Scarcity of Major Resistance Genes Against Verticillium Dahliae

Verticillium dahliae is a soil-borne fungal pathogen that causes vascular wilt disease in numerous plant species. The only described qualitative resistances against V. dahliae are the Ve1 gene and the V2 locus in tomato. These resistances have been overcome by virulent strains. We tried to identify additional resistances. Out of the methods we tested, comparing the canopy area of V. dahliae-inoculated plants with mock-inoculated plants yielded the best discriminative power in resistance tests. Out of six wild tomato accessions that were previously reported to possess some resistance, Solanum pimpinellifolium G1.1596 and S. cheesmanii G1.1615 displayed the lowest stunting and the least colonization by V. dahliae. Recombinant inbred line (RIL) populations were developed of both populations. No QTLs were identified in the G1.1596 RIL population. In the G1.1615 population, four small-effect QTLs were associated with reduced stunting. Many studies in other hosts also failed to discover major resistance genes against V. dahliae. We hypothesize that the scarcity of major resistance genes against V. dahliae is caused by its endophytic behaviour in nature. The limited damage in nature would not lead to evolutionary pressure to evolve major resistances. However, in agriculture V. dahliae can behave more pathogenic, leading to serious damage.

Hymenula cerealis (Cephalosporium stripe).

H. cerealis is a pathogen that causes a vascular wilt disease of gramineous hosts known as Cephalosporium stripe. It is the only known vascular wilt of small grasses and small cereal grains with a fungal aetiology. It causes what is referred to as a 'single-cycle' disease because it does not have an airborne, repeating phase. As such, it is not an invasive species per se.

Integrated management of the Fusarium vascular wilt disease of Cucurbita pepo in Iraq

Fusarium vascular wilt disease is one of the most harmful disease that affected broad range of plant species including zucchini (Cucurbita pepo). The objective of the research was to investigate the presence of the phytopathogenic gungus Fusarium oxysporum the causal agent of the disease in zucchini fields. Forty five isolates of F. oxysporum were isolated from four locations in province of Dyala during 2014-2015. Isolate Foq9 was most virulent in the pathogenicity test in vitro. Twenty nine isolates of them amplified their DNA positively with the universal primer of F. oxysporum in the polymerase chain reaction technique (PCR). In vitro significant suppression efficiency were observed of the fungicides Topsin M 70 WP (Tm) and Tecto 500 SC (Tc) and two botanical extract solution extracted from Garlic (Gr) and Ginger (Gn) against the pathogen on the potato sucrose agar (PSA). In greenhouse experiments all of the agents decreased the percentage of disease incidence and severity significantly, while the tetra-inoculum (Tm+Tc+Gr+Gn) was superior which exhibited 0% disease incidence and severity compared to the negative control which was 95%, 79% respectively, also the combined application of the botanical extracts (Gr+Gn) reduced the disease incidence and severity significantly. All of the treatment increased plant growth criteria represented by dry weight of the plant compared to the control.

Integrated management of the Fusarium vascular wilt disease of Cucurbita pepo in Iraq

Fusarium vascular wilt disease is one of the most harmful disease that affected broad range of plant species including zucchini (Cucurbita pepo). The objective of the research was to investigate the presence of the phytopathogenic gungus Fusarium oxysporum the causal agent of the disease in zucchini fields. Forty five isolates of F. oxysporum were isolated from four locations in province of Dyala during 2014-2015. Isolate Foq9 was most virulent in the pathogenicity test in vitro. Twenty nine isolates of them amplified their DNA positively with the universal primer of F. oxysporum in the polymerase chain reaction technique (PCR). In vitro significant suppression efficiency were observed of the fungicides Topsin M 70 WP (Tm) and Tecto 500 SC (Tc) and two botanical extract solution extracted from Garlic (Gr) and Ginger (Gn) against the pathogen on the potato sucrose agar (PSA). In greenhouse experiments all of the agents decreased the percentage of disease incidence and severity significantly, while the tetra-inoculum (Tm+Tc+Gr+Gn) was superior which exhibited 0% disease incidence and severity compared to the negative control which was 95%, 79% respectively, also the combined application of the botanical extracts (Gr+Gn) reduced the disease incidence and severity significantly. All of the treatment increased plant growth criteria represented by dry weight of the plant compared to the control.