| Abstrakt: |
The seed is one of the most important inputs of agricultural products and its quality and health can be affected by seed-borne fungi. Seed-borne fungal pathogens are a major threat to black cumin production and cause considerable yield losses every year worldwide. The aim of this study was to identify seed-borne fungi, the effects of natural fungal infected seeds on some seed quality indicators, and also to investigate cell wall degrading enzymes (CWDEs), pathogenicity and aggressiveness of the isolates obtained from seeds. The constituents of essential oils (EOs) from seeds of Iranian and Syrian black cumin populations were identified and their effect on [isolated] seed-borne Fusarium isolates. A total of 17 isolates were identified based on morphological and molecular characteristics of Fusarium oxysporum and F. solani species. The results of the standard germination test showed that there was a significant difference between the studied seed populations in the germination and vigor indices. Our results indicated that most of the identified isolates were in the seed coat, while a few isolates of F. oxysporum were located in embryos. The results of the pathogenicity test showed that about 42% of the isolates were pathogenic and 58% of the isolates were non-pathogenic. Different levels of pathogenicity and aggressiveness were observed for various isolates of Fusarium species. All Fusarium isolates were not capable of producing CWDEs as pathogenicity factors. Analyzing the activity of CWDEs, including cellulase, pectinase, xylanase and lipase produced by the Fusarium isolates, revealed that activity levels of CWDEs are positive and are correlated with variations in pathogenicity and aggressiveness of seed-borne fungal isolates on seeds. The EOs were identified by gas chromatography-mass spectrometry and the major constituents were identified as ρ-cymene, trans-anethole, thymoquinone, limonene, carvacrol and α-thujene. The results showed that the compounds ρ-cymene, limonene, carvacrol, thymoquinone and transanethole had antifungal effects against F. oxysporum isolate. It seems that the percentage of carvacrol and limonene composition in the EOs components can affect the presence of the seed-borne Fusarium. This is the first report on the effect of EO compositions of black cumin seed populations on seed-borne Fusarium isolated from the same seeds. The findings of this research showed that the amounts and types of constituents of EOs of black cumin seed populations are different and they can affect the abundance of seed-borne fungi and their level of pathogenicity and aggressiveness. [ABSTRACT FROM AUTHOR] |
