جستجوی مقالات مرتبط با کلیدواژه "differential lines" در نشریات گروه "گیاهپزشکی"

 In order to identify the new races, determine the virulence/avirulence formula and distribution of the causal agent of the wheat, in the spring of 2018 and 2019, respectively, 21 and 40 samples of leaf rust-infected leaves were collected from wheat fields in Khuzestan, Lorestan and Ardabil Mazandaran, Golestan, Kermanshah, Ilam, Sistan, Baluchistan and Fars provinces. The reaction of the isolates were evaluated by inoculating them on 38 differential lines under controlled greenhouse conditions. The results of this study led to the identification of 20 pathotypes and 13 races in the first year and 28 pathotypes and 11 races in the second year. PKTTS (28%) and PKTTT (18%) were the most prevalent races. The results of this study showed that differential cultivars carrying Lr19 and Lr9 resistance genes were resistant to all isolates and no virulence was observed on them. Lr2a gene with resistance reaction to 17 isolates was the most effective gene for resistance to wheat leaf rust after the two above-mentioned genes. Also, differential lines carrying Lr29, Lr10/Lr27+/Lr31 and Lr2b genes with resistance reaction to the majority of the isolates in two years were the most effective genes for resistance to wheat brown rust after Lr9, Lr19 and Lr2a genes.

Chickpea is the third most important food legume in the world. Ascochyta blight is the most destructive disease of chickpea caused by the fungus Didymella rabiei. Identification of resistance sources in germ plasm of chickpea is essential for breeding programs and management of disease. In order to investigate the effects of spore concentration and virulence severity of isolate on intensity of ascochyta blight in chickpea genotypes, a factorial experiment was conducted based on completely randomized design with three replications. Effect of two isolates (A3: moderately virulent & A6: highly virulent) and different spore concentrations (105, 2 × 105, 5 × 105 spores ml-1) were investigated on disease rate of 20 genotypes. Results showed that disease scale and its severity were affected by spore concentration, virulence severity of isolates and chickpea genotypes and there was significant difference between genotypes, isolates and spore concentrations. The disease severity increased with spore concentration from 2 × 105 to 5 × 105 spores ml-1 for resistant lines including, ILC 202, ILC72, ILC3279, ICC3996 and ICC12004, while the susceptible lines were affected by all of the conidial concentrations. The chickpea differential lines including ILC202, ILC72, ILC3279, ICC3996 and ICC12004 were resistant to all of the conidial concentrations of A3 (moderately virulent) while were susceptible to 2 × 105 spores ml-1 of A6 (highly virulent). The spore concentration of 2 × 105 spores ml-1 with A3 isolate developed the most discrimination between chickpea genotypes on the basis of mean disease scale. The obtained information can be used in breeding programs of chickpea and pathogenic diversity studies.

Sunflower rust is one of the most important diseases of the host in main cropping areas of Iran and resistance sources among the plant germplasm are accessible. Sunflower rust disease caused by Puccinia helianthi was reported first time at 1822 on collected samples from Eastern south areas of United States. It is considered as an important disease for sunflower cropping areas of South and North America, Argentina, Africa, India, China, and Australia and has been reported on the host worldwide. Incidence and severity of the disease on commercial hybrids had been increased up to early 1990s in Canada. Between 1988-89, the incidence on crop was reported up to 60 percent; whilst highly infected fields were appeared at the end of crop season. Puccinia helianthi has a worldwide distribution on sunflower and all species of Helianthus. There are also four other species which cause rust on cultivated and wild sunflowers. P. enceliae and P. masalis have been reported on wild sunflower and composites from southwest of United States. P. xanthi with a worldwide distribution on Xanthium Spp from Australia and Coleosporium helianthi from eastern areas of U.S. have been reported. Investigations reported some areas of Mazandaran and Golestan provinces showing infection including Behshahr, Kalaleh, Golidagh, Kalpoosh plain and Gonbad. Sunflower rust in Iran is considered as one of the important diseases which cause economic losses every few years. For instance, it caused 10 percent yield loss and 9.8 percent loss for oil yield. Genetic studies revealed that resistance is controlled by two dominant genes R1 and R2. By these identified genes, four physiological races of the pathogen became determinable. The presence of several resistant sunflower lines to rust with different origins reveals genetic variation for resistance to the disease. In this study, the variation of physiological races of sunflower rust was investigated to identify possible new races of the pathogen, Puccinia helianthi, and reaction of the host genotypes was also evaluated to the identified races.
Rust-infected leaf samples were collected from provinces Golestan and West Azarbayjan in 2010, and 8 isolates were inoculated on susceptible cultivar Record for physiological race identification purpose. Employing single pustule technique, the isolates were purified. The isolates after mass-production in separate chambers were inoculated on 9 standard differential lines. Inoculation and incubation methods were the same as for race identification procedure. The reaction of sunflower genotypes was evaluated by measuring pustule coverage percentage (PCP) according to computer-generated leaf diagrams depicting various percentages of leaf area covered with rust pustules. The interpreting resistance method proposed by Gulya and Masirevic (1995) was used in which three reaction patterns are defined as follows: immune (PCP= 0%), highly resistant (0.5%>PCP>0%) and susceptible (PCP.1%).
All collected isolates from the two main areas (i.e. Khoy and Golidagh) infected the non-resistant Perodovic cultivar indicating the pathogenicity of them. In addition, lines HA-335 and 803-1 were susceptible to all isolates. Lines RHA-265 and QHP1 demonstrated resistance to isolates collected from Golidagh, whereas the isolates of Khoy infected both lines. The results showed physiological differences between the main collection areas and presence of two dominant races. On the basis of pathogenicity similarities on common differential lines, races 302 and 300 were determined as dominant for Golidagh (Golestan) and Khoy (West Azarbayjan), respectively. Resistance evaluation of sunflower germplasm against rust disease was done under controlled greenhouse condition. The genotypes were tested by powdering the plants with mixture of the race's spore and Talc powder. The results demonstrated that 10 and 6 sunflower genotypes including hybrids Ghasem and Barzegar, their restorer lines and cultivar Gabor individuals were resistant against races 302 and 300, respectively.
Occurrence and distribution of physiological races of sunflower rust has importance in plant breeding research; as the process of breeding for resistant genotypes would be broken without considering the variation and distribution of the disease physiological races. In addition, genetic resistance to rust is controlled by dominant genes. Thus, access to new resistant sources in sunflower breeding is more likely. Among 23 lines and individuals of sunflower derived at the breeding processes, 16 resistant ones could help breeders to improve and release new hybrids or varieties containing resistance sources to the rust.

Pathogenicity of wheat stem rust was investigated during two cropping seasons of the years 2010 and 2011. towards this end, 47 isogenic lines of wheat stem rust along with 43 cultivars/lines of the crop were tested in field conditions (natural infection) and also in the greenhouse conditions. The results showed, similarity of pathogenicity for plants carring gene/s Sr7B, Sr8A, Sr8B, Sr9B, Sr9D, S9G, Sr11, Sr13, Sr16, Sr17, Sr25, Sr34 and SrDP2 as for two isolates. As for the in genetic variation of two wheat stem rust isolates (in greenhouse conditions), Kelardasht isolate did not show virulence for 15 isogenic lines carrying gene/s Sr5, Sr8A, Sr22, Sr24, Sr26+Sr9G, Sr27, Sr28, Sr29, Sr31, Sr32, Sr33, Sr35, Sr36, SrGT and SrWLD. From Dashte-Azadegan isolate of Khuzestan, virulence for gene Sr31 as a variant of Ug99 race was detected, while this isolate being avirulent on plants carrying gene/s Sr5, Sr22, Sr24, Sr26+Sr9G, Sr27 and SrGT. The results of evaluation of resistance for commercial wheat cultivars and elite lines indicated that, such new released cultivars as Morvareid, Sivand and Parsi were resistant with a range of reaction of 5R-50M to stem rust diseases as observed during the two years of the study.