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Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the major fungal diseases of Brassica napus L. To develop resistance against this fungal disease, the defensin gene from Raphanus sativus and chimeric chit42 from Trichoderma atroviride with a C-terminal fused chitin-binding domain from Serratia marcescens were co-expressed in canola via Agrobacterium-mediated transformation. Twenty transformants were confirmed to carry the two transgenes as detected by polymerase chain reaction (PCR), with 4.8 % transformation efficiency. The chitinase activity of PCR-positive transgenic plants were measured in the presence of colloidal chitin, and five transgenic lines showing the highest chitinase activity were selected for checking the copy number of the transgenes through Southern blot hybridisation. Two plants carried a single copy of the transgenes, while the remainder carried either two or three copies of the transgenes. The antifungal activity of two transgenic lines that carried a single copy of the transgenes (T4 and T10) was studied by a radial diffusion assay. It was observed that the constitutive expression of these transgenes in the T4 and T10 transgenic lines suppressed the growth of S. sclerotiorum by 49 % and 47 %, respectively. The two transgenic lines were then let to self-pollinate to produce the T 2 generation. Greenhouse bioassays were performed on the transgenic T 2 young leaves by challenging with S. sclerotiorum and the results revealed that the expression of defensin and chimeric chitinase from a heterologous source in canola demonstrated enhanced resistance against sclerotinia stem rot disease.

In this study the effect of two plant growth regulators (indolacetic acid, IAA and gibberellic acid, GA3) and also Trichoderma harzianum (T8) on the phytopathogen fungus Fusarium oxysporium (F15) was investigated. IAA and GA3 with 15 and 30 ppm concentration have no significant effect on T. harzianum (T8) growth. The biocontrol activity of T. harzianum on F. oxysporum was slightly decreased by the presence of IAA and/or GA3. Addition of 40 ppm of GA3 to the culture medium of F. oxsporum increased polygalacturonase activity about 100%. A strong increasing effect on chitinase activity (60%) by T. harzianum (T8) was observed in the presence of phytopathogenic fungus F. oxysporum, but 40 ppm IAA and/or GA3 decreased about 47% of chitinase activity of T. harzianum.

Fusarium yellow disease of chickpea (Cicer arietinum), caused by the vascular wilt pathogenFusarium oxysporum, is a major production constraint in chickpea-growing regions of Iran. Fifteen isolates ofF. oxysporumwere classified on the basis of vegetative compatibility (the ability to form heterokaryons). Vegetative compatibility was assessed by pairingnitmutants. The isolates were assigned to three vegetative compatibility groups (VCGs): VCG1, VCG2, and VCG3 with 5, 3, and 7 members, respectively. These isolates were also characterized by virulence assay. On the basis of disease severity on chickpea seedlings, they were divided into three groups: highly virulent (HV), moderately virulent (MV) and weakly virulent (WV). Twelve arbitrary decamer primers were tested on the fungal isolates by polymerase chain reaction. Random amplified polymorphic DNA (RAPD) analysis indicated considerable genetic variation among these isolates. Comparison of the results of VCG tests and the virulence assay indicated that all seven HV isolates belong to a single vegetative compatibility group (VCG3), and all three WV isolates are placed in VCG1. There was no relationship between RAPD groups and the other two characteristics of IranianF. oxysporumisolates. [ABSTRACT FROM AUTHOR]