Introduction: Getting rid of plant pests is one of the agricultural challenges, and farmers use a lot of chemical pesticides to fight these pests. However, these compounds have problems and negative effects. To address this challenge, various alternative methods have been investigated. Medicinal plants are one of the agricultural sectors where biotechnology has played an important role in development over the past several years.
This study aims to compare the aqueous extracts of Cichorium intybusL , Matricaria Chamomilla, Trachyspermum capticum, Zataria Multiflora Booiss, Peganum harmala, Piper nigarum, Capsicum annuum, Rosa damascena, and Allium sativum L, against two controls: water and a chemical pesticide, with a concentration of 1 gr in 500 cc of water, to control the growth of the fungus Alternaria under laboratory conditions.
In this research, the use of aqueous extracts of the plants in question, which have proven their high capabilities to control pathogenic fungi in many sources, was investigated as a promising solution in the biological control of Alternaria fungus. Although, despite proving the effect of these extracts in biological control methods, the comparison of the effect of these plants has not been done.
Methods: To prepare the aqueous extract of plants by boiling method, 20 gr of dried and eaten plants were placed in separate plastic bags under the biological hood and treated with UV light for 10 min. After that, they were boiled in separate containers with 400 cc of distilled water for 20 min. Then the above extracts were filtered and placed in sterile bottles and subjected to UV treatment for 10 min. A completely randomized design was designed with 9 treatments and 6 repetitions, and water was used as a negative control and copper oxychloride poison with a concentration of 1 gr in 500 cc of water was used as a positive control. At first, the amount of 1000 microliters of aqueous extract of the desired plants, in sterile conditions, poured into 6 cm plates by sampler and WA culture medium was added to them. Then the mushroom blocks were transferred to the center of the plates and the diameter of the colonies was measured for 5 days.
Results: Investigating the growth rate of fungal colonies in the treatments containing plant extracts compared to the water control showed that the treatments containing aqueous extracts of Matricaria Chamomilla , Capsicum annuum, and Rosa damascena had no controlling effect on the growth of Alternaria colonies compared to the water control. Surveys showed that treatments containing aqueous extracts of Trachyspermum capticum , Allium sativum L, Peganum harmala ,Piper nigarum ,Cichorium intybusL , and Zataria Multiflora Booiss, in comparison with the water treatment, had significant differences. All the above treatments can reduce the diameter growth in Alternaria. There is a significant difference between treatments containing aqueous extracts of Matricaria Chamomilla, Allium sativum L, Cichorium intybusL, Zataria Multiflora Booiss , Capsicum annuum , and Rosa damascena. These treatments, compared to the control containing toxins, have a lesser effect, making the use of toxins for controlling Alternaria a less appropriate method. The average effect of the extracts in controlling the growth of Alternaria indicates that the use of aqueous extracts of Trachyspermum capticum , Peganum harmala , and Piper nigarum, along with the water iscontrol, falls into the same statistical class, meaning these treatments are successful in controlling Alternaria. Additionally, treatments containing aqueous extracts of Trachyspermum capticum and Piper nigarumalso fall into the same statistical class as the water control, and on the other hand, do not have a significant difference with the treatment containing Zataria Multiflora Booiss. It is now evident that the Peganum harmala treatment has the same function as the toxin, and there is no significant difference with the treatment that does not contain toxins.
Conclusion: In this research, Peganum harmala extract demonstrated a significant effect in inhibiting the growth of Alternaria fungus and showed close competition compared to Peganum harmala. The results of the present research, like those of similar studies, indicate the ineffectiveness of treatments containing Rosa damascena and Matricaria Chamomilla extracts.
Among the treatments examined in this study, Peganum harmala, Piper nigarum, and Trachyspermum capticum exhibited greater and more effective results for Alternaria control.
This extract can be a suitable substitute for the chemical Peganum harmala in controlling Alternaria fungus.