بوته میری

Among the oilseed plants, safflower has a special place, for production under climate change conditions. One of the main problems of safflower cultivation is fungal attack, which ultimately reduces crop yield. Studies have shown that Fusarium solani is the cause of the disease. Fifty six safflower genotypes were evaluated for their response to Fusarium root rot in a completely randomized block design with three replications in greenhouse conditions. The response was assessed by measuring traits such as mortality rate, length of necrosis zone in roots, number of viable plants, dry root weight, and dry weight of aerial area, stem height and stem diameter. The results showed that there is a high negative correlation between the mean necrosis length on the root and the number of live plants in the greenhouse. Genotypes were divided into 5 groups (resistant, relatively resistant, tolerant, sensitive, and relatively sensitive). The most resistant genotypes were Padideh, Golmehr, and P. Kose was evaluated as susceptible genotype. Since the wild species of C. palaestinus (P) and some genotypes resulting from its interspecies had the highest survival rate and the lowest necrosis length and mortality rate and on the other hand, this species is the most similar in terms of agronomic traits to the domestic species, the use of this species and the lines resulting from its interspecies to create disease-resistant cultivars could be recommended.

Introduction:

The pathogenic fungus, Fusarium oxysporum f.sp. carthami (FOC) is one of the main causal agent of safflower damping-off in Iran and worldwide. Climate change and extending of safflower farming area, specifically in rainfed systems have caused considerable crop loss in recent years. This pathogen can cause damping-off in any growth stage.

The pathogen FOC was isolated from infected plants, purified by single sporing, identified to species level, followed by the pathogenicity test in the lab condition on the Petri plates containing SNA media using Soffeh, a cultivar of safflower. A high pathogenic isolate of FOC was selected for further investigation for disease resistance evaluation test in greenhouse condition. Resistance level of 16 safflower genotypes was determined using inoculum layer test method in which infestation of sterile soil was implemented using fungal mycelial mat cultured on agar disk. Each genotypes comprised of six replications. Three pots inoculated and three un-inoculated as the mock. 45 days later, the plants uprooted and washed. Since disease scoring might vary a lot in replications, three more traits including plant height, aboveground biomass weight and root weight were recorded in inoculated and un-inoculated pots and then compared with each other. In addition, disease severity (DS) using a 0-5 scale were recorded for each plant. Reduction percent of plant height (PHR), root weight reduction percent (RWR) and biomass reduction percent weight (PBR) were calculated using data obtained from inoculated and un-inoculated pots and subjected to statistical analysis using R programming software. Since dwarfing of the inoculated plants was an important symptom in the field and greenhouse, a disease index (DI) was identified by multiplication of PHR and DS for each genotype. All the traits were subjected to analysis of variance and comparison of means by least significant difference (LSD) method. Correlation test was conducted between all the traits to find if there is any statistically significant correlation between them. Reaction of genotypes to the disease was shown by a partitional cluster plot using k-means algorithm.

Different Fusarium species were isolated from infected root and crown of safflower. Fusarium spp. and Macrophomina phaseolina were the top two main agents of damping-off isolated from safflower farms in Karaj and Zabol. Three different pathogenic Fusarium species including F. oxysporum, F. solani and F. verticillioides were isolated out of 30 infected samples. G186 as a very aggressive isolate of FOC was selected in order to screen the genotypes in the greenhouse. Analysis of variance of the traits which measured in greenhouse showed that all of them are statistically different at 1% level. Least square difference (LSD) multiple comparison of the RWR trait showed that the cultivar Goldasht has the lowest decrease in root weight compared to the control. This cultivar had the lowest decrease in PBR and PHR traits among the genotypes as well. Comparing DI of 16 genotypes indicated that Goldasht had the lowest index followed by L160 and L136. Therefore, they can be considered the most tolerant ones to FOC. The Pearson correlation test suggested a statistically significant difference between the traits RWR and PBR. PHR had a stronger correlation with PBR, as well. Partitional clustering revealed 4 different clusters in which resistant genotypes including Goldasht, L160 and L136 grouped in the same cluster while the susceptible ones including Padideh, Ghazzaghi, L72 and L111 grouped together in another cluster.

Fusarium oxysporum was frequently isolated in Karaj and Zabol fields and is expected to be a major pathogen of safflower in other safflower growing areas that needs to be verified by collecting more samples. The inoculum layer test method of inoculation seems to be an effective method to cause disease symptoms on safflower genotypes. However, there should be more tests on safflower-Fusarium interaction using different Fusarium species., i.e. F. solani and F. verticillioides to find more sources of resistance using different methods of inoculations. Most of the worldwide researches on pathobreeding of safflower to Fusarium are conducting using FOC isolates. Isolation of F. verticillioides frequently in this research might indicate that this species can be an important threat to this crop in the coming years. This species is known to cause crop loss mainly in aboveground parts of corn and sorghum farms but now it is frequently observed in safflower fields. Application of machine learning techniques to cluster different genotypes based on their reaction to the disease might be regarded as a useful method to find reaction of each genotype to the disease more accurately. 

Charcoal rot caused by the fungus Macrophomina phaseolina is one of the most common soybean diseases in Iran. In this study, resistance of 35 soybean genotypes from maturity groups II to V were evaluated against Charcoal rot in the field and greenhouse conditions. In the field cinditions, the percent of infected plants and the percent height of internal stem discoloration, and in the greenhouse conditions, length of stem necrosis were measured. As the results, genotypes Katul, Saman, Gorgan3, RVB × Katul and Katul × Krasnodar778 have the lowest percent of infected plant, percent height of internal stem discoloration and length of stem necrosis and identified as moderately resistant genotypes. Genotypes Williams, Sepideh, Sahar, L 17, and Karbin × Valenta have the highest percent of infected plant, percent height of internal stem discoloration and length of stem necrosis evaluated as susceptible genotypes. The moderately resistant genotypes identified can be used as the sources for developing soybean cultivars with resistance to charcoal rot.

In this research, the seeds of 12 sugar beet hybrids along with four control genotypes were planted in microplot conditions. After evaluating the roots against Rhizoctonia solani AG 2-2, the six genotypes that had the lowest amount of fungal infection were selected and tested for their reaction to Rhizomania virus disease. After examining ten soil samples from the farms of Kermanshah province and microplots located in Mahidasht research station, the contamination of the microplots of the experimental site with Rhizomania was confirmed based on serological and molecular methods. The seeds of six selected genotypes were planted in sterile soil and the seedlings were transferred to the microplate at the four-leaf stage. After harvesting, the roots were evaluated for BNYVV contamination using the ELISA method and based on Duncan's comparative test, they were divided into three groups. In general, due to the favorable resistance of the hybrid genotype (SB36*7112)* S1-92309 to both diseases, the use of the parents of this hybrid is suggested to continue for breeding experiments.

Charcoal rot disease caused by Macrophomina phaseolina is the most destructive disease of sesame (Sesamum indicum) in Iran and other countries as well. The fungus has been more important in recent years because of climate change and global warming. In this research, 81 genotypes of sesame were sown in a hot spot farm at Behbahan Agricultural Research station in south of Khuzestan province as a simple lattice design during three successive years. Damping off was observed at all growth stages. None of the genotypes were immune of the disease. M. phaseolina was the dominant pathogen of sesame in soil of the disease plot. Damping-off was observed during all growth stages. None of the genotypes were immune to the disease. The corrected data were subjected to simple and compound analyses. The results indicated that Tarom landrace and Darab2 line had the highest level of resistance. 22 genotypes were determined as moderately resistant genotypes among which Potak-e- musian landrace had the lowest 3-years average of infection percent. The rest were recongnized as moderately susceptible, susceptible and highly susceptible genotypes.

To investigate the efficacy of azoxystrobin+mefenoxam (Uniform 44.6%), in the control cucumber damping-off disease, experiments were carried out with seven treatments and four replicates in a Randomized Complete Block Design (RCBD) in Tehran, Alborz and Semnan provinces. Treatments were included 0.75, 1, 1.25 and 1.5 ml L-1 rates of Uniform, ridomil+mancozeb (Rosalaxil WP 72%) 2 g L-1 along with inoculated and non-inoculated controls. Treatments were performed two times as soil drench system, first after seed sprouting and second after 2nd leaves stage. The results are reported as disease incidence percent when the plants were in 4th leaves stage. ANOVA and mean comparisons with Duncan Multiple Tests were performed using SAS software. However, combined analysis of variance revealed that there was significant difference in treatment×place interaction at 1% probability but due to the similarity in mean statistical grouping of separate and combined analysis, combined ANOVA means grouping was used for the results assessment. Results revealed that Uniform at the rates of 0.75, 1, 1.25 and 1.5 ml L-1 decreased the disease incidence by 69.95%, 76.82%, 76.45% and 87.01% compared with the inoculated control and located in the b, c, c, and d statistical groups respectively. Furthermore, the results revealed that the Rosalaxil 2 g L-1 as a reference fungicide decreased disease incidence up to 86.03% in comparison with the inoculated control. The results of this study reveal that the Uniform application at the rate of 1.5 ml L-1 could be recommended to be used to control damping-off disease of cucurbits.

Culture design for mass production of biocontrol agents is one of the main approaches in commercialization of biocontrol agents. In this work, effects of some micro-nutrients have been investigated on biomass production and efficacy of B. pumilus against R. solani, the causal agent of bean damping-off. Seven elements, Fe, Zn, Cu, Mo, Mn, Co and B have been used in three concentrations. Bacterial biomass increased significantly in medium ammended with maximum concentrations of Fe (36 and 72 µM) and Cu (7 and 14 µM) and minimum concentration of Mn (12.5 µM). Bacterial population decreased significantly in minimum and medium concentrations of Zn (35 and 70 µM) and maximum concentration of Cobalt (14 µM) compared to M1 basal medium. In greenhouse experiment, highest disease suppression achieved in medium concentration of Fe (36 µM) and maximum concentration of Cu (14 µM). In other hand, maximum concentration of Fe (72 µM), minimum concentration of Zn (35 µM), maximum concentration of Mn (50 µM) and medium concentration of Mo (8.1 µM) decreased efficiency of bacteria in suppression of bean damping-off, significantly. In conclusion, the optimum concentration was not the same for tested elements. Even in the case of individual element, there was difference between optimum concentration for biomass production and efficacy of bacteria in biological control of the plant disease.

Damping off caused by Rhizoctonia solani: is one of the most important diseases of beans. Some control methods have been applied to overcome it but none seemed to be satisfactory. Biological control has been explored as an additional or alternative means of managing R. solani damping off. In this study, biocontrol ability of 8 isolates of Pseudomonas fluorescens were evaluated against R. solani and potential of rhizosphere colonization of the selected isolate was investigated. In this study, pathogenic fungi were isolated from infected plants of common bean crop fields in Khomein. Fungal isolate with the most pathogenicity was selected. Growth inhibition of R. solani selected isolate was evaluated by dual culture test, the antifungal activity of bacterial volatile and nonvolatile metabolites and P13 strain which was capable to produce maximum inhibitory zone was selected for studying its ability to biocontrol of pathogen and colonization of the ectorhizosphere and endorhizosphere of bean in 15, 30 and 45 days after planting under greenhouse conditions. Although the initial population of bacteria decreased in rhizosphere in 15th day, the population of bacteria in days 30th and 45th days increased in ectorhizosphere and decreased in endorhizosphere. Population of P13 was in the endorhizosphere and ectorhizosphere, in the healthy soil pollution 3/2 × 105 and 1/1 × 107 Cfu/g (fresh weight of root) and in infected soil 2/8 × 105 and 1/06 × 106 Cfu/g (fresh weight of root), respectively. Results showed that the severity of R. solani was significantly decreased and plant growth parameters were increased by biocontrol bacterial density on rhizosphere. P13 with great population on ecto and endorhizosphere showed strong positive effect on plant growth and inhibition of R. solani in 45th days

The most important plant diseases of greenhouse plants is damping off by Phytophthora sp., the disease caused the most damage to these plants. The disease is distributed in the most parts of Iran, and it causes plant losses in about 25%. This disease is affected by environmental stresses. However, the management of these environmental factors, such as nutrition, salinity and acidity of soil could have an effective role on reducing disease. In this research, it was studied the effect of growth medium acidity on pathogen growth inhibition and the effect of some nutrients associated with the composition of changing of acidity, too. The results showed the effects of acidity on pathogen growth had significant difference between different treatments. KOH and HNO3had the highest (64.58%) and the lowest (26.25%) inhibitory effect on the pathogen growth, respectively. the results of the effect of nutrient solutions test showed that adding nutrient solution reduced the percent of damping off significantly compared to control in both Negin and Sina varieties. KNO3 had the highest reduction of damping off in both varieties of cucumber. K2SO4and KCl had most effective after potassium nitrate, and NH4NO3 showed the least effect. Based on the findings of the current study, it seems that improving plant nutrition could be a good way to reduce cucumber damping due to P. drechsleri.

Phytophthora root and crown rot caused by various species Phytophthora are the major threat to agricultural crops in Iran. Phytophthora melonis and P. capsici are reported on cucurbits in Iran but major species in cucurbits considered to be P.melonis and the importance of P.capsici in cucurbits has not been much investigated. In the present study the reactions of different cucurbits were compared to both species under greenhouse conditions. Two months old of 36 cucurbit species and cultivars were inoculated with vermiculite hempseed extract inoculums. The production of zoospore in drained water and reactions of cultivars were monitored during two months after inoculation. The results showed that cantaloupe and long melon were more susceptible to P. melonis and reacted differently to P.capsici. Pumpkin was resistant to both species but squash and water melon were more susceptible to P.capsici than P. melonis.

Phytophthora drechsleri Tucker which earlier was considered to be responsible for cucurbit root rot in various parts of the world including Iran is similar to P. melonis Katsura in terms of morphology and and temperature requirement. The objective of the present study was to compare pathogenicity and reaction of both species on 87 species and vareties of cucurbits including cantaloupe, long melon, cucumber, watermelon, squashes and pumpkin. Two month old cucurbit seedlings were inoculated with 4-6 week old inoculum of both species grown on vermiculate supplemented with hemp seed extract and evaluated after two months under green house conditions. The result showed that none of the cucurbit species infected with P. drechsleri and indicated that P. melonis is one of the major cucurbit root rot in Iran. The reaction of cucurbit species and cultivars showed that cantaloupeis the most susceptible host to P. melonis. Long melon and cucumber were less susceptible cucurbita species and watermelon was more resistant than other cucurbits used.

This study was carried out to evaluate the antifungal efficacy of garlic essential oil (Allium sativum L.) and two fungicides including Metalaxyl- Mancozeb and Mancozeb against Phytophthora melonis, P. drechsleri and P. capsici the causal agent of damping- off on Pepper, Melon and Cucumber, in vitro and greenhouse conditions. Fungal radial growth for each concentration of garlic oil on Phytophthora species was measured. The Median Effective Concentration (EC50) values (ppm) of garlic oil measured. The chemical composition of the essential oils was determined by gas chromatography-mass spectrometry (GC-MS). Results of in vitro studies indicated that plant extract of garlic caused a significant decrease in the mycelial growth of phytophthora species and it had Fungistatic properties. The inhibitory effect of plant essential oil was observed for P. capsici (EC50 = 43.293 ppm) and P. drechsleri (EC50 = 50.236 ppm), respectively. The profile of the extract components of Allium sativum showed that Diallyl tetra sulphide (31.32%), Allyl disulphide (26.78%), Nitrosothymol (8.64%), 1H-1,2,4-Triazole, 3-thiol-5-methyl (8.4%) and Allyl sulphide (6.15%) were the main compounds. The results of greenhouse showed that plant essential oil significantly reduced disease compared to control (P ≤ 0.05). Based on results from this research, the garlic essential oil was found to be fungistatic effect against damping –off diseae and may be used in the production of organically grown vegetables.