عقيل عماد محمد الزاملي

Root rot and seedlings death pathogens are important diseases in wheat-growing regions of Iraq, particularly Rhizoctonia solani as it considered the main causative agent. Therefore, biological control and genotypes with low susceptibility are considered an effective and environmentally friendly way to reduce the impact of this soil pathogen. Current study aimed to evaluate the effect of Trichoderma fungi in reducing the effect of three isolates of the pathogenic fungus Rhizoctonia solani isolates (Rh1, Rh2, Rh3) on three wheat varieties including Abaa, Adna, and Barcelona. Experiments were carried out in postgraduate laboratories of the Department of Plant Protection, Faculty of Agriculture, University of Kufa. Results showed that Rh3 isolate was the most effective in reducing seed germination and seedling death. The use of bio-fungi led to an increase in germination, a decrease in seedling death, and a reduction in the severity and percentage of infection, which positively impacted plant vegetative growth. Abaa variety appeared to be slight resistant to the studied isolates of the pathogen compare to other varieties. Pots experiment showed that Trichoderma isolates significantly reduced the growth of the pathogenic fungus in double culture dishes with inhibition rates ranging from 55.97% to 69.85%. The outcomes indicate that Trichoderma fungi represent a promising option for the biological control of wheat root rot and seedlings death diseases.

Different fungal pathogens that cause rot root disease have a significant impact on cucumbers, which has a tremendous economic limitation on the yield of this important vegetable crop. The current study aims to examine the effect of cold aqueous extract of three plants (Acacia farnesiana, Myrtus communis and Nerium oleander) on the radial growth and the biomass of some pathogenic fungi (Rhizoctonia solani and Macrophomina phaseolina) with the presence of Trichoderma harzianum as a bio-control agent. Fungal pathogens were isolated from root parts of infected cucumber plants that were collected from different regions of Najaf province, while the bio-control fungus was obtained from the Bio-control Laboratory, Faculty of Agriculture - University of Kufa. Results of the current study showed that 20% of the cold aqueous extract of M. communis powder was superior to the rest of the studied extracts in inhibiting the radial growth of studied fungi, as the radial growth of R. solani reached 3.49cm, M. phaseolina 3.02cm, and T. harzianum 3.67cm. Thely apparent effect of the same extra extract on the growth of the fresh and dry biomass of the aforementioned fungi. The outcomes demonstrated that the 20% concentration of cold aqueous extract of M. communis also increased the percentage of seed germination and the fresh weight of cucumber plants. The cold aqueous extract of M. communis leaves and T. harzianum as a biological can be used , to inhibit the growth of both pathogens of rot root disease, thus protecting cucumber seedlings and producing healthy plants.

Root rot fungal pathogens cause destructive diseases and threaten broad beans particularly in favorable environmental conditions. Experiments of current study were carried out to examine the efficiency of extracts of both cinnamon and thyme on the growth of pathogenic fungi Rhizoctonia solani and Macrophomina phaseolina that cause root rot disease on broad beans in the presence of some biocontrol fungi namely Trichoderma harzianum 1, Trichoderma harzianum 2 and Paecilomyces. Results indicated that R. solani and M. phaseolina isolated from bean roots reduced broad beans seed germination by over 40% compared to the control treatment and other biocontrol fungi used in the study. Moreover, the severity of infection of broad bean plants by R. solani was higher than M. phaseolina. A comparison was made between the unsterilized and heat-sterilized powdered extracts for both cinnamon and thyme plants. The outcomes of the study showed that adding unsterilized and heat-sterilized cinnamon powder extract individually reduced the radial growth of both pathogenic and biocontrol fungi in Petri plates. Compared to the other studied fungi, the biocontrol fungus (Paecilomyces) was the most affected in terms of radial growth rate by the unsterilized and heat-sterilized cinnamon and thyme powder extracts. The radial growth of Paecilomyces in both heat-sterilized cinnamon and thyme powder extract treatments was 1.69 and 1.51 cm, and for the unsterilized extract, it was 1.69 and 1.73 cm, respectively. Results showed no significant differences between adding unsterilized and heat-sterilized cinnamon powder extract. However, the results indicated significant differences between adding unsterilized and heat-sterilized thyme powder extract. Furthermore, the results showed that the radial growth inhibition of fungi increased with increasing concentrations of extracts of both plants, whether unsterilized or heat-sterilized. The study proved that high temperatures did not significantly affect the effectiveness of powdered from both plants studied extracts against the pathogenic fungi. © 2024 Friends Science Publishers

Rhizoctonia solani, the causal agent of stem canker and black scurf disease on potato is a real threat to potato crop with up to 50% yield reduction. Current study was carried out to determine the effect of some Trichoderma isolates with different types of soil on the above diseases under laboratory and glasshouse conditions. Eight non-pathogenic strains of Trichoderma were isolated from potato roots and surrounding soil and examined for antagonism of Rhizoctonia diseases. Results showed that strains T. hamatum T8 and T. harzianum T5 had great potential as biocontrol agents for inhibiting the pathogen growth in dual culture and culture filtrate methods. The effect of different types of soils on the radial growth of R. solani AG-3PT in plates showed that Dorrigo soil inhibited the pathogen growth in laboratory by 68% as the colony diameter of pathogen recorded 2.8 cm which exceeds other soil types. While most Trichoderma strains that isolated from this area had a potential of protecting potatoes from the infection by the pathogen and acted as a biocontrol agent. Applying non-pathogenic Trichoderma isolates was the best method when inoculated the soil of pots with conidial suspensions which promote the growth of potato plants.

Isolates of Hyaloperonospora brassicae inoculated onto cotyledons of 28 diverse Brassicaceae genotypes, 13 from Brassica napus, two from B. juncea, five from B. oleracea, two from Eruca vesicaria, and one each from B. nigra, B. carinata, B. rapa, Crambe abyssinica, Raphanus sativus and R. raphanistrum, showed significant effects (P ≤ 0.001) of isolate, host and their interaction. Host responses ranged from no visible symptom or a hypersensitive response, to systemic spread and abundant pathogen sporulation. Isolates were generally most virulent on their host of origin. Using an octal classification, six host genotypes were identified as suitable host differentials to characterize pathotypes of H. brassicae and distinguished eight distinct pathotypes. There were fewer, but more virulent, pathotypes in 2015– 2016 isolates than 2006–2008 pathogen populations, probably explaining the increase in severity of canola downy mildew over the past decade. Phylogenetic relationships determined across 20 H. brassicae isolates collected in 2006–2008 and 88 isolates collected in 2015–2016 showed seven distinct clades, with 70% of 2006–2008 isolates distributed within clade I (bootstrap value (BVs) of 100%) and the remaining 30% in clade V (BVs 83.3%). This is the first study to define phylogenetic relationships of H. brassicae isolates in Australia, setting a benchmark for understanding current and future genetic shifts within pathogen populations; it is also the first to use octal classification to characterize pathotypes of H. brassicae, providing a novel basis for standardizing phenotypic characterization and monitoring of pathotypes on B. napus and some crucifer species in Australia.

Some 154 Brassicaceae genotypes (78 Brassica napus, 38 B. carinata, 25 B. juncea, three Raphanus sativus, two each of Rapistrum rugosum and B. incana and one each of Crambe abyssinica, B. fruticulosa, Hirschfeldia incana, B. insularis, B. oleracea and Sinapis arvensis), were inoculated with a mixture of seven isolates of Hyaloperonospora brassicae to identify effective host resistances. Many highly resistant genotypes were identified, particularly R. sativus Krasnodar Market B (%Disease index 6.6) and Pegletta (%DI 9.0); B. carinata Tamn Rex-sel Green (%DI 7.6), BRA926/18 (%DI 9.7) and PI360884 (%DI 9.7); and B. juncea, Ringot1 (%DI 9.7). A further 13 B. carinata, seven B. juncea and single R. sativus (Boss) and B. incana (UPM6563) genotypes were also highly resistant (%DI 11.1), as were B. oleracea CPI106844 (%DI 14.6) and Crambe abyssinica (%DI 17.4). Almost all B. carinata and B. juncea genotypes showed high resistance (%DI 7.6–22.2). In contrast, B. napus genotypes showed wideranging responses, from high resistance in SN-8 (%DI 22.2%) to extreme susceptibility in Hyola 450TT and Thunder TT (%DI 83.7, 95.5, respectively). R. rugosum, B. fruticulosa, H. incana and B. insularis genotypes ranged from moderately to highly susceptible (%DI 55.2–78.8). This study highlights the ready availability of very high levels of pathotype-independent resistance across diverse Brassicaceae toH. brassicae, particularly R. sativus, B. carinata, B. juncea, B. oleracea and C. abyssinica. Resistances identified can be utilized as sources of resistance in oilseed and vegetable Brassicaceae breeding programs and/or directly deployed as new varieties where downy mildew is prevalent.