جستجوی مقالات مرتبط با کلیدواژه « تحریک رشد » در نشریات گروه « گیاهپزشکی »

The seeds of common bean plants (Phaseolus vulgaris) are among the most important food sources worldwide. The plant pathogenic fungus Rhizoctonia solani causes seed rot and seedling damping-off of bean plants and is one of the most important soil-borne pathogens in most cultivation areas of this plant. R. solani plays an important role in reducing the yield and quality of this crop. Biological control is a promising, effective, and sustainable solution for managing soil-borne fungal diseases. The simultaneous use of biological control agents, especially agents with different mechanisms of action, might increases the chance of success in disease management. Indeed, two living agents can show different types of interactions based on their inherent characteristics and ecological conditions. In the current research, the potential of co-application of mycorrhizal fungi and bacterial strains from different taxonomic groups was evaluated on increasing the growth of beans and suppression of bean damping-off.

In this research, the effect of 14 different bacterial strains on the mycelial growth of R. solani was investigated by dual culture and by the volatile compound production tests in the laboratory. The list of bacterial strains included: Bacillus megaterium B15, Bacillus thuringiensis B48Pet, Bacillus subtilis BS (B.s), B. subtilis AS, Lysinibacillus boronitolerans RUPB71 (Lysin), Pseudomonas putida RUP1, Arthrobacter citreus B27Pet, Alcaligenes faecalis 1624, Bacillus pumilus INR7, Bacillus thuringiensis 32B (B.thur), Azotobacter vinelandii RUA1 (Azoto), Delftia tsuruhatensis PIIR (Delft), Stenotrophomonas maltophilia S37 and Bacillus velezensis JPS19 (B.vel). In the dual culture test, B.s, B.vel, Alca, Azoto, Lysin, and Delft strains significantly reduced the mycelial growth of the pathogen. In volatile compounds production test, three strains, Alca, Azoto, and B.thur, significantly reduced the mycelial growth of the pathogen. Four bacterial strains, including B.s, B.vel, Alca, and Azoto, were selected for greenhouse experiment. The selected bacterial strains as separate and combined application with two species of arbuscular mycorrhizal fungi (AMF), including Funneliformis mosseae (F.moss) and Glomus claroideum (G.cla) were investigated for inhibiting the disease caused by R. solani, and for their effect on the growth parameters of bean plants in the presence of the pathogen. The greenhouse experiment was conducted as a completely randomized design with 16 treatments and five replications.

Many of the greenhouse treatments that were applied in this study, significantly reduced the severity of the disease compared to the diseased control. They significantly increased the fresh and the dry weight of the shoots, root fresh weight and root dry weight. Four treatments (F.moss, B.s, Alca and Azoto) significantly enhanced the root length and four treatments (Alca, B.s, B.vel+G.cla and Alca+G.cla) increased the shoot length. In terms of the effect on the disease, the B.s strain was the best treatment, which reduced the disease severity by 36.5% and showed the greatest effect in promoting the vegetative characteristics of the plant. Although the bacterial and mycorrhizal strains showed compatibility in many combined treatments, G.cla+B.vel was the only double treatment that showed an increasing effect on the fresh weight and shoot length compared to the separate applications. The other double treatments did not have an additive or synergistic effect in reducing the disease and improving plant growth. Even in some double treatments, in terms of reducing disease and improving plant growth, a weaker effect was seen than their single treatments. Among different treatments, Alca+G.cla and Alca+F.moss showed the highest and B.s+G.cla showed the lowest mycorrhizal colonization.

The effect of bacteria on mycorrhizal colonization was increasing, decreasing, or null depending on the combination of bacterial and mycorrhizal strains used. In many cases, there was no direct relationship between the amount of mycorrhizal colonization and disease control. Overall, before the commercial use of the combination of biological agents, it is necessary to check their interactions in greenhouse and field experiments and ensure their compatibility and lack of antagonistic effect on each other. If the biological agents present in a consortium are compatible, its biocontrol effect will be more stable, efficient and reliable, and it will be possible to use it in a wider range of variable soil ecological conditions. Moreover, the interaction of individuals within a given consortium is strain-specific, and the results of an experiment on specific strains cannot be generalized to other strains of the same species.

Wheat is one of the most important agricultural products in Iran, that plays an important role in ensuring food security. Crown and root rot disease by F. pseudograminearum is one of the most important pathogens that cause economic damages every year. In this study, 80 isolates of Bacillus were isolated from wheat rhizosphere. In dual-culture test, UTB 3, UTB 11, UTB 22, UTB 4 and UTB 7 isolates with 60, 55, 37.5, 22.5 and 20% maximum ability, respectively. In effect test of volatile metabolites on inhibination the growth of F. pseudograminearum, UTB 3, UTB 7 and UTB 11 with 54, 52 and 49% showed the highest percentage of inhibition of fungal growth. These isolates were also capable of nitrogen fixation, production of siderophore and extracellular enzymes involved in biological control (protease, lipase and chitinase), but none of the isolates were able to produce phosphatase enzyme. Greenhouse studies by treating wheat seeds with selected isolates showed that UTB 3 was able to control crown and root rot of wheat by 80.33% compared to the control treatment. Also, this isolate could increase the growth indices of wheat (stem length and root dry weight) in the presence and absence of pathogenic fungi. Therefore, this isolate is introduced as the selected isolate to control crown and root rot disease and increase wheat growth indices.

Chickpea (Cicer arietinum L.) is the third most important legume crop in the world. Ascochyta blight caused by Ascochyta rabiei (Pass.) Lab. is one of the most important threats for producing chickpea in most of the growing areas. The pathogen invades all aerial parts of the plant and causes severe yield and quality losses. The present study aims to evaluate the effect of some defense inducing volatile compounds in inhibiting A. rabiei, as well as the effect of these compounds on some chickpea growth traits at the presence of the pathogen.

First, six volatile compounds including methyl salicylate, 2,3-butanediol, methyl-jasmonate, acetoin, indole and 3-pentanol were prepared in sterile distilled water (100 μM) containing 0.2% Tween 20, and were used for laboratory and greenhouse studies. The in vitro antifungal activity of volatile compounds was tested on chickpea seed meal dextrose agar (CDA) medium. Then, a five-millimeter agar disk containing the mycelium of the pathogen was placed on the surface of CDA medium in 9 cm diameter Petri dishes. The Petri dishes were inverted and 100 μl of the emulsion of each volatile compound was placed inside the lid. The Petri dishes were sealed and kept at the same inverted position to avoid the dropping of volatile compounds over the culture medium. A greenhouse experiment with nine treatments (including six volatile compounds, chlorothalonil fungicide, healthy and diseased controls) was conducted in a completely randomized design. In addition, the emulsions of volatile compounds were sprayed on the leaf surfaces 12 days after sowing chickpea seeds (variety Bivanij). After 48 hours, the conidial suspension of the pathogen in water (2 x 104 conidia/mL) was sprayed to the surface of chickpea seedlings. Disease severity and plant growth indices including shoot fresh weight, shoot dry weight, root fresh weight and root dry weight were measured two weeks after inoculation. Statistical analyses were performed by SAS software (version 9.3). The means were compared by Duncan's test at a statistical probability level of 5%.

All volatile compounds inhibited the mycelial growth of A. rabiei on CDA with the highest (64.91%) and lowest (4.67%) inhibition obtained by 3-pentanol and methyl jasmonate, respectively. In the greenhouse test, all volatile compounds, except methyl jasmonate, reduced the incidence of blight symptoms compared to the diseased control. The highest disease reduction was obtained by chlorothalonil (86.04%) and methyl salicylate (55.81%). At the presence of the pathogen, all volatile compounds increased root fresh weight, root dry weight and shoot fresh weight, and increased shoot dry weight with the exception of 3-pentanol and methyl jasmonate. Compared to the diseased control, the effect of indole on root fresh and dry weight and shoot dry weight, as well as the effect of methyl salicylate on shoot fresh weight was more than other compounds. Methyl jasmonate had the least improving effect on growth traits compared to other volatile compounds.

The volatile compounds used in this study inhibited A. rabiei in both in vitro and greenhouse tests. They also improved chickpea growth parameters at the presence of the pathogen. The use of volatile compounds could be considered as a new and promising strategy for the integrated management of Ascochyta blight.

Fusarial yellowing and wilting caused by Fusarium oxysporum f. sp ciceris is one of the most important diseases of chickpea. The effects of separate and combined applications of Trichoderma harzianum T33, Pseudomonas putida RUP1 and Rhizophagus intraradices were evaluated on suppression of this disease and improving growth factors of chickpea in the presence of the pathogen. The experiments were conducted in greenhouse in a completely randomized design with four replications. Except for the triple treatment (consisting of three biocontrol agents), all treatments significantly reduced the yellowing symptoms of foliage and vascular necrosis caused by the pathogen and also increased the roots volume and dry weight and shoot dry weight. Also, in addition to the triple treatment and the combined treatment of R. intraradices and T. harzianum T33, other biocontrol treatments increased the fresh weight of roots and shoots. R. intraradices was able to colonize 60% and 74% of chickpea roots in the presence and absence of the pathogen, respectively. Despite their compatibility, the dual combination of biocontrol strains did not have a synergistic effect in improving biocontrol efficiency and chickpea growth promoting, and the triple combination of these factors did not have biocontrol capability or plant growth promoting. This study showed that the combination of biocontrol agents is not always synergistic or efficient.