| Endophytic fungi can be able to live inside of plant tissue in almost all plants on the world. Many endophytic fungi inhabit cucurbit plants. Some of them can promote plant growth. Fungi that provide benefit to plants are considered to be plant growth promoting fungi(PGPF) and can facilitate plant growth and protect host plants from a number of environmental stresses by different types of mechanisms. Plant growth-promoting fungal endophytes employ similar plant growth promoting mechanisms to those used by rizhospheric PGPF. In fact, among fungal endophytes that are PGPF that go one-step further, and colonize the inside of plant tissue and provide more efficient and prompted protection to their hosts compared to those that bind exclusively to plants’ rhizosphere. Therefore, it is likely that endophytic plant growth promoting fungi will be superior to similar non-endophytic fungal strains in promoting plant growth under a wide range of environmental conditions. This study compared the species diversity of endophytic fungi revealed by two isolation methods and explored growth promoting activity of endophytic fungi to cucumber(Cucumis sativus L.).In this work, three different species of symptomless common cucurbitaceous plants cucumber, loofah, and pumpkin were collected from Yanqing and Daxing of Beijing. Altogether 68 endophytic fungi strains were isolated from tissues of the upper stems, lower stems and roots of the plant samples with dilution-to-extinct culture and fragment plating methods. Based on morphological characteristics and DNA ITS sequence alignments, Fusarium is the most common isolated genus. Other genera are Trichoderma, Penicillium, Hypocrea, Corticium, Aspergillus, Colletotrichum, Cladosporium, Schizophyllum, Clonostachys, Alternaria and Nectria. The results showed that 30 endophyte fungi strains were only isolated from fragment plating and 28 only from dilution methods. Rests of 10 endophytic fungi strains were isolated from both methods. To evaluate the species richness through the isolation numbers of endophytic fungi, two methodologies of isolation were briefly compared according to the species richness.Altogether 43 selected strains of endophytic fungi were used for this study and were isolated from cucurbits plants by other students in our lab and reserved by ACCC(Agricultural Culture Collection of China). To explore a strategy to use endophytic fungi for promoting growth of cucumber, experiment was set up in pot culture with two different inoculation methods(fungal spore suspension inoculation and pure fungi culture inoculation) under greenhouse conditions. The results showed that plants treated with endophytic fungi in both methods exhibited significant increase in growth and all tested growth parameters, as compared to the control(CK). By following the results of comparison of an effective inoculum between two methods, cucumber plants showed good response for pure fungi culture methods. The highest biomass,according to the traits,obtained by the inoculations with pure fungi culture methods of fungi strains were 3F8(90.45%), Jcl44(89.79%) and F87(82.18%) compared to control plants. Analysis of superoxide dismutase(SOD) activity, showed similar trend as the growth biomass, indicating the inoculation of endophytic fungi benefited the growth of host plants. The highest was observed in plant treated with 4F8(1533.87±336.55 unit/ml), 3F59(873.79±147.62 unit/ml), Jcl44(737.58±98.49 unit/ml), as compared to 254.69±62.67 unit/ml for the control(CK). Auxin related indolic compounds Indole-3-acetic acid(IAA), indole-3-acetaldehyde(IAAld) and indole-3-ethanol(IEt), were found in fermented broth of 17 strains of plant growth promoting endophytic fungi. The test with replacement of MS culture medium for PDA along fungus strains suggested that the extracts of those strains could act as growth regulators in cucumber plant by replacing auxin to enhance growth of plants. Thus, maybe some of the endophytic fungi strains used for this experiment could be used as a growth promoter for cucumber plants. |
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