Effects Of Symbiotic Fungi On Seed Germination Of Interspecific Hybrids In Orchidaceae

Hybridization is an important mechanism of speciation.Orchidaceae is a highly evolved species.The number of natural hybrids is very rare.Symbiotic fungi play an important role in the germination and growth of orchids.The research about the hybrid with symbiotic fungi has rarely been reported.This study provides a new perspective for understanding the formation and evolution of the relationship between orchids and fungi through the symbiotic germination of hybrids and fungi,and also provides a theoretical basis of orchids seedling production using the way of seed symbiosis germination.we selected two kinds of fungi SSCDO-5(Tulasnella)and FDd1(Epulorhiza),which can effectively promote D.officinale and D.devonianum grow with strong specificity to carry out the symbiotic germination study for the D.officinale and D.tortile hybrid seeds.Studies have shown that when fungi and seeds are symbiotically cultivated for 68 days,both fungi can effectively promote the formation of protocorm and seedlings of hybrid seeds,there is no significant difference(P>0.05),and the seedling formation rate of SSCDO-5 strain is inoculated(22.13±6.62%)was slightly lower than the seedling formation rate of inoculated FDd1 strain(29.53± 5.51%).we selected two kinds of fungi SSCDO-5 and JC-1(Sebacina),which can effectively promote D.officinale and Dendrobium.nobile grow with strong specificity to carry out the symbiotic germination study for the D.officinale X D.guangxiense hybrids seeds.The study found that both fungi SSCDO-5 and JC-1 could promote the formation of protocorm and seedlings of hybrids.At 64 days of symbiotic culture,the seedling formation rate were(7.89±0.84%),(4.82±0.95%),respectively,fungal SSCDO-5 treatment was significantly higher than JC-1 treatment(P<0.05).The results of the two groups of experiments showed that the symbiotic germination fungi derived from the parent and other symbiotic germination fungi could promote the formation of protocorm and seedlings.The specificity of the parent and fungus did not appear in the offspring of the hybrid,which disaproved our hypothesis that the specificity of the commensal bacteria may be an important factor limiting the formation of orchid hybtids.In the first experiment,there was no significant difference in the rate of seedling formation between the two fungal treatments,but in the second experiment,the fungus SSCDO-5 from the parent D.officinale was more effective than the fungus JC-1 from the non-parent D.nobile.Combining the experimental results of the two groups,we speculate that this relationship between hybrids and symbiotic fungi is a compromise between genetics and the environment.Although hybrids inherited some of the connections between parents and fungi,it is necessary to compete with the parent in the natural environment for the fungal resources and to occupy the niche that suits them.These various factors cause the hybrid specific relationship with the fungus disappears or diminishes,and led hybrid select to form a symbiotic relationship with a wider range of fungal species.Since our current physiological mechanisms for seed and fungi specificity are still unclear,more case studies are still needed carry out from molecular and physiological aspects,and we believe that we can bring us new insights.