Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10878740 | Pedobiologia | 2005 | 9 Pages |
Abstract
Several fungi were isolated from rhizosphere soils of various crops through enrichment on l-methionine (l-MET) as a sole C and N source. These fungi were examined for their C2H4 production potential in vitro. GC-FID analysis indicated that 78%, 83%, 89% and 72% of fungi isolated from rhizosphere soil of wheat, maize, potato and tomato, respectively, produced C2H4 from substrate l-MET. Eight of the most efficient C2H4-producing fungal isolates (two from each crop) were further tested for their ability to produce C2H4 from 2-keto-4-methylthiobutyric acid (KMBA) and α-ketoglutaric acid (α-KGA). Interestingly, all eight fungi produced C2H4 from KMBA, but none used α-KGA as C2H4 precursor. This result implies that the METâKMBAâC2H4 pathway was most likely operating in these fungi. The most efficient C2H4 producer fungus (isolated from maize rhizosphere soil) was identified as Aspergillus terreus; this isolate was further studied to determine the optimal conditions for C2H4 production from l-MET. It was observed that a substrate (l-MET) concentration of 10 mmol lâ1, a glucose (C-source) concentration of 6.0 g Lâ1, no nitrogen, a pH of 6.0, an incubation temperature of 30 °C and an incubation time of 72 h were optimal conditions for l-MET-derived C2H4 biosynthesis by Aspergillus terreus. In addition, C2H4 released from precursor (l-MET) by Aspergillus terreus significantly affected the seedling length and stem diameter of etiolated pea seedlings in both sterilized and non-sterilized soils compared to a control. C2H4-producing microflora may be ubiquitous in soil, and the availability of a substrate like l-MET could enhance C2H4 synthesis in the rhizosphere of a plant, in turn evoking a physiological response. As far as we know, this study represents the first comprehensive screening of rhizosphere fungi for their ability to produce C2H4 from l-MET and KMBA.
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Authors
Muhammad J. Akhtar, Muhammad Arshad, Azeem Khalid, Muhammad H. Mahmood,