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.
Fusarium oxysporum f. sp. lycopersici inhabits most tomato-growing regions worldwide, causing tomato production yield losses. A molecular marker linked to resistance would be useful for tomato improvement programmes. Thus, a cleaved amplified polymorphic sequence (CAPS) marker TAO1 902 was developed to identify tomato genotypes possessing the I-2 gene, which confers resistance to F. o. lycopersici race 2. The RsaI or FokI restriction fragments corresponded to the presence or absence of the I-2 allele in a segregating 100 F 2 progeny, tomato cultivars, 16 resistant and 20 susceptible to Fusarium wilt, respectively, lines and F 1 hybrids, representing various tomato gene pools. TAO1 902 may be helpful for selection of F. o. lycopersiciresistant tomato germplasm.
Fusarium oxysporum Schlecht. f.sp. radicis-lycopersici Jarvis & Schoemaker (FORL) is a saprophytic fungus, responsible for the fusarium crown and root rot disease in tomato (Solanum lycopersicum L.). This is one of the most destructive pathogens of this species. A new cleaved amplified polymorphic sequence (CAPS) marker C2-25 was developed for the detection of the dominant gene Frl, which confers tomato resistance to FORL. C2-25 was amplified from a conserved ortholog set II (COSII) sequence C2_At2g38025. The XapI-derived restriction product of 700 bp was informative for the identification of FORL resistant tomato genotypes and can be used as a diagnostic marker in tomato breeding programmes and hybrid seed production.
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