Evaluation of Allelopathic and Antifungal Effects of Extracts of Leaves and Corm of Saffron (Crocus sativus L.) on Milk thistle (Silybum marianum L.) and Aspergillus sp.

Abstract

Introuduction: Saffron (Crocus sativus L.), belonging to the family Iridaceae, is a perennial plant with unique ecological adaptations. This plant is native to the Iranian Plateau and exhibits good compatibility with its specific climatic conditions, especially warm, dry, and moderate regions. This is a perennial crop with a longevity up to 12 years but the stands start self thinning after 5 or 6 years, therefore after 5-6 years the economic yield start reducing. It is well known that saffron leaves and corms produce bioactive compounds. Some of these compounds have a role in inhibition of plant growth and seed germination in their vicinity. The present research was conducted with the aim of evaluating the allelopathic and antifungal effect of extraction solution of leaves and corms of saffron on milk thistle and Aspergillus sp. Materials and Methods: In order to evaluate the allelopathic and fungicidal properties of saffron leaf and corm extracts on the germination and growth characteristics of milk thistle and Aspergillus, three separate experiments were conducted as factorials in a completely randomized design with three replications in the Seed Research Laboratory, Research Greenhouse, and Plant Disease Laboratory of the Faculty of Agriculture, University of Birjand in 2021. The treatments for the inhibitory effect of saffron extract on the germination characteristics of milk thistle seeds (first experiment) included two types of saffron organs (leaf and corm) and seven extract concentrations (0, 0.0625, 0.125, 0.25, 0.5, 1, and 2% w/v). The treatments for the inhibitory effect of saffron extract on the germination characteristics of milk thistle in pots (second experiment) were similar to the first experiment, and the treatments for the inhibitory effect of saffron extract on the growth of Aspergillus sp. (third experiment) were similar to the previous two experiments. Results and Discussion: The results of the first experiment showed that the interaction effect of extract type and extract concentration on germination percentage, allometric coefficient and stem dry weight was significant, and the lowest of the mentioned traits was obtained from the 2% concentration of leaf extract. The results of the analysis of variance of the second experiment showed that the simple effect of extract type on germination percentage, allometric coefficient and root length was significant, and the lowest of the mentioned indices was obtained from the leaf extract. The simple effect of extract concentration on germination percentage, germination rate and root length was significant, and the 2% concentration of extract had the lowest values of the mentioned traits. The interaction effect of treatments on stem length, stem dry weight and root dry weight was significant. The lowest stem length was obtained from the 0.5% concentration of corm extract. The 2% concentration of leaf extract had the lowest stem dry weight. The results of the antifungal experiment showed that the diameter of the Aspergillus fungus colony on the sixth and ninth days was affected by the interaction effect of extract type and extract concentration. The lowest fungal colony diameter on the sixth day was obtained from a concentration of 2% leaf extract, which had no statistically significant difference with a concentration of 1% leaf extract and concentrations of 1 and 2% corm extract. The concentration of 2% corm extract had the lowest colony diameter on the ninth day. Conclusion: Finally, the results of these experiments showed that the antifungal effect and also the effect of inhibiting the germination and growth of milk thistle in saffron leaf extract are greater than in corm extract. Therefore, by considering the results of this study and conducting more research in the field of fungicidal and allotoxic effects of saffron organ extracts, it is possible to produce natural fungicides and herbicides.