PYTHIUM ULTIMUM is one of the major causative agents responsible for damping off disease in cucumber plants. In the present study, the effect of potassium phosphite (KPhi) on defense response of P. ULTIMUM-inoculated cucumber plants was investigated. Different plant growth parameters as well as chlorophyll a content were studied to evaluate the healing effects of KPhi. Furthermore, the expression pattern changes of a pathogenesis-related chitinase gene was analyzed via qPCR. Results revealed that KPhi treatment significantly increased growth parameters i. e. shoot length, diameter and mean leaf number in cucumber seedlings. KPhi treatment at 1 and 4 gL-1 caused 31. 37% and 94. 48% increase in shoot diameter respectively compared to control plants while shoot length of plant treated with 1 and 4 gL-1 KPhi were increased 72. 14% and 78. 85%, respectively compared to control plants. The chlorophyll a content as well as plant leaf number was significantly increased in plants treated with 1 or 4 gL-1 KPhi compared to control plants. It was interestingly revealed that KPhi application decreased Chitinase gene expression compared to control plants. The findings of the present study would be implemented for designing a controlling strategy to decrease the adverse effect of P. ULTIMUM on cucumber plants.

Damage of the pathogens is one of the main limitations for cultivating and production of safflower. This study was performed to investigate reaction of safflower genotypes to PYTHIUM ULTIMUM during 2009 and 2010 under field conditions. The study was done in two parts, selection and evaluation of parents (part 1; 2009) and evaluation of the progenies (part2; 2010). In the first year, the experiment was performed as a randomized complete block design including selected seeds (seeds obtained on plants at infested soil) and unselected seeds (obtained seeds at sterilized soil) of 6 genotypes in 8 replications. In the second year, experiment was conducted in 3 different conditions. These conditions were included of two infested environments (environment 1 and 2) and one sterile environment. The suspension of 105 per ml zoospore was used for infection. Results showed that P. ULTIMUM damping-off decreased speed of emergence. Selection increased percent of emergence of genotype Zargan from 29.25% to 40.75%, of Syrian from 37.0% to 46.0% and of 34074 from 41.7% to 64.2%. Improving of percent and speed of emergence in infested soil with P. ULTIMUM showed that selection is an effective way for breeding resistance to this disease in some of safflower genotypes.

Identification and transfer of desirable genes from wild relatives to crop species is one of the breeding solutions for producing resistance to pathogens and pests. This study was conducted to evaluate crossability and the response to PYTHIUM ULTIMUMin three species of the genus Carthamus. To assess response to the pathogen, eight cultivated safflower (Carthamus tinctorius L.) genotypes, two ecotypes of wild species C. oxyacanthus collected from Tehran and Isfahan, and one ecotype of wild species C. lanatus collected from Golestan province as sub factor were cultured on pathogen-free and infested medium with zoospore suspension of P. ULTIMUM as main factor in a split plot design with 4 replications. Suspension of 105 zoospore per milliliter was used for inoculation. At the pathogen-free media, seed germination of cultivated and C. lanatus genotypes was higher than 90%, but at the infested media just cultivated genotypes had germination to this extent. The crossability experiment shows that, success in interspecific hybrid seed production is highly depended on choosing the seed producing parent. In the cross of cultivated species with C. oxyacanthus, more hybrid seed was obtained when C. oxyacanthus was female parent. Produced seeds on the cross of cultivated species and C. oxyacanthus had enough germination ability, but it was nothing for seeds obtained from cross of cultivated species and C. lanatus. Resistance of C. oxyacanthus to the pathogen PYTHIUM and success in hybrid seed production show the potential of this species for transferring of resistance and other favorable traits to cultivated safflower.

One of the major field constraints to seed production in safflower has proven to be soil born pathogens, Phytophthora drechsleri and PYTHIUM ULTIMUM. In order to evaluate the efficiency of a field-laboratory selection method to improve resistance of safflower against soil born pathogens, Ph. drechsleri and P. ULTIMUM, a two-year investigation was conducted. The results showed that selection is an efficient method for increasing resistance to seed and seedling death caused by Phytophthora and PYTHIUM in safflower. Selection could have improved germination percent, days to 50% germination, percent of undamaged seedlings and index of disease percent when genotypes were faced with both pathogens.Regarding kind of damages, PYTHIUM caused more seed rot and Phytophthora induced more seedling death. It could be concluded that selection for resistance to PYTHIUM, could also increase resistance to Phytophthora. Safflower was, however, more susceptible to Phytophthora than PYTHIUM. Also, genes for resistance to seed rot are different than those controlling resistance to seedling death, so preemergence damping off should be considered a completely independent trait from post-emergence damping off in safflower. It was concluded that used field-laboratory selection method could well improve resistance of safflower to pathogens Phytophthora and PYTHIUM and hence seed yield.

Some agricultural fields of Razevi and North khorasan provinces were sampled for identification and resistance to metalaxyl ofPYTHIUM ULTIMUM species isolates. Isolation was done between years of 2007 to 2009.Van der plaats- niterink key to species of PYTHIUM and specific ITS region of rDNA were used for morphological and molecular identification respectively. Micrometric characteristics of isolates sexual and asexual organs corresponded to van der Plaats-niterink criterion. Fourteen isolates were randomly selected among fourthy identified isolates ofPYTHIUM ULTIMUM for determination of sensitivity to metalaxyl.Concentration of metalaxyl which causes fifty percents growth inhibitions (EC50) obtained using logistic function; I=KC (erC). That varied between 0.0228-0.044 μg ml-1 i.e. the results indicate that all isolates were sensitive to metalaxyl, but there was significantly differences among isolates in response to metalaxyl.

Damping-off is an important disease of safflower in Iran, that caused by PYTHIUM ULTIMUM. Because of its importance, fungi isolates were sampled from infected plants grown in research farm of the College of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, in 2006. Also it has been proved that the disease caused by PYTHIUM ULTIMUM. Evaluation of seventeen safflower genotypes (Zarghan-259, Arak-2811, Isfahan, Syrian, Dinger, Hartman, Aceteria, CW-74, LRV-55-295, LRV-51-51, IUTM12, PI-250537, IL-111, 34062, 34074, 34040 and 541-5) for their response to causal agent were performed in 2007. The experiment was conducted in paper towel environment was done as split plot design in a complete randomized blocks in which two environments (sterile and infected) were included as main plot and also seventeen genotypes were as sub plot in four replicates. Artificial inoculation was conducted with 105 per mL oospore suspension of fungi agent. In sterile media percent and speed of seed germination and also dry weight of seedling and in infected media percent, real percent and speed of germination, number of infected seedlings and number of non-germinated seeds was recorded. Results showed that there was significant difference among the genotypes for all evaluated traits and also for reaction to disease. Comparison of means indicated that genotype Dinger with 79.7% had the highest real germination in infected media, and genotypes 34062 and Isfahan with 24.4 and 14.2 % were in the next rank in this regard, respectively. The lowest diseased seedling in infected media were belonged to IL-111 (6.3 seedlings), 34062 (6.8 seedlings) and Dinger (8.3 seedlings), respectively. Overall, the results of this study showed that some of non-Iranian genotypes were a good source for resistance to damping-off. Additionally, some of Iranian genotypes in respect to seed germination and related parameters were weak, however for resistance to the disease were superior to others. So, genotypes Dinger, Isfahan and 34062 could be used in breeding program of safflower to produce cultivars with resistance to damping-off.

Increased growth of wheat resulting from amendment of soil with strains of Trichoderma harzianum was investigated to determine if increased growth could be attributed to a direct effect of these Trichoderma spp. on the plant or a secondary effect due to control of plant pathogens. Three strains of T. harzianum (T.95, T-12B and T-12) and its parent's wild type (WT, isolated from a soil in Fortcollins) were grown on PDA.After 24h. sterile and washed cellophane membrane was placed on the growing mycelium. Seeds of wheat cv. Oslo (dwarf) and Butte (tall) were surface sterilized and placed on the membrane. The percentage of germination of seeds on the cellophane was more than the control (without T. harzianum). This experiment revealed that the exudates of T harziamum stimulated the germination of seeds. In the greenhouse experiments, wheat seed cvs Oslo and Butte treated with suspension of 108 spores per ml. the strains of T. harzianum and type (WT), were sown in the soil infected with P. ULTIMUM (300 CFU).The percentage of the infected root tips of the plants resulted from treated seeds was fewer than those of the control and wild type. The percentage of root pieces colonized by the propagules of the strains was more than the wild type. The fresh and dry weights of plants resulting from the seeds that have been treated with the T. harziamum were higher than the control. These experiments explore the possibility of biocontrol of some soil borne plant pathogenic fungi with strains of T. harziamum and increased growth response.

This study was performed to evaluate the effect of osmotic stress due to PEG on seed germination of safflower in PYTHIUM ULTIMUM infested environment. The experiment was conducted in factorial fashion in which four safflower genotypes (Dinger, Aceteria, LRV- 5151, and Arak 2811), and four osmotic stress levels (0, -10, -14, and -18 bar) were treated on paper towel media. The evaluated traits that were included, percent and speed of seed germination, speed of damping off, ratio of damping off to germination, and seedling dry weight. Results indicated that for the all traits, levels of osmotic stress had significant difference from control (0 bar). Unlike zero levels of osmotic stress (control) that fungal infection caused reduction in percent and speed of seed germination and seedling dry weight, in osmotic stress level (-10 bar) pathogen caused increases these traits. Increasing of osmotic levels from zero to -10 bar in infested environment caused reduction in speed of damping off, ratio of damping off to germination. Results showed that, although individual effects of osmotic stress and pathogen infection caused decrease in seeds germination and seedling growth properties, but their interactions improved percent and speed of germination in -10 bar in relation to control. Results of this study indicated that interaction between pathogen and osmotic stress had positive to some extant and could be useful for crop, so safflower could be cultivate in these conditions.