Application Of Piriformospora Indica In Rapid Propagation Of Cymbidium Hybridum

Cymbidium hybridum belongs to the Orchidaceae plants,also called cymbiduim orchid.C.hybridum reproduce mainly by tissue culture when the young seedling are removed from culture bottles,they grow slowly in the early days and have high disease occurrence rate.Piriformospora indica?P.indica?is a kind of beneficial endophytic fungus,having wide ranges of host.And it was thought to be the mycorrhizal fungal type of orchid plants.Now,it is suspected that whether P.indica and C.hybridum can form the mycorrhizal structure,facilitate its growth and strengthen the disease resistance.This paper mainly studies two problems:on the one hand,the microstructure and ultrastructure of two mycorrhizal structures have been compared.One is formed by P.indica DSM11827 and C.hybridum,the other is formed by epulorhiza ML01 and C.hybridum.We also have compared the symbiotic effect of each strain.On the other hand,we have compared the antagonistic effect of P.indica and Pseudo mycorrhiza Cy5-1 on Fusarium oxysporum T by the method of llat confrontation and co-culture in bottle.Therefore,we can explore the potential application of P.indica for the production of C.hybridum.The results of studies are as follows:1.In the culture medium DE,P.indica can form the mycorrhizal symbiosis structure with C.hybridum.The mycelium that around the root hair entered into the root of C.hybridum,extending continuously to form new hyphal branches.Those mycelium producted some spores on the short branches.They elongated in the intercellular space,growed in the apoplastic space and wound into a mycelial mass.All those features are in line with the structure characteristics of orchid mycorrhiza.The mycelium elongate and grow in the space between cells.Orchid mycorrhizal fungi hyphal extended in cortex cells reproduction and degraded after 20 days.Thus,it is reached a relative balance between hyphal and plants.2.In the co-culture environment of bottle,the kind of nitrogen source in the symbiotic medium have a great influence on the growth of C.hybridum and the symbiosis effect of all strains.The high ratio of ammonium nitrogen is beneficial for the increase of fresh weight,height and root growth of Cymbidium seedlings which is not mycorrhizaed.DSM11827can promote the increase of Cymbidium seedling fresh weight when the the ratio of NO₃^-:NH₄⁺is 4:1 and in the culture medium DE that is only added organic nitrogen source.While the strain ML01 can form the symbiosis system with C.hybridum and increase its fresh weight and promote the root growth only with inorganic nitrogen source.3.In the pot experiment,P.indica promote the accumulation of biomass and development of new roots.In addition,P.indica increase the accumulation of N and P elements in the aerial parts and promote the absorption of Fe in the underground parts.4.Under the condition of the plate confrontation,the combination of DSM11827 and Cy5-1 have the highest rate of bacteriostasis,about 16.52%.DSM11827 and F.oxysporum T form the antibacterial circle,but it had little effects on all bacteria.The Secretion of Cy5-1 inhibit the growth of pathogenic bacteria T greatly.In the co-culture environment of bottle,the index of disease and the incidence of disease decreased when the pathogenic bacteria T was inoculated in the symbiosis system of DSM11827 and C.hybridum,which can alleviate disease symptoms effectively.5.The symbiosis of P.indica and C.hybridum activated the enzyme activity of SOD,CAT and PPO on the aerial part of C.hybridum and the enzyme activities of PPO in the underground part,and improved the antioxidant capacity of plants.After F.oxysporum T was inoculated,the enzyme activity of CAT of the aerial part went up in the treat group of DSM11827,the enzyme activities of POD and PPO have peaked 10 days ahead of schedule.In the underground part,there is no significant difference of the enzyme activity of SOD,PO D,CAT and PPO between the control group and the treat group.Under the infection condition of F.oxysporum T,inoculation of P.indica enhanced the defense ability to pathogens of the upper part of orchid seedlings,while the effect was not obvious in the underground parts.6.When the C.hybridum was inoculated by P.indica,the enzyme activity of PAL continuously improved in the aerial and underground parts,which promoted the production of secondary metabolite of C.hybridum.When the C.hybridum is inoculated pathogenic bacteria T,the enzyme activity of PAL increased first and then decreased in the treatment group of DSM11827,which effectively inhibited the growth of pathogens of plant and alleviate the condition of Basal rot.