe first reports concerning green mold on Polish mushroom farms are from 2002. In Europe and the United StatesTrichoderma harzianumwas initially described as a causative agent of the disease. However, soon two biotypes ofTrichoderma, Th2 in Europe and Th4 in America, were recognised as responsible for commercial losses and were designated as a new species namedT. aggressivum.Until now it has not been clear which species ofTrichodermaand which form of the species was a causative agent of the disease outbreak in Poland and what was the main source of infection. Therefore, studies were conducted on the composition of theTrichodermaspecies in Polish mushroom farms and in compost samples. The isolates were identified by phenotypic and microscopic studies. The classification of the strains recognised asT. aggressivumwas then confirmed by PCR methods. The aggressiveness ofTrichodermaspp., especiallyT. aggressivum, was estimated inin vitrostudies. The most frequently isolatedTrichodermaspp. were:T. harzianum, T. aggressivum, T. atrovirideandT. longibrachiatum.Using the technique of PCR, multiplex PCR and PCR-RAPD it was determined that 24 isolates from Polish mushroom farms belonged toT. aggressivumf.europeanum(Th2). However, a large variation between isolates indicated the possibility that Polish biotypes ofT. aggressivumwere different from those, which were found in western Europe. All isolates ofT. aggressivumwere highly pathogenic towardsAgaricus bisporus.

Foliar application of a mixture of herbicides containing phenmedipham, desmedipham and ethofumesate to the plants of nine strawberry culfivars revealed that there were differences in the level of plant tolerance to the applied chemicals. Light, polarized light and scanning electron microscopy were used to explain differences in tolerance to herbicides. The surface of strawberry leaves and cells was examined for stomata, hairs, trichomes, surface structures, cucticle, vacuole and oxalate crystals. The thicker the cuticle on the adaxial leaf surface, the thicker the layer of epicuticular waxes, greater number of large vacuoles and greater number of calcium oxalate crystals in epidermis cells were characteristic for cultivars with very good tolerance to herbicides. The cracking of epicuticular waxes layer was typical to cultivars with respectively low tolerance to herbicides.

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